Chemical And Biochemical Physics: New Frontiers

CHEMICAL AND BIOCHEMICAL PHYSICS: NEW FRONTIERS

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CHEMICAL AND BIOCHEMICAL PHYSICS: NEW FRONTIERS

G. E. ZAIKOV EDITOR

Nova Science Publishers, Inc. New York

Copyright © 2006 by Nova Science Publishers, Inc.

All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter cover herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal, medical or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Library of Congress Cataloging-in-Publication Data Chemical and biochemical physics : new frontiers / G.E. Zaikov, editor. p. cm. Includes index. ISBN: 978-1-60876-244-6 (E-Book) 1. Chemistry, Physical and theoretical. 2. Physical biochemistry. I. Zaikov, Gennadii Efremovich. QD453.3.C44 2006 541--dc22 2006010331

Published by Nova Science Publishers, Inc. New York

CONTENTS Preface

vii

Chapter 1

Nikolai M. Emanuel is the Phenomenon in Science S. B. Varfolomeyev and G. E. Zaikov

1

Chapter 2

Scientific Ideas of Academician N.M. Emanuel and Modern Science E. B. Burlakova and G. E. Zaikov

9

Chapter 3

Energy of Chemical Bond and Spatial-Energy Principles of Hybridization of Atom Orbitals G. А. Коrablev and G. E. Zaikov

Chapter 4

Preparation and Application of Magnetic Adsorbents in Biological and Medical Investigations E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov, G. V. Stepanov, V. I Filippov, L. Kh. Komissarova, L. A. Goncharov, F. S. Bayburtskiy, T. V. Tsyganova and H. U. Lubman

Chapter 5

The Magnetic Sorbents Used for Detoxification of Blood N. P.Glukhoedov, M. V. Kutushov, M. A. Pluzan, G. V. Stepanov, L. Kh. Komissarova, V.I. Filippov, L. A.Goncharov, F.S. Bayburtskiy

Chapter 6

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate O. V. Burykina and F. F. Nijazi

Chapter 7

Functionalising of Low-Molecular, Oligomer Dienes and Olefins with S, O-Containing Compounds R. Z. Biglova, A. U. Galimzjanova V. A. Dokichev, G. V. Konesev, G. E. Zaikov, R. F. Talipov

Chapter 8

Fractal Model of Stability to the Cracking of Modified Polyethylene A. Kh. Malamatov and G.V. Kozlov

Chapter 9

The Theoretical Description of Modified Polyethylene Thermostability within the Framework of Anomalous Diffusion Models A. Kh. Malamatov and G.V.Kozlov

13

29

41

47

53

67

73

vi Chapter 10

Chapter 11

Chapter 12

Contents Quantum-Chemical Calculations of Analysis Reactivity S-and O-Annes, Generated from 6-Methyl-2-Thio-, 2-Alkyl(Aralkyl)Thiouracils A. I. Rakhimov, E. S. Titova, R. G. Fedunov, V. A. Babkin, G. E. Zaikov Mathematical Models of Tumor Processes and Strategies of Chemotherapy Yu. A. Ershov and V. V. Kotin One-Stage Method of Catalytic Oxidation of Vegetal Raw Materials by Oxygen: Novel Ecologically Pure Products and Perspectives of Their Practical Use A. M. Sakharov

Chapter 13

EPR-Spectroscopy of Complex Polymer Systems A. M. Wasserman and M. V. Motyakin

Chapter 14

Organosilicon Copolymers with Carbocyclosyloxane Fragments in Dimethylsiloxane Backbone O. Mukbaniani, G. Zaikov, N. Mukbaniani and T. Tatrishvili

Chapter 15

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure O. Mukbaniani, G. Zaikov and T. Tatrishvili

Chapter 16

Organosilicon Copolymers with Monocyclic Fragments in the Main Dimethylsiloxane Backbone O. Mukbaniani, G. Zaikov and T. Tatrishvili

Index

79

87

113 127

149 167

217 263

PREFACE «Dissemination of education means spreading of prosperity. I mean universal rather than private wealth. Prosperity is the only thing that will eliminate the most (significant) part of Evil.» Alfred Nobel Stockholm, Sweden «Be brave and use your mind.» I. Cant Koeniksberg, Germany

It’s a pity that Nikolai M. Emanuel has not lived up to his current anniversary. He died at 69 years old (October 1, 1915 – December 8, 1984). He was a remarkable scientist and an outstanding administrator of science (refer to Chapters 1 and 2 of the current manuscript). In this Collection, we discuss problems of chemical physics and biochemical physics. As a branch of science, chemical physics was established in the first three decades of the 20th century by some famous scientists (including the Nobel Prize Laureate, Academician Nikolai N. Semenov − the founder of the Institute of Chemical Physics, Academy of Sciences of the USSR). Biochemical physics, on the other hand, representing the area of knowledge at the junction of three natural sciences, was created in the middle of the 20th century. The leader of this creation was Academician N.M. Emanuel − the founder of the Institute of Biochemical Physics, Russian Academy of Sciences. N.M. Emanuel managed to apply the knowledge accumulated in the branches of chemistry and physics to solving problems in biology, medicine and agriculture. In this Collection we tried to gather new original articles of some students of N.M. Emanuel and corresponding reviews. These articles show current developments of the ideas, once spoken about by N.M. Emanuel in his works, at seminars, and at conferences. Prof. G. E. Zaikov (the student of Academician N.M. Emanuel)

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 1-8 © 2006 Nova Science Publishers, Inc.

Chapter 1

NIKOLAI M. EMANUEL IS THE PHENOMENON IN SCIENCE S. B. Varfolomeyev∗ and G. E. Zaikov N. M. Emanuel Institute of Biochemical Physics; Russian Academy of Sciences; Moscow, Russia

"Everything is afraid of time. And only time is afraid of pyramids" Proverb. Ancient Egypt

When successors write anniversary notes about the teacher who was a scientist they like to bear in the title such words as "outstanding", "world famous", "unique", etc. It seemed to us, that in the case of Nikolai M. Emanuel all this is not enough. For this reason we have decided to place there a word "PHENOMENON". A painting by Ivanov from the Tretyakov Gallery collection, "The Appearance of the Christ to the People," comes to mind in this case where people are overwhelmed and filled with admiration by this phenomenon. People and colleagues who worked with Nikolai M. Emanuel feel much the same as the people from the Ivanov painting. We have to confess, that this word was not thought up by us, but by Nikolai M. Emanuel, having said it on April 16th, 1981 during a meeting devoted to the 85th anniversary of his teacher - academician Nikolai N. Semenov. Nikolai N. Semenov, in addition to being a Nobel Prize winner, was the organizer and permanent director of the Institute of Chemical Physics (ICP) of the Academy of Sciences of the USSR (AS USSR) in the period between 1931 and 1986. Both Semenov and Emanuel (as well as many other scientists) have glorified our country and have helped usher in huge contributions to the development of science and practice. N. M. Emanuel was a physicist by education, but he worked not so much in physics, but in chemistry, biology and even medical science. He taught us that it is highly undesirable to be engaged for long time in the same field of science, and it’s better to periodically change ∗

[email protected]; [email protected]

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S. B. Varfolomeyev and G. E. Zaikov

our direction of scientific activity. This will allow to use the accumulated knowledge in new areas of science. Many of Emanuel’s colleagues did not wish to change the structure of their work nor become engaged in something new (polymers instead of low-molecular compounds or biology instead of chemistry). “We know nothing in this new area”, they exclaimed. “Fine!” he answered. “You are not burdened by the dogmas of that field of science which you’re entering, and the basics of this area you can find in books”. A conclusion: Nikolai M. Emanuel was an innovator and he called for others to be the same. One who works for a long time in the same narrow field of science involuntarily “levels off” and the probability that he/she will make something outstanding is very little. Usually in such cases scientists work by a principle, “from N to N+1”. Unfortunately, N. M. Emanuel died early at age of 69 years, 2 months and 7 days. He was full of a creative power, energy and new plans when he suddenly left us. It had occurred on December, 8th, 1984 in ICP branch in Chernogolovka (Moscow suburb) in his business apartment on Saturday. He was home alone preparing a report on an agriculture topic for a meeting on Monday, December 10th, with the General Secretary of the Central Committee of the CPSU1, M. S. Gorbachev. Suddenly, he felt badly and had called for an ambulance which quickly arrived. However, physicians did not have any medicines and they only checked-up Nikolai Emanuel, but failed to help. He died from a heart attack. One relaxation shot would have quelled the painful shock and his heart would not have failed, but those were times when nothing could be bought. Citizens of our country “did not buy things” those days, but “got them found”. The verb “to buy” has gone out of use and it has been replaced by the verb “to find” (for example, “I’ve found it!”). There was such joke those days, named “Paradoxes of Socialism”. Here is a chain of events describing it: “Nobody works in the country, but the plan is fulfilled and exceeded. The plan is fulfilled and exceeded, but grocery stores are empty. Grocery stores are empty, but people have plenty of food at home. People have plenty of food at home, but everyone is dissatisfied. Everyone is dissatisfied, but all together vote in favor of Socialism”. Nikolai Emanuel has died because there were many paradoxes in our country those days. Even at the end of his life, Nikolai Emanuel had time to promote worthy representation of our science at the International level. He was the head of the National Committee of the Soviet Chemists and he earned great respect among scientists in the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC Executive Committee had long ago decided to elect Nikolai Emanuel as Vice-president of the Union (in two years he would automatically become a President of IUPAC, and in two years - Past President) on IUPAC General Assembly in 1985. All application documents for a position of Vice-president had to be submitted to IUPAC Headquarters in Oxford (England) till December, 25th, 1984. The situation seemed so clear that nobody but Nikolai Emanuel submitted documents in Oxford. And suddenly, Nikolai Emanuel passed away. The overwhelming majority of National Committees of the various countries found out about it very late and nobody had time to prepare the documents. Only the National Committee of the Soviet Chemists had quickly presented to Oxford documents on the Member of the Central Committee of the CPSU, Vicepresident AS USSR and the President of the Siberian Branch of AS USSR, an academician, Valentin Afanasevich Koptyug. In spite of the fact that in the moment prior to his death Nikolai Emanuel was the only Academician-Secretary of Branch of the General and 1

Communist Party of Soviet Union

Nikolai M. Emanuel is the Phenomenon in Science

3

Technical Chemistry (BGTC) AS USSR, his influence at the International level was incomparably greater than of Valentin Koptyug. Since other countries did not practically have a chance to nominate anybody, Koptyug had been elected by “a socialist variant” - one candidate per one vacant place. Now we’ll turn to Nikolai Emanuel's biography since this article is written to commemorate his 90th birthday. He was born in Tima, a town in the Suburb of Kursk. He began work in ICP in Leningrad, in 1938. He had proven himself as a talented young scientist in the field of kinetics, and he possessed a characteristic work-style which was traced from the beginning of his scientific work and distinguished him on all subsequent ways of scientific creativity. His first project devoted to oxidation kinetics of hydrogen sulphide was of great importance for the development of the theory of branched out chain reactions in a gaseous phase. With the beginning of Great Patriotic War, he had left to defend his Motherland and battled in Estonia. Under the decision of the country leaders, talented scientists (those who were not killed in battles in the first months of war) were demobilized and relocated in the research centers to help the troops in carrying out applied research. In 1942, soon after demobilization from the army, he had defended his PhD thesis on the theme, “Oxidation of Hydrogen Sulphide”. He generalized this research in the book “Intermediate Products of Complex Reactions in Gaseous Phase (Moscow-Leningrad, Publishing house AS USSR, 1946) where, for the first time, it has been shown that such intermediate products as sulfur oxide possess properties of free radicals and can propagate oxidation. It was an important scientific benchmark. Since 1944 Emanuel supervised over the Laboratory of Kinetics of Intermediate Substances in ICP (Moscow) which in 1956 had been renamed into Laboratory of Oxidation of Organic Substances. In 1949 he had defended the thesis for a Doctor of Sciences degree, and had received a professor rank in 1950. Nikolai Emanuel always aspired to develop those directions in a science which were important at the present moment and could enrich not only fundamental science, but also bring a practical advantage of implementation. Since 1954 he supervised works on kinetical research and the mechanism of oxidation of hydrocarbons and other organic substances in a liquid phase. As a result of this research, the chain theory of liquid-phase oxidation of organic substances has been created and experimentally proved, and a number of original methods of synthesis of important chemical products have been proposed. A Moscow oil refinery in Kapotnya, manufacturing 10,000 ton/year of acetic acid and methylethylketone by liquid-phase oxidation of normal butane under conditions close to critical has been built. Together with the French company RhonePoulenc, pilot reactors on liquid-phase oxidation of propylene in propylene oxide – an initial raw material for polyurethane synthesis and rocket solid fuel - have been constructed on the basis of Nikolai Emanuel's ideas in Leon’s suburbs (France). The shop on oxidation of paraffins with production of laundry liquids has been created on Shchebekino chemical plant. Most importantly, between 1950-1960 N. M. Emanuel had became a world-recognized scientist. He was known by everyone who worked in the field of chain reactions, oxidation, chemical kinetics and chemical physics in general. In 1958 Emanuel was awarded the Lenin Prize in chemistry and the same year he was elected as a member-correspondent of AS USSR for works in the field of properties and features of chain reactions. In 1966 he had been elected as a full member of the AS USSR.

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S. B. Varfolomeyev and G. E. Zaikov

The works executed under direction of Nikolai Emanuel in the field of ageing and stabilization of polymers have large practical value. He headed this research not only in ICP where more than 10 laboratories (180 scientists) worked on the given subjects, but also in the AS USSR and in the Academies of Union Republics, within the Committee on the Science and Techniques, and in cooperation of Academies of Sciences of the Socialist Countries and the Council of Economic Mutual Aid. Nikolai Emanuel was more then just a fine scientist able to perform out-of-the-box thinking. He was also a unique manager of science. He appreciated in his successors an ability to think both as a scientist and as a manager. Now allow us to step a little away from the basic text of this article in area of lyrical reasoning. At first Nikolai Emanuel did not have such good relations with academician Valentin Alekseevich Kargin who headed polymer science in our country. It wasn’t until 1966 when they went on a business trip together that they became friends. Valentin Kargin was aware of Emanuel’s work on oxidation of organic compounds and suggested that Nikolai Emanuel personally head works on ageing and stabilization, and then on polymers’ flammability. ICP settled down earlier to the address of: Moscow, Vorobevskoe highway, 2B (Institute of Physical Problems of academician Peter Leonidovich Kapitsa was at Vorobvskoe highway, 2), while Soviet Prime-Minister Alexey Nikolaevich Kosygin resided at Vorobevskoe highway, 6 (N. M. Emanuel resided in the same street in building number 4). Each time there were elections in our country, Alexey Kosygin came to ICP building 1 for participation in the election. Obviously, during the same moment, all (or almost all) heads of the Academy of Sciences were there. Nikolai Emanuel was there too. As a rule, after voting, Alexey Kosygin followed academician N. N. Semenov (ICP director) to his office where perfect cognac and fine food were served and informal conversation about USSR development took place. Further, we simplify real events only to keep this article short. There once was such a dialogue: Alexey Kosygin addressed Nikolai Emanuel and said, “Nikolai Markovich! Why does our industry make such poor-quality polymeric products? It’s so easy to distinguish the quality of our polymeric film from a foreign one”. Nikolai Emanuel responded, “Because you have bought polymer technology plants abroad and have constructed a number of plants, but we do not have industry to manufacture stabilizers for polymers, and often our industry makes polymeric products without stabilizers”. А. K.: “What is stabilizer?” N. E. describes to А. K. the essence of a problem. А. K.: “What do we have to do? What can you propose?” N. E.: “Let's solve the problem for a whole country. I suggest constructing a building for Polymer Stabilization on a site of Moscow Trust of Green Plantings that is located between Semenov and Kapitsa institutes. We’ll hire scientists and we shall solve this problem both theoretically and practically with the creation of industrial production of Soviet stabilizers”. Alexey Kosygin had taken a sheet of paper and had written: “To Slavsky (one of the Ministers) - to construct the building of Polymer Stabilization in an area of 10000 m2. To Kostandov (Minister of the Chemical Industry) and Fedorov (Minister of the Petrochemical Industry) - to allocate financing for construction of the building. Complete construction by

Nikolai M. Emanuel is the Phenomenon in Science

5

1975”. However, as we all know, it’s hard to implement something in time. Construction had been completed only in 1985 by which time Nikolai Emanuel had already passed away. When Emanuel passed away there were academicians and other “supervising comrades” who declared that there is no such scientific problem as the ageing of polymers, but rather some practical problems for handicraftsmen instead of for true scientists. Apparently, those “representatives from a science” were not familiar with the journal, Polymer Degradation and Stability, published in Oxford publishing house Elsevier, which has one of the greatest citation indexes in scientific literature. Throughout 25 years there has always been one of Emanuel’s successors on the editorial board of this journal. Now, when such research in our country is recognized as having no perspective, our representatives in this journal are not present. Yet, there are more and more scientists from China, South Korea, Japan, India and Malasia, along with scientists from the USA and Western Europe. Nevertheless, the manufacturing of stabilizers (PHENOZANs) in our country was created by the efforts of Nikolai Emanuel and his co-workers (V. V. Ershov, G. A. Nikiforov, A. A. Volodkin and many others). PHENOZAN means PHENOls from a plant (“Zavod” in Russian) and Academy of Sciences (“Nauk” in Russian). The first production has been started up in Kapotnya. There were more manufactures, but most of them have come to be in the foreign countries after USSR disintegration. Under the direction of Nikolai Emanuel, forecasting criteria for stability of polymeric products in conditions of their manufacturing and storage were developed, mechanisms of polymers’ ageing were discovered, the quantitative description of these processes was developed, new mechanisms of polymeric materials flammability reduction were proposed, the new generation of antipyrenes was created, etc., etc. N. M. Emanuel was one of the founders of a new direction in science – physico-chemical biology. He proposed for the first time to use inhibitors of radical reactions (antioxidants and bioantioxidants) as anti-tumor and radioprotective agents. His successors, E. B. Burlakova and D. B. Korman, provided invaluable help to him in these works. When Nikolai Emanuel visited USA or Western Europe with reports on these themes in 1960 - 1970, other chemists quietly chuckled at him: “he is a physicist by education and a chemist by soul – what is he doing in biology and medicine? It’s not chemistry where everything is much easier”. However, years went by and today if you go into any drugstore worldwide you will find bioantioxidants - vitamin E (spatially hindered phenol) - or tocopherol (4 isomers). Now they do not like to recollect (and do not recollect) who has taught them. N. M. Emanuel was teaching in a sub-department of Chemical Kinetics at the Department of Chemistry at M. V. Lomonosov Moscow State University. From the moment of the foundation of the sub-department of Chemical Kinetics in December, 1944 he was the assistant to the Chair - N. N. Semenov – and he gave annuall lectures on chemical kinetics, supervised over scientific work of young scientists, post-graduate students and students carrying thesis research. He had written a textbook, “A Course of Chemical Kinetics,” (Moscow, “Vysshaya Shkola”, 1962) with academician Dmitry Georgievich Knorre (professor then), which has already sustained 4 editions and been translated into foreign languages. Academicians, members correspondents, and doctors of sciences and philosophy are among his successors, a few hundreds in total. The works of Nikolai Emanuel have received world recognition. His lectures and reports, which have been given in different countries of the world (USA, Canada, the Western Europe, Japan, China, etc.), were very popular.

6

S. B. Varfolomeyev and G. E. Zaikov

He had been selected as a full member of many Academies in the world, including New York Academy of Sciences (USA), a foreign member of the Swedish Royal Academy of Sciences, a doctor Honoris Causa of the Seged University (Hungary), a honorary member of the Hungarian Academy of Sciences, a member of the German Academy of Scientists “Leopoldina” (GDR2), a foreign member of the Academy of Sciences of GDR, an honorary doctor of sciences of Uspal university (Sweden), etc. N. M. Emanuel began his scientific-organizational activity in 1942 when ICP was in Kazan city. For many years he was a scientific secretary of ICP, and then a Science Deputy Director. Nikolai Emanuel was an academician-secretary of BGTC AS USSR from 1975 and up to the end of his days. For many years he was the editor-in-chief of “Uspekhi Khimii” journal and a member of editorial boards of many domestic and foreign journals, including industrial editions. In 1971 Nikolai Emanuel had been selected as a member of the Bureau and Executive Committee of IUPAC and he was a chairman of the National Committee of the Soviet Chemists. N. M. Emanuel – was the hero of socialist work, the winner of Lenin and State prizes, A. N. Bah premiums, the author of many monographies published in our country and abroad, and hundreds of reviews and original articles, the author of the registered discoveries. He has many awards and medals from the USSR. More than twenty years have passed since Nikolai Emanuel left us. There will not be enough pages in this article nor in the entire “Bulletin of AS” journal to describe all that was done by N. M. Emanuel for science. Everything he made for science has already entered deeply into the consciousness of his successors and is reflected in the foundation of a new scientific institute of the Russian Academy of Science - Institute of Biochemical Physics carrying the name of Nikolai Markovich Emanuel (IBCP of the Russian Academy of Sciences). This Institute has been created by order #227 (1994) of Presidium of the Russian Academy of Sciences “for development of fundamental research of physical essence of chemical processes in the biological and molecular-organized chemical systems”. In 1995 IBCP of the Russian Academy of Science was awarded by name of academician N. M. Emanuel. The first director of IBCP was academician Alexander Evgenevich Shilov (scientific supervisor of IBCP now), and the first deputy director on scientific work was professor Elena Borisovna Burlakova, who carries this duty these days. N. M. Emanuel was a cheerful person and, despite the many years since his passing, we still feel pain over the loss. There lives a grateful memory in those who were his friend, colleague or student. Three monographies will be published by Nikolai Emanuel's 90th birthday. One of them is N. M. Emanuel's selected works (Moscow, “Nauka”, 2005). Two others are reviews of his students and successors where they’ll show how N. M. Emanuel’s ideas have worked in his students’ and followers’ works for the last 20 years, in the English (Brill Academic Publishers, Leiden, The Netherlands, 2005) and Russian (Moscow - Ufa, “Khimiya”, 2005) languages. We’d like to finish this article with something informal. We recall that Nikolai Emanuel often went to the Department of Science and the Department of Chemistry of the Central Committee of the CPSU in Moscow downtown where he defended new scientific projects and 2

German Democratic Republic

Nikolai M. Emanuel is the Phenomenon in Science

7

new budget. Sometimes he was successful, sometimes he was not. Once, when he had returned to work full of negative emotions (he was not successful that time), he told that he had deduced the mathematical formula which describes our country, and, more precisely, a management of our country. In his opinion (for that moment), all this was described by a square root of minus one. Unfortunately, Nikolai Emanuel is no longer with us, and we do not know how to describe mathematically the attitude to a science of a present management of our country. Nikolai Emanuel was able to gather both young and mature scientists around him. Among the mature ones are members-correspondents AS USSR Iosif Abramovich Rappoport and the professor Lev Alexandrovich Blumenfeld, who worked in Emanuel’s department for many years. Among the young ones is Mikhail Arkadevich Ostrovsky (an academician of the Russian Academy of Sciences these days). Mikhail Ostrovsky was a timid young man who did not know, really, the dark side of life. Once there was a meeting where Nikolai Emanuel had told to everyone (including Ostrovsky): “We have to let Ostrovsky feel anger!” He wanted that Mikhail Ostrovsky understand a sense of real life as well. There were/are many co-workers and colleagues who worked with Nikolai Emanuel for years. We have already mentioned some of them in this article, but here we shall mention more. Here we wish to name Zynaida K. Majzus, Erna A. Blumberg, Tatyana E. Pavlovskoj, Ilya V. Berezin, Kira Е. Kruglyakova, Irina P. Skibida, Dmitry J. Toptygin, Lana P. Lipchina, Igor I. Sapezhinsky, Lyudmila S. Evseenko, Kirill M. Dyumaev, Leonid D. Smirnov, Georgy P. Gladyshev, Anatoly L. Buchachenko, Eugeny T. Denisov, Jury A. Shljapnikov, Victor Y. Shlyapintoh, Tatyana E. Lipatova, Rostislav F. Vasil’ev, Alevtina B. Gagarina, Lora B. Gorbacheva etc., etc. The full list should include 700 - 800 names. Hope the others will forgive us for not including everyone in this list Nikolai Emanuel was very glad and proud that his ICP department had (and still has) a vivarium with mice and rats. As it’s well known, the introduction of even one new medication in a clinical practice requires performing tests to reveal side effects, and that requires about 10 years of experiments. Nikolai Emanuel had introduced a number of anti-tumor medications in health care. There was/is a chemical-therapeutic building in the 2nd city hospital where his medications were tested after numerous approvals. We do not know whether he had thought this up himself or if someone told it to him, but once he told us this joke-riddle: Question: “Tell me, please, is communism a science or an art?” Answer: “Communism is an art” Question: “And why?” Answer: “Because, if it was a science, it would be tested on mice and rats first” Nikolai Emanuel tested his medications on animals and was proud that he did it himself. In some topics Nikolai Emanuel was not able to show persistence and win the battle. Nikolai Emanuel liked to drive his “Volga”. And once he was stopped by a GAI3 officer by the subway station, “Leninskie Gory”. Nikolai Emanuel went out of his car and began to explain what happened, and the officer was unmerciful and demanded the penalty. Luckily, one of Nikolai Emanuel’s employees, Leva Aramovich Piruzyan, drove by (now he is an academician of the Russian Academy of Sciences). He saw that Nikolai Emanuel was in trouble and needed help. Now almost everyone has a mobile phone, but those days only KGB officers and other high-ranked officials had portable phones. Leva Piruzyan has taken an 3

State Automobile Inspection, i.e. road patrol/police

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S. B. Varfolomeyev and G. E. Zaikov

ordinary desk phone from his office and has put it in his car “Volga”. Obviously, the phone was not connected and did not work as a communication device. However, passing by GAI officers with excessive speed, he picked up a telephone tube and shouted. “The First listens!” It used to create a terrifying effect. GAI officers saluted him with no questions asked. So, he passed Nikolai Emanuel and the GAI officer slowly and shouted again, “The First listens!”, and then he jumped out of his car and ran up to the GAI officer, asking, “What are you doing?!?” The GAI officer was surprised. “What’s a problem?” Piruzyan had whispered, as it was a secret, “you keep ‘closed’4 academician on the open place. Release him immediately”. The GAI officer was frightened. He apologized and let them go repeating “sorry, sorry”. Tatyana E. Pavlovskaya, the wife of Nikolai Emanuel, had been by him all his life. She has been a researcher. However, she had enough forces to create a comfort for Nikolai Emanuel that allowed him to work successfully. Their daughter, Olga Nikolaevna Emanuel, holds a PhD degree in Chemistry. She works in N. M. Emanuel IBCP. Great Russian/Soviet poet, Vladimir Vladimirovich Mayakovsky, wrote that the memories of outstanding people live in the names of cities, libraries, universities, etc. In the case of N. M. Emanuel, this is true twice: IBCP carries his name first, and second, all his scientific ideas live in the developments of his successors. His life goes on!

4

‘Closed’ people were/are carriers of state secrets, i.e. they were forbidden (‘closed’) to be exposed to other people

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 9-11 © 2006 Nova Science Publishers, Inc.

Chapter 2

SCIENTIFIC IDEAS OF ACADEMICIAN N. M. EMANUEL AND MODERN SCIENCE E. B. Burlakova∗ and G. E. Zaikov Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia "Gratitude is associated solely with bees and their gratitude is sweet." Sherlock Holmes Sir Arthur Conan Doyle

Usually, Sherlock Holmes was right in his conclusions and assessment of situations while applying his deductive method of analysis. However, in this case, his ideas do not work.. Our country (the USSR successor), Russian scientists, the world scientific community, followers, friends, and colleagues of Academician N.M. Emanuel, and all who knew and worked with him are grateful to him and keep dear memory of him. On October 1, 2005, we commemorated the 90th anniversary since the birthday of Nikolai Markovich. The Russian Academy of Sciences, the Department of Chemistry and Science of Materials, the Emanuel Institute of Biochemical Physics, the Semenov Institute of Chemical Physics, the Institute of Problems of Chemical Physics (Chernogolovka, Moscow Region), and the Faculty of Chemistry of Lomonosov Moscow State University commemorated the date and held a conference dedicated to the memory of Academician Emanuel. The title of the Conference, Scientific Ideas of Academician N.M. Emanuel and Modern Science, is significant because Nikolai Markovich put forward many scientific ideas and hypotheses, which were developed later in modern science. The Organizing Committee of the commemoration events and Conference included Academician N.A. Plate (Chairman, Vice-President of the Russian Academy of Sciences), Academicians V.A. Kabanov (Vice-Chairman), S.M. Aldoshin, M.V. Alfimov, A.I. Konovalov, V.V. Lunin, O.M. Nefedov, M.A. Ostrovskii, L.A. Piruzyan, and A.E. Shilov, Corresponding Members of the Russian Academy of Sciences K.M. Dyumaev, G.B. Manelis,

∗

e-mail: [email protected]

10

E.B. Burlakova and G.E. Zaikov

and V.F. Razumov, Drs. of Science E.B. Burlakova, A.A. Popov, S.D. Varfolomeev, and G.E. Zaikov, and Ph.D. V.P. Balakhnin. On September 30, 2005, a special session of the Scientific Council of the Moscow State University dedicated to the memory of Emanuel was held at the Faculty of Chemistry. Academicians V.V. Lunin (Dean), N.A. Plate, V.A. Kabanov, A.L. Buchachenko, I.P. Beletskaya, and Professors E.B. Burlakova and M.Ya. Melnikov spoke with recollections about Nikolai Markovich and his role in the development of Soviet science and education of young generations. On October 3, 2005, the scientific conference was opened at the Emanuel Institute of Biochemical Physics. Academician Plate delivered the opening speech. Professor Varfolomeev (Director) spoke about significant facts of life and scientific achievements of Emanuel; Dr. M.R. Lechinitser emphasized the importance of theoretical works of Emanuel for the formation of clinical oncology. Academicians V.A. Kabanov, A.E. Shilov, A.A. Berlin, K.M. Dyumaev, L.A. Piruzyan, G.B. Manelis, and L.V. Zabelin participated in the scientific discussion that took place at the session. The 2nd session of the Conference was held at the Institute of Problems of Chemical Physics (Chernogolovka) on October 4. The opening lecture was delivered by Academician S.M. Aldoshin (Director). This session included four presentations. Professor N.P. Konovalova reported on antioxidants and donors of nitrogen monoxide (antitumor effects of nitroxides and NO-donors); the report of N.A. Sanina and S.M. Aldoshin was concerned with a new class of NO-donors (synthesis, structure, properties, and practical use of sulfur-nitrosyl complexes of iron). Free-radical mechanisms of induction and development of secondary necrosis after gun wounds were the subject of the lecture by G.N. Bogdanov; L.D. Smirnov reported on pharmacological properties and promising clinical application of antioxidants of the heteroaromatic array. The 3rd session of the Conference (Oct. 4) included five presentations. The report by E.T. Denisov on the radical chemistry of artemisinine aroused great interest in the audience. The report by L.A. Ostrovskaya and D.B. Korman dealt with the use of nitrosoalkylurea in the antitumor chemotherapy. Special effects of peroxide oxidation of lipids of biological membranes in the presence of ultra-low concentrations of antioxidants were reported by N.P. Palmina; the report by L.B. Gorbacheva was devoted to biochemical studies on chemotherapy. L.K. Obukhova spoke about mechanisms of ageing of organisms and feasibility of lifespan prolongation. The 4th and 5th sessions of the Conference were held on October 5 at the Emanuel Institute of Biochemical Physics. The 4th session included seven reports. Dr. G.E. Zaikov presented the information about the latest achievements on reduction of inflammability of polymer materials and the use of nanocomposites as antipyrenes (substances that reduce the inflammability of polymer materials); Dr. A.A. Popov reported on the kinetics of destruction of strained polymers (strained molecules reactivity). The structural and dynamic parameters of interfacial layers in filled polymers were the subject of the report by A.L. Kovarskii and T.V. Yushkina; the report by G.B. Pariiskii, I.S. Gaponova, E.Ya. Davydov, and T.V. Pokholok dealt with the studies on mechanisms of generation of stable nitrogen-containing radicals in the presence of nitrogen oxides. Great interest was aroused by the report of a group of authors (Academician Yu.B. Monakov, Yu.S. Zimin, and V.D. Komissarov) on the kinetics and mechanism of ozonized oxidation of ketones. The work by V.A. Kuzmin, P.P. Levin, and A.S. Tatikolov contained an analysis of primary photochemical processes in

Scientific Ideas of Academician N.M. Emanuel and Modern Science

11

molecular pigments and akin organic compounds. The report by R.F. Vasilyev was concerned with chemoluminescence studies. At the 5th session of the Conference, six reports were made. Prof. E.B. Burlakova in the lecture, "Bioantioxidants is a new page in pharmacology," emphasized the importance and great practical use of the studies on bioantioxidants. The next five lectures delivered at the session were devoted to liquid-phase oxidation in microheterogeneous systems (O.T. Kasaikina), theoretical and practical aspects of the chemistry of spatially hindered phenols (V.B. Volyeva, I.S. Belostotskaya, N..L. Komissarov, and G.A. Nikiforov), principles of stabilization of subcellular structures by functioning (V.N. Luzikov), mechanisms of chaperone-like activation (B.I. Kurganov), and novel molecular mechanisms responsible for ageing (A.M. Olovnikov). A wide discussion of the reports delivered was held. The Conference showed that many ideas put forward by Emanuel have found a wide application; part of his hypotheses is being developed by his followers and scientists who work in the leading research centers of many countries and continents.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 13-27 © 2006 Nova Science Publishers, Inc.

Chapter 3

ENERGY OF CHEMICAL BOND AND SPATIAL-ENERGY PRINCIPLES OF HYBRIDIZATION OF ATOM ORBITALS G. А. Коrablev∗ and G. E. Zaikov Basic Research-educational Center of Chemical Physics and Mesoscopy, Udmurt Research Center, Ural Division, RAS, Izhevsk, Russia Institute of Biochemical Physics after N.M. Emanuel, RAS, Moscow, Russia

ABSTRACT Methods for evaluating energy directedness of atom orbital hybridization and calculating the energy of chemical bonds in simple and complex structures are proposed based on the application of spatial-energy parameter (P-parameter) concept. The appropriate calculations and comparisons for 68 compounds were made. The results of calculations are coordinated with experimental data.

Key words: spatial-energy parameter, hybridization of atom orbitals, bond energy.

INTRODUCTION The bond energy is a direct measure of chemical bond strength. Its value is determined by the work necessary to destruct the bond between the atoms of molecular structure (or the gain of energy in the formation process of this structure from atoms). If the molecule contains two or more similar bonds, the break-off energy of this bond differs from its average energy (by all bonds). The values of bond energy of electrons of free atoms are calculated by quantummechanical methods via the wave functions, for instance in [1]. But their practical application for determining the energy values of inter-atomic bonds of actual structures produces ∗

E-mail: [email protected]; [email protected]

G. А. Коrablev and G. E. Zaikov

14

significant difficulties since the values of electron bond energy in these structures depend upon the changes in electron and nucleus configuration of the systems, especially during the hybridization of atom orbitals. The prognostic evaluation of such processes is still not properly developed. Therefore the main computational method for determining the values of chemical bond energy is the use of corresponding thermal-chemical values (enthalpies of formation of reaction products and initial molecule). It is of interest both in theoretical and practical aspect to arrange a more direct dependence between the character of changes in initial energy characteristics of atom and value of chemical bond energy. In this respect it is perspective to experimentally study the electron spectra of different (not only molecular) structures by means of X-ray electron spectroscopy (XES) that allows estimating the electron bond energies in complex systems [2]. In this research the attempt is made to estimate the energy of chemical bonds based on initial spatial-energy characteristics of free atoms with the help of the concept on spatialenergy parameter (Р-parameter), taking into consideration their changes during the hybridization of atom orbitals.

METHOD SUBSTANTIATION The analysis of various physical-chemical macro- and microprocesses results in the conclusion that in many cases the inverse values of kinetic or energy parameters of subsystems are added when estimating the resulting interaction of atom-molecular structures. Therefore tabulated (initial) values of spatial-energy parameters can be calculated based on the principle of addition of inverse values of energy components of free atom systems [3]:

1

Р0

Р

E

=

1

q =

2

1

+

(1)

( wrn)i

∑ Р0 R

(2)

where: Wi – bond energy of electrons [1]; ri – orbital radius of i-orbital [4]; ni – number of electrons of the given orbital; q=Z*/n*, where Z* and n* – nucleus effective charge and effective main quantum number [5,6]; R – dimensional characteristics of atom bond. Values of Р0-parameter are constant for electrons of i-orbital of the given atom. As described in [3] РE-parameter numerically equals the energy of valence electrons in atom static model, is a direct characteristics of electron density inside the atom at the given distance from the nucleus and, therefore, can be used to estimate the kinetics of chemical reactions and chemical bond energy of structures.

Table 1. Р-parameters of atoms calculated via the bond energy of electrons Atom 1 Н

С

N

O

O

Valence electrons 2

W (eV) 3

ri (Å) 4

q2 0 (eVÅ) 5

Р0 (eVÅ) 6

R (Å) 7

Р0/R (eV) 8

1S1

13.595

0.5295

14.394

4.7985

2P1 2P2

11.792 11.792

0.596 0.596

0.5295 0.46 0.77 0.77 0.69

9.0624 10.426 7.6208 13.066 14.581

2P3г 2P1г 2S1 2S2 2S1+2P3г 2S1+2P2 2S1+2P1г 2S2+2P2 2P1 2P2 2P3 2P4г 2P5г 2S1 2S2 2S2+2P3 2P1 2P2 2P4 2S1 2S2 2S2+2P4

19.201

15.445

25.724 25.724

0.620

0.4875

0.521 0.521

35.395 35.395 5.8680 10.061

37.240

13.213 4.4044 9.0209 14.524 22.234 19.082 13.425 24.585

52.912

6.5916 11.723 15.830 19.193 21.966 53.283 53.283 10.709 17.833 33.663

17.195 17.195 0.4135 0.4135 71.383 71.383 6.4663 11.858 17.195 33.859 33.859

0.4135 0.450 0.450

71.383 20.338 72.620 72.620 12.594 21.466 41.804

0.77 0.77 0.772 0.710 0.710 0.77

11.715 18.862 28.801 26.876 34.627 31.929

0.71

9.2839

0.71 0.55 0.55 0.71 0.71 0.71 0.66 0.66 0.59 0.66 0.66 0.66 0.66 0.59

22.296 34.896 39.938 15.083 25.117 47.413 9.7979 17.967 20.048 30.815 19.082 32.524 63.339 70.854

k

РE/k

Р0/rI (eV) 12

9

10

rI (Å) 11

1

9.0624

1.36

3.528

1 2

7.6208 6.533

2.60 2.60

2.2569 3.8696

1

11.715

2.60 2.60

3.470 5.5862

4 3

7.2003 8.9587

4 4

8.657 7.982

2.60 0.20

9.456 122.9

3 3 5

5.2767 11.632 7.9876

1.48

10.696

5

9.4826

1.48

22.745

2

8.9835

1.36

8.7191

1.36

14.954

1.36

30.738

4

Table 1. Р-parameters of atoms calculated via the bond energy of electrons (Continued) 1

2

3

4

5

6

7

8

9

3P1

8.0848

1.068

29.377

6.6732

1.17 1.34 1.34 1.17 1.11 1.34 1.17 1.34 1.17 1.11 1.11

5.7036 4.990 8.1164 9.2974 12.402 10.723 8.4373 7.3669 13.428 23.952 21.295

4

1.24 1.39 1.24 1.39

5.6991 5.084l 9.7355 8.6649

3P2

10.876

3P3г

13.766

Si 3S1 3S2 3S + 3P2 3S1+3P3 4P1

14.690

0.904

38.462

9.8716

41.372

15.711 26.587 23.638 7.0669

2

Ge

F

7.8190

1.090

4P2

12.072

4Р3 4S1

15.803 10.855

15.059

0.886

58.223

4S2

18.298

4S2+4P2

30.370

4S1+4P3 2P1 2Р3 2P5 2S1 2S2 2S1+2P3 2S2+2P5

19.864

0.3595

93.625

42.792

0.396

94.641

26.658 6.6350 17.433 25.648 14.375 24.961 31.808 50.809

1.24 1.39 1.24 1.39 1.24 1.39

10

11

12

5.988 5.3238

0.39

68.172

0.65

18.572

4 4 4 4 4 4 4

8.7540 7.8094 14.756 13.164 24.492 21.849

69.023

0.64 0.64 0.64 0.64 0.64 0.64 0.64

0.44

10.367

1.33

4.9887

40.388 22.461 39.002 49.700 79.388

1.33

19.435

1.33

38.202

4

12.425

Table 1. Р-parameters of atoms calculated via the bond energy of electrons (Continued) 1

2 5P

1

3

4

5

6

7

8

7 .2124

1.240

47.714

7.5313

1.42 1.58 1.42 1.58 1.42 1.42 1.58 1.42 1.58 1.42 1.58 1.00

5.3037 4.7666 9.1613 8.2336 12.094 7.7838 6.9956 13.307 11.959 18.611 16.726

Sn 5P2 5Р3г 5S1

13.0091

12.965

1.027

65.062

5S2

Cl

Br

I

5P2+5S2 3P1 3Р3 3P5 3S1 3S2 3S1+3P3 3S2+3P5 4P1 4P3 4P5 4S1 4S2 4S1+4P3 4S2+4P5 5P1 5P3 5P5 5S1 5S2 5S2+5P5

17.173 11.053 18.896

13.780

0.7235

59.844

13.780 29.196 29.196

0.7235 0.660 0.660

59.844 79.928 79.928

12.438

0.8425

73.346

27.013

0.730

100.21

10.971

22.345

1.0215

0.876

77.651

103.44

26.427 8.5461 19.943 .27.196 15.526 1.00 1.00 26.002 35.468 1.00 53.198 1.00 9.1690 22.005 30.563 16.477 28.300 38.462 58.863

1.14 1.14

9.7936 23.462 32.548 16.459 28.400 60.948

1.35 1.35

1.14

9

8.5461

10

11

12

1.02

12.754

0.67 0.67 1.81

4.7216

8.867 1.81 1.96

29.391 4.6781

38.443

27.196 15.526 35.468 53.198

4

8.0430 26.809 14.454 24.825 33.739 51.634 7.2545 13.739 24.109 12.192 21.037 45.147

4

3

8.4348 (0.39) 2.20 4.580

150.93 4.4516

0.50

121.90

18

E.B. Burlakova and G.E. Zaikov

Р0 and РE-parameters of free atoms were calculated based on equations (1, 2), the results of which are given in Table 1. For hydrogen atom the value of Bohr radius of hydrogen atom equaled to 0.529Å and besides, for some cases – ionic radius (1.36Å) were used as the main dimensional characteristics. All atoms, covalent and ionic radii were taken basically according to Belov-Bokii. For atoms С, N and О also the possibility to change covalent radii depending upon the bond repetition factor was taken into consideration. For the same elements average statistical values of P-parameters are given as РE / k – where k – hybridization coefficient, that assumes the possibility to further calculate average value of bond energy.

SPATIAL-ENERGY PRINCIPLES OF HYBRIDIZATION Hybridization means the mixing of atom orbitals of different types of the given atom in one molecular (or atom) orbital. Hybridization principles are well-developed in accordance with the experimental data in the frames of general theories of valence bond (VB) and molecular orbitals (MO). But the sources of energy directedness of hybridization processes have to be further investigated and discussed. In [1] there is a conclusion based on the analysis of multiple computational and experimental data that the most valence-active are the orbitals with minimum values of P0parameters. Let us apply this principle to the hybridization of atom orbitals on the example of carbon and nitrogen atoms. 2

2

Carbon ( 2 s 2 p ). From Table 1 we can see that maximum value of P0-parameter of

2 p 2 -orbital equals 10.061 eVÅ, but the minimum value of P0-parameter of 2s 1 -orbital is 1

smaller (equaled to 9.029 eVÅ). This means that 2s - orbital is more valence-active than

2 p 2 -orbital. This conditions their hybridization. The calculation according to equation (1) 3

produces the value of P0-parameter of 2 p (hybridized) orbital equaled to 13.213 eVÅ. This 2

is much smaller than P0-parameter of 2s -orbital (14.524 eVÅ). Therefore, only the 3

1

2

1

1

1

following hybridization options can occur: 2 p + 2s ; 2 p + 2s ; 2 p + 2s ; this 3

2

corresponds to single, double and triple bonds of hybridization of sp , sp and sp types. 2

3

3

1

Nitrogen ( 2 s 2 p ). P0-parameter of 2 p -orbital equals 15.830 eVÅ, and 2s -orbital – 10.709 eVÅ. Therefore, they are hybridized with the formation of 2p4г-hybridized orbital responsible for σ -bond sp hybridization where Po =19.193 eVÅ. But this is still greater 2

than P0-parameter of 2s -orbitals (17.833 eVÅ). That is the hybridization process will 2

continue due to 2s -orbital with the formation of 2p5г-orbital ( Po =21.966 eVÅ) responsible for 2π-bond of s − p hybridization.

Scientific Ideas of Academician N.M. Emanuel…

19

These are main hybridization options of orbitals in carbon and nitrogen atoms in this 2

2

approach. Less possible are metastable states with the hybridization of 2s + 2 p type with 2

3

carbon and 2s + 2 p - of nitrogen. The initial hybridization principle is applied for the analysis of energy directedness of mixing of atom orbitals for some other structures (Table 2). Computational values of P0parameter of hybridized orbitals were further used to determine bond energies (Е). In the supposition of pair inter-atomic interaction the structural PC-parameter was calculated [1,7] following the principle of the addition of inverse values of initial values of Р-parameters, and in this case – based on the following equation:

1 1 1 1 = = + N Е Р С (Р E K )1 (Р E KN )2

(3)

where N – coefficient of bond repetition factor, К – hybridization coefficient that usually equals the number of registered atom valence electrons. The half of inter-nuclear distance was frequently used as a dimensional characteristics R for binary bond. The same – for hydrogen atom in halogen-hydrogen. The corresponding calculations for several structures are given in Table 2. From Table 2 it is seen that hybridization coefficient (K) in the crystalline carbon structures observed equals the coordination number. And for σ -bond of nitrogen К=3, this corresponds to the number of valence electrons 2 p -orbital: к1 = 3

n1 =3.

The comparison of computational values with experimental data by bond energy [8] given in Table 2 characterizes rather high efficiency of this method. Usually a ratio error does not exceed 0.1% and not more than 5% in other cases. Besides, it should be noted that the given model mainly confirms the approved conclusions and results of the corresponding computational methods of bond energies as applicable to certain structures, the list of which in this paper is limited only by the authors’ interests.

CALCULATION OF CHEMICAL BOND ENERGY VIA THE AVERAGE VALUES OF P0-PARAMETERS The application of methods of valence bond and molecular orbitals to complex structures meets significant difficulties regarding the prediction of hybridization energy directedness and type of bonds being formed. Let us consider several opportunities of using P0-parameter method. It is practicable to apply equation (3) to calculate the energy of chemical bonds, where К – mixing or hybridization coefficient that usually equals the number of registered valence electrons, and Рэ (N/к) has a physical sense of averaged energy of spatial-energy parameter falling on one valence electron of registered orbitals. But for complex structures

Рэ -parameter is averaged by all main valence orbitals.

20

E.B. Burlakova and G.E. Zaikov

Let us first approve such an approach on binary molecules. For binary molecules the dissociation energy (Do) corresponds to the value of chemical bond energy: Do=Е. The results of calculating the dissociation energy by equation (3) given in Table 3 showed that РС=D0. For some molecules containing F, N and О the values of ion radius (in Table 3 marked with *) were used to register the ionic character of the bond in the process of РE-parameter calculation. For molecules С2, N2, O2 the calculations were done by divisible bonds. In other cases, the average values of bond energy were calculated. Computational data are not in conflict with the experimental [8]. With similar computation of average values of bond energy in complex structures the average values of РE-parameters (taken from Table 1) were considered as well, but taking valence sub-levels into account (Table 4). In these cases РС=Е (bond energy). It is also shown that in most cases, due to the influence of all the valence electrons of atoms, it is possible as a first approximation to be limited with the estimation of interaction only between basic bond atoms (for instance, С-Н in hydrocarbon structures). To a greater extent this refers to hydrocarbon organic structures. But for nitrogen oxides and hydrides more accurate results are obtained with preliminary calculations of РС-parameters of reaction intermediate products following the equation (3). Then E is calculated according to the following equation: 1 = Е

1

+

(4)

1

РС1 РС 2

Where

РС1 and

РС2 - РC-parameters of complex structure parameters.

Calculations based on equations (3 and 4) are given in Tables 3 and 4. At the same time, in some cases the results of calculations of bond energy for fragments of NH2, NO2 and N2O that are introduced into other complex structures are given. The deviations of computational data from the experimental ones [8] do not exceed 10% for complex structures.

CONCLUSIONS 1. The energy of chemical bond in simple and complex structures can be satisfactorily determined by means of Р-parameter method based on initial spatial-energy characteristics of free atoms taking hybridization of their atom orbital into account. 2. The proposed method for estimating the energy directedness of mixing atom orbitals agrees with the experimental data.

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals

Structure

1 Diamond Graphite (1)

Bond

2

3

σ с−с

σ

с−с Graphite (2)

σ с−с

Carbyne (− с ≡ с − )m Ethylene H 2 C = CH 2

Hybridization

single

sp

Orbitals

4 3

2s

1

2p3г

7 0.772

8 28.801

9 1/4

10 28.801

11 1/4

.

(N/к)1

(eV)

Pэ

(N/к)2

Рс (eV)

(eV)

calculation

experiment

12 3.600

13 347.5

14 347.3

0.710

26.876

1/3

26.876

1/3

4.479

432.4

418.7460.6

s2 p2

2s 2 2 p2

14.524 10.061

24.585

0.710

34.627

1/4

34.627

1/4

4.3283

417.8

418.7

sp

2s 1

9.0209 4.4044

13.425* * 1/2

0.6895

9.7365

1/4

9.7365

1/4

1.2170

117.5

108.9

г

sp 2

2s 1 2 p2

9.0209 10.061

19.082

0.665

28.695

2/4

28.695

2/4

3.587

346.2

347

sp

2s 1

9.0209 4.4044

13.425

0.601

22.375

3/4

22.375

3/4

8.391

807.6

782

4.4044 4.4044

8.8088

0.601

14.657

1/4

14.657

1/4

1.832

176.8

НС≡ СН

с−с

2p

π

2s 1

+π

6 22.234

( Ao )

Рэ

 kJ  Е   mol 

19.082

σ

σ

5 9.0209 13.213

R = d2

″

9.0209 10.061

Acetylene

с−с

(eV)

(eV)

о

′

2s 1 2 p2

2p

с−с

∑Р

Ро

′

sp 2

1

σ

Rk

′

1

г

2p

1

г

984.4

962.3

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals (Continued) 1 Methane (1)

СН 4 Methane (2) Ethane

σ

2

C-H C-H

σ

Н 3С − СНс − с N-N

3

sp

3

2s

2p3г

σ

SiН4

6 22.234

7 0.546

8 40.722

¼

9

4 . 7985 0 . 546

10

11 1/1

12 4.716

13 455.3

435.1

14

2s 2 2 p2

14.524 10.061

24.585

0.77

31.929

¼

9.0624

1/1

4.243

409.6

410

sp 3

2s 1

9.0209 13.213

22.234

0.772

28.819

¼

28.819

¼

3.6024

347.7

345.6

6.5916 6.5916

13.183

0.71

18.658

1/3

18.658

1/3

3.095

298.7

318

11.723 11.723

23.446

0.63

37.216

1/3

37.216

1/3

6.2026

598.7

586

2p4г

19.193

19.193

0.55

34.896

1/3

34.896

1/3

5.8161

561.4

543.4

2p5г

21.966

21.966

0.55

39.938

1/5

39.938

1/5

3.9938

385.5

3s2 3p2

15.711 10.876

26.587

1.11

23.952

¼

23.952

¼

2.994

946.9 289

3p3г 3s1 3p3г

13.766 9.8716 13.766

13.766 23.638

1.34 0.738

10.273 32.030

1/3 ¼

10.273 9.0624

1/3 1/1

1.712 4.251

165.3 410.3

3

2p _

г

2 p1 2 p1

N=N

Silicon Si2 → 2Si

5 9.0209 13.213

_

Nitrogen N2

N2 N≡N

4 1

_

2 p2 2 p2

sp

N-N 2π N-N N-N σ +π Si- Si

σ

Si-Н

2

s p sp

3

2

947.6 305 ± 3 309.6 ± 13 176 395

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals (Continued) 1

2

3

4

5

6

7

8

9

10

11

12

13

14

Germanium Ge2 → 2Ge

Ge-Ge

sp3

4s1 4p3г

10.855 15.803

26.658

1.22

21.851

1/4

21.851

1/4

2.7314

263.6

273 278 ± 13

4p3г

15.803

15.803

1.39

11.369

1/3

11.369

1/3

1.895

183

168

Tin Sn2 → 2Sn Sn(||) Sn(|\/ )

HF

σ

Sn- Sn

5p3г

5p3г

17.173

17.173

1.42

12.094

1/3

12.094

1/3

2.016

194.6

Sn- Sn Sn- Sn

p2

5p2 52 5s2

13.009 13.009 18.896

13.009 26.427

1.63 1.58

7.981 16.726

1/2 1/4

7.981 16.726

1/2 1/4

1.995 2.098

192.6 202.5

192.5 ± ± 16.7 192.5 192.5

2s 1

14.375 17.433

31.808

0.64

49.700

1/4

4.79851/ 0.438

1/1

5.822

562

566

15.526 19.943

35.468

1.00

35.468

1/4

4.7985/ 0.529

1/1

4.482

432.6

427.8

16.477 22.005 23.462

38.462

1.14

33.734

1/4

1/1

3.769

363.9

362.5

23.462

1.35

17.379

1/3

4.7985/ 0.704 4.7985/ 0.8045

1/1

2.94

283.7

294.6

σ F-H

HCl

σ Cl-H

HBr

σ

HI

Br-H I -H

2

s p sp 2

2

3

sp

2

sp 2 p3

2p 3s1 3p2 4s1 4p3 5p3

 kJ    mol 

Table 3. Dissociation energies of diatomic molecules – D0 

First atom Structure 1 CCl CBr CJ CN CN C-O NO CH OH ClF ClO ClО FO NF NCl H2 Li2 B2 C-C C=C N-N N=N O-O O=O *

Orbitals

N/k

РE (eV)

2 2Р1 2Р1 2Р1 2Р2 2Р2 2P2 2Р1 2Р2 2Р2 3S23P5 3S23P5 3Р1 2Р1 2P3 2P3 1S1 2S1 2Р1 2Р1 2Р2 2P3 2S22P3 2Р2 2S22P4

3 1/1 1/1 1/1 2/2 2/2 1/2 1/1 1/2 1/2 1/7 1/7 1/1 1/1 1/3 1/3 1/1 1/1 1/1 1/1 2/2 1/3 2/5 1/2 2/6

4 7.6208 7.6208 7.6208 13.066 14.581 13.066 9.2839 13.066 17.967 29.391* 29.391* 4.7216* 4.9887* 10.696* 22.296 9.0624 2.2419 5.4885 7.6208 13.066 10.696* 22.745* 8.7191 30.738*

Second atom РE N k 5 7.6208 7.6208 7.6208 13.066 14.581 6.533 9.2839 6.533 8.9835 4.1987 4.1987 4.7216 4.9887 3.5653 7.432 9.0624 2.2419 5.4885 7.6208 13.066 3.5653 9.098 4.3596 10.246

Orbitals

N/k

РE (eV)

6 3Р1 4Р1 5Р1 2S22P3 2P3 2P2 2Р2 1S1 1S1 2S22P5 2Р2 2S22P4 2Р2 2Р1 3Р1 1S1 2S1 2Р1 2Р1 2P2 2P3 2S22P3 2Р2 2S22P4

7 1/1 1/1 1/1 2/5 2/3 1/2 2/2 1/1 1/1 1/7 2/2 1/6 1/2 1/7 1/1 1/1 1/1 1/1 1/1 2/2 1/3 2/5 1/2 2/6

8 8.5461 8.0430 7.2545 47.413 25.127 17.967 20.048 9.066 9.066 38.202* 8.7191* 30.738* 8.7191* 38.202* 8.5461 9.066 2.2419 5.4885 7.6208 13.066 10.696* 22.745* 8.7191 30.738*

Calculations of РE-parameter are given using ion radius based on the equation: РE=ΣР0 / rI

РE N k 9 8.5461 8.0430 7.2545 18.965 16.751 8.984 20.048 9.066 9.066 5.4574 8.7191 5.123 4.3596 5.4574 8.5461 9.066 2.2419 5.4885 7.6208 13.066 3.5653 9.098 4.3596 10.246

РС (eV)

D0 calculation

D0 experiment

10 4.0209 3.9130 2.2523 7.7358 7.796 3.782 6.346 3.7969 4.5118 2.5579 2.8337 2.450 2.327 2.486 3.9751 4.533 1.121 2.744 3.810 6.533 1.783 4.549 2.1798 5.123

11 388.9 377.7 217.4 746.7 752.5 365 612.5 366.5 435.5 246.9 273.5 237.2 224.6 239.5 383.7 437.5 108.2 264.9 367.8 630.6 172.1 439 210.4 494.5

12 393.3 364 209.2 755.6 755.6 356 626.8 333±1 423.7 229.1 264 264 219.2 298.9 384.9 432.2 98.99 276±21 376.7 611 161 418 213.4 498.3

kJ  Table 4. Energy of bond breaking-off in complex structures – Е    mol 

No

First atom

Reactions

Bond breaking-off

orbitals

N/k

1

2

3

4

1 2 3 4 5 6

СН2=СН+Н СН3=СН2+Н СН4=СН3+Н С2Н4=С2Н3+Н С2Н6=С2Н5+Н С6Н6=С6Н5+Н

С---Н

7

СН2=СН+Н

С---Н

8 9 10 11 12 13 14 15

СН4=СН2+Н2 С2Н5=СН3+СН2 С2Н6=2СН3 С3Н8=С2Н5+СН3 О2=О+О СН3О·ОН= СН3О+ОН Н2О2=2ОН Н2О2=2ОН

16

17

2S22P2

2P2 2

1/4

1/2

Second atom РE (eV) РI 5

7.982

orbitals 6

1S1

6.533

1S1 1

Calculation

Experiment Е

N/k

РE (eV)

Е

7

8

9

1/1

9.0624

409.7

10.426

436.4

1/1

9.0624

366.5

С---(Н2)

2P

1/2

6.533

1S

2·1/1

2·9.0624

463.6

С---С

2S22P2

1/4

7.982

2S22P2

1/4

7.982

385.2

О=О -О-О-О-О(ОН)-(ОН)

2P2 2P4 2P2

2/2 1/4 1/2

17.967 14.954* 8.7192 4.5118

2P2 2P4 2P2

2/2 1/4 1/2

17.967 14.954* 8.7192 4.5118

N2=2N

N–N

2S22P3

1/5

22.745

2S22P3

1/5

22.745

N2Н2=NН+NН

N=N

2S22P3

2/5

2S22P3

2/5

8.898*

22.745

2 =8. 5 *

898

180.4 210.4 217.8 219.5 (2.275 eV) 439.1

10

430±12.6 457±12.6 >434.8 435±4.2 438.9 445.2 457.3 338.9 364 432.6 416.7±8.4 372.4 380.7 — 181.5±19 231.8±2.5 231.8±2.5

472.8±33.5

kJ  Table 4. Energy of bond breaking-off in complex structures – Е   (Continued)  mol 

No 18

1 NН2=N+Н2

19

N2Н4=2(NН2)

20 21

*

Reactions

СН3NHNH2= СН3NH+ NH2 NO2=NO+O

Bond breaking-off

First atom

Second atom РE (eV) РI 5 10.696*

orbita ls 6 1S1

РE (eV)

Е

Е

7 1/1

8 9.0624

9 (Рi-5.118 eV)

10

5.118*

247

252.7±16.7

3

1/3 1/5

10.696* 22.745*

172.1 219.5

175.7 217±4

4.4525

2P2

2/2

8.7191*

284.5

305.9

1/1

9.2839

1

2P

1/1

9.7979

460.2

481.8

— 1/5

22.745* 9.4826

— —

— —

8.7191* 8.9835

172.5 445.3

167.4 439.3

N/k

2 N=N (NН2)(NН2)

3 2P3

4 2/3

N-N N-N

2P3 2S22P3

1/3 1/5

10.696* 22.745*

(≡N=O)---O

2S22P3

—

5.118*

22

N2O=NO+N

N-O

2P

23 24

N2O=(N2)+O NO2=N+O2

(N2)=O (N)-(O2)

— 2S22P3

calculations of РE-parameter are done using the ion radius (rI)

Experiment

N/k

orbitals

1

Calculation

2P3 2S22P

Energy of Chemical Bond and Spatial-Energy Principles…

27

REFERENCES [1] [2]

[3] [4] [5] [6] [7]

[8]

Fischer C.F. Average – Energy of Configuration Hartree – Fock Results for the Atoms Helium to Radon//Atomic Data.-1972. №4. p. 301-399. Klyushnikov O.I., Salnikov V.R., Bogdanovich N.M. Investigation of pyrovakites La0.8ХSr0.2MnO3 by means of X-ray electron spectroscopy. Chemical physics and mesoscopy. 2001. v.3. №2. p. 173-185. Korablev G.A. Spatial-Energy Principles of Complex Structures Formation. Netherlands. Brill Academic Publishers and VSP. 2005. 426 p. (Monograph). Waber J.T., Cromer D.T. Orbital Radii of Atoms and Ions //J.Chem. Phys —1965.-V 42.-№ 12.-р. 4116- 4123. 5 Clementi E., Raimondi D.L. Atomic Screening constants from S.C.F. Functions. 1.// J.Chem. Phys.-1963.-v.38.-№11.-p.2686-2689. Clementi E., Raimondi D.L. Atomic Screening Constants from S.C.F. Functions. II.//J. Chem. Phys.-1967.-V.47. № 4.-p. 1300-1307. Korablev G.A., Kodolov V.I. Dependence of activation energy of chemical reactions upon spatial-energy characteristics of atoms – Chemical physics and mesoscopy. UdRC RAS. Izhevsk. 2001. №2.v.3. p.243-254. Gurvich L.V., Karachentsev G.V., Kondratjev V.I. et al. Breaking-off energies of chemical bonds. Ionization potentials and affinity with an electron. M: Science. 1974. 351 p.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 29-40 © 2006 Nova Science Publishers, Inc.

Chapter 4

PREPARATION AND APPLICATION OF MAGNETIC ADSORBENTS IN BIOLOGICAL AND MEDICAL INVESTIGATIONS E. K. Dobrinskiy 1, S. I. Malashin 1, V. G. Gerlivanov 1, G. V. Stepanov 1∗, V. I. Filippov 2, L. Kh. Komissarova 2, L. A. Goncharov 2, F. S. Bayburtskiy 2†, T. V. Tsyganova 2 and H. U. Lubman 2 1

Research Institute of Chemistry and Technology of Hetero-organic Compounds, Moscow, Russia 2 N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Science, Moscow, Russia

ABSTRACT The plasmachemical technology of iron–carbon adsorbent production was developed and optimized. The adsorbent was thoroughly studied by physical, chemical and biological methods, and was found to have high sorption capacity, long desorption time, high magnetization and low toxicity. The adsorbent is intended to be used for magnetically guided transport and forming a depot of anti-cancer drugs in the tumor zone.

Keywords: Magnetic adsorbent; plasmachemical technology; activated charcoal; adsorption; toxicity; magnetically guided transport of drugs; oncology.

∗

†

E – mail: [email protected], [email protected] E – mail: [email protected], [email protected]

30

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

INTRODUCTION At the First International Conference on Scientific and Clinical Applications of Magnetic Carriers (1996) we described the clinical applications of magnetic adsorbent particles [1], including detoxification of biological fluids [2], concentrating of pathogens for diagnostic purposes [3], protection of implants [4] and magnetically controlled transport of anti-cancer drugs [1]. Oncological applications of the adsorbents [1,5,6] are aimed at solving the problem of localizing a highly toxic cytostatic drug in the tumor and thus reducing the general toxic effect of chemotherapy on the organism. This is accomplished in several steps. The drug is first adsorbed on the particles, a suspension of which is injected through a catheter into a regional artery feeding the tumor. An external magnetic field (generated by a source outside the organism), superimposed onto the tumor zone, causes the particles to aggregate and presses the formed clusters against the blood vessel walls. The aggregates are retained in the tumor both by the field and by getting stuck in capillaries inside the tumor. Such «microembolization» reduces the blood supply to the tumor. The drug is slowly released from the particles over a period of time, creating a high local concentration of the drug in the tumor tissue, while minimizing the amount of the drug throughout the rest of the patient’s body. Since the late 1980s this method has passed a full cycle of animal studies and clinical trials in Russia’s clinics, including more than 150 patients with the advanced stages of the disease. Majority of the patients have shown improvement in their condition, some made full recoveries [1,6]. The targeted drug delivery using magnetic particles and external magnetic field imposes several requirements on the adsorbent particles. The particles themselves must be biologically inert and biodegradable. They must also have high sorption capacity for the drug and the rate of the drug desorption in an organism needs to be slow, so that the high concentration of the cytostatic drug can be maintained in the tumor area for a prolonged period of time. Since the particles must be effectively controlled by the applied magnetic field, both their magnetic properties and their dispersity and agglomeration degree are important. High magnetic susceptibility and high saturation magnetization allow the particles to be effectively controlled by a relatively weak field and rapidly aggregate in it. Low coercive force will prevent aggregation of the particles prior to superimposition of the field. Size is also a crucial factor: very small particles (less than 0.1 lm in diameter) have a small magnetic moment and a relatively large surface. This makes it difficult to overcome hydrodynamic forces (e.g., in the bloodstream) for these particles with currently feasible magnetic forces. On the other hand, it is difficult to form stable suspensions of dense particles larger than 2 µm, and it difficult to inject suspensions of such particles through a catheter. The adsorbent also should not contain a free-flowing non-ferromagnetic fraction because it could carry the drug but would not be controlled by the magnetic field and thus can migrate to other organs. The Cefesorb-type particles (produced by joint reduction of carbon monoxide CO and iron oxides FeXOY), which were used in our earlier studies [1 – 6], generally meet the above criteria. However, their sorption capacity is relatively low (less than 27 µg/mg) and characteristics of this type of particles are not very stable (small variations in manufacturing conditions lead to rather significant changes in the product properties, thus properties of differente batches can very widely.

Preparation and Application of Magnetic Adsorbents…

31

The magnetic particles can also be produced by two other methods: (1) long-term joint grinding of iron and carbon powders [1, 7] and (2) plasmachemical re-condensation of iron and carbon [1,8]. The main drawback of the first method is that it produces a significant nonferromagnetic fraction, which is not controlled by the field and can be carried (along with a highly toxic drug) by the bloodstream to other (healthy) organs. The plasmachemical method typically produces dense particles with a small specific surface and, therefore, low adsorption capacity. In this paper, we describe a new method of production of highly efficient magnetic adsorbents using plasmachemical technology.

PLASMACHEMICAL TECHNOLOGY The magnetic adsorbents were produced using direct current arc plasmathrones (Figure 1). Particles of pure iron and of activated carbon (10–20 lm diameter) were injected into the plasmathrone chamber through an opening in the electrode with the flow of argon (Ar) as a carrier gas. The gas stream brought the particles into the high temperature (6000°C) zone of the argon, where they were evaporated. Up to 20% of the arc’s energy was estimated to be used for evaporation of the particles. As soon as the vapors reached the condensation chamber, they were rapidly cooled by cyclonic flows of arc. These conditions led to the formation of finely dispersed particles. Varying the evaporation / cooling parameters and the composition of the initial mixture allows to create a wide variety of particles with different properties.

Figure 1. Sketch of the plasmathrone chamber used for preparation of adsorbents.

Significant research and engineering efforts aimed at the optimization of the process parameters resulted in the development of the plasmachemical technology for manufacturing a highly efficient magnetic adsorbent «FerroCarbon-4» (FC-4), as well as other FCadsorbents. It was found, that the key requirement for producing highly efficient magnetically guided adsorbents is to achieve the regime, in which iron particles are fully evaporated, while activated carbon particles are only partially disintegrated and sublimated, thus conserving

32

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

their porous structure with a large specific surface. During rapid cooling in the condensation zone, iron re-condenses on the remaining particles of activated carbon, probably as a film initially. However, the temperature at this point is high enough for the liquid iron to form droplets due to surface tension (σFe metall = 1.8 N / m [9]). The droplets attach to the carbon structures, hence a magnetically guided adsorbent with a large specific surface is formed. The carbon vapor partially condenses on the existing particles, and the rest of it forms dense or filamentous structures.

Physical Properties of the Adsorbent The FC-4 powder was studied using a Philips Scann scanning electron microscope (Figure 2). Low magnification (Figure 2A) shows porous clusters of particles, consisting of spherical iron particles (majority 4h 44 % α - Fe, 55 %, amorphous C, < 1 % other 0.46 g / cm2 146 m2 / g 692 mg / kg 50 mg / kg

ACKNOWLEDGEMENTS Supported in part by the grant «Developing of new methods of diagnostics and treatment of oncological diseases» from the Moscow city government.

40

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

REFERENCES [1]

Filippov V. I., Harutyunyuan A.R., Dobrinsky E. K., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 379. [2] Kutushov M.V., Filippov V.I., Dobrinsky E. K., Komissarova L. Kh. in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 391. [3] Vladimirsky M. A., Filippov V. I., Malashin S. I. in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 353. [4] Makhmudov S.Ya., Komissarova L. Kh., Filippov V. I., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New -York, 1996, p. 495. [5] Holodov L. E., Volkonsky V. A., Komissarova L. Kh., Filippov V. I. USSR patent No 1722256, claim SU 4767768 (1989). Europatent No 90917517.6 (1990). US patent application No 730837. [6] Komissarova L. Kh., Filippov V. I., Holodov L. E., Kolesnik N. F., Proc. 6th Int. Conf. Magnetic Fluids, Paris, 1992, p. 474. [7] Allen L. M., Kent T., Wolfe C., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 481. [8] Dobrinsky E. K., Malashin S. I., Gerlivanov V. G., USSR patent No 221368 (1985). [9] Weast R.C. (Editors), Handbook of Chemistry and Physics, CRC Press, Boca Raton, FL, 1987, F-22. [10] Kudrin A. N., Ponomareva G. T., Mathematics Application in Experimental and Clinical Medicine, Medicina, Moscow, 1967.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 41-46 © 2006 Nova Science Publishers, Inc.

Chapter 5

THE MAGNETIC SORBENTS USED FOR DETOXIFICATION OF BLOOD N. P. Glukhoedov1, M. V. Kutushov 1, M. A. Pluzan 1, G. V. Stepanov 1∗, L. Kh. Komissarova 2, V. I. Filippov 2, L. A. Goncharov 2, F. S. Bayburtskiy 2† 1

Research Institute of Chemistry and Technology of Hetero-organic Compounds, Russian Federation, Moscow, Russia 2 N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Science, Russian Federation, Moscow, Russia

ABSTRACT In given article use of magnetic sorbents for detoxification of blood has been investigated. Restored-iron, iron-carbon and iron-silica do not cause changes in erythrocyte's osmotic resistance and possess high sorption efficiency for substances of different molecular mass. These magnetic carriers can be recommended for extracorporeal blood detoxification of low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

Keywords: Absorptive capacity; sorption efficiency; erythrocyte; toxicity test (osmotic); heme protein; restored-iron; iron-silica; iron-carbon; surface modification; blood detoxification; barbiturates; bilirubin; blood purification.

∗

†

E – mail: [email protected], [email protected] E – mail: [email protected], [email protected]

42

N. P. Glukhoedov, M. V. Kutushov, M. A. Pluzan et al.

INTRODUCTION Magnetic carriers (MC) can be used in biochemistry and biotechnology for cell separation, immobilization of enzymes and other biologically active compounds [1,2]. The use of MC is particularly important for extracorporeal blood purification [3 – 5]. MC used for extracorporeal blood purification require a high absorptive capacity, should be selective for eliminated substances, should be hemocompatible and should have a high magnetic susceptibility so that they can be separated using a magnetic field intensity of not more than 1 T [5]. MC of iron-carbon and restored-iron types meet many of these demands but they are not hemocompatible. The encapsulation of magnetic particles is not favored as it is known [6] that the encapsulation of coal adsorbents with biocompatible polymers reduce the absorption of low molecular weight substances (MW 10,000 Da). Polystyrene microspheres usually used for the absorption of proteins or for covalent coupling of ligands are not intended for the sorption of low and middle molecular substances [7]. Our aim was to find a hemocompatible coating for magnetic particles, which on one hand did not reduce the sorption capacity of low and middle molecular substances, and which on the other hand promoted the adsorption of high molecular substances. We investigated different magnetic carriers consisting of iron-silica composites, iron-carbon, but also restorediron, which is a highly dispersed powder of metallic iron containing less than 10 % of iron oxides.

MATERIALS AND METHODS MC of different types (restored-iron, iron-carbon and iron-silica) were all obtained using the same technology [8]. First, highly dispersed particles of restored-iron were fractionated at defined intervals of gas flow speeds (0.02 – 1.00 m / s) and a defined intensity of magnetic fields (10 – 10 3 A/m) in order to get fractions of particles sized 0.2 – 2 µm. The following thermal process was then carried out at 800 – 1000°C in a flow of inert gas, which contained either coal microparticles or silicon oxides. The composition of the studied MC is shown in Table 1. Their magnetic properties were studied with Faraday's magnetometer (Bruker) [5]. Measurements of the magnetic moment were performed at 20°C in a magnetizing field changing from 0 to 10 kOe. The analysis of the magnetization curves allowed the determination of the saturation magnetization (ISAT ) and made it possible to obtain the data necessary to predict the behavior of the particles in various fields. The magnetization of the particles reached saturation in a magnetic field of 1 – 2 kOe. The saturation magnetization for different types of MC are also given in Table 1. The particles with 90 % iron had an ISAT of up to 180 emu / g. Different types of MC (iron-carbon, iron-silica, restored-iron) had ISAT between 50 and 180 emu / g. The surface of restored-iron and iron-carbon particles was covered by human albumin or gelatin using Widder's method [9] in our modification [8,10]. The magnetic carrier's surface was coated with albumin or gelatin by mixing a suspension of MC and albumin or gelatin using ultrasound. The suspensions were then heated to 120°C followed by cooling to room

The Magnetic Sorbents Used for Detoxification of Blood

43

temperature (for albumin) and washing with water (for albumin and for gelatin). Surfacemodified particles were kept at 10 % concentration in distilled water at 2 – 4°C. Hemoglobin obtained from donor blood was used as high molecular weight substance. The heme proteins myoglobin, hemoglobin, methemoglobin and carboxyhemoglobin were received from the blood taken from patients with crush-syndrome, hemolysis and carbon oxide poisoning. Cyanocobalamin (Russia) and bilirubin (Lachema, Czech Rep.) were used as middle molecular weight substances. The barbiturates sodium thiopental, sodium hexenal and sodium phenobarbital were used as low molecular weight substances. Human albumin (Sigma, Germany) and gelatin (Russia) were used to coat the MC. The sorption efficiency of MC was determined as the ratio of the quantity of the adsorbed substance to its initial amount (w / w), expressed in % for a certain ratio (w / w) of adsorbent to substance. Optimal ratios of adsorbent to substance equal 15 – 20 for barbiturates, 20 – 25 for cyanocobalamin and bilirubin, and 40 – 50 for hemoglobin. The initial concentration of absorbed substances was 100 – 200 µg/ml. The substances were incubated for 1min with MC either in physiological solution or in donor plasma and donor blood at room temperature (pH 7.4). The concentration of substances in the solutions was measured by differential visual and UV-spectroscopy. Concentrations of substances in blood and plasma and adsorption of total plasma proteins was determined by thin-layer chromatography with a fluorescent label. Osmotic resistance of erythrocytes was studied by the method of HCl-hemolysis [10]. Table 1. Properties of the studied magnetic carriers (MC) Contents of MC (%) Type

Restored-iron Fe-coal Fe-silica

Metallic iron

Iron oxides

Coal

Silica

> 90 10 – 70 80 – 88

< 10 < 10 < 10

0 20 – 80 0

0 0 2 – 10

Saturation magnetization (emu / g)

175 – 180 50 – 120 140 – 150

RESULTS AND DISCUSSION More than 50 patterns of different types of MC were studied. The results of sorption efficiency of the best patterns of MC to different molecular mass substances are represented in Tables 2 – 6. The sorption efficiency of MC for different barbiturates was identical, and the results shown are thus only for sodium phenobarbital. The highest sorption of 85.7 % for phenobarbital in physiological solution was reached by the ironsilica composite (see Table 2). It was also most effective for cyanocobalamin at 33.9 %. The modification of iron-carbon particles by gelatin did not change their sorption efficiency for phenobarbital and cyanocobalamin. The maximum sorption efficiency values of hemoglobin (more than 50 %) was reached by restored-iron, followed by iron-carbon modified with gelatin, and then the unmodified MC (less than 40 %). Table 3 demonstrates that iron-carbon composite, modified by gelatin or albumin absorbs large amounts of phenobarbital and hemoglobin in donor plasma. The sorption efficiency results of MC to bilirubin in physiological solution and plasma are interesting. Table 4 shows that iron-carbon composites modified by gelatin or albumin have higher sorption efficiencies for bilirubin than unmodified particles. Also,

44

N. P. Glukhoedov, M. V. Kutushov, M. A. Pluzan et al.

albumin coated MC have a higher sorption efficiency for bilirubin in plasma than particles coated with gelatin (59.7 % versus 39.3 %, respectively). Table 5 shows that the sorption efficiency of gelatin-modified restored-iron for heme proteins (myoglobin, hemoglobin and carboxyhemoglobin) in donor blood is rather high (52 – 84 %) and it is lower for methemoglobin (22 %). The initial concentration of myoglobin does not seem to influence the sorption efficiency of MC. Table 2. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in physiological solution at pH 7.4 Sorption efficiency, average ± SD (%) Phenobarbital MW 232 GelatinUnmodified modified

Type

Restored-iron Fe-carbon Fe-silica

38.3 ± 6.3 49.9 ± 6.8 85.7 ± 10.2

40.4 ± 7.4 55.2 ± 7.0

Cyancobalamin MW 1355 GelatinUnmodified modified

9.0 ± 6.1 21.4 ± 5.3 33.9 ± 7.7

Human hemoglobin MW 64.000 GelatinUnmodified modified

11,1 ± 3.4 23.2 ± 6.1

32.3 ± 7.1 37.6 ± 7.6 22.5 ± 5.8

54.4 ± 8.2 52.7 ± 7.8

Table 3. Sorption efficiency of magnetic carriers (MC) in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%) Type

Fe-carbon Fe-silica

Phenobarbital MW 232 AlbuminUnmodified modified 46.8 ± 7.9 43.1 ± 7.2 67.3 ± 8.4

Cyancobalamin MW 1355 AlbuminUnmodified modified 13.5 ± 4.1 15.7 ± 5.8 23.1 ± 4.3

Human hemoglobin MW 64.000 AlbuminUnmodified modified 39.4 ± 7.0 44.5 ± 6.6 11.9 ± 3.8

Table 4. Sorption efficiency of magnetic carriers (type Fe-carbon) for bilirubin (MW 584) Medium of incubation (pH 7.4)

Physiological solution Donor plasma

Sorption efficiency, average ± SD (%) Without modification

Gelatinmodified

Albuminmodified

29.0 ± 5.7 0

66.7 ± 7.4 34.3 ± 5.9

70.8 ± 8.6 59.2 ± 8.1

Changes in the erythrocytes' osmotic resistance were not observed. Adsorption of total plasma proteins on modified MC was lower than 12 %, but it was about 60 – 70 % on unmodified particles. Table 6 summarizes the results obtained of MC sorption efficiency to substances of different molecular mass in donor plasma. The sorption mechanism of low and middle molecular weight substances (phenobarbital and cyanocobalamin) on iron-carbon and restored-iron MC is apparently connected with absorption of molecules into the sorbent's pores. Iron-carbon composites have a more porous structure than restored-iron, therefore the

The Magnetic Sorbents Used for Detoxification of Blood

45

sorption efficiency of iron-carbon MC is higher than that of restored-iron (see Table 2). The results show that the modification of the particle surface with gelatin or albumin does not interfere with this process. The high sorption efficiency of the iron-silica composite for phenobarbital is caused by the interaction of silica OH-groups with the barbiturate's molecules. High sorption efficiency of iron-carbon composite modified by albumin or gelatin to bilirubin in physiological solution (see Table 4) is probably connected to the formation of hydrogen bonds of bilirubin methyl-groups with carboxy-groups of albumin or gelatin [6]. Adsorption mechanism of hemoglobin and other heme proteins on the surface of MC modified by gelatin or albumin at pH 7.4 (see Table 5) can be explained by an electrostatic interaction of gelatin or albumin carboxy-groups with amino-groups of the heme proteins [10]. Such electrostatic interactions are due to the differences in isoelectric points of heme proteins on one hand, and albumin or gelatin on the other. Table 5. Sorption efficiency for heme proteins of 2 mg of the gelatin-modified restored-iron MC in 10 ml of donor blood Heme proteins

Myoglobin (ng / l) Hemoglobin (µg / l) Methemoglobin (%) Carboxyhemoglobin (%)

Concentration, average ± SD (%) Befor After 1000 ± 62.3 300 ± 22.0 640 ± 16.7 240 ± 19,8 280 ± 19.0 45.7 ± 4.1 40.6 ± 4.5 12.7 ± 1.30 27.5 ± 3.1 21.3 ± 0.9 17.0 ± 3.9 8.0 ± 0.7

Sorption (%) 70 62.5 83.8 60.7 22.5 52.9

Table 6. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%) Substances Fe-silica Phenobarbital Cyancobalamin Bilirubin Human hemoglobin

67.3 ± 8.4 23.1 ± 4.3 < 42 11.9 ± 3.8

Fe-carbon modified with gelatin 46.8 ± 7.9 13.5 ± 4.1 34.3 ± 5.9 39.4 ± 7.0

Fe-carbon modified with albumin 43.1 ± 7.2 15.7 ± 5.8 59.2 ± 10.3 44.5 ± 6.6

SUMMARY The novel magnetic carriers of an iron-silica type iron-carbon or restored-iron composites modified by gelatin as well as the albumin do not cause changes in erythrocytes' osmotic resistance and no noticeable adsorption of total plasma proteins. The magnetic carriers have good magnetic characteristics and a high sorption efficiency for substances of different molecular mass. They can be recommended for extracorporeal blood detoxification for low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

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REFERENCES [1] [2]

Sharles S. O., Norman S., // J. Immunol. 73 (1984) 41. Safarik I., Safarikova M., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 24. [3] Stockmann H. B., Hiemstra C. A., Marquet R. I., Ijzermans J. N. // Ann. Surg. 231 (2000) 460. [4] Weber C., Falkenhagen D., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 371. [5] Komissarova L. Kh., Filippov V. I., Kutushov M. A., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 380. [6] Gorchakov V. D., Vladimirov V. G. Selective Hemosorbents, Moscow, Medicine, 1989. [7] Fishers R. C., Microsphere Selection Guide, 9025 Technology, March, 2000. [8] Komissorova L. Kh., Gluchoedov N. P., Kutushov M. V., Russian patent No. 2109522, 1998. [9] Widder K., Fluoret G., Senyei A. // J. Pharm Sci. 68 (1979) 79. [10] Komissarova L. Kh., Filippov V. I. // Izv. AN USSR, Ser. Biol. 6 (1988) 78.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 47-52 © 2006 Nova Science Publishers, Inc.

Chapter 6

INFLUENCE HEXSAAZOCYCLANES ON A MICROSTRUCTURE OF POLYETHYLENE TEREPHTHALATE O. V. Burykina and F. F. Nijazi Kursk state technical university, Kursk, Russia

ABSTSRACT Research of influence of introduction of hexsaazocyclanes on a microstructure of polyethylene terephthalate is carried out. The increase in ability modified PETP to crystallization, in comparison with not modified PETP, as hexsaazocyclanes play a role of the original centers of crystallization is revealed. Research plasticization effect of hexsaazocyclanes on polyethylene terephthalate is carried out. It is revealed, hexsaazocyclanes introduction influences a maximum of a tangent of dielectric losses polyethylene terephthalate, displacing it aside smaller temperatures.

INTRODUCTION One of the most effective ways of new polymeric materials, obtaining with the properties, given before is modification of known polymers by target additives. Changing chemical structure and quantities of the additive – the modifier, it is possible to improve in a proper way, those operational properties which are required for the given consumer.

EXPERIMENTAL PART Hexsaazocyclanes (HZ), were taken as additives, which have the advanced circuit of interface, high photo stability and thermo stability.

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Figure 1. Structural formulas used hexsaazocyclanes

Availability chromatic groups, allows to use them in addition as dyes of polymers [1]. Proceeding from this, it was represented to us expedient, to compare thermal characteristics of additives and initial polymer, and also to define compatibility of these connections with fusion PETP. Characteristics of the used additives of modifiers are submitted in table 1. Table 1. Characteristics hexsaazocyclanes

ГЦ-1

600

λ макс., nanometer (solvent acetone) 360

ГЦ-2 ГЦ-4

580 454

380 400

Designation

Average molecular weight

Painting of dye

Т fusion, 0С

Т the beginnings of destruction 0С

yellow

305

330

citric beige

327 345

345 330

Temperatures of fusion and the beginning of decomposition hexsaazocyclanes are in limits Тfusion. = 305-3450С and Т destruction. = 330-3450С, that speaks about a potential opportunity of introduction of the given connections in fusion PETP as their thermo stability surpasses temperature of reception and formation PETP. Polyethylene terephthalate modification hexsaazocyclanes by additives was carried out and fibers were formed. Additives introduction did not influence on the process of formation, and, consequently on the polymer fiber properties.

DISCUSSION OF RESULTS For studying structure of polymer and influence of introduction of additives HZ-1; HZ-2; HZ-4 the method of micro photographing has been applied. Cuts of polymeric fibers photographed at 40 multiple increase, on a microscope "Polar" which had a special nozzle for photographing. It follows from the analysis of micro photos (Figure 2-3), that hexsaazocyclanes introduction does not break uniformity of the polymeric structure that speaks about good solubility of hexsaazocyclanes in fusion PETP.

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate

49

In a photo of cross-section cut initial PETP fibres (Figure 2) are observed two areas: amorphous and crystal.

Figure 2. Micro photo of a cross-section cut initial PETP: 1) an amorphous part; 2) a crystal part

In crystal area lamellar and fibrillation formations are visible, but they are not advanced enough. The amorphous part occupies great volume from the general space of polymer. On Figure 3 micro photos PETP – the fibers modified HZ-1 (а) are represented; HZ-2 (б); HZ-4 (в), and their cross-section cuts. From comparison of a micro photo initial and modified PETP, it is necessary to note, that modified PETP shows the big tendency to crystallization. In pictures of the fibers painted HZ-1, HZ-2, HZ-4, are visible lamellar and fibrillation formations and are also observed spherallites.

Figure 3. Micro photo of the PETP modified HZ-1 (а); HZ-2 (b) and HZ-3 (с)

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It is well visible in micro photos, that the quantity of an amorphous part of the modified fibers decreases. It raises durability of a fibre and improves his mechanical characteristics as the amorphous area is the most vulnerable for action loadings and pressure as it contains areas of the least order in the macromolecules packing, and the places focusing defects. In micro photos of the modified fibers is the fibrillation structure of a fiber, and visible introduction hexsaazocyclanes in PETP promotes to increase order and density of the structure of the polymer. It was revealed earlier [2], that hexsaazocyclanes additives cause temperature reduction of polyethylene terephthalate fusion, i.e. they have a plasticization effect on polymer. Plasticization proves to be true by measurements of electro physical characteristics at modified polyethylene terephthalate (figure 4).

Figure 4. Dependence of a tangent of a corner of dielectric losses on temperature initial and modified samples PETP: 1-initial PETP;2-PETP+0,1% HZ-2;3-PETP+0,5% HZ-2,4-PETP+3,0% HZ-2

For initial polyethylene terephthalate the maximum of a tangent of dielectric losses (tg δ), corresponding depolsegmentation mobility, is observed at 1150 C. At concentration of the modifier of 1-3 % sharp increase of value tg δ and displacement of a maximum accordingly on 100С and 250С in area of lower temperatures that confirms plasticization action of the modifier is observed. In some works [3, 4] it is supposed, that PETP can have two morphological forms of crystals which define double endothermic effect in the field of fusion. Form I, to which more high-temperature corresponds originally endothermic peak of fusion, has been attributed folded structure, and for the form II responsible for more low-temperature peak of fusion, the crystal structure from more extended circuits has been offered. Thus the length fold forms I causes a degree of perfection of the crystal form II created by partial expansion fold of form I though the nature remains obscure.

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate

51

The analysis of micro photos of received samples PETP– fibers has shown, that in the received polymer there are both morphological forms of crystals. Prevalence of one of morphological forms will define, apparently, size of temperature of fusion. On curves DTA initial PETP - fibres and modified hexsaazocyclanes (Figure 5), the peak of fusion represents the area having one maximum that confirms the assumption made earlier of dependence of temperature of fusion from a morphological structure of poly mer.

Figure 5. Curves DТА for unmodified (1) and modified HZ-1 (2), HZ-2 (3) and HZ-4 (4) PETP - fibres

Displacement of peak of fusion on curves DТА in area of smaller temperatures specifies that in the modified fibres crystals have mainly morphological form II (the extended circuits of polymers incorporated into crystallites) while in initial PETP crystals mainly have morphological form I (folded structure). Therefore for initial PETP it is observed endothermic effect at temperature 2690С – speaking by fusion flat folded crystallites (morphological form I). At modified PETP – fibers this effect is observed at temperature 245 – 2630С, it speaks fusion of spherallite (the morphological form II).

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At heating samples PETP on thermogramms the thermal effects, connected with the fusion crystallites, were fixed. On curves DТА modified PETP – fibers it is visible, that at them the breadth of peak of fusion is more, than at initial PETP. Proceeding from the aforesaid, it is possible to admit, that modified hexsaazocyclanes PETP - fibres possess the greater degree crystalline state. It once again confirms the conclusion made earlier, that entered molecules hexsaazocyclanes become the additional centers of crystallization, thus, increasing a degree crystallization modified PETP - fibers.

REFERENCES [1] [2] [3] [4]

Savenkova I.V., Nijazi F.F., Siling S.A., Burykina O.V., Russian polymer news, 2001, vol.6, No.4, s. 61-62. Burykina O.V., Nijazi F.F., Siling S.A., News high schools Chemistry and chemical technology, 2002, vol. 45, No. 5, s. 73-74. Bell P.J., Dumbleton S.H., Polymer Sci., 1969, pt. A-2,V.7,№2, p.1033. Neaiy D.L., Davis T.G., Kibier C.J., J. Polymer Sci., 1970, pt. A-2, V.8, №2, p. 2141.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 53-66 © 2006 Nova Science Publishers, Inc.

Chapter 7

FUNCTIONALISING OF LOW-MOLECULAR, OLIGOMER DIENES AND OLEFINS WITH S, O-CONTAINING COMPOUNDS R. Z. Biglova 1, A. U. Galimzjanova 1, V. A. Dokichev 2, G. V. Konesev 3, G. E. Zaikov 4, R. F. Talipov 1 1

Bashkir State University, Ufa, Russia Institute of Organic Chemistry, Ufa Centre of Science, Russian Academy of Sciences, Ufa, Russia 3 Ufa State Petroleum Technical University, Ufa, Russia 4 N.M.Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia 2

Functionalization of piperylene fractions, oligodienes and oligoolefins by element sulfur, phenols has been carried out. Functionalized compounds have been shown to be multipurpose additives exhibiting highly antiwear, antiscuff and simultaneously antioxidant and viscous properties. Multipurpose additives to polymers, as well as batch additives to various oils with a complex of necessary properties find increasingly wider application [1, 2]. This fact has resulted in the investigation of element sulfur reactions with dienes, oligodienes and oligoolefins. Cheap and available piperylene fraction (multi-tonnage waste in obtaining isoprene in rubber manufacture), its oligomerization products, as well as oligomerization products of used up buten-isobutane fractions of various molecular weights have been used as initial hydrocarbons. As antiscuff, anti-wear properties of additives depend on the covalent-bonded sulfur contents, the selection of optimum conditions to effect sulfuring processes has been set with introducing the greatest amount possible of covalent sulfur. For this purpose functionalizing of diene and olefin hydrocarbons was conducted on a wide time-temperature mode. Considering that the temperature of boiling piperylene fraction low (42-44ºС), sulfuring was carried out in a constantly temperature-controlled autoclave in the presence of the catalyst cobalt phthalocyanine [3], in the medium of non-polar solvents (for example, heptane). Under

54

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al.

conditions of synthesis: 130ºС, 3 hrs, >C=С C=С C=С C=С< bonds (by bromine number) correlate with the spectral data. The data on interaction of oligopiperylene (ОPP) and oligoisobutylenes (ОIB, М п= 390; 880) with element sulfur are given in Tables 2, 3. According to the results of the element analysis, the contents of sulfur in the obtained products grows both with the rise in the synthesis temperature and with the increase in process length. When the ratio of the initial substances exceeds equivalent mole ratio of oligomers and sulfur, no appreciable change of values of a mass content of sulfur in a product is detected. Modification of oligopiperylene at the temperature over 140ºС results in cross-linking of macromolecules. The reaction with element sulfur in the nonpolar solvent (octane, kerosene) medium does not affect the percentage of sulfur in the product and reduces an opportunity of resinification, and leads to lower sulfur contents in aromatic hydrocarbons. Depending on the product molecular weights and the sulfur content in them, mono- and disulfide bridges can be found in macromolecules. The latter corresponds to the data [4] studying sulfur interaction with isobutylene within the interval between100º to 140ºС. On the example of isobutylene oligomers and a link of oligopiperylene, containing double > C=С < bond the scheme of the processes can be given as: Table 2. Functionalization of oligopiperylene with element sulfur at а) * t = 120ºC; b) * t = 130ºС; c) t =130ºС, τ=8 h. A parameter - the sulfur contents of in a product, mass %

a

b

Conditions of functionalization > C=С C=С C=СC=C
> δ1, δ2. by such effect one may significantly reduce stationary value ( 2)

z 3 and consequently kill population of atypical cells.

Figure 8. The curves of growth of normalized model (solution of equations system (37)) at pn = 1; pa = 1/5; b = a1 = a2 = d =1, δ1 = δ2= δ4 = 0,01; δ3 = 0,001; f1 = f2 = 2; x = 15. ( 2)

Let study stationary stages of equilibrium of atypical cells population z 3 at the change of coefficients of toxic action δ3, δ4 of toxicant x on rates of growth pa and loss d. ( 2)

The surface of stationary states z 3 (δ 3 , δ 4 ) at the change of weights δ3 and δ4 is shown ( 2)

in Figure 9a and in Figure 9b you may see sections of this surface at z 3 = const.

( 2)

Figure 9. The surface of equilibrium states z 3 (δ 3 , δ 4 ) . pn = 1; pa = 1/20; x = 1.

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Yu. A. Ershov and V. V. Kotin

One may reduce concentration of atypical cells by both at the expense of selection of medical substance and by increase of doze. By this action of substance is strengthened on both atypical and normal cells that leads to effect of side action of medical treatment. ( 2)

Change of equilibrium concentration z 3 as function of concentration of toxicant x and influence of this toxicant on growth rate δ3 are presented in Figure 10.

( 2)

Figure 10. The surface of equilibrium states z 3 (δ 3 , x) . pn = 1; pa = 1/5; δ4 = 1.

More advantageous approach in relation to organism is selective acceleration of rate of atypical cells loss under the action of medical substance. And this substance doesn't influence on rates of growth of all types of cells. Such situation of atypical cells loss is shown in Figure 11. The surface of stationary states ( 2)

z 3 (x, δ 4 ) is uniformly decreased with the rise of toxicant x concentration and strengthening of atypical cells sensitivity to medical effect δ4 at the expense of correct selection of the last one.

( 2)

Figure 11. The surface of equilibrium states z 3 (δ 4 , x ) . pn = 1; pa = 1/5; δ3 = 0,1.

Mathematical Models of Tumor Processes and Strategies of Chemotherapy

109

All mentioned above surfaces of equilibrium states contain special points of stable nodes type. Now let analyze reduced system (39). For it the special points are written in the following way: (1)

(1)

(1)

z1 = 0, z 2 = 0, z 3 = 0;

(2)

z1 =

( 2) (2) p + p + δ x ( 2) ( 2) σ 4µ 3 (f1 − σ1σ 2 ) a (p − δ 3 x ) 1 a , z 2 = z1 n , z 3 = z1 f 2 2 a . σ1 (σ 4µ 3 + f 2 σ 3µ 2 ) f1b a1 (d + δ 4 x )

(41)

With the change of toxicant x concentration in accordance with (41) the stationary ( 2)

occupancies z will be changed. Curves families of equilibrium numbers of atypical cells for set of coefficients values of toxic action δ3, δ4 = const are presented in Figure 12. The characteristic feature of these plots is the fact that at equal value of x extinction occurs faster at the value δ3 lower than δ4. This fact shows to the best advantage the action of toxicant namely on the rate of atypical cells growth, i.e. at successive selection of preparation at which δ3 is high one may faster and with higher efficiency inhibit population z3 than by other preparation but with the same amounts effecting on mortality via sensitivity coefficient δ4.

Figure 12. The family of phase-parametritic diagrams zst(x). a) δ3 = 0,01; δ4 = const; b) δ3 = const; δ4 = 0,01.

(2 )

Stationary state z 3

is changed with the change of coefficients of toxic action. Figure 3 (2 )

illustrates dependence z 3 (δ 3 ) at various values of x and δ4. Interesting particularity is noticeable in Figure 13a. Total extinction of population of atypical cells occurs beginning from the only value δ 3 =0,2. This fact means that it is possible to drive out population cr

completely only at ioncrease of parameter δ3 at the expense of selection of toxic preparation. However, Figure 14 shows that such tactics leads only to asymptotical reduction of level (2 )

z 3 down to zero at any levels of concentration of toxicant x and δ3. This fact testifies that while influencing only on population mortality it is impossible to destroy it completely.

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Figure 13. The family of phase-parametritic diagrams zst(δ3). a) δ4 = 0,01; x = const; b) δ4 = const; x = 1.

Figure 14. The family of phase-parametritic diagrams zst(δ4). a) δ3 = 0,01; x = const; b) δ3 = const; x = 1.

Figure 15. The dependence of roots of characteristic equation of system (37) on toxicant concentration.

Mathematical Models of Tumor Processes and Strategies of Chemotherapy

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We should note that all equilibrium states listed above are stable nodes. It is obvious from Figure 15 in which substantial parts of roots of characteristic equation calculated on the (2 )

(2 )

multitude of equilibrium values z 1 and z 3 are presented as functions of toxicant concentration. Curves Re[p1] and Re[p2] lay in the region of negative values and consequently equilibrium values corresponding to them are stable nodes.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25]

Yu.A. Ershov, Dokl. RAN, 352, No.5, 1 (1997) (in Russian). Yu.A. Ershov, Zh. Fhizicheskoi Khimii, 72, No.3, 553 (1998) (in Russian). Yu.A. Ershov, Oxidation Communications, 21, 441 (1998). Yu.A. Ershov, Applied Biochemistry and Microbiology, 35, No.3, 245 (1999). N.N. Semenov, On some problems of chemical kinetics and reaction ability, Moscow: AN SSSR (1958) (in Russian). N.M. Emanuel, Kinetics of experimental tumor processes, Moscow: Nauka (1977) (in Russian). H.E. Skipper, F.M. Schobel, W.S. Wilcox, Cancer Chemother. Rep., 35, 3 (1964). E. Schreck, Amer. J. Cancer, 24, 897 (1935). H.J. Bagg, J. Jackson, Amer. J. Cancer, 30, 539 (1937). W.C. Summers, Growth, 30, 333 (1966). W.R. Laster, et al., Cancer Chemother. Rep., Part I, 53, 169 (1969). V.V. Alekseev, I.I. Kryshev, Physical and Mathematical Modeling of Ecological Systems, St. Petersburg: Gidrometeoizdat (1992) (in Russian). A.D. Bazykin, Mathematical Biophysics of Concurrent Populations, Moscow: Nauka (1985) (in Russian). Yu.A. Ershov, T.V. Pleteneva, T.K. Slonskaya, Bull. Experiment. Biologii i meditziny, No.5, 594 (1997) (in Russian). Yu.A. Ershov, N.B. Esmenskaya, T.K. Slonskaya, Khim.-farmatz. Zh., No.11, 6 (1995) (in Russian). Yu. Odum, Basic Ecology, Philadelphia: Saunders (1983). M. Begon et al., Ecology: Individuals, Populations, and Communities, Oxford: Blackwell (1986). Yu.A. Ershov, N.N. Moshkamborov, Kinetics and thermodynamics of biochemical and physiological processes, Moscow: Meditzina (1990) (in Russian). G.S. Yablonskii et. al., Kimetic models of catalytic reactions, Novosibirsk: Nauka (1983) (in Russian). Mathematical problems of chemical kinetics, Ed. by K.I. Zamaraev, G.S. Yablonskii, Novosibirsk: Nauka (1989) (in Russian). S.D. Varfolomeev, S.V. Kalyuzhnyi, Biotechnology. Kinetic bases of micro-biological processes, Moscow: Vyssh. Shkola (1990) (in Russian). O.S. Frankfurt, Cellularr cycle in tumors, Moscow: Meditzina (1975) (in Russian). D. Khimmel'blau, Ananlysis of processes by statistical methods, Moscow: Mir (1973) (in Russian). Biological cells in culture, Leningrad: Nauka (1984) (in Russian). http://www.pivnik.ru/works/new/newmet_020_1.doc.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 113-125 © 2006 Nova Science Publishers, Inc.

Chapter 12

ONE-STAGE METHOD OF CATALYTIC OXIDATION OF VEGETAL RAW MATERIALS BY OXYGEN: NOVEL ECOLOGICALLY PURE PRODUCTS AND PERSPECTIVES OF THEIR PRACTICAL USE A. M. Sakharov N.M. Emanuel's Institute of Biochemical Physics Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Ecological problems become one the main problems of humanity during last years. Chemical industry takes one of the first places among origins of dangerous pollutions of the environment and in this connection the search of principally novel chemical processes differing by lower level of energy consumption and minimum formation of side products is necessary. This fact relates to practically all chemical processes including processes of organic compounds oxidation by oxygen which allow obtaining of the wide spectrum of necessary products for various branches of industry and agriculture. Professor N.M. Emanuel was at the beginning of works on search of principally novel processes of organic compounds oxidation by oxygen differing by high productivity and formation of minimum amounts of side products. As it is consequent from fundamental works of N.M. Emanuel the most perspective direction for increase of selectivity of reactions of liquid-phase oxidation is the use of metal complex catalysis [1]. In this case application of corresponding ligands allows changing of catalysts structure and properties in such way to make proceeding of side process unfavourable. In works made under direction of N.M. Emanuel they showed that catalytic system [Cu2+…A-…O2] where А- − the anion form of substrate (anion form of substrate was formed at the expense of its deprotonation under the action of bases introduced into the system) is extremely effective in reactions of oxidation of fluorinated alcohols with general formula H(CF2CF2)nCH2OH (where n=1-6) [2], camphor [3] and diacetone-L-sorbose [4] with

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formation of correspondingly fluorine-containing acids H(CF2CF2)nCОOH, camphor and diacetone-2-keto-L-gulone acid. As the investigation of alcohols oxidation reactions mechanisms in the presence of copper and bases ions showed the participation of Cu2+ in the process of electrons transfer from coordinated anion form of substrate to O2 molecule opened possibility of reaction proceeding by concert multi-electron mechanism without formation of free radicals. Proceeding of process by thermodynamically advantage multi-electron mechanism of oxygen reduction allows reaching of high rates of oxidation at room temperatures at selectivity of formation of final products exceeding 90% [5]. Process of oxidation of organic compounds by oxygen in the presence of copper compounds and bases may be widely applied in the field of processing of nature raw materials. One of the most interest directions in the field of large-capacity chemistry at present is its sharp turning in favor of using of products of native origin as initial raw materials for synthesis of reagents used in various branches of industry. The novel chemistry calling "green" chemistry is conceived. The process of oxidative modifying of starch and other polysaccharides with obtaining of valuable oxygen-containing products differing by improved properties in comparison with initial compounds takes important place in it. The methods of oxidative modifying of polysaccharides with receiving of polyacids as main products are widely used in practice due to availability of initial raw material and high consumer properties of oxidized polysaccharides. Salts of polyacids are widely used as watersoluble glues in production of paper, cardboard, in processes of materials dressing, as components of drilling agents, etc.. However, as well as for a lot of other processes of organic compounds oxidation as oxidizing agent of polysaccharides the hypochlorites and periodates [6, 7], hydrogen peroxide [8] and not gaseous oxygen are used till recently that is connected with low activity of oxygen in processes of polysaccharides oxidation. It turned out that in the presence of copper complexes and bases not only simple in their structure alcohols and ketones but also polysaccharides (starches, dextranes, cellulose) may be oxidaized by oxygen with high rates. High rates of polysaccharides oxidation by oxygen exceeding oxidation rates by hypochlorites and other oxidizing agents are reached at temperatures 40-90°C [9-11]. As well as under oxidation of monoatomic alcohols [5] the anion form of substrate (A- − deprotonated polysaccharide) forms the adducts (Cu2+…A-) with copper ions and the role of catalyst, Cu2+ ions is to activate deprotonated form of substrate in relation to oxygen. We may suppose that role of divalent copper is in oxidation of substrate anion form with following interaction of intermediate radicals or anion radicals with O2. However high-molecular polysaccharides with low content of end aldehydes groups in anaerobic medium are redoxinactive and the rate of valent transitions Cu2+→Cu+ at the expense of electron transfer from substrate anion form to Cu2+ proceeds with rates in dozens of times lower in comparison with the rate of oxygen adsorption during the process of polysaccharides oxidation in alkaline mediums. They showed that namely direct interaction of oxygen with anions A- in coordination sphere of copper ion led to formation of hydroxycarboxylates as main primary products of oxidation [12]. Absorption of oxygen is completely stopped after neutralization of introduced alkali by formed during the oxidation process polyoxyacids. Thus, by varying of amount of introduced alkali we may change the degree of polysaccharides oxidation into

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polyacids. This allows changing of final products viscosity, bonding ability, solubility in water, etc.. As initial raw materials for receiving of salts of polyoxyacids one may use not only starch, but any other starch-containing raw materials: corns of maize, oats, rice, etc., including ill-conditioned raw materials (grain-crops affected by various fungus diseases, waste of rice slashing, waste of mill houses, etc.) [9, 10]. This fact allows decreasing of prime price of final product production in dozens times. Oxidized starch-containing reagents (OSR) may be used as ecologically pure reagents in production of resin-bonded chipboard and cane fiber board, components of drilling solutions and oil-removing liquids, as components of architectural mixtures, fire-retardant additives relating to the class of coke-forming extinguishants, components of cleansers, stimulators of plants growth and in a number of other fields where modified and non-modified polysaccharides are used.

APPLICATION OF OXIDIZED STARCH-CONTAINING REAGENTS (OSR) AS BINDING AGENTS IN PRODUCTION OF RESIN-BONDED CHIPBOARD AND CANE FIBER BOARD Oxidized starch-containing raw materials obtained from both starch and starch-containing raw materials (for example from affected amaize corns) may be used as ecologically pure bonding agents in production of resin-bonded chipboard and cane fiber board [9, 10]. Table 1. Physical-mechanical characteristics of resin-bonded chipboard obtained with the use of mixture of phenol-formaldehyde resin (KF-MT) with OSR* Structure of bonding agent, mass % KF-MT – 100 OSR – 0 KF-MT – 95 OSR – 5 KF-MT – 90 OSR – 10 KF-MT – 85 OSR – 15 KF-MT –80 OSR – 20 KF-MT – 75% OSR – 25% *

Density, kg/m3

Breaking point at bending, MPa

Tensile strength, MPa

708

11,9

0,11

711

12,2

0,12

726

13,4

0,15

704

12,5

0,15

725

12,1

0,16

717

15,0

0,17

OSR was obtained by oxidation of affected maize corns and represented water solution of polyacids salts with the content of dry substances 17 mass %

Particle board with sizes 600 ¯ 600 ¯ 16 mm was obtained in laboratory conditions with the use of mixtures of OSR and phenol-formaldehyde resin of KF-MT brand. OSR was introduced as 17 mass % water suspension. Physical-mechanical characteristics of these

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boards are presented in Table 1. As it is obvious from this Table substitution of the part of phenol-formaldehyde resin by OSR leads to strengthening of boards. However, the most important feature of OSR usage is lowering of toxicity of boards at the expense of decrease of diffusion of phenol and formaldehyde from particle board samples. As tests showed, toxicity of boards under the use of OSR as one of the bonding agent in mixture with KF-MT was reduced by 30÷40% in comparison with boards obtained with the use of one KF-MT.

2. OSR AS COMPONENTS OF DRILLING SOLUTIONS AND OIL-SWEEPING LIQUIDS At present water-soluble polymers are widely used in oil-production branch of industry as lowers of water filtration of drilling solutions, oiling additives, plasticizers, corrosion inhibitors, etc.. As carried out laboratory and industrial tests showed oxidized starch reagents might be successfully used as main components of drilling solutions on water base and might substitute expensive carboxymethylcellulose (CMC) and reagents on acrylonitrile base applied at present. And in many cases technological properties of drilling solutions are improved [13]. It is extremely important that oxidized starch reagents are highly effective corrosion inhibitors of black metals [14] that reduces costs on carrying out of drilling operations connected with equipment deterioration. One the most important properties of drilling solutions assigned for drilling in unstable depositions is their dispersion ability which determines possibility of maintaining of the minimum permissible concentration of solid phase in solution. Ability of salts of oxidized polysaccharides to adsorb on stratum particles surface screening active zones and preventing transition of these particles into structure forming phase of drilling solution opens wide perspectives of OSR application as highly effective inhibitors of drilling solutions. Inhibiting ability of OSR is sharply increased when substituting the part (about 50%) of Na or K ions by multivalent cations: Ca, Fe, Al and this is reached by simple addition of water-soluble salts of listed metals to water OSR solutions. The data on inhibiting ability of drilling solutions treated by OSR (K-Ca and K-Al-forms in comparison with non-treated solutions and treated Na-CMC (sodium salt of carboxymethylcellulose are widely used at present reagent for drilling solutions)) are presented in Table 2. Inhibiting ability was determined by the following technique: bentonitic clay in the form of grit with particles sizes 3mm in amount of 25g was introduced into 500ml of tested solution and mixed for 4 hours. Then the solution was passed through the system of vibration sieves with cells sizes 3, 2 and 1mm. Separated on sieves fractions were dried until constant weight at temperature 105°C and their weight percent was determined in relation to introduced amount of clay. Analyzing the data presented in Table 2 we may conclude that application of OSR as drilling solution inhibitor (Ca-K and Al-K-form) leads to significantly higher dispersion of grit in comparison with solutions treated by Na-CMC. Solutions containing aluminapotassium modification of OSR (oxidized affected maize corns in which 50% of potassium ions are substituted by ions of three-valent aluminum) possesses the lowest dispersion ability that opens wide possibilities of usage of this modification as component of drilling solutions.

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Table 2. Inhibiting ability of drilling solutions treated by OSR.

Structure of drilling solution Initial bentonitic solution + 1,5% Na- CMC + 1,5% -OSR К-Са-form + 1,5% -OSR К-Аl-form

Fractional structure of grit, mass % not less than from 2 to from 1 to 2 3 mm 3 mm mm 22,7 30,3 12,4 18,0 20,0 16,1 77,8 11,8 1,4 11,8 0,8 83,4

Total amount of grit, mass % 65,4 56,3 92,0 95,3

OSR may be used in structure of oil-sweeping liquids. Injection of polymers water solutions into heterogeneity layers provides oil recovery at the expense of increase of coefficients of layer coverage as a result of decrease of ratio of water mobility and displaced oil. At present for oil displacement from layers carboxymethylcellulose (CMC) are the most widely used. However, wide application of CMC in oil-production industry is limited by limited volumes of its production and high cost [15]. OSR as it was already mentioned was significantly cheaper than CMC and might be obtained from agricultural waste that makes it even more advisable. Laboratory experiments on testing of possibility of OSR application as additive to water with the aim of its densifying and improvement of washing properties were carried out on the plant modelling the process of oil displacement from porous stratum at given rate of filtration and pressure close to real observed [16]. Final coefficients of oil-recovery were calculated as ratio of oil mass displaced from model to oil mass initially containing in porous stratum. In Table 3 we present the data on influence of viscosity of CMC and OSR water solutions on oil-recovery coefficient for two types of oils. Received data testify that water solutions of OSR possess higher oil-sweeping properties in comparison with CMC solutions of the same viscosity. This fact is explained by higher surface activity of OSR solutions on the interface with oil [16]. Table 3. The influence of viscosity of OSR and CMC water solutions on oil-recovery coefficient Oil-recovery coefficient, % Reagent

*

Viscosity, mPa⋅sec

Romashkinskaya oil*

Pionerskaya oil*

Water

1,0

46,8

34,4

CMC OSR CMC OSR CMC OSR CMC OSR

1,4 1,4 5,0 5,0 10,0 10,0 20,0 20,0

52,3 54,2 57,3 60,9 60,1 65,0 61,9 68,5

39,5 41,5 43,4 45,2 46,1 48,2 48,2 50,8

Romashkinskoe oil-filed: viscosity is 15Pa⋅sec, Pionerskoe is 226 Pa⋅sec.

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OSR may be used as high-effective isolating agent in flow-deflecting technologies allowing intensification of production of residual oil. It is connected to a great extent with unusual effect of interaction of OSR solutions with boric acid. It turned out that additives of small amounts of boric acid to OSR gels (of low degree of oxidation) lead to formation of high-viscous structured gels possessing non0linear-viscous properties [17, 18]. And such effect is reached already at weight ratio OSR/H3BO3=100 in calculation to dry substance. Structuring of gels occurs (at content of OSR in water more than 5-10 mass %) practically immediately after addition of small amounts of boric acid solution to water solution of OSR. Such gels possess over-anomalous rheologic properties. Dependence of viscosity on deformation rate for 15% solution of OSR (oxidized rice) as without additive (curve 1), so with addition of Н3ВО3 (curve 2) are presented in Figure 1. Content of boric acid is 1,5 mass %. It is obvious that addition of boric acid to gel of OSR sharply changes rheologic properties of system. Dependence of shear stress on deformation rate takes extreme character with minimum in the region 5 sec-1 that testifies t formation of gel structure strong enough. The region of sharp linear growth up to the rate of deformation 5,5 sec-1 corresponds to undestructed structure and system behave at Shvedov-Bengam solid with plastic shear stress equal to 0,17Pa and structure viscosity 1,45 Pa⋅sec. Decrease of shear stress at further increase of deformation rate indicates on spatial structure, and the following linear section of curve is connected with complete destruction of gel structure and system acts as Newton liquid with viscosity 0,13 Pa⋅sec. 14

2

shear stress, Pа

12 10 8 1

6 4 2 0 0

20

40

60

80

shear rate, 1/sec

Figure 1. Dependence of viscosity on deformation rate for 15 mass % solutions of OSR (oxidized rice). 1 − boric acid concentration is 1,5 mass %, 2 − without addition of Н3ВО3.

The viscosity of cross-linked by boric acid OSR gel with undestructed and destructed structures is differed in more than 10 times that allows suggesting of given reagent as isolating agent in flow deflecting technologies. At high rates of flow in tubes and bottomhole formation zone the solution of cross-linked OSR will possess low viscosity and will be easily injected. At low rates of deformation in layer depth the given system will behave as viscous plastic and isolate high-permeability stratums.

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3. APPLICATION OF OSR IN ARCHITECTURAL MIXTURES Oxidized starch and oxidized starch-containing raw materials may find wide application in construction industry. As investigations showed, additives of OSR allowed imparting large plasticity to cement solutions and increasing strength of both cement and concrete solutions after drying. OSR may be used as gluing additive for filling, emulsion paints and also for producing of heat- and soundproof materials. OSR are effective decelerators of plaster and concrete hardening. The dependence of plaster hardening time on concentration of introduced OSR is presented in Figure 2 (oxidized maize corns, curve 1). The data on the influence on CMC hardening time (curve 2) and lignosulfonate (curve 3) widely used at present as bonding agents are presented for comparison. As it is obvious from the Figure the OSR possess significantly higher exploitation properties as decelerator of plaster hardening in comparison with known bonding agents. 80 Time of hardening (stiffening), min.

1

60 2 40

3 20

0 0

0,25

0,5

0,75

1

Additive concentration, mass % Figure 2. Dependence of hardening (stiffening) time of plaster on concentration of additives, mass %: 1 − CMC, 2 − lignosulfonate, 3 − OSR (oxidized maize corns).

Estimation of quality of dry plaster mixtures under the use of OSR as bonding agent showed that fillings were differed by high elasticity, were easily leveled on surface of wall and possessed high adhesion to various surfaces. The data on influence of OSR (oxidized rice and oxidized maize corns) on physicalchemical properties of dry architectural mixtures on the base of plaster and vermiculite (ratio plaster: vermiculite = 7 : 3) are presented in Table 4. As it is obvious additives of OSR allow significant increasing of both time of stiffening and samples (arms) strength.

120

A. M. Sakharov Table 4. Physical-chemical properties of dry plaster-vermiculite mixtures with the use of OSR OSR amount (mass % by plaster) ----12∗ 33∗ 31∗∗

*

Time of stiffening, min beginning

end

9 19 18 25

12 30 90 150

Compressive resistance, kg/m2 3,12 5,70 4,80 8,40

Heat conduction coefficient, Vt/m.degree 0,13÷14 0,13÷14 0,13÷14 0,13÷14

oxidized rice; oxidized maize

**

OSR may be used in production of ecologically pure fillings. Carried out investigations of fillings on chalk base with additives of OSR showed that they possessed wonderful physical-mechanical properties. So, strength of cohesion of fillings containing OSR as bonding agents with concrete is more than 5 kg/cm3 and of all-Union State Standard 24064 require not less than 1,5 kg/cm2.

OSR AS WATER-SOLUBLE ADDITIVE FOR INCREASE OF FIRE EXTINGUISH ABILITY OF WATER AND ANTIPYREN As investigations showed, oxidized starch reagents may be applied as effective fireprotective impregnations, antipyren additives under production of various polymer materials on the base of water-soluble polymers and latexes, and also under fire extinguishing [19]. Obtained results turned to be very surprising since nobody assumed that starch-containing reagents might possess high fire extinguishing properties. Determination of oxygen index (OI, minimum oxygen content in air at which samples burning begins) for various paper types, sawdusts and synthetic materials show that OI in all cases exceeds 25%, and in some cases exceeds 40% [19]. Thus, OSR may be recommended as component of impregnation fire-protecting compositions. Water solutions of OSR possess significantly higher fire extinguish ability in comparison with pure water. Influence of OSR additives (oxidized potato starch) on fire extinguish efficiency of fine-disperse water was estimated by decrease of average time of burning process quenching of cotton fabric impregnated by otor oil AS-8. At other equal conditions introduction of OSR into water in amount 50÷150 g/l allows decreasing of extinguishing time from 15÷16 sec down to 10÷6 sec [19]. As investigations show OSR may find application as file-protecting coverings for wood products. At present wood is one of the most widely used architectural materials due to its relatively high strength, low thermal conductivity and density, easiness of mechanical treatment, etc.. the main disadvantage of wood under the use in construction is its high fire risk. One of the most prevalent method of decrease of wood combustibility is application of antipyrens. In ideal case antipyrens should reduce all parameters of fire risk: combustibility, inflammability, flame spreading on surface, smoke-forming ability and toxicity of burning

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products. As investigations show, these strict requirements are fulfilled when one uses oxidized starch reagents as antipyrens [20-22]. Among great number of developed means of fire-protection the most effective are coverings and compositions of foaming type. The compositions on the base of OSR are in particular such substances. The mechanism of fire protecting action of such coverings is bonded with formation on treated surface at high-temperature heating or at direct influence of fire of foamed coke layer. The layer of foam-coke reveals heat-protecting and barrier effects at mass-transfer of both combustible materials to zone of flaming reaction and of air oxygen to material surface. Results of estimation of efficiency of fire protecting action of coverings on the base of oxidized starch-containing raw materials on amount of applied reagent carried out by standard method (all-Union State Standard 16363-98) are presented in Figure 3. As it is obvious, all compositions already at one-layer covering of pine samples by oxidized starch reagent (with consumption of OSR 100 g/m2) provide fire-protection of the II group and reaching of rank of hardly-inflammable wood. With increase of covering number up to 3÷4 (OSR consumption 300÷400 g/m2) mass losses at fire testing are significantly decreased and studied antipyrens allow obtaining of the I group of fire-protection − hardly-inflammable wood. Important index of fire risk is toxicity and smoke-forming ability of materials. According to statistics 70% of cases of people death in conflagrations occur due to poisoning by toxic products of burning, in particular carbon oxide. Strong bloom during conflagration plays decision role in appearing difficulties under people evacuation from buildings and under conflagration localization and liquidation.

30

25

mass loss, %

20

15

10 3 2

5

1

0 0

100

200

300

400

500

2

Consumption, g/m

Figure 3. Dependence of mass losses of wood samples on amount of applied fire-protecting coverings on the base of modified polysaccharides: 1 − oxidized starch (high degree of oxidation), 2 − oxidized rice (high degree of oxidation), 3 − oxidized starch (average degree of oxidation).

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Index of toxicity of untreated pine (HCL50) in smouldering regime (450оС) is equal to 31,4 g/m2 (high toxicity). At the same temperature the sample treated by OSR have average toxicity (HCL50 = 46÷50 g/m3). In regime of fire combustion of wood (750оС) the products of burning of untreated wood are formed in amount presenting high danger (HCL50=33,2 g/m3). Treatment of pine surface by OSR compositions in this case also allows decreasing of poisoning danger in several times [21]. Results of investigations of heat generation characteristics under wood combustion with coverings on the base of OSR also confirm high efficiency of their fire-protecting action. The mechanism of fire protection together with foaming and carbonization of covering (OSR) with formation on the surface of wood of coke layer with high heat-isolating ability is obviously also connected with the change of thermal-chemical properties of materials [22].

5. APPLICATION OF OSR AS COMPONENTS OF DETERGENTS Oxidized starch reagents may be used in washing powders as substituents of polyphosphates [11]. As investigations show OSR possess the number of unique physicalchemical properties allowing hoping on their application as one of the main components of detergents. One of the most important characteristics of detergents is their ability to remove adhered to surface contamination particles and transfer them into suspension state. If there is liquid oil dirt the improvement of selective moistening promoting pushing off of dirt by water solutions of detergents from washing surfaces plays important role. The characteristic of selective moistening is the value of contact angle of oil drop on glass surface. Technique of experiments of determination of reagents efficiency in the structure of detergents was in the following: oil drop was placed on glass surface, then the glass was placed into investigated solution containing OSR and with the help of horizontal microscope the contact angle was measured (oil drop was in water solution at the lower surface of glass). Maximum time of contact angle measuring was 20 min. As tests showed oxidized starch reagents of various nature significantly reduced contact angle of moistening, and their mixtures with isopropyl alcohol (2 mass % of OSR + 0,6 mass % of isopropanol) caused drop dispersion (Table 5). Table 5. The values of contact angles of selective moistening of oil drop on glass by solutions containing OSR Solution Water Wtaer + 2 mass % of OSR (oxidized rice) The same + 0,6 mass % of isopropanol

Value of contact angle, α 130о 70о Oil drop is dispersed

The most interesting results were obtained under investigation of dispersion ability of OSR mixtures with sodium dodecylsulfate. Results of influence of OSR mixture structure (oxidized rice) with sodium dodecylsulfate on value of contact angle of moistening are presented in Table 6. As it is obvious from Table 6 moistening ability of OSR is lower than for solutions of sodium dodecylsulfate. But the most surprising fact is that solutions with low

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123

content of sodium dodecylsulfate and high content of OSR content possess highest moistening ability. Such compositions are differed by unique high moistening ability and causes practically immediate dispersion of oil drop and its washing way from glass surface. Table 6. Influence of composition structure sodium dodecylsulfate / OSR (oxidized rice) on the value of contact angle of moistening Components content in solution, g/l Sodium OSR dodecylsulfate 4,8

0

3,0

1,8

2,4

2,4

0,9

3,9

0,24

4,56

0

4,8

Change of contact angle, α

Results of observation

After 2-3 min. oil drop goes away from glass surface After 2-3 min. oil drop goes away from glass о о 90 -30 surface After 1 min. drop splitting starts and then drop о о 120 -40 goes away from glass surface After 1 min. drop splitting starts and then drop 110о-40о goes away from glass surface Practically immediately the angle is increased down to 30° and drop goes away from glass surface For 15 min the angle is not changed. Detachment 120о-45о of drop is observed in two cases from10. 60о-30о

Thus, substitution of the main part of expensive anion SAS by cheap reagents (OSR) may lead to both reduction of prices of detergents and to increase of their efficiency.

6. APPLICATION OF OSR AS FILM FORMING SUBSTANCE FOR PREPLANT TREATMENT OF SEED Preplant treatment of seed by pesticides with addition of film-forming substances (incrustation of seed) gives possibility of dosage of protectant amount with high accuracy and it is effective mean of fixation of pesticides, growing stimulating substances, microelemts, etc around the seed. Sodium salt of CMC (Na-CMC) is widely used in incrustation processes. Disadvantages of Na-CMC as film-forming substance are high viscosity of recommended for treatment solutions, often seed conglutination, and also comparatively low adhesion and consequently significant sloughing of pesticides and other components from seed surface. The growth of scale of seed incrustation application poses the problem of application of cheap, non-toxic and fast decomposing in soil reagents as film formers. As investigations showed OSR related to such type of substances. Composition, containing OSR are well soluble in cool water, possess optimal viscosity, after drying on seed stable film is formed. The data on films strength on seed durfaces with the use of Na-CMC and OSR as incrustrator (oxidized maize corns) are presented in Table 7. As it is obvious from this Table OSR form on seed surfaces significantly more strength to sloughing films in comparison with Na-CMC.

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Table 7. Sloughing of films containing tetramethylthiuramdisulfide (TMTD) as protectants from the surface of maize corns with the use of Na-CMC and OSR as film forming substances after 30 min of agitation Sloughing of film after 30 min of agitation, % to initial amount Film formatting agent

Na-CMC CMC (from maize corns)

Content of TMTD (g/kg of seed) 0,5

1,0

36,0 8,0

56,0 10,0

As investigations showed OSR form stable to sloughing films and possessed pronounced stimulating properties [23] that significantly broadened the field of application of reagents of such type in agriculture. Presented examples show that under the use of oxygen as the most cheap and ecologically pure oxidizer and simple catalytic system [Сu2+…substrate…base] we are succeeded in developing of principally novel processes of oxidative modification of vegetable raw materials with obtaining of valuable from practical point of view products. Invaluable contribution into developing of such processes was made by Professor N.M. Emanuel who stood at the beginning of works.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

N.M. Emanuel, Uspekhi khimii, 47, No.6, 1329 (1978) (in Russian). Certificate of authorship 1026416 USSR. Certificate of authorship 1129875 USSR. Certificate of authorship 1462751 USSR. I.P. Skibida, A.M. Sakharov, N.M. Emanuel, Itogi nauki i tekhniki, Ser. Kinetika i kataliz, 15, 110 (1985) (in Russian). M. Floor, A.P.G. Kieboom., H. van Bekhum, Starch, 41, 303 (1989). E. Santacesria, F. Trulli, G.F. Brussani, D. Gelosa, M.Di Serio, Carbohydrate Polymers, 23, 35 (1994). Stefan J.H.F. Arts, Erwin J.M. Mombarg, Herman van Bekkum, Roger A.Sheldon, J. Synhtesis, No.6, 597 (1997). I.P. Skibida, An.M. Sakharov, A.M. Sakharov, International application published in accordance with patent cooperation (РСТ), WO 93/15094 (1993). Patent 2017750 Russia. Europe Patent 0548399 (1993). A.M. Sakharov, I.P. Skibida, Khimicheskaya fizika, 20, No.6, 101 (2001) (in Russian). Certificate of authorship 1828118 USSR. Certificate of authorship 1542100 USSR. L.E. Lenchenkova, Nedra, 393 (1998) (in Russian). A.Yu. Serebryakov, A.A. Balepin, A.M. Sakharov, Nauka i tekhnologiya uglevodorodov, No.2, 73 (2003) (in Russian).

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[17] T.I. Zainetdinov, Dissert. Of candidate of technical sciences, Ufa (1999) (in Russian). [18] A.G. Telin, T.I. Zainetdinov, I.P. Skibida, A.M. Sakharov, Proceeding of an International Conference on Colloid Chemistry and Physical-Chemical Mechanisms, Moscow (1998) (in Russian). [19] Patent 2204547 Russia. [20] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.1, 39 (2002) (in Russian). [21] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.2, 21 (2002) (in Russian). [22] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.3, 13 (2002) (in Russian). [23] Certificate of authorship 1692006 USSR.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 127-148 © 2006 Nova Science Publishers, Inc.

Chapter 13

EPR-SPECTROSCOPY OF COMPLEX POLYMER SYSTEMS A. M. Wasserman and M. V. Motyakin N.N. Semenov's Institute of Chemical Physics Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Professor Nikolai M. Emanuel paid great attention to creation of development of novel methods of chemical physics. One of such methods is EPR-spectroscopy. In Department directed by Nikolai Emanuel the method of EPR-spectroscopy of spin marks and probes, in particular with the aim of investigation of polymer and polymer systems was actively developed. Special attention Nikolai M. Emanuel paid to the problem of chemical physics of polymer ageing and stabilization. Results obtained at that time were summarized in monograph by N.M. Emanuel and A.L. Buchachenko [1]. We shall consider only some results of investigation of complex polymer systems by method of EPR-spectroscopy obtained recently (results obtained earlier were considered in details in works [2, 3]). We shall discuss possibilities of method of EPR-spectroscopy of spin marks and probes for determination of macromolecules conformation in solid state, and also the results of investigation of molecular dynamics and organization of micelle systems − complexes polyelectrolyte−SAS. We shall also discuss some results obtained with the use of method of EPR-spectroscopy and its modification − the method of EPR-tomography for revealing of particularities of spatial distribution of active sites resulted from process of thermo-oxidative destruction of solid polymers.

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1. EPR-SPECTROSCOPY OF SPIN-MARKED MACROMOLECULES AS THE METHOD OF POLYMER CHAINS DETERMINATION IN AMORPHOUS SOLID POLYMERS Determination of macromolecules conformations is one of the basic problems of science about polymers. Simultaneously with development of theory [4-6] the perfection and enrichment of experimental methods of determination of macromolecules conformations in various phase and aggregate states occurs. However the method of neutron scattering was almost the only one method allowing reliable determination of polymer chains conformation in solid amorphous state until now [7]. Not long ago they begun to use with this aim also the method based on measurement of rate of electron excitement transfer between molecules of chromophores covalent bonded with polymer chain [8]. In works [9, 10] the method of polymers chains conformations determination in solid state based on the use of EPR-spectroscopy of spin-marked macromolecules was proposed. When solving this problem the analysis of dipole broadening of EPR bands by spin markers covalent bonded with polymer chain is carried out. Usually in physical chemistry of polymers they consider three states of flexible polymer chain: Gauss ball, swollen ball and globule. The state of swollen ball is characteristic for macromolecule in "good" solvent in which interaction polymer−solvent prevails over interaction polymer−polymer. Macromolecule has configuration of Gauss ball in θ−solvent in which interaction between units of polymer chain doesn't differ from interaction polymer−solvent. State of globule is realized in "bad" solvent in which intramolecular interaction of polymer units significantly exceeds interaction of macromolecule's units with solvent [4-6]. The ratio between average square of distance between two ends of polymer chain and polymerization degree P for macromolecule is usually written as follows [6]: = P2να2

(1)

here α − mean-square length of monomer unit, i.e. effective length which falls at one monomer (the value α characterizes the polymer chain rigidity); ν − coefficient characterizing conformational state of polymer chain. Coefficient ν depends on macromolecule conformation: for Gauss chain it is ν = 1/2, for swollen in "good" solvent ball it is ν = 3/5 (more accurate value is ν =0,592/11/), for globule it is ν =1/3/4-6/. The problem of determination of average square of distance between end of linear chain is come to determination of parameters ν and α in equation (1). The procedure of determination of parameter ν is come to determination of parameter ∆ for frozen (at 277K) solution of spin-marked polymer. This parameter depends on dipoledipole broadening of EPR-spectra of spin markers and probes [12]: ∆ = d1/d – (d1/d)0

(2)

where d1/d – the ratio of sum intensity of end components of spectra to intensity of central component at given concentration of paramagnetic sites; (d1/d)0 − the value of parameter d1/d

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129

at such concentration at which dipole broadening is not revealed in EPR-spectra (Figure 1). Then the solution of spin probe is selected (solution of nitroxyl radical not bonded with macromolecule) in the same solvent in which parameter d1/d has at 77K the same value, as for solution of spin-marked polymer; spectra of markers and probes are normalized by equal concentration of paramagnetic sites and the ratio of intensities of central components of spectra of probe (dp) and marker (d1) is determined. This ratio is compared with theoretical dependences of ratio dp/dl on parameter ∆ calculated for three conformational states of macromolecule: Gauss ball, swollen ball and globule (Figure 2). Such comparison allows selecting form three conformational states of polymer chain.

Figure 1. Examples of EPR-spectra of solutions of spin-marked poly-4-vinylpyridine (PVP-1, polymerization degree P = 500) (0,5 mass %) in methanol at 77K. The number of markers on polymer chain: 85 (1) and 3 (2).

For determination of the value of α in equation (1) it is necessary to compare the experimental value of parameter ∆ with theoretical; theoretical dependences of parameter ∆ on content of spin markers on macromolecule (β=m/P, here m − the number of units of macromolecule containing spin marker) at various values of α for Gauss and swollen chains are presented in works [9, 10]. If we know values of α and ν from ratio (1) we may easily calculate the mean-square distance between ends of polymer chain. The method described here was used for determination of conformational state and distance between polymer chain ends of various spin-marked polymers.: poly-4-vinylpyridine (PVP*), polymethacrylic acid (PMAA*), sodium salt of polymethacrylic acid (PMAA*-Na), styrene and maleic anhydride copolymer (STMAL*) [9, 10, 13] (formulas of spin-marked macromolecules are presented in Scheme 1; molecular masses of polymers and used solvents are presented in Table 1).

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Figure 2. Theoretical dependences of ratio of central components of normalized (corrected to one concentration of paramagnetic sites) EPR-spectra of probe (dp) and marker (d1) on parameter ∆: I − globule, II − Gauss chain, III − swollen in "good" solvent ball. Points are experimental values of ratio dp/dl, 77K. Number of points correspond to numbers of systems in Table 23.1.

In Figure 2 the experimental values of ratio of intensities of normalized EPR-spectra of probe and markers in solid state (at 77K) for systems presented in Table 1 are compared with theoretical; it is obvious from these data that conformational state of all investigated systems correspond to conformation of Gauss ball. In other words, in solid polymers and also in used by us vitrificated solvents all investigated macromolecules at 77K have conformations of Gauss ball. This result at first glance is seemed to be surprising enough, since various systems were studied. However, we should take into account that here we determined conformational state of macromolecules modified by spin markers. Moreover, the quality of solvent depends on temperature and probably θ-temperature of solutions of spin-marked polymers in used solvents is insignificantly differed from vitrification temperatures of these solvents. The conclusion that macromolecules of spin-marked PVP and PMAA in non-marked polymer have conformation of Gauss ball corresponds to Flory's theory about macromolecules conformations in undiluted amorphous polymers [5] and also to experimental data on determination of macromolecules conformation in solid amorphous state by method of neutron scattering [7].

EPR-Spectroscopy of Complex Polymer Systems

Scheme 1. Spin-marked macromolecules.

131

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A. M. Wasserman and M. V. Motyakin Table 1. Conformational characteristics of spin-marked macromolecules at 77K

œ

Number of system

Polymer

Molecular mass

β,œ mole %

1

PVP*-1

5·104

17

2

PVP*-1

5·104

3

PVP*-1

4

α, Å

1/2, Å

methanol

10

220

17

n-propanol

9

200

5·104

17

PVP

11

240

PVP*-1

5·104

9

methanol

10

220

5

PVP*-2

1,4·105

20

ethanol

10

360

6

PVP*-2

1,4·105

20

PVP

9,5

350

7

PVP*-2

1,4·105

8,5

ethanol

9

330

8

PVP*-1

1·106

10,5

methanol

11

1070

9

PVP*-1

1·106

10,5

PVP

10

980

10

PMAA*

1,4·105

23

methanol

11

440

11

PMAA*

1,4·105

23

PMAA

12

380

12

PMAA*

1,4·105

23

methanol

12

480

13

PMAA*

1,4·105

23

methanol (60 mass %)−water

13

520

14

STMAL*

6·104

12

dimethylforma mide

9

220

Solvent

Mole content of spin markers on polymer chain

The values of mean-square length of monomer unit and distance between polymer chain ends are presented in Table 1. It is important to pay attention to the fact that sizes of macromolecule ball in vitrificated low-molecular solvents and in solid non-marked polymer are differed insignificantly. When the salt of PMAA is formed the rigidity of polymer chain is increased a little that leads to little increase of values of mean-square length of monomer unit and distance between polymer chain ends. The result obtained under addition to polymer salt solvent in methanol (40 vol. % of water, at large content of water the solution is not vitrificated, but is crystallized) represents special interest; at that the macromolecule in solid state keeps conformation of Gauss ball (Figure 2), however, as we should expect, rigidity (parameter α) and sizes of ball are increased (Table 1). Presented here results allow making conclusion that method of EPR-spectroscopy of spin markers is effective method of determination of macromolecules conformation in solid state. This method may significantly enlarge information obtained by other methods, in particular by method of neutrons scattering. The advantage of this method is in the fact that it may give information about conformational state of comparatively small parts of solid polymers chains.

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133

The disadvantage of the method is that as a rule it requires significant modification of polymer chain as a result of introduction of essential number of spin markers. Introduction of markers may change polymer properties. However, this disadvantage may be removed by the use of modern impulse methods of EPR-spectroscopy (see for example [14,15]) which are more sensitive to dipole-dipole interaction of uncoupled electrons than traditional methods of EPR-spectroscopy.

2. MOLECULAR DYNAMICS AND ORGANIZATION OF COMPLEXES POLYELECTROLYTE−DETERGENT Method of EPR-spectroscopy of spin markers and probes turned to very informative under investigation of self-associating polymer systems, in particular complexes of polyelectrolytes with surface active substances (SAS). Application of this method allowed establishing of particularities of molecular dynamics and local organization of SAS molecules, and also segment mobility of macromolecules in such complexes [16-26]. The interest to complexes is caused by various reasons. Firstly, it is a novel class of polymer materials possessing unusual physical-chemical properties. Moreover, possible application of such complexes for solution of practically important problems is of great interest, for example as sorbents for removal of toxic substances from water mediums, for purposeful transport of medicines in organism, etc. (see for example [27]). There are complexes of polyelectrolytes with ionic and nonionic SAS. In the first case formation of micelles occurs on polymer chain that may lead to both the change of conformation and segment mobility of macromolecules and to the change of aggregation number and local organization of micelles included into the complex. In the second case as a rule the numbers of micelles aggregation included into complex and "free" micelles are practically not differed, however, under formation of complex macromolecule conformation and local mobility of detergents molecules may be significantly changed. The results of investigation of molecular dynamics and organization of complexes obtained by EPRspectroscopy method of spin markers and probes will be considered below.

2.1. Complexes of Linear Polyelectrolytes with Ionic SAS 2.1.1. Molecular Dynamics and Organization of Complexes Micellar Phase Usually they distinguish two types of complexes polyelectrolyte−ionic SAS. Firstly, complexes in which only the part of polymer units is connected with SAS iones. Such complexes are soluble in water; their solubility is determined by the presence of polymer units not connected with SAS ions. Secondly, the complexes in which all or almost all units of polymer chain are connected with SAS ions. Such complexes are insoluble in water and are precipitated. Schematically soluble and non-soluble complexes of polyelectrolyte−SAS (on the example of complexes of polycarbonic acids with alkyltrimethylammonium bromides) are presented in Figure 3.

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A

B

Figure 3. Macromolecular organization of soluble (a) and non-soluble (b) complexes of polycarbonic acids with alkyltrimethylammonium bromides.

The particularities of molecular dynamics and local organization of micellar phase of complexes were formulated on the example of complexes of polyacrylic (PAA), polymethacrylic (PMAA) acids and polystyrenesulfonate (PSS) with dodecyl- (DTAB), tetradecyl- (TTAB and cetyltrimethylammonium (CTAB) bromides, and also of poly-N,N'dimethyldiallylammonium chloride (PDAC) and poly-N-ethyl-4-vinylpyridinium bromide (PEVP) with sodium dodecylsulfate (SDD) (formulas of polymers are presented in Scheme 2).

Scheme 2.

Particles of complexes of PAA and PMAA with alkyltrimethylammonium bromides include one macromolecule and micellar phase is formed as one "big" micelle (Figure 3). complexes of PSS are also formed in the volume of one macromolecule, however in contrast to complexes of polycarbonic acids micellar phase is formed as "not big" aggregates [28]. Quite the contrary, the particles of complexes of PDAC with SDD are consisted of dozens of

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135

polymer macromolecules and dozens of thousands of SAS ions [29]. Macromolecular organization of complexes of PEVP with SDD depends on polymer molecular mass: complexes on the base of PEVP with polymerization degree Pw = 1000 represent strongly associated particles including not less than 50 macromolecules and 2500 ions of SDD, whereas particle of complexes on the base of PEVP Pw = 2000 includes one macromolecule and approximately 500 ions of detergent [30]. General regularities of molecular dynamics and local organization of micellar phase of polyelectrolytes complexes with ionic SAS [16-22, 26] were formulated; for the solution of this problem spin probes were used. Formulas of some of the last ones are presented in Scheme 3. CH3(CH2)17-n

(CH2)n-2COOH

C

O

N

O

N

O

N C2 H5

R2

n=5 (5DSA); n=16 (16DSA) O

. O

N

N

N CH2

N C6H13

C

R2’

CH

R4’

Scheme 3. Formulas of spin probes.

According to our opinion usage of spin probes of various structures allows obtaining of the information about various parts of micellar phase of complexes. Probe 5DSA is built into micellar phase in such way that carboxyl group is situated close to interface, whereas paramagnetic fragment is localized deeper, on the distance of 5-7Å from interface [31]. Probe 16DSA in complex micelle as a rule takes on relatively "elongated" conformation in which paramagnetic fragment is localized near the "nucleus" of micelle (in contrast to "free" micelles in which probe molecule takes on U-shaped conformation and paramagnetic fragment is situated close to charged groups of SAS) [32]. Paramagnetic fragments of probes R2, R2' and R4' are situated close to interface; these are relatively "big" probes which give "averaged" information about molecular mobility of micellar phase. When analyzing experimental EPR spectra of spin probes in micellar phase of complexes we used the model "Microscopic Order and Macroscopic Disorder" (MOMD) [33]. This model is often used for description of EPR spectra of spin probes in micelles, dispersions, vesicles and other microscopically ordered but macroscopically disordered systems [34, 35]. The parameters of model are: −

the main values of tensor of ultrafine interaction and g-tensor of nitroxyl radical;

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A. M. Wasserman and M. V. Motyakin −

− −

coefficients of rotational diffusion of spin probe in relation to axes perpendicular (R⊥) and parallel (R||) to main axes of molecular rotation. Average time of correlation τ, is connected with coefficients of rotational diffusion by the ratio: τ = 1/6Rav, where Rav = (R⊥2 · R||)1/3. angle β between directions of main axes of diffusion tensor and tensor of ultrafine interaction (or g-tensor); parameter of order S, which depends on orientational potential and is determined by the ratio S = ½ < 3cos2θ − 1 >, where θ − the angle between anisotropy direction of medium and long axis of pin probe symmetry (for more details see [33, 36]); this parameter characterizes degree of order (local organization) of micellar phase of complexes.

The following results were obtained: 1. Rotational mobility of spin probes in micellar phase of polymer complexes is significantly lower than in "free" micelles. This is general regularity which is observed for all studied complexes with the use of various spin probes. As an example in Figure 4 we compare EPR spectra of probes 5DSA and 16DSA in "free" micelles of SDD and in complexes PEVP−SDD; it is obvious that these spectra are strongly differed. These results allow unambiguous concluding that mobility of spin probe in complex is significantly lower than in "free" micelle. This result is not surprising and is explained by the fact that interaction of SAS molecules with polymer chain in complex leads to significant decrease of local mobility of detergent molecules. It is important to mark that local mobility of detergent molecules in micellar complex depends on a lot of factors such as interaction polymer−detergent, segment mobility of macromolecules, length of hydrocarbon part of detergent molecule, etc. and it may be significantly differ for various complexes (for details see [22]). 2. Micellar phase of complexes polyelectrolyte−detergent near the charged SAS groups is highly organized molecular system. This conclusion is made on the base EPR-spectra analysis of probe 5DSA, paramagnetic fragment of which is localized on the distance 57 Å from interface. The values of order parameter (S) of probe 5DSA in some organized molecular systems, including micellar complexes polyelectrolyte−SAS are presented below. In "free" micelles of SDS the value of S is equal to 0,3-0,37 [31], in SDS mono-layers localized on the surface of oil emulsion in water it is 0,45–0,48 [31, 35], in vesicles of dioctodecyldimethylammonium chloride − 0,6 [34], phospholipids membranes − 0,65-0,68 [37]. In complexes polyelectrolyte−SAS the values of S are equal to: PAA−DTAB, 0,44-0,46 PAA−TTAB, 0,48-0,50, PAA−CTAB − 0,55-0,56, PSS−DTAB 0,42-0,52, PSS−TTAB 0,44-0,56, PSS−CTAB 0,58-0,62, PDAC−SDD 0,61-0,62 [22], PEVP−SDD 0,62 [26]. Thus, by the level of molecular organization at least in the place of localization of paramagnetic fragment of probe 5DSA, micellar phase of complexes polyelectrolyte−SAS significantly exceeds "free" micelles and approaches to phospholipids membranes. 3. Parameter of order and correlation time of probe rotation are increased with increase of length of hydrocarbon part of detergent molecule. This is a general regularity. For

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137

example, correlation times of probe 5DSA rotation in micellar phase of polystyrenesulfonate complexes with alkyltrimethylammonium bromides are equal to: for system PSS-DTAB 1,9⋅10-9 sec, for PSS-TTAB 2,4⋅10-9 sec, for PSS-CTAB 3,2⋅10-9 sec [22]. Presented result demonstrates the role of hydrophobic interactions in formation of micellar phase of complexes polyelectrolyte−SAS. 4. Far from interface, close to micelle "site" (in that place where paramagnetic fragment of probe 16DSA is localized) molecular order of micellar phase of complexes is significantly lower, than near the interface. Obviously, far from interface hydrocarbon "tails" of detergents molecules are curved, entangled and form the medium which properties are insignificantly differed from isotropic. 5. Molecular mobility and order parameter of spin probes in soluble and insoluble complexes practically are not differed. This important result was obtained under investigation of complexes of PAA, PMAA with alkyltrimethylammonium bromide and also of complexes PDAC and PEVP with SDD with the use of various spin probes. This result means that local organization of micelle formed in soluble complexes is practically not changed under formation of insoluble complexes (see Figure 2). 6. Under transition from molecular-disperse complexes PEVP−SDD (Pw = 2000) to aggregated (Pw = 1000) differences in EPR-spectra of various spin probes were not observed [26]. Local organization and local dynamics of micellar phase of complexes don't undergo any noticeable changes at very significant reduildings of macromolecular structure of complexes in solution. Under the influence of polymer chains of various molecular masses the complexes of various sizes, structure and macromolecular organization may formed, however elementary sections of micellar phase of which complex is consisted remain practically unchangeable.

1

1

2

2 '

2A ll

3

3

20 ГС

20 ГС

'

2A l (app)

A

B

Figure 4. EPR-spectra of spin probes 5DSA (a) and 16DSA. 1 − SDD micelles, [SDD]=0,03 mole/l; complexes PEVP−(Pw=1000)−SDD: 2 − soluble complexes, 3 − insoluble complexes. Firm line presents experimental spectra, dotted line presents calculated spectra.

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A. M. Wasserman and M. V. Motyakin

2.1.2. Segment Mobility of Macromolecules in Complexes The influence of complex formation on segment mobility of polymer chains was studied on the example of PMAA complexes with DTAB, TTAB and CTAB [19], and also PEVP complexes with SDD [26]. The formula of spin-marked PMAA (PMAA*) is presented in Scheme 1; formula of spin-marked PEVP (PEVP*) is presented in Scheme 4. Content of spin marks in the case of PMAA was mark per 30 units, in the case of PEVP 1 mark was per 100 macromolecules.

CH2

CH2

CH

1% J

C2H5

CH

N

N

N CH2

CH2

CH

84%

15%

Br

C O

NH N O

Scheme 4. Formula of spin-marked PEVP*.

When determining segment mobility of spin-marked macromolecules we used the model according to which spin mark participated in two types of motion: slow isotropic rotation together with segment of macromolecule with effective correlation time τsegm and fast vibration (vibration angle α) in relation to macromolecule segment with correlation time τ1 7 macromolecule takes conformation of swollen statistical ball. Change of macromolecule conformation with change of pH is caused by the action of electrostatic repulsion forces between likely charged carboxyl groups. Change of pH leads to sharp change of EPR-spectrum of spin-marked PMAA* (Figure 5): transition of PMAA* macromolecule from compact conformation (pH=6) into conformation of swollen ball (pH=9) is accompanied by the growth of segment mobility ad angle of fast vibrations of nitroxyl. On the base comparing of EPR experimental spectra with ca;lculated ones the values of τsegm and α were determined. In compact conformation τsegm=80nsec, and α=66°, in conformation of swollen ball they are segm=20nsec, and α=100°.

EPR-Spectroscopy of Complex Polymer Systems

139

Formation of complex PMAA* with DTAB at pH=6 leads to significant changes of EPR spectra, segment mobility of PMAA* and amplitude of nitroxyl vibrations in complex (τsegm=20nsec, and α=98°) are significantly higher than for PMAA* in water solution at the same conditions and are insignificantly differed from corresponding values for PMAA* solution at pH=9. on the base of these results we may unambiguously conclude that under formation of complex PMAA*−DTAB the compact structure of PMAA is destructed that is accompanied by increase of segment mobility of macromolecule and side groups vibrations amplitude.

Figure 5. Experimental (firm line) and calculated (dotted line) EPR-spectra of spin-marked PMAA (PMAA*) and complexes PMAA*−DTAB in solution. 1 − PMAA*, pH=6; 2 − PMAA*, pH=9; 3 − soluble complex pH=6, Z=0,2; 4 − soluble complex pH=9, Z=0,2; 5 − insoluble complex pH=9, Z=1,0. Z is the ratio of mole concentrations of SAS ions and carboxyl groups in system.

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In alkali mediums at pH=9 where macromolecule is in conformation of swollen ball formation of water-soluble complexes doesn’t lead to noticeable change of segment mobility; EPR-spectrum of soluble in water complex PMAA*−DTAB is slightly differed from PMAA* spectra at pH=9 and complex's EPR-spectra at pH=6 (Figure 5). Experimental EPR-spectrum of complex PMAA*−DTAB at pH=9 is satisfactorily agreed with theoretical one, calculated with the use of almost the same parameters (τsegm=20nsec, and α=98°) used for modelling of water solution of PMAA* at pH=9 and complex PMAA*−DTAB at pH=6. Thus, segment mobility of PMAA* in soluble complexes PMAA*−DTAB is practically independent from solution pH and is insignificantly differed from PMAA* segment mobility in water solution at pH=9. One may assume that life time of single salt bond PMAA−DTAB is significantly lower than correlation time of segment motions of macromolecule and that is why formation of such bonds practically doesn’t influence on segment mobility of macromolecule. Under formation of insoluble in water complexes in which all ionic groups of PMAA are connected by salt bonds with SAS ions the sharp change of spectrum of spin-marked macromolecule is observed (Figure 5, spectrum 5). While modelling this spectrum we assume that τsegm=∞, and α=84°. In other words segment mobility of macromolecule in insoluble complex PMAA*−DTAB is strongly limited, whereas local mobility of side groups is high enough and is insignificantly differed from mobility of side groups in soluble complexes. Obviously in given case transition from soluble to insoluble complexes is accompanied by sharp increase of local concentration of macromolecules units whereas packaging density of SAS ions in micellar phase is practically not changed.

1

2

3

4

5

6

Figure 6. Experimental (firm line) and calculated (dotted line) EPR-spectra of spin-marked PEVP* (Pw=1000) in solution (1) and in complexes PEVP*−SDD at various mole ratios Z = [SAS]/[PEVP]: Z = 0,1(2); Z=0,2(3); Z = 0,3(4); Z =0,4(5); Z=1,0(6).

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141

Experimental and calculated EPR-spectra of spin-marked PEVP* in solution and also in soluble and insoluble complexes with SDD (details of calculation are presented in [26]) are presented in Figure 6. It is important to note, that EPR-spectra of all soluble complexes are the superposition of spectrum of "free" polymer in solution (Figure 6, spectrum 1) and polymer spectrum in insoluble complex (Figure 6, spectrum 6). This fact means that in given case (in contrast to complexes PMAA*−DTAB) the segment mobility of macromolecule units participating in complex formation remains constant under transition from soluble to insoluble complexes. Moreover, segment mobility of free sections of macromolecule not participating in complex formation is not changed as a result of complex formation. As a result of modelling the following values were obtained: − −

for polymer in solution τsegm(1)=9,7nsec, and α=100°; for polymer in complex τsegm(2)=25nsec, and α=75°.

Thus, in dependence on the way of macromolecule conformation change, ratio of life times of salt bonds and correlation time of macromolecule segment rotation, change of local macromolecule units density, under formation of complex polyelectrolyte−SAS segment mobility of macromolecule may be increased, decreased or remains constant.

2.2. Complexes of Linear Polyelectrolytes with Nonionic SAS Polyacids complexes (for example polyacrylic and polymethacrylic) with nonionic SAS on the base of polyethyleneglycol (PEG) are formed in water solutions at the expense of hydrogen bonds between non-dissociated carboxyl groups of polyacid and hydrogen atoms of PEG [42, 43]. At small concentrations of SAS in solution but higher than critical concentration of micelle formation (CCM) the decrease of sizes (compacting) of polymer ball occurs. Further increase of detergent content in solution leads to increase of polymer ball sizes. Observing particularities are explained by the fact that at low concentrations of SAS the complex is formed in which PEG groups of detergent molecules are connected mainly by hydrogen bonds with hydroxyl groups of polyacid. With the rise of SAS content in solution rebuilding of complex structure occurs, the associate is formed in which considerable part of PEG groups is free, not connected with macromolecule by hydrogen bonds [44]. Proposed structures of compact and swollen states of complex are presented in Figure 7. Let consider regularities of molecular dynamics of micellar phase of complexes polyacid−SAS on the example of PMAA complexes with dodecylsubstituted polyethylene glycol (DD-PEG, formula is presented below) [22, 23]. Analogous regularities were observed under investigation of PAA complexes with DD-PEG [24]. СН3(СН2)11- О – (СН2СН2О)38-Н DD-PEG

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A. M. Wasserman and M. V. Motyakin

Figure 7. Hypothetic structure of complex of polycarbonic acid with dodecylsubstituted polyethyleneglycole at low (compact ball) (a) and high (swollen ball) (b) contents of detergent in solution.

The examples of EPR-spectra of probes 5DSA (its formula is in Scheme 3) and R15 (the formula is presented below) at various mass ratios of components φ = [DD-PEG] : [PMAA] but at constant PMAA concentration (0,3 g/dl) are presented in Figure 8; in all cases SAS concentration in solution was significantly higher than CCM. It is reasonable to assume that as well as in other micellar systems the paramagnetic fragment of probe 5DSA is localized in micelle nucleus whereas of R15 probe it is close to interface:

C 15 H31CONH

.

N O

R15 EPR-spectrum of probe 5DSA in polymer complex at low content of detergent (at φ=0,5) is sharply differed from spectrum 5DSA in "free" micelle (Figure 8a). Correlation times of probe rotation (τ) calculated by model of isotropic rotation are equal to 1,8⋅10-8sec in polymer complexand to 1,9⋅10-9sec in free micelle. Formation of polymer complex is accompanied by sharp decrease of local molecular mobility of micellar phase caused by interaction of detergent molecules with polymer chain. Under the rise of detergent content up to φ=4 EPRspectra of spin probe are practically not changed. This fact means that "free" micelles are absent in system and local mobility of micellar phase in the place of localization of paramagnetic fragment of spin probe for complexes with structure φ ≤ 4 is differed insignificantly. At φ = 5 changes in spectrum are observed which may be caused for example by rebuilding of complex structure. It is not excluded however that at φ = 5 "free" micelles may be formed in the system. At φ = 10 the amount of "free" micelles is so large that EPR spectra of probe in micellar system in the presence and absence of PMAA are practically not differed.

EPR-Spectroscopy of Complex Polymer Systems

A

143

B

Figure 8. EPR spectra of spin-probe 5DSA (a) in "free" micelles DD-PEG and in the system PMAA-DDPEG at various mass ratios (φ) of components in water solution of PMAA (0,3g/dl).

Under the use of spin probe R15 more complex picture is observed. At φ = 0,5 EPRspectrum of spin probe is the superposition of spectra of spin probes and their correlation times are noticeably differed (τ1= 9·10-9sec, relative part of such probes is χ=90%, τ2=1,4·109 sec, χ=10%). In "free" micelle correlation time of probe R15 rotation is equal to 7⋅10-10 sec. these result confirm the conclusion that local mobility of detergent molecules in micelle phase of complex is significantly lower than in "free" micelle. Observing superposition of spectra is caused by dynamic micro-heterogeneity of micellar phase and allows concluding that local mobility of various parts of micellar phase of complex (where paramagnetic fragment of probe is localized) is noticeably differed. Obviously, the probes rotating relatively "slow" are localized near the detergent molecules connected by hydrogen bond with polymer chain, whereas probes rotating "fast" are situated near the detergent molecules which polyethyleneglycol groups are free and not bonded with polymer chain (Figure 7). Under the rise of SAS content in system for example at φ=1 correlation times of probes rotation localized in differing in mobility parts of complex micellar phase are practically not changed (τ1= 9·0-9sec, τ2=1,4·10-9sec), whereas relative part of probes rotating fast is increased up to 25%. Probably under the rise of micelle amount in system the part of detergent molecules in micellar complex not bonded with macromolecule (Figure 7) and consequently probes part rotating "fast" are increased. This regularity is observed also with further increase of detergent content in the system. So, at φ>1 superposition of spectra is not observed, however correlations times of probe rotation are monotonously decreased with the rise of SAS content in solution. Correlation times are equal to: at ϕ = 2, τ=3,5·10-9sec, at ϕ =3, τ=3·10-9sec, at ϕ =4, τ=2,6·10-9sec. It is important to mark that all observing particularities of spectra are connected with the change of local mobility of detergent molecules caused by rebuilding of

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A. M. Wasserman and M. V. Motyakin

complex structure. At φ=5 appearance of free micelles in system is possible and at ϕ = 10 their amount is so large that spectra of probe in micellar system in the presence and absence of polymer are practically not differed. Obtained results allow formulating general regularities of molecular dynamics of detergent molecules in micellar phase of polyacids complexes with nonionic SAS. Local mobility of detergent molecules in polymer complexes is significantly lower than in "free" micelles. This fact is caused by formation of hydrogen bonds between for example PEG groups of SAS molecules and non-dissociated carboxyl group of polyacid. In complex local mobility of SAS molecules connected with polymer chain is significantly lower than mobility of detergent's molecules not connected with macromolecule. With the rise of micelles amount the part of SAS molecules is increased in complex, which PEG groups are free and not bonded with polymer chain. As a result mobility of detergent's molecules in complex micellar phase is increased.

3. EPR-TOMOGRAPHY OF POLYMERS DESTRUCTION REACTION In the department managed by N.M. Emanuel they showed by the method of spin probe that during thermo-oxidation process the process leading to both polymer destruction and structuring might proceed. So, for example at the first stages of polyorganosiloxane oxidation on air at high temperatures destruction process occurs as a result of which low-molecular products are formed. Plasticizing action of low-molecular products leads to increase of segment mobility of polymer regusted by method of EPR-spectroscopy of spin probe. At deep stages of oxidation processes of structuring and polymer chains grafting proceed as a result of which segment mobility is sharply decreased [1, 45]. Method of EPR-tomography developed in the Institute of Chemical Physics of RAS [46] allows both detecting of molecular mobility and its change at thermo- or photo-destruction of polymer in various points of sample and registration of the distribution of oxidation active sites through the sample. This method allows identification of polymers parts in which destruction process proceeds. Solution of this problem is of great importance for selection of conditions of polymer materials exploitation. Developed in works [47-50] idea of application of EPR-tomography method for investigation of polymers destruction processes lies in the following. Hindered amine which formula is presented below is introduced into polymer. As a result of amine reaction with peroxide radicals formed during polymer oxidation process (Scheme 5) stable nitroxyl radicals are formed. Nitroxyl radicals may be formed only at those parts of polymers where there are peroxide radicals, i.e. process of thermo-oxidative (or photooxidative) destruction proceeds. Then one determines spatial distribution of nitroxyl radicals through the sample and so, it becomes possible to identify those regions of polymer in which oxidation reaction proceeds. Let consider two examples. In works [46-48] by method of EPR-tomography thermo- and photo-oxidation of poly(acrylonitrile-butadiene)styrene (ABS) copolymer were studied. This polymer is structurally and dynamically micro-heterogeneous, i.e. there are regions with high content of polybutadiene and regions with high content of polystyrene or polyacrylonitrile. In polymer

EPR-Spectroscopy of Complex Polymer Systems

145

the EPR-spectrum of nitroxyl radical resulted from hindered amine by Scheme 5 is the superposition of spectra of radicals rotating "fast" (in regions enriched by polyburtadiene) and "slow" (in regions enriched by polystyrene or polyacrylonitrile) (the inset in Figure 9).

O H

N

O

OC(C H2)8C O

N

H

P NH

POO

NO POOP

NOP POO

Scheme 5. Reactions of spatially hindered amines (see formula) with peroxide radicals.

Distribution of concentration of nitroxyl radicals resulted from hindered amine in the process of ABS-copolymer thermo-oxidative destruction through the sample thickness (concentration profile) is presented in Figure 9a. It is obvious that maximum concentration of nitroxyl is observed near the surface of sample. This fact means that in given case process of destruction proceeds mainly near the surface; in the middle of sample the process of oxidative destruction practically doesn't proceed. We should note that under oxidation namely in those regions of sample where process is the most intensive the EPR-spectrum of nitroxyl radical is changed: relative part of radicals rotating "fast" is decreased [46-48]. Consequently, during oxidation process the grafting of polymer chains occurs in regions enriched by polybutadiene; as a result segment mobility of macromolecules is decreased and consequently the rotational mobility of spin probes localized in these reasons. Concentration profile of nitroxyl radicals resulted from thermo-oxidative destruction of other polymer − ethylene copolymer with propylene is presented in Figure 9b. In this case maximum concentration of nitroxyl radicals is observed not on the borders but in the center of sample: the process of thermo-oxidative destruction proceeds mainly in sample depth [49]. We shall not carry out kinetic analysis of obtained results in this work; we shall only notice that EPR-spectroscopy is more sensitive method for polymers destruction investigation than traditional methods such as method of IR-spectroscopy [47, 50]. Presented in this work results allow concluding that method of EPR-tomography is perspective and very promising method of investigation of polymers destruction processes.

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3300

3320

3340

3360

3380

3400

Магнитное поле, Гс

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

a

thickness, mm

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

b

thickness, mm Figure 9. Distribution of nitroxyl radicals concentration by thickness of sample underwent thermo-oxidative destruction at 120°C: a − poly(acrylonitril-butadiene-styrene (ABS) copolymer), thickness of sample is 3,8mm; b − polypropylene copolymer with polyethylene, thickness of sample is 3,4mm. The inset is the example of EPR-spectrum of nitroxyl radical in ABS-copolymer.

REFERENCES [1] [2] [3]

N.M. Emanuel, A.L. Buchachenko, Chemical physics of polymers ageing and stabilization, Moscow: Nauka (1982) (in Russian). A.M. Wasserman, A.L. Kovarsky, Spin marks and probes in polymers physical chemistry, Moscow: Nauka (1986) (in Russian). A.M. Wasserman, Spin Labels and Spin Probes in Polymers. In Book: Electron Spin resonance, 15, London: The Royal Society of Chemistry (1996).

EPR-Spectroscopy of Complex Polymer Systems [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

[14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]

147

M.V. Vol'kenstain, Configuration statistics of polymer chains, Moscow, Leningrad (1959) (in Russian). P. Flory, Statistical mechanics of chain molecules, Moscow (1971) (in Russian). De Zhenn P., Idea of scaling in polymers physics, Moscow (1982) (in Russian). D.M. Sadler, in Comprehensive Polymer Science, Eds. C.Booth and C.Price, Oxford (1989). K.A. Peterson, A.D. Stein, M.D. Fayer, Macromolecules, 23, 111 (1990). T.N. Khazanovich, A.D. Kolbanovsky, A.I. Kokorin, T.V. Medvedeva, A.M. Wasserman, Polymer, 33, No.24, 5208 (1992). A.M. Wasserman, A.D. Kolbanovsky, A.I. Kokorin, T.V. Medvedeva, T.N. Khazanovich, Vysokomol. Soed., 34A, No.10, 75 (1992) (in Russian). A.Yu. Grosberg, A.R. Khokhlov, Statistical physics of macromolecules, Moscow: Nauka (1989) (in Russian). A.I. Kokorin, K.I. Zamaraev, Biofizika, 17, No.1, 34 (1972) (in Russian). A.M. Wasserman, T.N. Khazanovich, New Frontiers in Spin Probe and Spin Label SPR Spectroscopy of Polymers. In Polymer Yearbook, Hardwood Academic Publishers, 12, 153 (1995). A.D. Milov, A.G. Matyasov, Yu.D. Tsvetkov, Appl. Magn. Res., 15, 107 (1998). A.D. Milov, Yu.D. Tsvetkov, F. Formaggio, et al, Phys. Chem., Chem. Phys., 6, No.13, 3559 (2004). A.M. Wasserman, Yu.A. Zakharova, M.V. Motyakin, V.A. Kasaikin, L.A. Krinitzkaya, Vysokomol. Soed., 37B, 1561 (1995) (in Russian). А.М. Wasserman, T.N. Khazanovich, V.A. Kasaikin, Appl.Magn. Res., 10, 413 (1996). V.A. Kasaikin, Yu.A. Zakharova, M.V. Motyakin, A.M. Wasserman, Kolloid. Zh., 58, 454 (1996) (in Russian). A.M. Wasserman, Yu.A. Zakharova, M.V. Motyakin, V.A. Kasaikin, et. al., Vysokomol. Soed., 40A, 942 (1998) (in Russian). V.A. Kasaikin, A.M. Wasserman, J.A. Zakharova, M.V. Motyakin, Colloids and Surfaces, 147A, 169 (1999). Yu.A. Zakharova, M.V. Otdel'nova, I.i. Aliev, A.M. Wasserman, V.A. Kasaikin, Kolloid. Zh., 64, 170 (2002) (in Russian). A.M. Wasserman, V.A. Kasaikin, Yu.A. Zakharova, et. al., Spectrochimica Acta, 58A, 1241 (2002). L.L. Yasina, I.I. Aliev, A.M. Wasserman, V.Yu. Baranovskii, Vysokomol. Soed., 44А, 1017 (2002) (in Russian). V. Doseva, L.L. Yasina, I.I. Aliev, A.M. Wasserman, V.Yu. Baranovskii, Kolloid. Zh., 65, 1 (2003) (in Russian). A.M. Wasserman, L.L. Yasina, I.I. Aliev, V. Doseva, V.Yu. Baranovsky, Colloid. Polym. Sci., 282, 402 (2004). A.M. Wasserman, M.V. Otdel'nova, Yu.A. Zakharova, M.V. Motyakin, et. al., Khimicheskaya fizika, 24, No.3, 29 (2005) (in Russian). E.D. Goddard, K.P. Ananthapadmanabhan (Eds), Interaction of Surfactants with Polymers and Proteins, London: CRS Press (1993). E.B. Abuin, J.C. Scaiano, J. Am. Chem. Soc., 106, 6274 (1984). V.A. Kasaikin, E.A. Litmanovich, A.B. Zezin, V.A. Kabanov, Dokl. RAN, 367, 359 (1999) (in Russian).

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[30] M.V. Otdel'nova, Yu.A. Zakharova, E.M. Ivleva, et. al., Vysokomol. Soed., 45A, 1524 (2003) (in Russian). [31] V.A. Livshitz, B.G. Dzikovskii, Zh. Fiz. Khimii, 68, 1650 (1994) (in Russian). [32] A.M. Wasserman, Uspekhi khimii, 63, No.5, 391 (1994) (in Russian). [33] D.E. Budel, S. Lee, S. Sexana, J.H. Freed, J. Magn. Res., 120, 155 (1996). [34] P.J. Brat, L. Kevan, J. Phys. Chem., 96, 6849 (1992). [35] B.G. Dzikovski, V.A. Livshits, Phys. Chem. Chem. Phys., 5, No.23, 5271 (2003). [36] D.J. Schneider, J.H. Freed, Calculation slow motional magnetic resonance spectra, in L.J. Berliner, J. Reuben (Eds.) Biological Magnetic Resonance, 8, New York: Plenum Press (1989). [37] M.D. Reboiras, D. Marsh, Biochem. Biophyc. Acta Biomemr., 1063, 259 (1991). [38] V. Timofeev, B. Samarianov, Appl. Magn. Res., 4, No.4, 523 (1993). [39] V. Timofeev, B. Samarianov, J. Chem. Soc. Perkin Trans II., 1345 (1995). [40] B. Bednar, H. Moravetz, J.A. Shafer, Macromolecules, 10, 1940 (1985). [41] J. Pilar, J. Labsky, Macromolecules, 24, No.14, 4188 (1991). [42] S. Saito, T. Tanigichi, Kolloid. Z., 248B, 1039 (1971). [43] A.D. Antipina, V.Yu. Baranovskii, A.M. Papisov, V.A. Kabanov, Vysokomol. Soed., 14A, 941 (1972) (in Russian). [44] V.Yu. Baranovskii, V. Doseva, S. Shenkov, Kolloid. Zh., 57, No.3, 293 (1995) (in Russian). [45] A.L. Kovarskii, S.M. Mezhikovskii, A.M. Wasserman, Vysokomol. Soed., 15А, No.3, 650 (1973) (in Russian). [46] O.E. Yakimchenko, A.I. Smirnov, Y.S. Lebedev, Appl. Magn. Reson., 1, 1 (1990). [47] M.V. Motyakin, S. Schlick, Polymer Degradation and Stability, 76, 25 (2002). [48] M.V. Motyakin, J.L. Gerlock, and S. Schlick, In Mallinson L.G. (Ed.) Ageing Studies and Lifetime Extension of Materials, New York: Kluwer Academic/Plenum Publishers (2001). [49] M.V. Motyakin, S. Schlick, Macromolecules, 35, 3984 (2002). [50] M.V. Motyakin, Abstracts of “Modern Development of Magnetic Resonance”, Kazan, August 15-20, 83 (2004) (in Russian).

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 149-165 © 2006 Nova Science Publishers, Inc.

Chapter 14

ORGANOSILICON COPOLYMERS WITH CARBOCYCLOSYLOXANE FRAGMENTS IN DIMETHYLSILOXANE BACKBONE O. Mukbaniani*1, G. Zaikov2, N. Mukbaniani1 and T.Tatrishvili1 1

2

I.Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Nowadays the reactions of hydride polyaddition are in a great use in siliconorganic chemistry. Recently a great importance is paid to this reaction in the field of obtaining complicated monomers [1] and also in the field of investigation the mechanisms of additions on the various catalyst systems Pt, Pd, Co, carbonyl of metals and investigation of specificity of actions of various catalytic systems [2-5]. From literature it’s known, that introduction of cyclic fragments in dimethylsiloxane chain is resulted in variation of the spiral-shaped structure of dimethylsiloxane polymers, which causes variation of their physical and chemical properties [6]. For the purpose of increasing the thermal-oxidative stability of siliconorganic polymers a great importance is paid to the method of synthesis of functional group containing organocyclosiloxanes and to the methods of modification of linear siloxane chains by single or condensed cyclic fragments by using reactions of hydride polyaddition. Besides HFC reaction of preliminarily prepared cyclic organosiloxanes with functional groups and difunctional organosilicon compounds, which give an opportunity to preserve cyclic groups in the polymeric backbone, hydride polyaddition is also widely used, which proceeds under soft conditions and does not involve cyclic structures, introduced into the backbone [7-9]. The synthesized carbosiloxane copolymers with disilylethylene groups in the main chain possess less thermal-oxidative stability in comparison with polyorganosiloxane analogues, but they have greater thermal stability at the absence of oxygen [9].

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Reviewed in this paper is synthesis of cyclolinear carbosiloxane copolymers with regular disposition of mono-, bi- and tricyclic fragments in dimethylsiloxane backbone using hydride polyaddition reaction as the method for synthesis of polymers.

1. CARBOSILOXANE COPOLYMERS WITH MONOCYCLIC FRAGMENTS IN THE CHAIN For the purpose of synthesizing poly(carbosiloxane) with cyclic tetrasiloxane fragments in the methyl siloxane backbone, hydride polyaddition of divinylorganocyclosiloxane by dihydrodimethylsiloxane was studied [10]. Polymers were synthesized in argon at 1:1 molar ratio of the initial reagents in the absence of diluter or in inert organic solvent (toluene) at 100 - 110°C. The reaction temperature was selected at the level causing no scission of organosiloxane rings. Platinum hydrochloric acid, double added to the reaction mixture in amount 1÷1.5×10-5 g of H2PtCl6x6H2O per 1 g of the initial mixture, was used as the catalyst. A half of this amount was added before the reaction initiation, and the second half 25÷140 hours after beginning of heating. Platinum hydrochloric acid was added in the form of 0.01 M solution in tetrahydrofuran. Isopropyl alcohol, used as diluter for H2PtCl6x6H2O, decreased relative viscosity of synthesized polymers, apparently, due to proceeding of side alkoxylation reaction: ≡Si-H+HO-C3H7 → ≡Si-O-C3H7 +H2 Linear poly(organocarbosiloxanes) with cyclic structures in the backbone were synthesized in ac-cordance with the following scheme [10]:

x [Me2SiO]2[MeVinSiO]2 +x H(SiMe2O)n-1SiMe2H

H2PtCI6

Me2 Si Me Me O O CH2-CH2 Si Si-CH2CH2-(SiMe2O)n-1SiMe2 O O Si Me2 I

x

Scheme 1

where n = 0, 1, 4, 5, 6, 10, 20, 27, 34, 57, 94, 150, 200. Synthesized polymers represent viscous and highly viscous colorless transparent liquids, soluble in cyclic hydrocarbons and lower eaters. The effect of reaction proceeding in an inert organic solvent (for example, toluene) on inherent viscosity of derived polymer is negligible. Obtaining of high viscosity values in the presence of solvent requires just longer-term heating up of the reaction mixture. To the authors’ point of view, polymers of such structure,

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

151

possessing cyclic fragments in the backbone, are of interest due to their high reactivity. For example, these polymers are capable of easy formation of cross-linked structures in anionic catalysts. Initial divinylhexamethylcyclotetrasiloxane was synthesized by combined hydrolysis of dimethyldichlorosilane and methylvinyldichlorosilane. Despite the appli-cation of efficient rectification columns and analytical chromatograph with preparative add-on device, the attempts of the authors to separate isomeric 1,3- and 1,5divinylhexamethylcyclotetrasiloxanes, which may be formed in cooperative hydrolysis, have failed. That is why isomeric structural groups as follows (XIII) may also be present in synthesized polymers:

Me CH2-CH2 Si

Me O

O Me2Si

Si-CH2-CH2-(SiMe2O)n-1SiMe2 O

O

SiMe2 II

x

Semi quantitative assessment of the ratio of isomeric 1,3- and 1,5-cyclic structures in synthesized polymers with the help of NMR spectra was performed, which was found 1:1. In a series of processes variation of functional groups’ content (≡Si-H due to IRspectroscopy data) during reaction proceeding and type of the increase of reaction mixture specific viscosity were studied. Maximal viscosities of polymers ([η] = 0.17 - 0.97 dl/g) are reached after 50 – 160 hours of heating and in majority of cases depend on the length of α,ω−dihydropolydimethylsiloxane chain and purity of initial compounds used. Studies of IR spectra of synthesized poly(organocyclocarbosiloxanes) and preliminary experiments on long-term heating of the mixture of initial hexamethyldivinylcyclotetrasiloxane isomers under polyaddition conditions allow a suggestion that polymers are synthesized due to hydride polyaddition proceeding with preservation of structures of initial compounds, but not polymerization of cyclic hexamethyldivinylcyclotetrasiloxane. The presence of organocyclotetrasiloxanes fragments in the structure of synthesized poly(organocyclocarbosiloxanes) may be proved by their transition into non-fusible, insoluble state due to polymerization of organosiloxane cycles existing in the polymer structure. As reprecipitated polymers are heated at 100-110°C in the presence of 0.001–0.01 wt % of anionic polymerization catalysts, viscosity is considerably increased and gel is formed. Varying length of alkylenesiloxane bridge between organocyclotetrasiloxanes fragments of poly(organocyclocarbosiloxanes) backbone, one may change the average distance between cross-link points and, consequently, properties of cross-linked polymers formed. Hydride polyaddition between 1,5-divinyl-1,5-dimethyl-3,3,7,7-tetraorganocyclotetrasiloxane and me-thylphenylsilane has been studied [11]. All attempts to separate initial divinylorganocyclotetrasi-loxanes into cis- and trans-isomers have failed. Thus, according to NMR data, initial divinylorgano-cyclotetrasiloxanes represent a mixture of cisand trans-isomers. The reaction proceeds as follows:

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CH2=CH2

x CH2=CH

Me

Me

+ x H Si H Ph

H2PtCI6 0

TC

Me

R' R"

CH2

R' R"

Me CH2-CH2 Si CH2 Ph Me

R' R"

x

I Scheme 2

Where: R′ = R′′ = Me = Ph; R′ ≠ R′′. Polyaddition was carried out at 60 – 70°C, and at the final stage the mixture was heated up to 100°C. The catalyst in amount 5×10-4 mol Pt/mol was added to vinylcyclosiloxane, heated up to 50°C. Some parameters of synthesized copolymers are shown in Table 1. For the purpose of synthesizing carbosiloxane copolymers with organocyclopentasiloxane fragments in the dimethylsiloxane backbone, hydride polyaddition of α,ωdihydridedimethylsiloxanes to l,5-ivinyl-l,5-dimethylhexaphenylcyclopentasiloxane in the presence of platinum hydrochloric acid as a catalyst was studied at temperatures below 100°C: at 75°C, 80°C and 85°C. Forasmuch as the initial 1,5-divinyl-1,5dimethylhexaphenylcyclopentasiloxane represents a mixture of cis- and trans-isomers (at the ratio copolymers derived from them are atactic. Preliminary heating of initial compounds within the temperature range of 80 - 95°C in the presence of the catalyst indicated that under these conditions organocyclopentasiloxane fragments are not polymerized. Table 1. Physical and chemical parameters of poly(organocarbosiloxane) copolymers of cyclolinear structure

No

1 2 3

Copolymer

Me CH2

R' R"

R' R" *

Me CH2-CH2 Si CH2 Ph Me

R′

R′′

[ η], dl/g

Me Me Ph

Me Ph Ph

0.08 0.06 0.04

Tdegr* of 5% mass Loss

Coke residue, (800°С), %

240 320 370

52 45 41

Тg, °С

-7 26 13

x

TGA data on polymers processed by heptamethylvinylcyclotetrasiloxane.

Copolymer structure was determined from 29Si NMR spectral data. The reaction proceeding was detected by a decrease of amount of active ≡Si-H groups. It was observed that the rate and depth of pol-yaddition decrease with the increase of α,ωdihydridedimethylsiloxanes chain length. Hydride polyaddition proceeds in accordance with the following scheme 2 [12,13]:

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

Ph2

Vin x Me

153

Me H PtCI + xH(SiMe2O)n-1SiMe2H 2 0 6 TC Vin

Ph2 Ph2 Ph2 Me CH2-CH2 (SiMe2O)n-1SiMe2CH2

CH2 Me

Ph2 Ph2

x

III

Scheme 3

Where: n = 2 ÷23. Table 2. Physical and chemical parameters of structure III carbosiloxane copolymers containing cyclopentasiloxane fragments

№

Copolymer

nSiO

1 2 3 3′ 3′′

CH2

Ph2 Me

Me Me C2H4 (SiO)n-1SiCH2 Me Me

Me Ph2 Ph2

4 5 *

x

Yield, %

Reactio n T,0C

η*sp

Tg, 0 C

d1 , Å

5% mass losses

Μω x10-3

2

75

85

0.09

0÷-2

9.20

320

189

4

80

85

0.14

-22

-

-

-

6

92

75

0.15

-

-

-

-

6

93

80

0.18

-

-

-

-

6

95

85

0.20

-53

-

295

211

12

95

85

0.24

-82

-

-

-

23

96

85

0.31

-123

7.21

285

236

0

In toluene at 25 C

As a result of the reaction, copolymers with ηspec = 0.09 – 0.26 are obtained, which are liquid or glassy light-yellow products, soluble in ordinary organic solvents. Some physical and chemical parameters and the yield of copolymers are listed in Table 2. As indicated by the data in the Table, in the case of short lengths of the dimethylsiloxane backbone, n, the yield of copolymers is low. This may be explained by the fact that besides intermolecular reaction, intramolecular cyclization proceeds forming a polycyclic structure. This conclusion is in agreement with data from the literature [13 - 18]. The amount of active ≡Si-H groups was decreased during proceeding of hydride polyaddition. Figure 1 shows that the rate of hydride polyaddition increases with temperature (at one and the same values of dimethylsiloxane units, n), but on the other hand, with an increase of the length of dimethylsiloxane links (n) at the same temperatures, the rate of hydride polyaddition decreases. Figure 1 shows that conversion of active ≡Si-H groups is not complete and decreases from 20% (n = 6) to 15% (n = 12).

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Figure 1. Time dependence of changes in active ≡Si-H% groups during polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) with 1,5-divinyl-1,5-dimethylhexaphenylcyclo-pentasiloxane: 1 - at 85°C; 2 - at 80°C and 3 - at 75°C.

It was found that polyaddition is the second order reaction. The reaction rate constants and the activati-on energy were calculated: k75oC=1.4004×10-2, k80oC=1.965×10-2, k85oC=2.559×10-2 l/mol⋅s; Eact=62.1 kJ/mol, respectively. 1 H NMR spectra of copolymers indicate that catalytic hydride polyaddition mainly proceeds by the Farmer rule with formation of dimethylenic bridges. In these spectra a reflex of –СН2-СН2- group with chemical shift δ=0.34 ppm is observed; it is indicated that hydride polyaddition partly (about 6-7%) proceed by the Markovnikov rule. Cyclolinear carbosiloxane copolymers with 1,7- and 1,5-disposition of dimethyloctaphenylcyclohexa-siloxane fragments in the dimethylsiloxane backbone were synthesized by hydride polyaddition of α,ω-dihydridedimethylsiloxane to 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyloctaphenylcyclohexasiloxane in the presence of a catalyst. Polyaddition reactions were studied below 100°C. It was also indicated that under these conditions polymerization or polycondensation of initial compounds does not take place. Polyaddition proceeds in accordance with the following scheme 3 [19-21]:

Me x Vin

Me

O(SiPh 2 O) l Si

Si

+ xH (SiM e 2 O) n-1 SiMe 2 H

O (SiPh 2 O) m Vin Me CH2 Si

Me

O(SiPh2O)l

Si C2H4 O(SiPh2O)m IV, V

Scheme 4

H 2 PtCI 6 0

T C

Me Me (SiO)n-1SiCH2 Me Me

x

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

155

Where: m = l = 2 (IV); n = 2 ÷ 23; l = 1, m = 3 (V); n = 2 - 23. Forasmuch as 1,7- and 1,5-divinylcyclohexasiloxanes, used in polyaddition, represent mixtures of cis- and trans-isomers of the approximate 52:48 ratio, synthesized copolymers are atactic. Reprecipitation of copolymers from toluene solution by methyl alcohol has given viscous or solid (with regard to the value of flexible junction) transparent products with ηspec=0.09-0.29, well soluble in different organic solvents. It is found that at short length of dimethylsiloxane unit (n ≤ 4), copolymer yields are slightly decreased that may be explained by partial proceeding of hydride polyaddition by intramolecular cyclization mechanism (see Tables 3 and 4). Table 3. Physical and chemical parameters of carbosiloxane copolymers with 1,7disposition of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure IV) №

Copolymer

1 2 3 3′ 3′′ 4 5 *

Me

Ph 2 Ph 2

Me

Ph 2 Ph 2

Me Me C 2H 2 (SiO)n-1SiCH 2 Me Me x

nSiO

Yield, %

Reaction T,0C

η*sp

Tg, 0 C

d 1, Å

2 4 6 6 6 12 23

74 80 94 94 95 96 95

90 90 80 80 85 90 90

0.10 0.12 0.17 0.17 0.18 0.23 0.29

+5 -10 -40 -68 -123

9.31 8.81 8.40 7.24

5% mass losses 280 280 260

Μωx1 0-3 174 194 231

In toluene at 25°C.

After solvent removal from the mother solution of re-precipitated copolymer 1 (Table 2), a semicry-stalline compound with the molecular mass equal ~1100 was obtained [20, 21]. The product of intra-molecular cyclization of 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,3-dihydride-tetra-methyldisiloxane of the following structure only may display the current molecular mass: because divinylorganocyclohexasiloxane of the trans-structure participates in formation of macromolecular chain. Table 4. Physical and chemical parameters of carbosiloxane copolymers with 1,5– position of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure V) № 1 2 3 3′ 3′′ 4 5 *

Copolymer

Ph2 Me Me Me C2H2 (SiO)n-1SiCH2 Me Me Ph2 Ph2 Ph2 x

Me

In toluene at 25°C.

Tg, 0 C

d 1, Å

0.09

+8

9.60

5% mass losses 270

0.11

-12

-

-

-

0.15 0.18 0.15 0.22 0.28

-38 -72 -123

8.90 8.34 -

265 260

180 210 -

nSiO

Yield, %

Reaction T,0C

η*sp

2

72

10

4

84

85

6 6 6 12 23

86 89 94 95 95

80 90 100 100 100

Μωx1 0-3 159

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Structure and composition of synthesized cyclolinear carbosiloxane copolymers were determined by functional and ultimate analysis, IR and NMR spectral data. Some parameters of copolymers are shown in Tables 3 and 4. A reflex with chemical shift at δ = 0.35 ppm typical of –СН2-СН2-group is observed in 1 Н NMR spectrum of copolymer 1 (Table 3). This indicates that polyaddition proceeds pursuant to the Farmer rule. A duplet centered at δ=1.06 ppm, corresponded to methyl protons in =СН-СН3 group, is also observed in the spectrum. Based on the ratio of intensities, it was concluded [20, 21] that polyaddition partly proceeds by the Markovnikov mechanism (6 –8%). A complex multiplet with chemical shift at δ=5.6 - 6.2 ppm typical of vinyl protons not entered polyaddition reaction, and a singlet for ≡Si-H protons with chemical shift at δ = 4.4 ppm, not participated in the reaction, too, were observed in the spectra. Hydride polyaddition proceeded at different temperatures. Figures 2 and 3 show variations of ≡Si-H bond concentration during polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyloctaphenylcyclohexasiloxane. It is observed that hydride polyaddition depth is increased with the reaction temperature. Moreover, the effect of 1,7- or 1,5-disposition of vinyl groups in cyclohexasiloxane fragments is the negligible factor for their reactivity. It is found that at the initial stages, polyaddition represents the second order reaction. In the case of 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane, polyaddition rate constants for different tempera-tures were determined as follows: k90oC = 3.0797×10-2; k85oC =2.3007×10-2; k80oC = 1.6781×10-2 l/mol⋅s. Activation energies for 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyl-octaphenylcyclohexasiloxane were also calculated: Еact= 66.7 and Eact =69.7 kJ/mol, respectively. Obviously, these values are very close.

Figure 2. Decrease of ≡Si-H bond concentration during hydride polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,7-divinyl-1,7-dimethyloctaphe-nylcyclohexasiloxane: 1 - 90°C; 2 85°C; 3 - 80°C.

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Figure 3. Decrease of ≡Si-H bond concentration during hydride polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,5-divinyl-1,5-dimethyloctaphenyl-cyclohexasiloxane: 1 - 100°C; 2 - 90°C; 3 - 80°C

X-ray diffraction studies have indicated that copolymers are single-phase amorphous systems, and maximal interchain distance is observed for short dimethylsiloxane unit length (n = 2); hence, for copolymer 1 (Table 4), d1 = 9.60 Å. This value is slightly greater than the interchain distance of carbosiloxane copolymer 1 (Table 3) with 1,7-disposition of cyclohexasiloxane fragment in the dimethylsiloxane backbone (n = 2). As flexible junction length is increased, d1 decreases and approaches the interchain distance in PDMS; it increases with the volume of cyclic fragment at the same lengths of flexible dimethylsiloxane unit, i.e. at transition from cyclopentasiloxane to cyclohexasiloxane fragment. Thermogravimetric studies of carbosiloxane copolymers have indicated 5% mass loss of the compounds in the temperature range of 250 - 260°C. The main degradation process proceeds in the range of 380 - 630°C, and above 700°C the mass loss is not observed. It is found that thermal oxidative stability of copolymers is decreased with increase of the cyclic fragment volume, i.e. at the transition from cyclic pentasiloxane to hexasiloxane fragments in cyclolinear carbosiloxane copolymer. It is also found that carbosiloxane copolymers with 1,7and 1,5-disposition of cyclic hexasiloxane fragments in the backbone are characterized by almost identical thermal oxidative stability. Thus, it was concluded [20, 21] that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane fragment in carbosiloxane copolymer is negligible for thermal oxidative stability of copolymers (Figure 4). On the other hand, compared with pure siloxane analogues, thermal oxidative stability of carbosiloxa-ne copolymers is lower. Thermogravimetric studies have displayed that the cyclic fragment causes a considerable effect on carbosiloxane copolymer at n=12 only, and at n=23 no effect of cyclic fragment on the glass transition temperature of the copolymer is observed. Figure 5 shows dependence of Tg on the length of dimethylsiloxane unit for cyclolinear carbosiloxane copolymers.

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Figure 4. Thermogravimetric curves of carbosiloxane copolymers: 1 – copolymer 4 (Table 4) with 1,5disposition of cyclic hexasiloxane fragment in the backbone; 2 –co-polymer 1 (Table 3) with 1,7-disposition of cyclic hexasiloxane fragment in the back-bone; 3 – copolymer 1 (Table 2) with cyclic pentasiloxane fragment in the backbone.

Figure 5. Dependence of Tg for cyclolinear carbosiloxane copolymers on the length of dimethylsiloxane unit: 1 – copolymer with 1,7-position of cyclic hexasiloxane fragment; 2 – copolymer with 1,5-position of cyclic hexasiloxane fragment.

It has been found that expansion of the cyclic fragment volume at the same length of dimethylsiloxane unit, i.e. introduction of a single diphenylsiloxane unit, Tg of the copolymer is increased by ~10°C. It is also shown that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane fragment on Tg of the copolymer is negligible, which conform to the previous results on pure siloxane copolymers [22].

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2. CARBOSILOXANE COPOLYMERS WITH TRICYCLIC FRAGMENTS IN THE BACKBONE The present Chapter discusses synthesis and studies of carbosiloxane copolymers containing flexible dimethylsiloxane and decaorganotricyclodecasiloxane fragments in the backbone [23, 24]. For the purpose of synthesizing carbosiloxane copolymers, hydride addition of α,ω-dihydridedimethylsiloxane to 1,3-divinyl-1,3,9,9,11,11-hexamethyl5,7,13,15-tetraphenyltricyclodecasiloxane was performed at temperature below 90°C. Therefore, cyclosiloxane ring disclosure did not take place under conditions of hydride polyaddition. Preliminary heating of initial divinylorganotricyclodecasiloxane during 10 hours by temperature of 70 - 90°C in the presence of rhodium acetylacetonatedicarbonyl or platinum hydrochloric acid as a catalyst did not initiate polymerization of the primary divinyltricyclodecasiloxane. Thorough analysis of the reaction mixture by gas liquid chromatography method has detected the presence of initial organosiloxanes. Besides, there are no changes in the NMR and IR spectra of divinyl-containing compounds and dihydridedimethylsiloxanes. Hydride polyaddition of divinyl-containing compounds was carried out for various lengths of α,ω-dihydridedimethylsiloxanes. The reaction run was searched by a decrease of active ≡Si-H groups’ concentration. It was found that for rhodium acetylacetonatedicarbonyl as a catalyst, copolymers soluble in organic solvents were obtained, which were structured after some time. This may be explained by the fact that in spite of polymers re-precipitated from toluene solution by methyl alcohol, rhodium catalyst remains in polymeric systems, which decompose and induce structuring (cross-linking) of copolymers. Therefore, copolymers were synthesized in the presence of platinum hydrochloric acid as the catalyst. The rate and depth of polyaddition are decreased with the increase of α,ωdihydride-dimethylsiloxane chain length. Figure 6 shows that conversion of ≡Si-H bond is incompletely and decreases from 95% (n = 4) to 83% (n = 12). Hydride polyaddition of α,ω-dihydridedimethylsiloxane to divinylorganotricyclodecasiloxane proceeds in accordance with the general scheme as follows [23, 24]: R m Vin

R Vin + mH(SiMe2O)n-1SiMe2H

Cat

R

R

C2H4

C2H4-(SiMe2O)n-1 SiMe2

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Me2

Me2

Me2

Me2 VI

Scheme 5 Where: n = 2 ÷21; Cat is H2PtCl6.

m

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Figure 6. Time dependence of ≡Si-H group concentration (%) for polyaddi- tion of α,ωdihydridedimethylsiloxane to divinylorganotricyclodecasiloxane at 90°C for dimethylsiloxane backbone lengths: 1) n = 12; 2) n = 6; 3) n = 4

As a result of the reaction, synthesized copolymers possess ηspec = 0.08 -0.26 and represent liquid or glassy-like light yellow transparent products, soluble in ordinary organic solvents. Some physical and chemical parameters, molecular weights and yields of synthesized copolymers are shown in Table 6. Table 6. Some physical and chemical parameters of carbosiloxane cyclolinear copolymers with tricyclodecasiloxane fragments in the backbone №

1 2 3 4 5 6 7 *

Copolymer structure

R C2H4

nSiO

R C2H4(SiMe2O)n-1SiMe2

Ph

Ph

Ph

Ph

Me2

Me2

m

2 4 4 4 6 12 21

Yield, % 80 83 88 91 92 93 94

Treact, 0 C 90 70 80 90 90 90 90

η*sp

Tg, 0C

d1,Å

Μω*10-3

0.08 0.09 0.11 0.11 0.14 0.20 0.26

-12 -50 -96 -123 -123

10.20 8.68 7.54

72 85 110

In toluene at 25°C; molecular masses were determined by the gel chromatography method.

The reaction proceeding was also monitored by viscosity increase of synthesized copolymers. It was found that viscosity of copolymers and the hydride polyaddition degree increase with temperature rise to 70 - 90°C. In hydride polyaddition of α,ωdihydridedimethylsiloxane to divinylorganotricyclodecasiloxane, conversion of ≡Si-H bond increases with temperature as follows: from 85% (70°C) to 95% (90°C). Figure 7 shows time dependence of ≡Si-H concentration (%) decrease for various temperatures. Time dependence of reverse reagent concentration displays the second order of hydride polyaddition. Further on, reaction rate constants for various temperatures were calculated:

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

161

k700C≈1.1086x10-2, k800C≈ 1.6196x 10-2, k900C≈2.3834x10-2 l/mol⋅s. It was shown that the reaction rate constants increase by 1.5 times, approximately, for every 10°C of temperature rise. Activation energy of hydride polyaddition was derived from dependence of the reaction rate constant logarithm on reverse temperature: Eact=64.4 kJ/mol.

Figure 7. Time dependence of ≡Si-H group concentration (%) in polyaddition of α,ωdihydridedimethylsiloxane (n = 4) to divinylorganotricyclodecasiloxane: 1 - 90°C; 2 - 80°C; 3 - 70°C

Study of 1H NMR spectrum for copolymer 2 (Table 6) displays that catalytic hydride polyaddition mainly proceeds by the Farmer rule with formation of dimethylene bridges. NMR spectrum also displays a reflex of -CH2-CH2- group with chemical shift of δ=0.35 ppm. A duplet reflex centered at the chemical shift of δ=1.12 ppm, corresponded to methyl protons in =CH-СН3 groups with 5–6% concentration was also observed. Integral ratios of methyl and phenyl protons correspond to the formula of copolymer 2(Table 6).

Figure 8. Tg dependence of cyclolinear carbosiloxane copolymers (VI) on length of linear poly(dimethylsiloxane), n.

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Thermomechanical studies of synthesized copolymers indicate that the glass transition temperature of copolymers is decreased with an increase linear dimethylsiloxane backbone length, n (Figure 8). Since n=12 carbotricyclodecasiloxane fragments in copolymers cause no effect on the dimethylsiloxane backbone and Tg of copolymer 6 (Table 6) remains equal 123°C. Contrary to previous considerations [25], dimethylsiloxane backbone length increase (n=21) does not cause formation of two-phase systems in cyclolinear copolymers with rigid decaphenyltricyclodecasiloxane fragments and flexible dimethylsiloxane units (n = 25). Comparison of copolymers containing carbotricyclodecasiloxane and tricyclodecasiloxane fragments [[25] displayed lower glass transition temperatures of the former, which may be explained by excessive concentration of flexible -CH2-СН2- groups in its backbone.

Figure 9. Thermogravimetric curves of cyclolinear carbosiloxane copolymers: 1 - copolymer 7; 2 copolymer 5; 3 - copolymer 1(Table 6, in air, at 5 deg/min heating rate)

Thermogravimetric studies of copolymers show (Figure 9) their higher thermal oxidative stability for short length of the dimethylsiloxane backbone, n. As the length of dimethylsiloxane backbone increases, thermal oxidative stability of copolymers decreases. Compared with siloxane analogies, thermal oxidative stability of carbotricyclodecasiloxanecontaining copolymers is lower [25]. In the temperature range of 300 - 350°C mass losses of the polymer are below 3 - 7%, and the main degradation process proceeds at 400-650°C. Above 650°C, the curves of mass losses are preserved unchanged (Figure 9). As carbotricyclodecasiloxane fragments are introduced into the dimethylsiloxane backbone, the main degradation process proceeds at temperature by 80 - 100°C higher than for unblocked poly(dimethyl-siloxane).

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Synthesized copolymers were studied by the X-ray diffraction method. Diffraction patterns of amorphous polymers (Figure 9) show that the interchain distance reaches its maximum (d1=10.24 Å) at short lengths of flexible dimethylsiloxane backbone, n. As the length of dimethylsiloxane backbone increases (n = 21), the interchain distance decreases and for copolymer 5 reaches 7.54 Å (Table 6).

Figure 10. Diffraction patterns of copolymers: 1 - copolymer 5; 2 – copolymer 1 (Table 6).

Thus copolymer 7 does not form a two-phase system, as observed for copolymers with decaphenyltricyclodecasiloxane fragments in the dimethylsiloxane backbone. This may be explained by the presence of combination of rigid carbotricyclosiloxane and flexible dimethylsiloxane fragments in it. Therefore, copolymers represent single-phase systems. For the purpose of synthesizing carbosiloxane copolymers with tricyclohexasiloxane fragments in the backbone, hydride polyaddition of α,ω-dihydridepoly(dimethylsiloxanes) to 1,7-divinyl-1,7-dimethyl-3,5,9,11-tetraphenyltricyclohexasiloxane was studied [26]. The reaction was implemented in anhydrous toluene in the presence of platinum-hydrochloric acid in tetrahydrofuran and in the temperature range of 70 – 170°C according to the following scheme:

Ph x

Ph

O

R Si Vin

Me Me Me + x H-Si-O-(Si-O)-Si-H Si n Vin Me Me Me O R

O

O Ph

H2PtCI6

Ph

R

Ph O

Ph O

C2H4 Si

R Si C2H4 (SiMe2O)n+2

O Ph

O Ph VII

Where: R = Me, Ph; n = 0 ÷ 86.

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New cyclolinear carbosiloxane copolymers containing organotricyclohexasiloxane fragments in backbones were synthesized in the reaction. They represent viscous liquids with molecular mass varying in the range of 35x103 - 45 x103. The influence of organotricyclohexasiloxane fragments in carbosiloxane copolymer on thermal oxidative degradation proceeding was studied. It is found that the increase of concentration of rigid organo-tricyclohexasiloxane fragments in linear chains of polymers rise their resistance to thermal oxidative degradation. For example, 15% mass loss of structure VII copolymers (R =Ph, n = 74 and R = Me, n = 86) is observed at 380 and 420°C, respectively. For copolymer with n = 0, it is observed at 540°C. Thus, the increase of cyclic fragments’ concentration in the linear chain induces rise of macromolecular chain rigidity and leads to formation of a one-phase system. The increase of cyclic fragments’ concentration in the macromolecular chain raises thermal oxidative stability of the copolymers.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8]

[9] [10] [11] [12]

[13]

Pomerenceva M.G., Beliakova Z.V., Golubtsova S.A. In the book “obtaining carbofunctional organosilanes by addition reaction”. M., NIITEkhim., 1971. (Rus) Reikhsfeld V.O., Vinogradova V.N., Fillipova N.A. Zhurn. Obshch. Khim., 1973, v.43, №10, p. 2216. (Rus) Fillipova N.A., Reikhsfeld V.O., Zaslavskaia T.N., Kuzmina T.A. Zhurn. Obshch. Khim., 1977, v. 47, №6, p.1374. (Rus) Andrianov K.A., Magomedov G.K. Dokl. AN USSR, 1973, v. 228, No5, p. 1094. (Rus) Watanabe H,m Kitahara T., Motegi X., Nagai H. Journ. Organometallic Chem., 1977, v.139, No2, p.215. (Rus) Mileshkevich V.P., Kauchuk i Resina, 1978, № 6, p. 4. (Rus) Andrianov K.A., Souchek I., Khananashvili L.M. Uspekhi Khimii, 1979, v. 48(7), p.1233. Mukbaniani O.V., Zaikov G.E. New Concepts in Polymer Sciences, Cyclolinear Organosilicon Copolymers: Synthesis, Properties, Application, VSP, Utrecht-Boston, 2003, p. 499. Severni V.V., Flaks E.Yu., Zhdanov A.A., Vlasova V.A., Andrianov K.A., Vishnevski F.N. Vysokomol. Soedin., 1974, v.16(A) (2), p. 419. (Rus) Zhdanov A.A., Andrianov K.A., and Malyikhin A.P., Doklady AN SSSR,1973, v. 211(5), p. 104. (Rus) Zhdanov A.A., Pryakhina T.A., Strelkova T.V., Afonina R.I., and Kotov V.M., Vysokomol. Soed., 1993, v. 35(5), p. 475. (Rus) Karchkhadze M.G., Mukbaniani N.O., Samsonia A.Sh., Tkeshelashvili R.Sh., Kvelashvili N.G., Chogovadze T.V., and Khananashvili L.M., Bull.Georg. Acad. Sci., 1998, v. 158(1), p. 75. Mukbaniani O.V., Organosiloxane Copolymers and Block-copolymers With Different Cyclic Structure of Macromolecules, Doctor’s Dissertation on Chemistry, 1993, Tbilisi State University, Tbilisi, Georgia. (Rus)

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[14] Koiava N.A., Mukbaniani O.V., and Khanashvili L.M., Vysokomol. Soedin.,1985, v. 27A, №11, p. 2261. (Rus) [15] Koiava N.A., Mukbaniani O.V., and Khananashvili L.M., Abstr. Commun.27th Intern. Symp. Macromol., Strasburg, 1981, p. 18. [16] Mukbaniani O.V., Meladze S.M., and Khananashvili L.M., Vysokomol.Soedin., 1984, v. 24B №4, p. 250. (Rus) [17] Andrianov K.A., Nogaideli A.I., Makarova N.N., and Mukbaniani O.V., Izv. AN USSR, Ser. Khim., 1977, №6, p. 1388. (Rus) [18] Zhdanov A.A. and Astapova T.V., Vysokomol. Soedin., 1981, v. 23A, №3, p. 626. (Rus) [19] Mukbaniani N.O., Synthesis and Investigation of Properties of Carbosiloxane Cyclolinear Copolymers, Candidate’s Dissertation on Chemistry, 2001, Tbilisi State University, Tbilisi, Georgia. [20] Karchkhadze M.G., Mukbaniani N.O., Khananashvili L.M., Meladze S.M., Kvelashvili N.G., and Doksopulo T.P., Intern. J. Polym. Mater., 1998, v.41, p. 89. [21] Mukbaniani N.O., Karchkhadze M.G., Samsonia A.Sh., Tkeshelashvili R.Sh., and Khananashvili L.M., Bull. Georg. Acad. Sci., 1999, v. 160, №1, p. 84. [22] Andrianov К.А., Tsvetkov V.N., Tsvankin D.Y., Nogaideli A.I., Makarova N.N., Vitovskaia M.G., Genin Y.V., Kolbina G.F., Mukbaniani O.V. Vysokomol. Soed., 1976, v.18А, № 4, p.890. [23] Mukbaniani O.V., Khananashvili L.M., Karchkhadze M.G., Tkeshelashvili R.Sh., and Mukbaniani N.O. In: Synthesis and Properties of Polymers, Nova Science Publishers, Inc., Commack., 1996, p.89. [24] Mukbaniani O.V., Khananashvili L.M., Karchkhadze M.G., Tkeshelashvili R.Sh., and Mukbaniani N.O. Intern. J.Polym. Mater., 1996, v.33, p.47. [25] Inaridze I.A., Synthesis and Investigations of Polyorganosiloxanes with organocyclosiloxane and orgacarbocyclosiloxane Fragments in the Chain, Candidate’s Dissertation on chemistry, Tbilisi State University, 1993, Tbilisi, Georgia. [26] Klementiev I.Yu., Investigations in the Field of Synthesis and Transformation of Polycycloorganosiloxanes, Candidate’s Dissertation on chemistry, M.V. Lomonosov Institute of Fine Chemical Technology, 1979, Moscow, USSR. (Rus).

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 167-216 © 2006 Nova Science Publishers, Inc.

Chapter 15

ORGANOSILICON OLIGOMERS AND COPOLYMERS OF BEAD-SHAPED STRUCTURE O. Mukbaniani1, G. Zaikov2 and T.Tatrishvili1 1

2

I. Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION The present state of the synthesis of silicon organic oligomers and polymers of beadshaped struc-ture is reviewed by condensation techniques, but not by polymerization or exchange polymerization, because in the latter cases, primary siloxane procurements may not be preserved due to instability of ≡Si-О-Si≡ bond in cyclosiloxanes. Equilibrium rigidity of cyclolinear polyorganosiloxanes, macromolecules of which are composed of different sized rings linked by oxygen atoms or other flexible bond bridges, depends upon the number of flexible units both in the ring and linear chain. A broad selection of cyclic structures in the chain (“beads in the necklace”), regulation of their size and type of bonding allow significant variations in properties of cyclolinear poly(organosiloxanes). Recently, contribution of dimethylsiloxane unit in the series of cyclic (D3 - D8) and linear (D2 - D11) oligodimethylsiloxanes with various end groups was studied [1–4]. It is indicated that absolute values of the activation energy of viscous flow of each cyclic compound are higher, compared with linear ones possessing the same number of dimethylsiloxane units in the molecule. Later on, Andrianov et al. have studied contribution of cyclic groups in polydimethylsiloxane up to direct bonding of organocyclosiloxanes to one another [5]. Comparison of properties of compounds which are structural isomers have indicated that in the absence of dimethylsiloxane bridges eva-poration temperatures and activation energies of viscous flow of bicyclic ones are higher than for their structural isomers possessing dimethylsiloxane units between cycles. The values of the activa-tion energy obtained for bicyclic compounds with dimethylsiloxane bridges of different lengths indicate that higher cohesive energy and, consequently, stronger intermolecular interactions are ty-pical of bis(organocyclosiloxy)oxides.

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1. BEAD-SHAPED ORGANOSILOXANE OLIGOMERS AND COPOLYMERS WITH ORGANOCYCLOTETRA(PENTA, HEXA)SILOXANE FRAGMENTS IN THE BACKBONE The present section discusses investigation results of the basic regularities and mechanisms of dihydroxyorganocyclosiloxanes interaction with dihydroxy(dichloro, dihydride)organocyclosiloxa-nes, clears up synthetic abilities of homo- and heterofunctional condensation in the field of syn-thesizing cyclolinear oligomers, and considers surveys of thermal and other physical and chemical properties of synthesized oligomers. Described in the literature is the method for obtaining cyclolinear oligomers by homocondensation of 1,3-dihydroxytetraphenylcyclotrisiloxane in the toluene solution [6]. Deep-level proceeding of condensation reaction is detected by elimination of ≡Si-H absorption band in IR-spectra. For obtain-ing organosiloxane oligomers of the bead-shaped structure, homocondensation of 1,3-dichlorotetra-organocyclotrisiloxane in the presence of sodium hydroxide in xylene solution has also been studied [6, 7]. The reaction proceeds in accordance with the scheme as follows: Ph

O

m CI-Si

Ph Si-CI

O

2m NaOH

Ph HO

O

Si

Si-O

H

-2mNaCI

O

O

R'

R

O Si

Si R

Ph

R'

m

I

Scheme 1

Where: R=Ph, p-C6H4CH3; m≈3÷50. Indicated in the present work is that the reaction results in formation of difficultly soluble com-pounds, which apparently shows that the effect of sodium hydroxide on 1,3dichlorotetraphenyl- cyclotrisiloxane induces disclosure of organocyclotrisiloxane unit, because the catalyst used may not only induce homocondensation, but also acts as the anionic catalyst of organocyclosiloxanes poly-merization. As a result, composite materials derived from these oligomers were suggested as elec-trical insulating materials. Homofunctional condensation of dihydroxyorganocyclosiloxanes was studied using catalysts of sila-nol condensation [8]. Despite high variety of catalysts accelerating silane condensation due to cata-lytic action, they may be divided into two groups, which are equilibrating and non-equilibrating ca-talysts [9 – 11]. To the first group the catalysts are corresponded, in the presence of which conden-sation proceeds with ≡Si-O-Si≡ bond cleavage, and the second group is composed of catalysts, which do not induce cleavage of the siloxane bond. Studying synthesis of organosiloxane oligomers, the authors of the present monograph have sur-veyed reactions of homofunctional condensation of 1,5dihydroxyorganocyclotetrasiloxanes [12, 13] 1,5-dihydroxyorganocyclopentasiloxanes [14] and 1,7-dihydroxyorganocyclohexasiloxanes [15] in different solvents in the presence of the catalyst (activated coal), and at boiling temperature of solvents used.

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Homofunctional polycondensation of studied dihydroxy-containing organocyclotetra(penta, hexa)-siloxanes proceeds in accordance with the schemes follows:

O(SiPh2O)k R R Càct, solvent m HO Si Si OH O(SiPh2O)l

O(SiPh2O)k

R HO

Si

R Si O H

O(SiPh2O)l

m

Scheme 2

Where: R=Me, Ph, l=k=1 (II), l=1, k=2 (III); l=k =2 (IV); m=4÷30. Synthesized copolymers of the bead-shaped structure are colored light yellow transparent products, well-soluble in organic solvents. Application of solvents with different boiling temperatures to this reaction causes variation of the polymerization degree (m). The level of homofunctional poly-condensation is increased with the boiling temperature of the solvent. The polycondensation level is also highly dependent on concentration of the catalyst applied to the reaction, which is activated coal. As the concentration of activated coal is increased from 7 to 15 wt.%, in the case of organo-cyclotetrasiloxane, the polymerization degree is increased, approximately, by 10 units. It should be noted that the increase of radical volume at silicon atom in organosilsesquioxane unit of organocyclosiloxanes induces a decrease of the polymerization degree (m) of oligomers. As the volume of cyclic fragments is increased, i.e. at transition from organocyclotetrasiloxane to organo-cyclopenta- and -hexasiloxane fragments, the depth of homofunctional condensation is decreased. To compare the depth of homo- and heterofunctional condensation of organocyclosiloxanes, cataly-tic dehydrocondensation of dihydroxyorganocyclotetra(penta, hexa)siloxanes with dihydride orga-nocyclotetra(penta, hexa)siloxanes was studied [16]. Recently, catalytic dehydrocondensation reacti-ons were successfully applied to synthesis of linear organosiloxane copolymers [17– 21]. The study of this reaction between tetramethylcyclotetrasiloxane and cis-1,3,5,7-tetrahydroxytetraphenylcy-clotetrasiloxane in the presence of potassium or sodium methoxide is considered [22]. It indicates that insoluble polymer content is increased with the hydrogen conversion. In spite of contradictory data on the application of platinum-hydrochloric acid in dehydrocondensation reaction, present in the literature [23, 24], besides platinum-hydrochloric acid, catalytic quantity of anhydrous powder-like caustic potash as the catalyst was used in catalytic dehydrocondensation reactions of dihydroxy-organocyclosiloxanes with dihydride organocyclosiloxanes [16], which are to synthesize organosilo-xane copolymers of the bead-shaped structure. Preliminary heating of initial organocyclosiloxanes during several hours at 40 - 50°C in the presence of anhydrous caustic potash (0.1 wt.% of total quantity of the initial components) and 0.1 M of platinum-hydrochloric acid solution in tetrahydro-furan (~5×10-4 g per 1 g of the substance) has indicated that no polymerization of initial cycles proceeds. Catalytic dehydrocondensation has been studied at different temperatures (20, 30 and 40°C) in the absolute toluene solution. It has been found that at initial stages of the reaction a short induction period (~1 – 2 min) is observed. Hydrogen conversion in the reaction with time has been studied. It has been found that in dehydrocondensation reaction, hydrogen conversion is

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

increased from 66-80% (at 20°C) to 82-97% (at 40°C) with temperature (Catalyst H2PtCI6 and KOH accordingly). To increase the level of catalytic dehydrocondensation at the final stage of the reaction, the reaction products were heated up to 80°C during 3 – 4 hours. General scheme of dehydrocondensation proce-eding is as follows [16, 25]:

R

O(SiPh2O)n R

Me

Si OH + x H Si

x HO Si

O(SiPh2O)m Me Si H O(SiPh2O)m

O(SiPh2O)n

Cat -H2

R O(SiPh2O)n Me O(SiPh2O)m H O Si Si O Si Si H O(SiPh2O)n R O(SiPh2O)m Me x Scheme 3

Where: R = Me, Ph; m = n = 1, 2. Resulting the above-mentioned reaction, solid transparent copolymers, well soluble in usual organic solvents with ηspec = 0.06 – 0.13, are obtained after reprecipitation. Some properties of obtained co-polymers are shown in Table 1. Since initial dihydride- and dihydroxyorganosiloxanes, used in dehydrocondensation, represent a mixture of cis- and trans-isomers, synthesized copolymers possess atactic structure. As observed from the data, catalytic dehydrocondensation proceeds at a deeper level with formation of higher molecular products, than in the case of homofunctional products. It is shown [16, 25] that besides the origin and quantity of the catalyst, temperature and origin of the solvent, etc., reactivity of ≡Si-H bond is highly affected by steric and inductive factors, induced by cyclic structures and framing groups disposed at silicon atoms. Figure 1 show hydrogen conversions for dehydrocondensation at different temperatures of catalysts. It has been found that catalytic dehydrocondensation reaction displays the second order. Dehyd-rocondensation reaction rate constants are determined, and catalytic dehydrocondensation activation energies are calculated: Еact = 28.1 –28.5 kJ/Mole. As a consequence, for anhydrous caustic potash and platinum hydrochloric acid application as the catalyst activation energies are almost the same. It should be noted that in both cases formation of hindered compound of the following structure V: R O(SiPh2O)n R Si Si

O

O(SiPh2O)n

O

O(SiPh2O)m Si R

Si O(SiPh2O)m

R

Structure V

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

171

by homo- and heterofunctional condensation reactions is eliminated [12–16, 25] due to steric hindrances and reaction proceeding in concentrated solutions. X-ray diffraction analysis indicates that the bead-shaped oligomers and copolymers are amorphous systems, and the interchain distance, d1, is increased with the volume of cyclic fragments.

Figure 1. The hydrogen liberation rate in dehydrocondensation reaction of 1,5-dihydride-1,5dimethyltetraphenylcyclotetrasiloxane with 1,5-dihydroxy- 1,5-dimethyltetraphenylcyclotetrasiloxane, where 1 – at 40°C; 2 – at 30°C; 3 – at 20°C (with KOH as the catalyst).

Table 1. Some physical and chemical parameters and the yield of bead-shaped structure polyorganosiloxanes, synthesized in catalytic dehydrocondensation

O(SiPh2O)nR x

H R

Si O

O(SiPh2O)mMe

O(SiPh2O)n

Si

Si

Yield, %

ηspec**

R

m

n

80 83 84 91 93 94 86 94 85 93 84 93 81 82

0,04 0,06 0,10 0,07 0,09 0,13 0,09 0,12 0,07 0,10 0,08 0,10 0,06 0,07

Me Me Me Me Me Me Ph Ph Me Me Ph Ph Ph Ph

1 1 1 1 1 1 1 1 2 2 2 2 2 1

1 1 1 1 1 1 1 1 1 1 2 2 1 2

Тreact, 0 С 20 30 40 20 30 40 40 40 40 40 40 40 40 40

Catalyst H2PtCI6 H2PtCI6 H2PtCI6 KOH KOH KOH H2PtCI6 KOH H2PtCI6 KOH H2PtCI6 KOH H2PtCI6 H2PtCI6

Тsoft, С 75-85 74-80 81-87 78-83 62-69 80-85 64-72 65-73 0

d1,Å 10,20 10,20 10,20 10,57 10,57 10,57 10,57

Si O H

Me

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Copolymer

O(SiPh2O)m

№

*

Molecular masses were determined by the light scattering method. ** In toluene at 25°C.

M*ωx10-3 55 61 53 37

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Thermogravimetric studies of copolymers have shown that at 300°C mass losses do not exceed 3 – 6%, but are regularly increased with temperature. The main destruction process proceeds in the tem-perature range of 450 - 700°C and final mass losses increase with the volume of the cyclic fragment, respectively. Copolymers with cyclotetrasiloxane fragments in the backbone are characterized by higher thermal oxidative stability, than copolymers with cyclohexasiloxane ones, which is explained by variation of silsesquioxane (T) and siloxane (D) fragments. To synthesize cyclolinear bead-shaped polyorganosiloxanes, various HFC reactions in accordance with the following schemes are used [26]: branched sp a tia lly c ro ss-lin k e d p r o d u cts

NH2

H 2N R

R S h

4

Scheme 4. OH

HO R

R

+

R O

CI

CI R

R

R

x

Scheme 5.

OR

RO R

reaction term inated

R

Scheme 6.

It has been shown by gel permeation chromatography (GPC) and NMR methods that cyclolinear structure of the backbone of synthesized polymers is obtained at the interaction of dichlororgano-cyclosiloxanea and dioxy-derivatives in the presence of HCl acceptors only. The conclusion about cyclolinear structure of synthesized polymers is based on the data of hydrodynamic studies, MMD values and results of equilibrium rigidity determination. Cyclolinear structure of the backbone is also proved by NMR-spectroscopy method on 29Si nuclei. HFC reaction between 1,5-dichlorohexaorganocyclotetrasiloxanes and appropriate dihydroxyde-rivatives in the presence of hydrogen chloride acceptor has synthesized beadshaped cyclolinear organosiloxane polymers [27 – 31] in accordance with the general scheme as follows: R R

R R x

HO

R'

R'

+ x R' OH R

Scheme 7

R

R R R'

CI

R' O H

2xAc . HCI HO R' 2xAc CI R R

R R

2x

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

173

Where: R=R’=Me, Ph; R≠R’ Applied difunctional organocyclotetrasiloxanes, both pure cis- and trans-isomers and their mixtures with isomers in various ratios, were of interest as model compounds for synthesizing stereo-regular poly(organocyclotetrasiloxanes) (POCS-4): trans-tactic, cis-tactic and with strict regular alternation of cis- and trans-sequences. Table 2. Physical and chemical parameters of POCS-4 of the structural formula as follows:

R' R R Si O Si O O O Si O Si R R' R n № 1 2 3 4 5 *

R

R’

Ме Me Ph Ph Ph

Ph Ph Me Me Ph

Isomeric composition, % cis trans 50 50 0 100 50 50 0 100 50 50

[η], dl/g 0,17 0,1 0,05 0,06 0,05

Тg,0С 0 +7 +43 +46 +220

Тmelt,0 С 100* 142* -

Data of X-ray diffraction analysis prove the presence of crystalline phase.

Applied difunctional organocyclotetrasiloxanes, both pure cis- and trans-isomers and their mixtures with isomers in various ratios, were of interest as model compounds for synthesizing stereo-regular poly(organocyclotetrasiloxanes) (POCS-4): trans-tactic, cis-tactic and with strict regular alternation of cis- and trans-sequences. For synthesizing POCS-4 (poly-1,5-dimethyltetraphenylcyclotetrasiloxane, poly-1,5diphenyl-tetra-methylcyclotetrasiloxane, poly(hexaphenylcyclotetrasiloxane) and poly(hexamethylcyclotetrasilo-xane) – PMCS-4), trans-1,5-dichlorohexaorganocyclotetrasiloxane and appropriate trans-dihyd-roxyderivatives, as well as several mixtures with different ratio of cis- and trans-isomers were used [27–29] in accordance with the scheme 7. Some physical and chemical parameters of polymethyl-phenylcyclotetrasiloxanes are shown in Table 2. PMCS-4 with different ratios of trans- and cis-sequences in the backbone possess one and the same glass transition temperature, and the crystallinity degree is lower that for PDMS. While polymeric chain is enriched by trans-units, crystallinity increases [27]. By methods of DSC, X-ray diffraction and thermooptical analysis, it have been detected that besides glass transition (Tg) and melting (Tmelt), polymers synthesized from monomers containing up to 95 – 100% of trans-isomers display a phase transition in the temperature range of 70 - 90°C, which is simulated as a transition from meso-morphous to isotropic state (Figure 2). Detection of thermotropic mesophase presence in PMCS-4 has induced different opinion on poly-organocyclosiloxanes), because heretofore poly(dimethylsiloxane) had been considered one of the most flexible-chain polymers. More thorough study of the spatial structure of PMCS-4, performed by 29Si NMR spectroscopy method, has shown that HFC

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reaction of 1,5-dichlorohexaorga-ocyclotetrasiloxanes with appropriate dihydroxy-derivatives proceeds (depending on selected condi-ions) with both preservation and inversion of isomers’ configuration. This made the authors to clear up the effect of such factors as the reaction temperature, acceptor basicity and solvent polarity in the HFC reaction on formation of different configurations of PMCS-4 units by 29Si NMR method.

Figure 2. DSC curve for trans-microtactic PMCS-4

Studied in ref. [26] is the effect of HFC reaction conditions on the configuration sequences in POCS-4. Since the mesomorphous state in PMCS-4 is formed in stereoregular trans-tactic polymers only [27, 32] and spatial configuration of initial monomers is not always fully preserved in poly-mers, the effect of HFC conditions on transformation of ≡SiCI and ≡Si-OH centers in initial com-pounds has been studied. The detected fact of cyclosiloxanes partial inversion at CI atoms substi-tution at silicon was expected, as reported before [33, 34]. More detailed description of reflex correlation was carried out in ref. [35]. Symbols and mark projections of units and bonds to the pla-ne perpendicular to the cycle plane. Thus, 29Si NMR spectra in PMCS-4 allow a conclusion about distribution of sequences from two units (tt, tc, (ct), and cc dyads) and the ratio of trans- and cis-units in the backbone. For these atoms, the following alternatives of spatial ringing are possible:

tt

tc

ct

cc

Figure 3. Alternatives of spatial ringing

and Symbols and mark projections of units and bonds to the plane perpendicular to the cycle plane. Correlation by reflexes from D fragments can be performed in the presence of reflexes from T-fragments of trans- and cis-units, calculated by ratios. Table 3 shows that low-polar D reflexes in the whole series are more intensive than high-polar ones. That is why the former reflex is related to trans-units.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

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Table 3. Conditions of synthesis, chemical shifts and intensities of reflexes in 29Si NMR spectra of PMCS-4 [35] Trans-/cis-isomer ratio in initial monomers Polymer, №

*

Relative intensity of δ Si reflexes for dyad units and sequences D Т

НС1 acceptor

In chloride

In diol

1

0.95/0.05

0.95/0.05

2

0.95/0.05

0.95/0.05

C5H5N

0.62

0.38

3

0.95/0.05

0.95/0.05

C5H5N*

0.63

0.37

4

0.95/0.05

0.95/0.05

(C4H9)3N

0.59

0.41

5

0.95/0.05

0.95/0.05

(С5Н11)3N

0.54

6

0.70/0.30

0.70/0.30

C5H5N

0.64

7

0.95/0.05

0.50/0.50

C5H5N

0.60

(C2Н5)3N

tc -65.47 0.11

ct -65.77 0.20

сс -65.68 0.01

0.61

0.18

0.19

0.02

0.31

0.35

0.33

0.02

0.17

0.42

0.32

0.03

0.46

0.15

0.41

0.40

0.04

0.36

0.40

0.22

0.25

0.13

0.40

0.32

0.25

0.27

0.16

-19.27

-19.31

0.80

0.20

tt -65.53 0.78

The acceptor represents solvent, simultaneously; in all other reactions, benzene, toluene or diethyl ether is used as solvents.

Data on intensities of reflexes in T-fragment spectra of PMCS-4 indicate that HFC reaction of initial dichlorohexamethylcyclotetrasiloxane induces different reflexes of CI atoms. These data contradict to the previously published results on dioxy- and dialkoxyderivatives, which indicate that the ring configuration does not change during the reaction [26, 28, 36], i.e. in spite of hydrolysis, in HFC reaction with appropriate dioxy-derivatives dichlorocyclotetrasiloxane is partly inverted. Data in Table 6 show that the inversion degree varies in a broad range and for units in the case of N(C2H5)3 acceptor equals 13%, and in the case of N(C5H11)3 is 88%. Though inversion and estimation of stereospecificity of HFC reaction require more thorough studies, already existing data indicate that the reaction represent the multi-stage process. At the first stage, interaction between dihydroxycyclotetrasiloxane and amine forms a structure. The second stage (the structure interaction) proceeds under different conditions with regard to the structure stability. In cases, when structures with amines of similar basicity are formed, their stability is approximately the same. However, depending on transitional amine structure, the attack may proceed from the front via formation of a trigonal pyramid. The first path proceeds via inver-sion of ≡Si-CI reaction center in the ring, and the second one via pseudo-rotation with the configu-ration preserved.

HO Me

Me OH

Me

k1 k2

H O

R R R

N

O

Me

H Nu

Scheme 8

N

R R R

176

O. Mukbaniani, G. Zaikov and T.Tatrishvili CI Me

Me

CI

Nu

+ Nu

Me

Me

Inversion CI . CI -NR3 HCI Me

Me O Me

OH Me

CI CI

Me Nu

Me

CI

Pseudo rotation

CI

-NR3. HCI Me

Me O Me

Me OH

Scheme 9

Table 4. Dependencies of the fracture of cis-units on the quantity of units, formed from dichlorohexamethylcyclotetrasiloxane, and the degree of inversion of dichloride units with regard to HCl acceptor used Polymer, No. 1 2 3 4 5

Acceptor (С2Н5)3N C5H5N C5H5N (C4H9)3N (С5Н11)3N

Fracture of cis- Degree of inversion of units units 0.17 0.13 0.36 0.34 0.67 0.69 0.81 0.84 0.84 0.88

As different configurations of the backbone units are formed from the same trans-isomers of initial dichloro- and dihydroxy-derivatives, the PMCS-4 chain configuration is generally regulated by chosen HCI acceptor. Studies of HFC reaction of 1,5-dichloro-1,5-diphenyl-3,3,7,7-tetramethylcyclotetrasiloxane with the appropriate dioxy-derivative in the presence of HCl acceptor by 29Si NMR spectroscopy method have indicates that reflexes from phenylsilsesquioxane Tfragment fall within the area of -79 ppm and are split into four components; reflexes from Dfragment are observed at -17 ppm and split into two components. If the same selection of HCI acceptors and solvents are used in HFC reaction, lower affinity of units from dichlorocyclosiloxane to inversion is observed (Table 6). While (C2H5)3N and С5Н5N acceptors are used, the inversion degree of ≡Si-CI centers in dichloromethylphenylcyclotetrasiloxane equals 4 – 6%, and for N(C4H9)3 acceptor - 30%. Reduction of inversion of ≡Si-CI centers in the ring, all other conditions being absolutely the same, may be associated with the effect of bulky phenyl substituting agent only, which renders difficulties to inversion of the reactive centers. For spatially hindered molecules of bi- and polycyclic structures, it is observed that substi-tution of CI atom at Si atom proceeds with preservation of the configuration [37]. The effect of tacticity of the polymeric backbone on properties of POCT-4 has been searched for [26]. Figure 4 shows curves for PMCS-4 with different backbone structure, obtained by the diffe-rential scanning calorimetry (DSC) method (curves 1 – 4). For atactic polymer the only transition, corresponded to Tg, is observed on curve 1, above which, in accordance with the data of X-ray dif-fraction analysis, the polymer is amorphous (two amorphous haloes at 2 θ = 8 – 11° and 20-35°). As the polymeric backbone is enriched with

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

177

tt-sequences (curves 2 – 4), additional phase transitions are observed. For different cooling rates and annealing temperatures, it has been observed that depen-ding on PMCS-4 enrichment by tt units the number of endothermic peaks and the temperature range between endoeffects from Тmelt to Тinv vary.

Figure 4. DSC curves for PMCS-4 (Table 2.3) of various stereo regular structure: 1 – atactic; 2, 2’ – transtactic polymer 2 (2- heating, 2’ – cooling); 3 – heating of polymer 3; 4—heating of polymer 4

Figure 5. Diffraction patterns for PMCS-4 (Table 6): a – polymer 2 at 12°С (1) and 74°С (2, 3); b - polymer 4 at 20°С (1), 86°С (2) and 96°С (3) (I, dimen- sionless units)

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Heating of trans-tactic PMCS-4 at 60 - 70°С induces gradual elimination of the greater part of ref-lexes, four of which only remain on the diffraction pattern already at 74°С (Figure 4). The character of 2d temperature dependence and correlation between angular positions of these reflexes allow a supposition that they relate to regulation in the basic plane of the rectangular cell with dimensions а=17.27 Ǻ and b=8.46 Ǻ. The first transition is not accompanied by significant variations in the basic plane package, but is associated with the loss of the farther translation order. Temperature in-crease above 74°C leads to elimination of low-intensive reflexes in angles (2θ =14 – 30°). Fusing of reflexes at 2θ =10 – 11° into a single one is observed on diffraction patterns in the temperature range of two following endothermal transitions (Figure 3, curve 2). This may testify about packing vari-ation in the basic plane. This effect is screened by isotropization (Figure 4). Final isotropization of polymer 2 proceeds at 110°C. Thus in spite of atactic PMCS-4, transition of trans-tactic PMCS-4 from crystalline to amorphous state is preceded by polymorphous transition of the mesophase II - mesophase I type. To obtain fuller picture on the cyclolinear polyorganosiloxanes tacticity effect on formation of crys-talline and mesomorphous states, by N.N. Makarova and her co-workers the PMPCS-4 and PPCS-4 were synthesized and their properties were studied.

Me

Ph

Me

Ph Ph O

Ph O Ph

Ph Me

Me PMPCS-4

Ph Ph PPCS-4

Figure 5 shows DSC curves for trans-PMPCS-4 and trans-PPCS-4. In spite of the aboveconsidered trans-PMCS-4, trans-PMPCS-4 displays lower crystallinity degree (~60%) at room temperature, though its saturation by tt-sequences is higher. As temperature increases, a single endothermal tran-sition at 197 - 202°C only is observed in it. In accordance with RSA data, this transition is associat-ed with polymer melting. Under different modes of annealing, cooling and repeated heating of PMPCS-4 sample, cold crystallization at 36°C and crystal II – crystal I transition at 119°C were ob-served. At 56 – 58°C, the DSC curve for PPCS-4 enriched with tt-sequences (Figure 5, curve 1) dis-plays the area of glass transition, and at 170-180°C– low endothermal effect with ∆Н =1,0 J/g. Com-paring data on RSA and DSC, the authors concluded that below 250°C PPCS-4 exists in the meso-morphous state. In accordance with the data of thermooptical analysis, isotropization of PPCS-4 is observed in the temperature range of 320 - 340°C, simultaneously with degradation of the polymer. More detailed description of PPCS-4 polymesomorphism and calculations of the cell parameters at chain packing in the basic plane are given in ref. [38]. Thus considered data on three POCS-4 possessing different spatial structures do not allow an un-ambiguous conclusion that enrichment of the polymer by tt-sequence units always causes occurren- ce of a mesophase, but hence, in the majority of cases the crystallinity degree is increased. Apparently, the data obtained should indicate that higher contribution to stabilization of the mesophases is provided by strong intermolecular

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

179

interactions; therefore, the side framing is the determining factor for realization of polymesophase transitions in cyclolinear POCS-4.

Figure 5. DSC curves for PPCS-4 (1) and PMPCS-4 (2)

The authors have also studied the effect of organic framing on properties of POCS-4 polymers. It is common knowledge that introduction of side groups of various origin causes changes in properties of linear poly(diorganosiloxanes) [39-42]. The above-mentioned data on PMCS-4 and PMPCS-4 show similar dependence of the phase states of polymers on the origin of organic substituting agents in POCS-4 polymers. That is why for better understanding of the influence of intermolecular inte-ractions on POCS-4 properties, poly(hexaalkylcyclotetrasiloxanes) (PACS-4) were synthesized [43]. Table 6 shows main parameters of PACS-4. Studies of PACTS properties by RSA method have shown that atactic PACS-4 with ethyl (PECS-4) and n-propyl substituting agents (PPCS-4) are not crystallized, but a single narrow reflex at 2θ=10-11° and amorphous halo at 2θ=20° are observed on the diffraction pattern in a broad temperature range. If methylsubstituting agent is changed by ethyl or propyl one, the narrow reflex is shifted towards low angles. The character of PACS-4 distribution image in the temperature range from Tg to 230°C for ethyl substituting agent and to 270°C for n-propyl one does not change. RSA data and clarification temperatures, Tcl, indicate that above Tg, atactic PACS-4 (except for methyl one) exists in the mesophase and transits to isotropic melt either at 220 - 230°C (as for PECS4) or at polymer degradation temperature (as for PPCS-4). Since for these polymers such factors as MM, MMD and tacticity of polymeric chain are close, one may conclude that occurrence and formation of the mesophase is stipulated by the increase of intra- and intermolecular interactions between alkyl substituting agents in cyclolinear polymeric chain. Table 6. Physical and chemical parameters and interchain distances of atactic POCS-4 № 1 2 3 4

R = R’ in POCS-4 СН3 С2Н5 n-С3Н7 С6Н5

Tg0C -51 -110 -55 +58

T cl00 280 300 >300

d1, Å 8.4 8.8 10.4 11.2

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

Comparing phase diagrams of PACS-4 and linear polydialkylsiloxanes, one may easily observe general tendency of Tg and Tinv variation in organosiloxane polymers, for PACS-4 all temperature transitions being shifted towards higher temperatures [43, 44]. For polymeric chains from tt-sequences, analysis of PACS-4 structure, carried out on Stewart – Briegleb models, indicates a tendency of plane zigzag formation by the siloxane backbone, formed from intercyclic oxygen atoms [43]. Evidently, PACS-4 may be approximated by cylinders, diame-ters of which increase with the volume of alkyl substituting agent. Interchain distance, d1, indicated by X-ray diffraction data, varies from 8.4 (PMCS-4) to 10.4 Å (PECS- 4). Figure 4 shows a hypo-thetical model of POCS-4.

Figure 4. Hypothetical model of POCS-4.

Basing on the present model, one may suppose existence of a package representing somewhat peculiar packs of polymeric disks. However, for PACS-4, interchain distance, detected by the RSA method, is by 3.0 Å shorter than for the model suggested. In this connection, two variants are possi-ble: the first one suggests occurrence of second one drives rings to some angle to the main axis of the macromolecule. Figure 5 shows diagrams of the phase state of PMPCS-4 and PPCS-4. Contrary to PACS4, for PMPCS-4 clear dependence of temperature range of the mesophase existence on the number of phenyl substituting agents is absent. Apparently, irregular distribution of bulky substituting agents in cyclic fragment in every particular case introduces its own specific features. Among all the above-considered POCS-4, one polymer only possesses the mesophase obtaining it from the monomer - octaphenylcyclotetrasiloxane [38]. Summing up the data on POCS-4 phase transitions, unambiguous answer cannot be given, if side substituting agents stabilize the mesomorphous state of the polymer or not. Melting temperature of the polymer increases with the number of phenyl groups in the unit, and the range of existence of one- and two-dimensional regular structures is converged, because the initial degradation tempera-ture is about 300°C.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

181

The effect of POCS-4 molecular mass on the phase states is detected. Among works devoted to the study of MM effect on isotropization temperature variation, Tiso, in organic LC-polymers, the ones by Blumstein et al. should be outlined [45, 46]. These works show that Tiso increases with MM, for organic LC-polymers with mesogenic groups in the backbone in a quite narrow range of molecular masses.

Figure 5. Influence of the number of phenyl groups, N, in POCS-4 unit on phase transitions

Study of the molecular mass effect on the mesophase – isotropic melt phase transition, carried out for polydiethyl- (PDES) and polydipropylsiloxanes (PDPS), has shown that border values of Tiso are reached for PDES at the polymerization degree above 3,000 [42] and for PDPS at 600 [41]. For PMCS-4, the effect of molecular mass was considered for three samples. Data from Table 5 indicate that the mesophase - isotropic melt temperature transition occurs and reaches border values at much lower polymerization degrees. Data from works [29, 43] on Tiso variation for PACS-4 prove that border values by Tiso for these polymers are also reached at much lower molecular masses. For the purpose of studying the effect of cyclic unit on polymeric chain, the HFC reaction of 1,5-dichloroorganocyclopentasiloxanes with 1,5-dihydroxyorganocyclopentasiloxanes in the presence of hyd-rogen chloride acceptor and synthesized polyorganocyclosiloxanes (POCS-5) were studied in accor-dance with the scheme as follows [27, 36, 47, 48]: R R R'

+x

x CI

R' R

R

R

R

R R

R R

CI

OH

R'

R'

HO R

R

2xAc 2xAc .HCI

R R Scheme 10

HO

O

R'

H

R' R

R

R III

R 2x

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

Where: R = R’ = Me [27], Et [47], n-Pr [47]; R ≠ R’; R = Me; R’ = Ph [48]. Forasmuch as neither of initial compounds was separated into spatial isomers (though the affinity to enrichment of a mixture of trans-isomers was observed), synthesized polymers possessed atactic structure. Table 6 shows physical and chemical parameters of synthesized POCS-5. Data of RSA and DSC in-dicate variations of Tg of POCS-5 analogous to PACS-4 with regard to the length of alkyl substi-tuting agents. However, the difference in Tg of PMCS-4 and PMCS-5 should be outlined, which equals approximately 20°C. Hence, Tg of PECS-4 and PECS-5 are equal (Table 6). Table 6. Physical and chemical parameters of POCS-5 Polymer, № 1 2 3 4 *

R in POCS-5

Yield, %

[η] 250С

Мn х 10-3

Тg, °С

Me Et* н-Pr Ph**

75 57 60 59

0.27 0.11 0.09 0.11

30.12 -

-72 -111 -80 -35

Тiso = 40 - 50°С. ** POCS-5 with methyl groups in organosilsesquioxane fragments partly substituted by phenyl ones.

All POCS-5, except for PECS-5, are amorphous above Tg; according to RSA data, PECS-5 is mesomorphous above Tg, which is proved by three narrow reflexes at 2 θ = 8.98°, 9.57° and 9.93°. This diffraction is preserved up to 40 -50°C. At this temperature on the DSC curve, termination of heat absorption is observed. For PECS-5, variations on the diffraction pattern at 20°C correlate well with the beginning of heat absorption on the DSC curve (Figure 6). At the same temperatures (5-20°C) texture disappearance is observed on a polarization microscope.

Figure 6. DSC curve for PECS-5 (1) and diffraction patterns at 50°C (2), 11°C (3) and 0°C (4) (I is separate units)

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

183

For low-temperature phase of PECS-5, rectangular cell is the most probable in the basic plane; it is also probable 10°C above the transition point. Thus for PECS-5, which unit is represented by asym-metrical rings, formation of highly ordered crystalline as well as oneand two-dimensional ordered structures is hindered. However, due to intensification of intraand intermolecular interactions of or-ganic groups, conditions for overlapping between macromolecules may occur. Finally, introduction of polar groups may induce a mesogenic fragment to become more symmetrical. More representatives of bead-shaped cyclolinear polymers are POCS-6, backbones of which are composed of cyclohexasiloxanes. They differ from POCS-5 by inclusion of one more diorganosilo-xane fragment to the ring and the ratio between diorganosiloxane fragments to diorganosilsesqu-ioxane ones reaching the value of two. In spite of difunctional octaorganocyclopentasiloxanes, in the majority of cases, dichloro- and dihydroxy-derivatives of decaorganocyclohexasiloxanes are easily divided into cis- and trans-isomers, which gives an opportunity to obtain polymers with various se-quences in the configuration. HFC reaction of 1,7-dichlorodecaorganocyclohexasiloxanes with 1,7dihydroxydecaorganocyclohexasiloxanes mainly proceeds by the scheme as follows: R2 R2 x

R'

R'

2xAc HO OH -2xAc . HCI

+ x

CI

CI R2 R2

R2 R 2

R2 R2

R'

R'

OH

R' O

R'

R2 R 2

R 2 R2

Scheme 11

H 2x

Where: R = R’ = Me [27], Et [36], Ph [49]; R ≠ R’; R = Me; R’ = Ph [50]; R =Ph, R’ = Me [49, 50]. Synthesized in this HFC reaction were copolymers, completely soluble in usual organic solvents with [η] = 0.10 - 0.24. The authors of the works have studied the influence of HFC reaction conditi-ons on configuration sequences of synthesized polymer. 29Si NMR spectra of pure trans-isomers and mixtures with different ratios of cis- and trans-isomers have indicated that spatial configuration of initial monomers is not fully preserved, and in some cases, inversion of ≡Si-CI centers exceeds 50% [35]. Factors affecting variations in configuration of initial difunctional organocyclohexasiloxanes during HFC reaction were also studied by 29Si NMR analysis. By analogy, relation of reflexes in 29Si NMR spectra to spatial tt, ct, tc and cc configurations is based on the fact that fission of silses-quioxane atom may be stipulated by spatial isomerism of the back-bone components only. Data from Table 7 on PMCS-6 prove that HFC reaction in the presence of HCl acceptor (pyridine) proceeds with partial inversion of dichlorodecamethylcyclohexasiloxane, because three reflexes are detected in spectra. In the case of partial inversion of dioxy-derivatives, polymers 1 and 2 would contain all possible combinations of units, i.e. four reflexes of Tfragments. A series of experiments studying the effect of acceptor and solvent origins in the HFC reaction during PMCS-6 synthesis give results analogous to the ones, previously executed for PMCS-4. However, one more additional factor affecting on the inversion degree of the initial dichlorodeca-methylcyclohexasiloxane was observed: configuration of preceding unit in the backbone (configu-ration of dihydroxy-derivative). As trans-isomer of the initial monomer

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diol (Table 7) is used, the ratio of cis- and trans-units in the polymer becomes equal 0.72:0.28 from the initial one in dichloro-derivatives, which equals 0.52:0.48 [35]. Table 7. Conditions of synthesis, chemical shifts and intensity of reflexes in 29Si NMR spectra for PMCS-6 Polymer, №

1 2 3

Trans-/cis-isomer ratio in initial monomers In dichloride

In diol

0.52/0.48 0.52/0.48 0.52/0.48

1.00/0 0/1.00 0.52/0.48

Relative intensity of δ and Sequences D T -21.95 -67.60 0.28 0.23

Si

reflexes for dyad units

-67.63 0.35 0.23 0.23

-67.55 0.37 0.21 0.24

-67.58 0.56 0.30

Pure cis-dihydroxy-derivative was one of the initial products for synthesizing polymer 2, and units formed from dichloro-derivative preserved the configuration ratio, present in the initial monomer. Because minimal inversion equals 12 – 13%, it is quite probable that ≡Si-CI center is inverted not in the initial molecule of cyclic dichloride, but in oligomer composed of tt-sequences. This molecule consists of ~5 units (as shown below, equilibrium rigidity of trans-tactic PMPCS-6 is higher than that of atactic polymers). That is why for somewhat decrease of the backbone rigidity, one ≡Si-CI center is inverted in the HFC reaction starting from a definite length of oligomers at consecutive act of addition of initial diol or interaction of two oligomers (of any length). There are no grounds for considering inversion proceeding at the interaction of two initial organocyclohexasiloxanes only, as it has been suggested for PMCS-4. But simultaneously, there are no data disproving the supposition that the inversion proceeds at the stage of oligomerization. The latest results of synthesis of oligo-mers with strictly defined polymerization degree (three, five, seven repeated units) prove the case, when ≡Si-CI center is inverted as the end group in oligomers [51]. The effect of chain tacticity on the phase states of POCS-6 has been studied. On the example of two POCS-6 polymers, the influence of configuration sequences on thermal transitions has been investigated [52]. For this purpose, cis- and trans-isomers of 1,7-dihydroxydecamethylcyclohexasiloxane, 1,7-dichloro-1,7-diphenyl-3,3,5,5,9,9,11,11-octamethylcyclohexasiloxane and its pure cis- and trans-dihydroxy-derivatives were used. Polymers enriched with tc- and ct-sequences were synthe-sized by interaction of mixture of dichlorodecamethylcyclohexasiloxane cis- and trans-isomers with trans-diol (Table 8, polymer 1), cc-sequences being completely absent. Polymer 3 (Table 8), in which ttsequences were absent, was synthesized from pure cis-dihydroxydecamethylcyclohexasiloxane. Structures of polymers 1 and 3 are the following:

tt-tc (polymer 1)

tc-cc (polymer 3)

The image of sequences in the cyclolinear chain represents projections of cyclic units and bonds connecting them to the plane perpendicular to the ring plane. The structure of polymer

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

185

1 is named trans-microtactic one, and structure 3 is cis-microtactic one. Atactic polymer 3 contained all types of tt, tc, ct and cc configuration sequences in approximately equal fractures. Four cyclolinear PBPCS-6 polymers of different structures were synthesized from pure cis- and trans-isomers of dichloro- and dihydroxyderivatives of diphenyloctamethylcyclohexasiloxanes: the first one is enriched with tt-sequences in the absence of cccombinations (trans-tactic polymer); the second one is enriched with cc-sequences in the absence of tt ones (cis-tactic polymer); the third one is mostly enriched with tc-sequences from cis-dichloro derivative and trans-diol (due to partial inversion of dichloride, ttsequences are present; that is why spatial structure of the third polymer is similar to the first one); the fourth one represents atactic polymer. Table 8. Some physical and chemical parameters of PMCS-6

№

Trans-/cis-isomer ratio in initial monomers

Yield, %

[η ] at 25°C,

Mesophase-isotropic melt transition Mx10

-3

Тmelt, 0 С

Тcl 0С

Тiso, 0 С

∆Hiso, kJ/mol

-91*

320

4.3

7.2

295-305

-

-91

310

5.4

-

270-290

0.15

-

-91

250

2.9

5.5

250-260

0.17

24.1

-91

294

4.6

8.1

220-240

In dichloride

In diol

1

0.70/0.30

1.00/0

71

0.15

46.0

2

0.55/0.45

1.00/0

79

0.24

3

0.40/0.60

0.03/0.97

76

4

0.50/0.50

0.50/0.50

80

dl/g

∆S, J/mol-deg

In the first two cases, tc-sequences are present in the NMR spectrum due to partial inversion of ini-tial dichloro-derivative. All polymers with different tacticity types displayed high yields, except for the polymer of cis-tactic structure, the yield of which is much lower due to intramolecular cyclizati-on reaction, which induces formation of tricyclosiloxane (in the case of methyl groups at silicon atoms). The phase state of PMCS-6 polymers of different tacticity were identified by the methods of DSC, RSA and thermooptical analyses. Figure 7 shows DSC curves for PMCS-6 polymers of various tac-ticity. Thermal characteristics of all transitions in PMCS-6 are shown in Table 8. Therefore, Tg is defined by chemical structure of the polymer unit and is independent of its spatial structure. The melting point is observed only for trans-microtactic PMCS-6 (polymer 1), the melting heat and, consequently, degree of crystallinity of PMCS-6 (polymer 1) being low. Above Tg, atactic and cis-microtactic PMCS-6 polymers exist in the mesomorphous state up to 300°C; trans-microtactic PMCS-6 polymer is the only one transiting into the crystalline phase above Tmelt. Such interpreta-tion of phase states is proved by RSA data. PMCS-6 diffraction patterns in the temperature range from Tg to 250 - 300°C displays a single nar-row reflex (1/2∆ = 20′) of high intensity at 2θ =0.5°, corresponded to the interchain distance. Opti-cal observations on a polarization microscope indicate that the polymers possess the birefringence property [32].

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Figure 7. DSC curves for PMCS-6 of different structures: 1 – atactic polymer; 2 – cis-microtactic polymer; 3 – trans-microtactic polymer.

In spite of PMCS-6, DSC curves of PMPCS-6 independently of the tacticity type of polymeric chain display additional endothermal transitions, induced by melting. Proceeding of PMPCS-6 crystalli-zation is proved by RSA data. The ability to crystallization of PMPCS6 samples depends on the co-oling rate, but the mesophase is formed in these polymers even at 300 deg/min cooling rate, and me-somorphous glass is formed below Tmelt. The mesophase – isotropic melt phase transition was de-tected for cis-tactic PMPCS-6 polymer only; the rest polymers remain in the mesophase in the temperature range from Tmelt to 300°C. Hence, it was concluded [27, 36, 50] that independently of dominance of one of the sequence types (tt, cc or ct) or they all exist simultaneously (atactic polymer), all POCS-6 polymers may exist in the mesomorphous state in a wide temperature range. Dependencies of Tg, Tmelt and Tiso on content of phenyl groups in PMPCS-6 polymers and copo-lymers are shown in Figure 8. The phase diagram of PMPCS-6 indicates that sequential substitution of methyl groups by phenyl ones causes a monotonous increase of Tg. Differences between Tg of PMCS-6 and linear PDMS polymer are low, and some increase of Tg reflects restrictions of the lo-cal mobility caused by the presence of cyclic sequences in the chain. Tg values of homopolymers and PMPCS-6 copolymers fall within the range, limited by glass transition temperatures of PDMS and PDPS polymers. All PMPCS-6 polymers possess the ability to crystallization. Values of Tmelt of PMCS-6 polymer fall within the range typical of PDMS melting. Introduction of phenyl substitu-ting agents increases Tmelt of PMPCS-6, which is the most abrupt at introduction of initial ones. Crystalline and mesomorphous phases in PMPCS-6 are identified with the help of RSA data, which prove the fact of their partial crystallization. Above Tmelt, all PMPCS-6 polymers and copolymers display the mesomorphous phase. The effect of molecular mass on occurrence of the mesomorphous phase in POCS-6 polymers is de-tected. Results displayed for POCS-6 polymers, in which configuration sequences of units alternate irregularly along the backbone, indicate that the ability to crystallization in them is disturbed. For the mesomorphous phase, strict regularity of units is not the necessary condition of its occurrence. In connection with the difference between studied POCS-6 polymers by the type of tacticity and mole-cular mass, the authors have separated effects induced by these two factors and detected more accu-rate, which type of configuration sequences creates conditions for mesophase stabilization.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

187

Figure 8. Dependencies of Tg, Tmelt and Tiso on the quantity of phenyl groups N, in POCS-6 polymers

To study dependencies of POCS-6 translucence temperatures on molecular mass (MM), PMPCS-6 and PMCS-6 were fractioned, and molecular masses and isotropization temperatures of the fractions were determined [43,53, 54]. Data in Table 9 show that atactic PMCS-6 possesses the mesophase in all fractions. The isotropization temperature is decreased slowly first and then abruptly with the po-lymerization degree. Such type of Tiso dependence on MM of cyclolinear polymers is quite different from the analogous dependence for PDES [42] and PDPS [41], in which (as mentioned above) the ability to form the mesophase is observed at polymerization degrees as follows: P>200 for PDPS and P>500 for PDES. For fractioned PMCS-6 samples, isotropization heat and entropy are much higher and the tempera-ture range is much narrower, which may be induced by the solvent applied and conditions of sample precipitation during fractionation. A sharp dependence of Tiso on polymerization degree, mesophase occurrence in lowmolecular fractions, high values of Tiso and a broad range of mesomorphous phase existence are the indirect factors proving quite high equilibrium rigidity of atactic PMCS-6 polymer. Table 9. Description of PMCS-6 fractions Fraction №

[η], dl/g (25°С)

Μω

Polymerization degree

Тg, °С

Тg, °С

∆Нiso, kJ/mol

∆Siso, kJ/mol-deg

1 2 3 4 5 6,7 8 9 Non-fractioned sample

0.07 0.09 0.11 0.13 0.17 0.18 0.24 0.28 0.14

8250 8750 14400 16000 29000 34000 44000 76000 24000

19 20 34 37 67 79 102 176 61

-88 -88 -88 -89 -88 -89 -90 -89 -90

202 257 277 286 294 295 310 313 279

4.40 4.50 4.60 3.76 5.65 5.50 5.65 5.56 4.40

9.70 8.54 8.40 6.84 10.0 9.80 9.80 9.66 8.05

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The packing structure of POCS-6 chains in the mesomorphous phase is of special interest. Consider the structure and conformation of decaorganocyclohexasiloxanes unit on the Stewart-Brigleb models and compare with the temperature dependence of d1 reflex. Figure 9a shows a disk-like structure of the unit with d1=11.5 Å at the cycle layer thickness d1=7.8 Å. Disks combines in a chain form plates looking like the so-called sanidic mesophase [55] in organic LC-polymers. The height of POCS-6 macromolecule layer is close to that determined for PMCS-6 polymer (d1=8.4 Å). The presence of long-range order in the packing with the lower cohe-rence border at 400 Å indicates that packing types shown in Figures 9b and 9c are exclusively possi-ble at the current intermolecular distance (though similar distances are realized in the ring, too, ho-wever, so high long-range order cannot exist in them; moreover, temperature dependencies of inter-and intramolecular distances are different). The model suggested indicates presence of a single ma-ximum corresponded to the long-range order in one direction, perpendicular to the plane of the ring, which is the polymer backbone unit.

Figure 9. A hypothetical model of POCS-6 polymer unit (a), POCS-6 backbone fragment (b), and POCS-6 chain packing (c). Temperature dependence of interchain distance, d1, for mesomorphous component of PMCS-6 polymer (d) and typical diffraction pattern of POCS-6 in the mesomorphous phase (e) (I, dimensionless units)

Cyclolinear structure of synthesized POCS-4, POCS-5 and POCS-6 polymers was proved by hydro-dynamic study of properties of their solutions [56]. The expected results of these investigations should indicate the predominant influence of the equilibrium flexibility of macromolecules and other specific properties of polymeric chains in block on occurrence of the thermotropic mesophase in cyclolinear organosiloxanes. The polymers were fractioned into 8 – 14 components by coacervate extraction from the benzene – methanol system. For fractions and nonfractioned polymers, characteristic viscosities [η], were me-asured. Because that was the first example of studying conformations of macromolecules of this ty-pe in diluted solutions, authors of the work [56] paid much attention to selection of an equation, which would adequately describe hydrodynamic behavior of polymeric chains. Figure 10 shows de-pendencies of [η] on molecular mass (MM), represented in double logarithmic coordinates. Parame-ters of the Mark-KuhnHauvink equation for toluene medium at 25°C were determined from the slo-pe and disposition of the straight lines.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

189

Figure 10. Dependence of lg[η] on ω lgM for: 1 – PMCS-5 polymer; 2 – PMCS - 4 polymer; 3 – PMCS - 6 polymer

Table 10. Conformation parameters of poly(organosiloxanes) Polymer

Unit structural formula

Me2SiO

PDMS

Me2

PMCS-4

Me

а*

Kuhn segment,А

References

0.5 - 0.8

10

[57]

0.71

29

[56]

0.64

23

[56]

0.78

38

[56]

0.98

80

O Me Me2

Me2

PMCS-5

Me O

Me Me2 Me2

Me2 Me2

PMCS-6

Me O

Me Me2 Me2

Me2 Me2

PMPCS-6 (atactic)

Ph

[26]

O Ph

1.16

115 [26]

O Ph

Poly(organo Silsesquioxanes)

*

Me2 Me2

Me2 Me2 Ph

PMPCS-6 (transmicrotactic)

In the equation [η] =ΚΜα

Me2 Me2

RSiO1,5

0.5-1.8

50 -130

[58 - 60]

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

For some POCS conformation parameters and the value of the Kuhn segment A are shown in Table 10 are determined. Deviation of parameter a from 0.5 in this equation may be caused by volumetric effects in good sol-vents or partial hydrodynamic permeability of the coil, promoted by skeletal rigidity of macromo-lecules. Selection of a model for quantitative estimation of rigidity by these properties is usually complicated by the absence of reliable criterion, especially in the cases, when the value of parame-ter a falls within the range of 0.5 – 0.8. That is why to describe behavior of macromolecules in tolu-ene, the authors [56] have used the model of perturbed Gaussian non-permeable coil and the model of worm-like backbone.

Figure 11. Extrapolation by the Fixman-Stokmayer method: 1 - PMCS-6 polymer; 2 - PMCS-5 polymer

Figure 11 shows experimental dependencies of [η]/М1/2 on М1/2 for PMCS-5 and PMCS6 samples, parameters a of which are mostly different. As a consequence, conformation parameters and the va-lue of the Kuhn segment, A, values of which are shown in Table 10, are determined [57]. Found values of conformation parameters of these polymers indicate that equilibrium rigidity of macromolecules is increased with the size and symmetry of siloxane unit. Hydrodynamic behavior of PMCS-4 and PMCS-6 give no reason for corresponding these polymers to classic flexible chain ones [61]. Introduction of phenyl substituting agents to organocyclohexasiloxane unit increases ri-gidity of macromolecules (the Kuhn segment 80 A). As for trans-microtactic PMPCS-6, further on, the macromolecule rigidity is increased, which is comparable with rigidity of ladder poly(organosil-sesquioxanes) [58 –61]. Simultaneously, thermomechanical investigations were performed [28], obtained under continuous impact of compressing stress (100 g/cm3) on the sample in accordance with the technique [62]. Glass transition temperatures, shown in the Tables, are determined from the primary deviation of thermomechanical curve run in the area of positive deformations. Depending on the spatial structure of the cycle, synthesized atactic and syndiotactic polymers are characterized by almost equal glass transition temperatures, Tg. Thermogravimetric studies of synthesized polymers indicate different types of copolymers dest-ruction with due regard to substituting agents at silicon atom. For example, PMCS-4 methylsiloxane copolymer with regular alternation of dimethylsiloxane and methylsilsesquioxane units displays S-shaped curve of the mass loss, which reaches 98 – 99% at 650°C, and differential thermal curve dis-plays a single maximum. Determination of volatile degradation product composition under isother-mal conditions at 500-700°C has

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

191

indicated that polymethylbicyclosiloxanes and polymethyltricyclo-siloxanes of T2Dn and T4Dn composition (n=2, 3, 4) are main products of the process. However, be-sides polymethylcyclosiloxanes, D3 and D4 ones were detected, D4 content being below 3 – 4%. The data shown indicate degradation proceeding by the depolymerization mechanism. For copolymers containing diphenylsiloxane and phenylsiloxane units, the mass loss reaches 28 – 30% at 900°C, and DTA curves display three maximums at 490, 530 and 565°C. In the case of PMCS polymers, the composition of volatile degradation products displays benzene, methane and hexamethylcyclotrisi-loxane. At simultaneous presence of methyl and phenyl substituting agents, the composition of vo-latile products indicates more complicated proceeding of degradation. However, if formation of ben-zene and methane can be explained by radical-type Si-C bond break, D3 formation cannot be exp-lained in the frames of previously suggested depolymerizational mechanism due to formation of transient four-center complex [63, 64]. As shown in the literature, recently, a new type of polymers was synthesized which, besides three usual (solid, glassy and liquid) phases, display liquid-crystal and mesomorphous phases [65, 66]. Two types of thermotropic liquid-crystal polymers were of special interest, i.e. polymers with me-sogenic groups in the backbone and polymers containing mesogenic groups in comparatively short side chains. On the other hand, some polymers are known, capable of forming thermotropic meso-phase without mesogenic groups. Polydiethyl(propyl)siloxanes [67, 68] and polyphosphazenes [69] are the most wellknown polymers of these group. In this relation, the above-mentioned stereo regular cyclolinear methyl- and methyl-phenylsiloxane copolymers with different-size rings and framing groups in the macromolecular backbone are of special interest. Similar to poly(diethylsiloxanes) and poly(phosphazenes), meso-phases in cyclolinear organopolysiloxanes are formed in the absence of mesogenic groups, which makes representatives of this class quite interesting.

2. BEAD-SHAPED METHYLPHENYL(ETHYL)SILOXANE COPOLYMERS WITH ETHYLENE BRIDGES BETWEEN CYCLES Synthesis of carboorganosiloxane copolymers and polymers is based on hydride polyaddition of organohydrosiloxanes to organoalkenyl silanes [69]. Recently, this reaction is of great interest in the field of obtaining complex monomers [70], as well as in the field of study of addition mechanisms on various Pt, Pd, Co and metal carbonyl catalysts [71-74] and specificity of actions of one or other catalytic systems [75]. Besides carboorganosiloxane oligomers and linear polymers, other compo-unds were also synthesized by this method [76 – 78]. Discussed in the present chapter are synthesis and investigation results on properties of carbosi-loxane copolymers containing, besides organocyclotetrasiloxane fragments, organocyclopenta- and organocyclohexasiloxane fragments. The first cyclolinear organosiloxane polymer with ethylene bridges between rings was synthesized by hydrosilylation of 1-hydro-3-vinylhexamethylcyclotetrasiloxane. Hydrosilylation performed in CCI4 medium at 75°C in the presence of the Spire catalyst

192

O. Mukbaniani, G. Zaikov and T.Tatrishvili

(H2PtCI6x6H2O) has synthesized a poly-mer, viscous-flow at room temperature, in accordance with the following scheme [79]: Me Me nH

Vin

Me Me Vin

Me Me C2H4

H2PtCI6 H

Me Me Me Me

T0C

Me Me Me Me

Me Me Me Me

n-1

V

Scheme 12

Synthesized cyclolinear polymers consist of tetrasiloxane rings as elementary units, bound by ethy-lene bridges. It is found that hydrosilylation proceeds without breaking cyclotetrasiloxane ring and a low-molecular polymer with molecular mass M=2260 is synthesized in the reaction, well-soluble in benzene and other organic solvents. Besides the peak displayed by ≡Si-Me groups, the NMR spectrum possesses one non-splitted peak typical of ≡Si-СН2- groups with chemical shift (in relation to ≡Si-Me groups) equal δ = 0.35 ppm. Cyclolinear polymers were synthesized by hydrosilylation reaction of dihydridecontaining organo-cyclotetrasiloxanes with divinyl containing organocyclotetrasiloxanes [80]: Vin

Me Me Vin

R R' R' Me Me H H

Me R'

R

R R'

Vin

R=R'=Me (1a) R=Me; R'=Ph (1b) R=R'=Ph (1c)

R

Vin R' Me Me R' H R

R=R'=Me (3a) R=Me; R'=Ph (3b) R=R'=Ph (3c)

R R'

R

R R'

H Me

R=R'=Me R=Me; R'=Ph R=R'=Ph

(2a) (2b) (2c)

R=R'=Me R=Me; R'=Ph R=R'=Ph

(4a) (4b) (4c)

The polymers were synthesized by hydride polyaddition with 0.01N platinumhydrochloric acid-tetrahydrofuran solution as the catalyst. The catalyst concentration equaled 5x10-6 g per 1 mole of vinyl component in the temperature range of 60 - 150°C. It has been found that the reaction pro-ceeding at high temperatures displays formation of branched structures. The effect of initial mo-nomers’ structure on the formation rate of polymers, as well as on physical and chemical properties and structural features of synthesized polymers are traced. The reaction proceeds by the general scheme as follows [80]:

nH

H + n Vin 1

H2PtCI6

Vin 3

Scheme 13

Vin + nH

nVin 2

H

H2PtCI6

4 Scheme 14

C2H4 2n (Polymer D,F,G)

C2H4

2n (Polymer A,B,C)

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

193

The reaction proceeding was traced by viscosity increase of 1% polymer solution in toluene. It is found that at the same framing and under equal conditions rings possessing functional groups in 1,5-position enter the reaction of polyaddition at higher rate and form polymers with higher molecular masses. However, it has been observed that the rings with functional groups in 1,5- position are not only higher reactive, but also subject to side reactions. For example, soluble polymer A is formed at 60°C only, polymer B – at 60 - 70°C, and already at 120°C branching proceeds. For polymer C, the loss of solubility is observed at temperature above 80°C. Polymers D, F and G can be easily syn-thesized at 50 - 80°C, and the loss of solubility is not observed in this case. Table 12 shows some physical and chemical parameters of cyclolinear polymers with ethylene bridges bonding rings. Table 12. Some physical and chemical parameters of cyclolinear polymers with ethylene bridges bonding rings №

Initial monomers

Reaction temperature,

η

spes

3

m /kg

°C

1 2 3 4 5

6 *

2a+4a (R=R’=Me) 1a+3a (R=R’=Me) 2b+4b (R=Me, R’=Ph) 1b+3b (R=Me, R’=Ph) 2c+4c (R=R’=Ph) 1c+3c (R=R’=Ph)

[η ]⋅ 10

Мх10-3 Light By ≡Si-H Scattering groups,%

80 60 60 150 60 100 100

0.06 0.12 0.12 0.26 0.12 0.16 0.09

0.08 0.14 0.12 0.22 0.12 0.07

67 100 200 616 154 53

53 142 108 48

100 150 180 100

0.12 0.22 0.25 0.04

0.13 0.04

51 172 250 7

40 6.5

Polymer

А D B F C

G

At 25°C in toluene.

As follows from the data shown, that soluble polymer A is synthesized at 60 and 100°C, and already at 120°C branching processes are observed. There are data in the literature indicating that as heated with silicones [81] and silanes [82], catalysts from the platinum group are capable of detaching methyl or phenyl group at the catalyst concen-tration from 0.01 to 1%. Spire et al. [83] has observed detachment of methyl group at hydride addi-tion of bis(trimethylsiloxy)methylsilane to hexane-2 at 50°C and Н2РlСl6x6Н20 concentration equal 5×10-5 mole per vinyl group. It is shown [79] that as heated with polymer 4a under the reaction con-ditions, platinum-hydrochloric acid does not detach methyl group, and the ring does not enter reg-rouping or disproportionation reaction. Possible side reactions were estimated by GLC and 1H NMR-spectroscopy methods. The study of thermal oxidative degradation of synthesized polymers at heating with the rate equal 5 deg/min indicates that the temperature of decomposition beginning of polymer depends on the origin of framing groups. Polymers A and B, which contain methyl groups only, begin degrading at 250°C independently of molecular mass within its range from 6×104 to 2×105. Substitution of a part of me-thyl groups by phenyl ones induces the increase of the initiation temperature of decomposition up to 350 - 370°C, which is associated with increased

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resistance of phenyl groups to oxidation, as well as their inhibiting effect of methyl groups on oxidation [84]. Besides 1,5-divinyl(dihydride)-1,5-dimethyltetraphenylcyclotetrasiloxane, the authors [85] have us-ed 1,5-divinyl(dihydride)-1,5-dimethylhexaphenylcyclopentasiloxane and 1,7divinyl(dihydride)-1,7- dimethyloctaphenylcyclohexasiloxane as initial compounds in hydride polyaddition reaction, by which cyclolinear organosiloxane copolymers with ethylene bridges between rings containing orga-nocyclotetrasiloxane, organocyclopentasiloxane and organocyclohexasiloxane fragments are synthe-sized. As the catalyst for polyaddition, 0.01 M solution of platinum hydrochloric acid in tetrahydrofuran was used. Polyaddition proceeds in argon at equimolar ratio of initial substances (1:1) in the absence of solvent and in the temperature range of 75 - 115°C. It is found that the above-mentioned con-ditions do not induce scission of the siloxane ring. As a consequence, hydride polyaddition under se-lected conditions proceeds in accordance with the scheme as follows [85 - 87]:

Ph2 Ph2 O(SiO) O(SiO) Me Me Me m Me k 0 Si Vin Cat., T C Si H + x Vin Si x H Si O(SiO)n Ph2

O(SiO)l Ph2

Ph2 Ph2 O(SiO) O(SiO) Me Me Me Me k m Si Si CH2CH2 Si Si CH2CH2 O(SiO)n Ph2

Scheme 15

O(SiO)l Ph2

x

where k = n = m = 1, l = 2 (VI); k=n=1, m = l = 2 (VII); k=m =1, n = l = 2 (VIII); k = 1, n = m = l = 2 (IX); k = n = m = l = 2 (X). Copolymers with ηspec = 0.13 - 0.18 representing slightly yellow glassy like transparent products, which are soluble in usual organic solvents, were synthesized in the reaction. The reaction pro-ceeding was traced by the increase of 1% toluene solution viscosity (Figure 12). It has been found that viscosity growth rate is increased with temperature increasing from 95 to 115°C, and increase of the cyclic fragment volume induces deceleration of the viscosity increase. 1 H NMR spectral studies display that polyaddition mainly proceeds by the Farmer rule with formation of dimethylene bridges between cyclic fragments. Copolymer 1 (Table 13) displays a complex multiplet in the range of 6.9 - 7.6 ppm typical of protons of phenyl groups, and the reflex centered at 0.28 ppm belongs to protons of methyl group. The reflex with chemical shift at 0.32 ppm is corresponded to protons of methylene group (-CH2-CH2-). Moreover, the spectrum displays reflexes from protons of non-reacted vinyl groups (a complex multiplet in the area of 5.6 – 6.1 ppm) and ≡Si-H groups (at 4.4 ppm). The spectrum also displays a doublet reflex with chemical shift centered at 1.05 ppm, which may be related to methyl protons in =СН-СН3 group with the quantity below 8%.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

195

Table 13 shows some properties of carbosiloxane co-polymers with cyclic fragments in the back-bone.

Figure 12. Variation of optical density of ≡Si-H bond and specific viscosity with time by reaction (17): 1 and 1’ – copolymer 4 (Table 13) at 75°C; 2 and 2’ – for copolymer 1 at 95°C; 3 – for copolymer 1 (Table 13) at 115°C

Table 13. Some physical and chemical parameters and yields of copolymers (VI-X) containing cyclotetra(penta, hexa)siloxane fragments in the backbone № k

n

m

l

1

1 1 1 2 2 2 2 2

1 1 2 1 1 1 2 2

2 2 2 2 2 2 2 2

2 3

4 5

1 1 1 1 1 1 1 2

Yield , % 94 95 91 90

92 90

Reaction temperature, 0 C 95 115 115 75 95 115 95 115

ηspe

Тsoft,0 С

d1,Ǻ

Mnx10-3

0.15 0.18 0.16 0.11 0.14 0.18 0.10 0.11

48-50 51-54 43-46 45-48 42-44 39-41

9.40 9.50 9.50 9.72

97 87 51

The copolymers were thermogravimetrically studied with the help of Seteram Co. thermoweighing machine B-60 in argon (at the heating rate of 5 deg/min) with simultaneous selection and analysis of gaseous degradation products, and the effect of introduction of bulky cyclic fragments into the back-bone on their thermal stability was traced. Figure 13 shows the investigation results indicating that initial mass losses are observed at 280 - 350°C depending on the volume of cyclic fragments in the chain. In the temperature range of 400 - 450°C hydrogen and methane are liberated, which is caused by ≡Si-C and С-Н bond break and leads to cross-linking by methyl and phenyl groups [88, 89]. Similar effect is also observed at thermal degradation of both carbosiloxane [90] and organosiloxane copolymers [90]. Degradation proceeds by the radical mechanism with formation of oligomeric products [91, 92].

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Figure 13. Thermogravimetric analysis of cyclolinear carbosiloxane copolymers.

This gives an opportunity to suggest [86, 87] that besides the backbone break, radical cross-linking reactions by methyl and phenyl groups proceed at thermal pyrolysis of carbosiloxane copolymers, which is also accompanied by liberation of hydrogen, methane and other low-molecular organic compounds of benzene and other types. Above 600°C, breakthrough of the mass loss curves hap-pens. Final mass losses fall within the range of 34 – 38%. Thermomechanical studies have indicated that the glass transition temperature of synthesized copo-lymers is decreased as the volume of cyclosiloxane ring in the chain is increased. The results of X-ray structural analysis indicate that the copolymers represent amorphous systems, and increase of cyclic fragment volume leads to an insignificant increase of the interchain distance. To detect the effect of the size of cyclosiloxanes, cross-linking bridges between them and deli-mitation of their roles in ability of polymers to self organize as mesomorphous structures, investi-gators [93] have studied polyaddition of dihydroalkylcyclotetra(hexa)siloxanes to divinylorgano-cyclotetra(hexa, octa)siloxanes in the presence of different complex platinum catalysts (dicyclo-pentadienylplatinum dichloride, the Carsted catalyst) and their reduced forms by the scheme as follows: R x H

O(R2SiO)n Si

R

R

O(R2SiO)n

R Pt x Si + Si Si O(R2SiO)n H H2C CH O(R2SiO)n CH CH2 Scheme 16

O(R2SiO)n R

R Si

Si CH2 CH2 O(R2SiO)n

2x

Where: n = 1 - 3, R = Me, Et. All synthesized polymers are completely soluble in usual solvents. The effect of platinum colloid forms used in polyaddition reaction on molecular structure of synthesized cyclolinear polyalkylcar-bosiloxane polymers has been studied. In accordance with the opinion [93], application of plati-num-hydrochloric acid [80] to polyaddition of dihydromethyl-

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197

phenylcyclotetrasiloxanes to divinyl-methylphenylsiloxane induces side reactions, which disturbs the regularity. This is proved by dis-crepancy between molecular masses and viscosity parameters. The possibility of side reactions pro-ceeding in the case of polyaddition is indicated in the work [94]. Taking into account the data obtained [85-87, 93-96] for the synthesis of cyclolinear alkylcarbosilo-xanes, special attention was paid to determination of optimal reaction conditions of polyaddition [93], in particular, selection of a catalyst providing for formation of polymers of strict cyclolinear structure. Formerly, Levis [97] has found that hydrosilylation proceeds with high efficiency on platinum complexes, reduced to the colloid form. Preliminary results show that polyaddition of 1,5-dihyd-rohexaethylcyclotetrasiloxane to 1,5-divinylhexaethylcyclotetrasiloxane on reduced CPDP in the form of colloid platinum decreases polydispersion degree of carbosiloxane polymer from 8.21 to 10.3. Taking into account encouraging results of the work [96], a sequence of cyclolinear carbo-siloxane polymers were synthesized [93] in the presence of three different forms of platinum cata-lysts, introduced into the reaction mixture after preliminary formation. Table 14. Some parameters of cyclolinear poly(alkylcarbosiloxanes) with regard to synthesis conditions Polymer №.

1 2 3 4** 5 6 7 8 9 10 11 12 13 14 *

R

n

Ме Ме Ме Et Et Et Me Me Me Et Et Me Me Me

1 1 1 1 1 1 2 2 2

Reaction conditions Reaction Time, Catalyst* Temp.,°C hour

NRF YC BC NRF YC BC NRF YC BC NRF YC NRF YC BC

70 70 70 70 70 70 25 25 70 130 130 70 70 70

1 1 20 10 20 47 168 144 50 9 10 10 10 10

[η]

0.31 0.21 0.12 0.08 0.15 0.08 0.80 1.30 0.13 0.14 0.24 0.12 0.14 0.06

Μ ωx10 -3

Μ ω/Μn

Μz /Μ ω

46.0 49.5 26.0 322.1 462.2 29.0 50.9 67.3 46.9 34.0 21.0

-

-

4.34 3.10 10.1 7.10 2.08 13.7 3.30 -

2.81 2.40 6.27 5.20 1.72 6.51 2.20 -

NRF is the non-reduced form of dicyclopentadienyl-platinum dichloride (CPDP); YC is the yellow colloid of CPDP; BC is the black colloid of CPDP. **After 10 hours polymer transforms into the cross-linked form. ***Polymers represent cyclolinear carbosiloxane copolymers with regular alternation of decamethylcyclohexasiloxane and tetradecamethylcyclooctasiloxane fragments. **** In toluene 250С dl/g.

Table 14 shows that the form of platinum compounds display different catalytic activities. Usually, yellow colloid form is more active compared with the black one, but lower polydispersion degrees are typical of polymers, synthesized in the presence of the latter one. As a consequence, the use of black colloid for obtaining polymers of regular structure is optimal, though due to low catalytic activity of it either high temperature of the reaction or

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high reactivity of initial reagents is required, which, for example, takes place for polymer 9 (Table 14). For synthesized carbosiloxane polymers, MMD curves were determined by the gel permeation chro-matography (GPC) method. Table 14 shows Мω, Мω/Мn and Мz/Мω values for polymers with dif-ferent sizes of cyclic fragment, from cyclotetrasiloxane to cyclooctasiloxane. Data on MMD (Table 14) indicate that cyclolinear polymers with the most homogeneous structure and composition are formed on the reduced catalyst. The more so, every particular case displays its own optimal type of the reduced form, i.e. catalytic system for synthesizing cyclolinear polymers should be selected with regard to activity of dihydrorganocyclosiloxane in polyaddition reaction. It should be noted that as yellow colloid is applied as the catalyst, the reaction temperature has no ef-fect on the shape of MMD curves for ethyl-substituted polymers with tetra- and hexasiloxane cyclic fragments. Cyclolinear structure of synthesized polymers is proved by the results of NMRspectroscopy studies. For all polymers independently of MMD, 29Si NMR spectra display two groups of reflexes in the area of -20.0 – 23.0 ppm, corresponded to atoms of silicon in R2SiO and RSiCН2CH2 groups (Table 14). Reflexes typical of silicon atoms in the branching centers are absent. The quartet of reflexes from RSiCH2CH2, observed in 29Si NMR spectra of polymers №8 and 9 (Table 14) confirms atactic structure of synthesized products. Analysis of NMR spectra of polyaddition products indicates that the reactions proceed by the Farmer rule forming CH2-CH2 bridges between rings in more than 95% of cases. By the methods of differential scanning calorimetry (DSC), X-ray structural analysis (RSA) and op-tical microscopy, parameters of thermal transitions in synthesized cyclolinear polymers with diffe-rent structures of units, MM and polydispersion degree were determined. Table 15 shows that Tg of all other polymers are higher than Tg of cyclolinear siloxane polymers, but this difference is decreased with increase of the quantity of diorganosiloxane groups in cyclosiloxanes. Regularities observed for Tg shift with variations of the cyclosiloxane size and length of side substituting agents of carbosiloxane polymers are similar to these, previously detected for pure cyclolinear polysiloxa-nes at analogous variations of the chemical structure [49]. Independently of molecular mass and polydispersion degree, all cyclolinear carbosiloxane polymers with cyclic tetrasiloxane fragments (Table 15, polymers №1-6) and the ones with decamethylcyclo-hexasiloxane fragments (Table 15, polymers №7-9) do not display mesomorphous properties. RSA data (Figure 14) indicate that polymers №2 – 9 are amorphous, because their diffraction patterns are similar by type to these of amorphous polyorganosiloxanes. They contain two amorphous halos: symmetrical intensive one at 2θ (∆1/2 =1.8°) and diffuse low one at 2θ. Distribution of amorphous scattering intensity, in particular, angular 2θ position, depends on the sizes of cyclic fragment and side substituting agent (Figure 14). Because compounds representing the mixture of cis- and trans-isomers were used in polyaddition reactions, carbosiloxane polymers should possess the atactic structure. Such conclusion is also pro-ved by the above-mentioned NMR spectra data. In this connection, the absence of ability to crystal-lize in the majority carbosiloxane polymers is quite explainable. However, the absence of mesomor-phous properties in polymer with decamethylcyclohexasiloxane fragments is the unexpected result. The case is that at the polymerization degree P≥5, atactic non-crystallizing cyclolinear polyorganosi-loxanes with

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

199

decamethylcyclohexasiloxane fragments are mesomorphous, temperature range of mesophase existence increasing with molecular mass (MM) [56]. It should be noted also that the average intermolecular distance d1≈8.3 Å for polymers №.7-9 (calculated from 2θal) is practically coincident with the similar value d1≈8.6 Å for amorphous cyclolinear poly(organosiloxanes) with decamethylcyclohexasiloxane fragments [98]. The latter are characterized by the polymerization degree, P, below 5. Comparison of the above-shown data on cyclolinear carbosiloxanes with pre-viously published results on the phase structure of cyclolinear organosiloxane homo- and copoly-mers [99] indicates that introduction of different groups between cyclic siloxanes (flexible junc-tions) causes a significant decrease of isotropization temperature.

Figure 14. Diffraction patterns: a – polymer № 3 at 20°C (1) and 73°C (2), polymer №9 at 20°C (3), copolymer № 12 at 20°C (4); b –polymers №6 (1) and 11 at 20°C (2)

At some critical distance between cyclic rings in considered carbosiloxane copolymers, as well as in cyclolinear siloxane copolymers [48, 100], the ability of molecules to form the mesomorphous phase is suppressed: above Tmelt, crystallizing copolymers transit into the melt, and non-crystallizing ones are amorphous in the whole temperature range. For example, copolymers with –R2SiO- junction pre-sserve mesomorphous properties, whereas copolymers with O(СН3)2SiСН2СН2Si(СН3)2O, R2SiO)2 and -СН2-СН2- junctions lose these properties. There is another fact of special interest, which may affect the mesomorphism of copolymers: lower flexibility of -CH2CH2- groups compared with oxy-gen. By increasing the elementary unit to tetradecamethylcyclooctasiloxane, an attempt was made [93] to change the ratio of distances between rings and junctions. Carbosiloxane copolymers №12-14 with regular alternation of decamethylcyclohexasiloxane and tetradecamethylcyclooctasiloxane fragments

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

in the chain was synthesized by polyaddition on different non-reduced and reduced colloid forms of the CPDP catalyst (the attempt to synthesize dihydrotetradecamethylcyclooctasiloxane has failed [101]). Table 15. Calorimetric and structural parameters of cyclolinear carbosiloxane copolymers Polymer*, №. **

*

Тg,°С

Тmelt, °С

2θ, deg

Chemical shifts Si 29Si NMR, ppm R2SiO

RSiCH2CH2

2

-30

42

12.0

-18.99

-19.14

6

-74

-

13.0

-20.85

-20.22

9

-69

-

10.6

-21.76 21.77

11

-104

220***

9.80

-22.95

13

-75

-

9.37

-

-21.59 -21.61 -21.66 -21.69 -23.62 -23.69 -

Polymer numeration in accordance with Table 14. Isotropization temperature.

**

Melting heat Qmelt = 167.6 J/mol.

***

Thus, substitution of oxygen bridges between cyclic fragments by -СН2СН2- groups leads to the loss of the ring ability to intra- and intermolecular correlations and, consequently, to the loss molecule ability to self-organization and formation of mesomorphous structures. Introduction of ethyl substi-tuting agents at hexasiloxane rings form additional intra- and intermolecular interactions, due to which the ability of macromolecules to self-organization occurs.

3. OLIGOMERS AND COPOLYMERS WITH ORGANOCYCLOCARBOSILOXANES FRAGMENTS IN THE CHAIN To synthesize oligomeric organocyclocarbosiloxanes, the reaction of dihydroxyorganocyclocarbo-siloxane homofunctional condensation in 60% toluene solution was studied [102] on the Dyne–Stark device both in the presence (7%) and in the absence of activated coal. As a consequence, dihydroxy-containing organocyclocarbosiloxanes oligomers were synthesized in accordance with the scheme as follows [102, 103]: C2H4 Me m HO Si Si OH O O Si Ph2

C2H4 Me Si Si O H O O Si m Ph2 XI

Me

Me

-H2O Scheme 17

HO

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

201

where: m = 8, 11. Organocyclocarbosiloxane oligomers obtained represent solid products, well soluble in various or-ganic solvents. It is found that “non-equilibrating” catalyst which is activated coal, used in homo-functional condensation, does not induce scission of the organocyclocarbosiloxane ring. X-ray diffraction analysis indicates that oligomers are amorphous systems with the interchain dis-tance equal d1≈8.64 Å. Thermogravimetric studies show that by thermal oxidative stability oligo-mers are behind polyorganocyclotetrasiloxanes only. For the purpose of synthesizing organocyclocarbosiloxane oligomers and polymers with different ratio of SiO/SiC groups in the complex repeated unit and studying the effect on their ability to self-organization in bulk and in ultra thin films, HFC reaction of dihydroxymethylcyclosiloxalkanes with dichloromethylcyclosiloxalkanes proceeding in the presence of pyridine acceptor in accordance with the scheme as follows was studied [104]: Me Me Me (CH2)n (CH2)n 2mPy HO mHO Si Si OH + mCI Si Si CI - 2mPyHCI O O O O Si Si Me Me Me Me Me

Me (CH2)n Si Si O H

Me

O

O Si

Me

Me

m

XI

Scheme 18

Where: n = 2, 3; Me

Me2 Me2 OSiCH2SiO

Me

Me2 Me2 OSiCH2SiO SiOH

SiCI + HOSi

xCISi OSiOSiO Me2 Me2

Me

Me

OSiOSiO Me2 Me2

Me

Scheme 19

2xPy HO -2xPyHCI

Si

Me2 Me2 OSiCH2SiO Si O H OSiOSiO Me2 Me2 Me 2x XII

Composition and structure of synthesized oligomers is proved on the basis of the ultimate analysis and by IR, 1Н and 29Si NMR spectral data. Spectral data (oligomers №1–3, Table 2.18) indicate that the presence of cis-trans, trans-trans and trans-cis combinations of rings in the polymer chain is si-milar to polydecaorganocyclohexasiloxanes [26]; in the case of transdihydroxyorganocyclohexasi-loxane, cis-cis-combination in the polymer chain is absent. They display atactic structure of cycloli-near chain, enriched with trans-trans-sequences.

4. SILARYLENE CYCLOSILOXANE AND SILARYLENE CARBOORGANOCYCLOSILOXANE OLIGOMERS AND COPOLYMERS Introduction of phenylene unit into the polyorganosiloxane chain causes a significant variation of the chain configuration and flexibility, which affects physical and chemical parameters of the po-lymer. Moreover, different combinations of linear ≡Si-O-Si≡ or silarylene fragments with cyclic on-es may change conformational flexibility of the chain

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

[105]. As indicated [106, 107], the origin (chemical and geometrical) of substituting agent at the atom of silicon may induce increased chain rigidity, if substituting agents between siloxane chains are composed of -СН2-СН2- and ≡Si-C6H4-Si≡ fragments [108, 109]. For the purpose of synthesizing dihydroxy-containing silarylene cyclosiloxane oligomers, HFC reac-tion of 1,4-bis(chlorodimethylsilyl)benzene, synthesized by the known technique, with 1,5-dihyro-xyhexaphenylcyclotetrasiloxane and 1,7dihydroxydecaphenylcyclohexasiloxane was studied [87, 110 – 112] at the molar ratio of reagents as follows: 1:0.9, 1:0.95 and 1:1, respectively. The reaction proceeded in 60 - 70% solution of anhydrous toluene in the presence of pyridine, the acceptor of hydrochloric acid, at room temperature with consequent boiling of the solution up to the boiling point of the solvent used. Generally, the reaction proceeds by the scheme as follows: O(SiPh2O)k Ph Me Ph x HO Si Si OH + yCI Si Me O(SiPh O) 2

k

Ph HO

Me

2yPy

Si CI Me

-2yPyHCI

O(SiPh2O)k Ph Me Si Si O Si

Me

Me O(SiPh2O)k Scheme 20

Me

Si O

H m

where: k = 1 (XIII), 2 (XIV); m = 4 – 16. The HFC depth can be varied by changing the ratio of initial components. Equimolar ratio of the ini-tial components gives maximal depth of HFC reaction. After partial overprecipitation by methanol from toluene solution, synthesized oligomers become yellow or light-brown transparent products, well-soluble in various organic solvents. Some parameters of the oligomers are shown in Table 16. Silarylenecyclosiloxanes of structure XIV with higher molecular mass were synthesized by catalytic dehydrocondensation of 1,7-dihydride-1,7-dimethyloctaphenylcyclohexasiloxane and 1,4-bis(hydro-xydimethylsilyl)benzene [111, 112]. For the purpose of synthesizing silarylenecyclohexasiloxane copolymers, catalytic dehydroconden-sation of 1,7-dihydride-1,7-dimethyloctaphenylcyclohexasiloxane with 1,4bis(hydroxydimethylsi-lyl)benzene, at different temperatures (30, 40 and 50°C) in the solution of anhydrous toluene (C= 0.4686 mol/l) in the presence of powder-like caustic potash has been investigated. Recently, it has been shown that during catalytic dehydrocondensation of linear α,ω-dihydridediorganosiloxanes with α,ωdihydroxydiorganosiloxane in the presence of caustic potash, depending on the length of siloxane fragments, both individual organocyclosiloxanes and linear copolymers are synthesized [113]. Besides, it was shown that during catalytic dehydrocondensation of dihydrideorganocyc-losiloxanes with dihydroxyorganocyclosiloxanes in the presence of nucleophilic anhydrous potas-sium hydroxide, the break of cyclosiloxane rings does not take place [114]. Dehydrocondensation reaction proceeds according to the following scheme [111, 112,114]:

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

Me

O(SiPh2O)2 Me Me Me x HO Si Si OH + x H Si Me O(SiPh O) 2

Si H Me

2

T0 C (x-1)H2 Me

O(SiPh2O)2 Me Me Me H O Si Si O Si Me O(SiPh O) 2

203

Si

H

Me m

2

Scheme 21 where: T = 30, 40, 50°C. During catalytic dehydrocondensation of 1,7-dihydrideorganocyclohexasiloxane with l,4bis(hyd-roxydimethylsilyl)benzene in the presence of potassium hydroxide, the reaction order, rate constants and activation energy were determined. Catalytic dehydrocondensation is the second order reaction. Some physical and chemical parameters of low-molecular copolymers are shown in Table 16. Table 16. Yield and physical and chemical parameters of α,ω−dihydroxysilarylenecyclo(tetra)hexasiloxanes №

m

ηspec

XIII

Yield, % 76

4

0.04

1

XIII

81

6

0.04

1

XIII

85

16

0.06

2

XIV

80

4

0.04

2

XIV

86

12

0.05

7*

2

XIV

93

13

0.08

8*

2

XIV

93

-

0.09

9*

2

XIV

95

16

0.09

Oligomer structural unit

k

Structure

1

Me Si

1 2 3 4 6

*

Ph2 O(SiO) k Ph Me Ph O Si

Si O Si O(SiO)k Ph2

Me

Me

m

Тg,0 С 5561 6165 6368 6165 6771 6165 6466 6771

d1,Å 9.98 10.04 10.08 10.04 10.04

The oligomers were synthesized by dehydrocondensation reaction.

It is shown that the temperature coefficient of this dehydrocondensation reaction equals γ≈1.5. From the dependence of the reaction rate constants logarithm on reverse temperature, the activation energy of the reaction was calculated, which equals Ea = 32.55 kJ/mol. For copolymers №7* and 9* (Table 16), quantitative values ofMn,Mω,Mz andMω/Mn were determined by gel permeation chromatography methods, which equalMn=1.05-1.62×104 andMω≈1.69-1.98×104; polydispersion degrees, D, of copolymer № 7* and 9* (Table 16) equal ~1.46 and 1.22, respectively.

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Arylenecyclosiloxane oligomers were synthesized in HFC reaction of 1,4bis(dichlororganosilyl)-benzene with dihydroxydiphenylsilane and dihydroxydiphenylsiloxanes in 50–60% anhydrous tolu-ene solution at 1:2 ratio of the initial components both in the presence and in the absence of pyri-dine, which is hydrogen chloride acceptor. The reaction proceeded at room temperature; at the final stage the reaction mixture was heated up to 100°C. The reaction scheme is as follows [87]: R x CI2 Si

R

HO

SiCI2 + 2x HO(SiPh2O)nH

-HCI

Scheme 22

R

R O(SiPh2O)n

Si

Si O(SiPh2O)n

HO

H H

x

Where: R = Me, Ph; n = 1 - 3. After over-precipitation from toluene solution with methyl alcohol, the oligomers synthesized repre-sent solid products with ηspec=0.05-1.0. It is shown that at short length of linear diphenylsiloxane unit, n≤2, oligomers completely soluble in various organic solvents are obtained. The yield of solu-ble part of oligomers is decreased with the length increase, n. Synthesized silarylenecyclosiloxane oligomers and copolymers represent amorphous systems, and the interchain distance in oligomers equals d1=9.98-10.08 Å, approximately. The results of thermo-gravimetric analysis indicate that 5% of the mass is lost at 430-450°C; the main degradation process proceeds in the range of 500-700°C, and in the area of 800°C the mass loss curves become evanes-cent. Further on, dihydroxyarylenecyclosiloxanes were used for synthesizing cyclolinear organosili-con block-copolymers. To clear up action of the origin of organic radicals in organocyclotetrasiloxane fragments on polyad-dition process, as well as to determine contribution of ethylene and phenylene units containing orga-nocyclotetrasiloxane fragments of 1,5- and 1,3-position into cyclolinear copolymers, investigators have studied 1,4-bis(dimethylsilyl)benzene hydride polyaddition to 1,5-divinyl-1,5-dimethyltetra-organocyclotetrasiloxane and 1,3-divinyl-1,3dimethyltetraorganocyclotetrasiloxane in the presence of the catalyst (0.1 M solution of platinum-hydrochloric acid in tetrahydrofuran) [115]. Me n CH2=CH-A-CH=CH2 + n H Si Me

Me H PtCI6 Si H 2 Me

Me Si Me

Me Si-CH2-CH2-A-CH2-CH2 Me

n

Scheme 23

R' R" Me Si H2C=HC Si O Me O O CH=CH2 , Si Si Where: A = O H2C=HC O SiO Me R'R"Si O XV R' R" R’ = R” = Me; R’ = Me, R” = Ph; R’ = R” = Ph.

Me Si CH=CH2 O SiR'R"

XVI

Initial divinylcyclosiloxanes, used in polyaddition reactions, represent a mixture of cisand trans-isomers (at 46:54 ratio). Because these isomers could not be separated by rectification or fractional over-precipitation [115], synthesized silarylene

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

205

carboorganocyclosiloxanes are considered to be atactic copolymers. Hydrosilylation conditions depend on reactivity of the initial monomers. As 1,4-bis(dimethylsilyl)benzene is quite active hydrosilylating agent, already at 60 70°C it inter-acts with divinylorganocyclotetrasiloxanes containing even four phenyl groups at atoms of silicon; in the case of methyl substituting agents only the reaction proceeds at 50°C. All synthesized copoly-mers are transparent colorless compounds which, in the unique case of methyl substituting agents at atoms of silicon in initial cyclosiloxanes, represent highly viscous-flow polymers; in the case of diphenyl substituting agents, they are transparent solids forming friable soluble films. Table 17 shows physical and chemical parameters of silarylene carboorganocyclosiloxanes. Note that the hig-hest values of [η]=0.42 and 0.48 dl/g are displayed by polymers containing rings with methyl and phenyl groups at single atom of silicon, which are copolymers №1 and 5 (Table 17). In its turn, location of vinyl groups in 1,3- or 1,5-position in OVCS induces clearly determinable regularity. In all considered cases, PFOS viscosity is higher, when two vinyl groups are located in 1,5-position of tetrameric ring. This is apparently associated with disposition of vinyl groups more suitable for hydrosilylation and formation of more symmetrical structure in copolymers №1–3 (structure XV). Table 17. Physical and chemical parameters of silarylene carboorganocyclosiloxanes №

Copolymer structure

R′

1 2 3 4 5

XV XV XV XVI XVI XVI

Me Me Ph Me Me Ph

R″

[η], dl/g

Тdegr* of 5% mass loss, °С

Coke-like residue (800°С), %

Тg,0С

Me Ph Ph Me Ph Ph

0.36 0.48 0.40 0.25 0.42 0.26

450(250) 470(450) 450(350) 325(300) 420(400) 400(375)

50 48 45 57 48 40

-11 +20 +27 -5 +16 +50

In 1H NMR spectra of silarylene carboorganocyclosiloxanes in the area of 5.8 and 4.5 ppm, reflexes from protons belonged to ≡Si-СН=СН2 and ≡Si-Н groups of initial monomers are absent. The reflex at 1.0 ppm, corresponded to protons of -CH2-CH2- group, formed in hydrosilylation reaction. Gene-rally, location of reflexes and the ratio of their intensities in 29 Si and 1H NMR spectra prove the supposed structure of silarylene carboorganocyclosiloxanes. In the case of equimolar ratio of the components, under selected conditions hydrosilylation is almost completed: by NMR and IR-spec-troscopy methods no residual end groups were detected. High-molecular product synthesized posse-sses MM within the range from 1.0×105 to 5.0×105. At the same time, taking into account high volatility of 1,4-bis(dimethylsilyl)benzene compared with divinylcyclotetrasiloxane, the quantity of int-roduced dihydride derivative was increased by 0.1% of the theoretical one, because ≡Si–Н groups are present at the ends of the chain. To eliminate the effect of end groups on physical and chemical parameters, on thermal stability of silarylene carboorganocyclosiloxane, in particular, copolymer so-lution in benzene is treated by the excess of vinylheptamethylcyclotetrasiloxane before over preci-pitation in accordance with the scheme as follows:

206

O. Mukbaniani, G. Zaikov and T.Tatrishvili Me Me Si Me Me Me O O Me H PtCI 2 6 Si H + Si Si Si Me H C=HC O O Me Me Si 2 Me Me Scheme 24

Me Si Me

Me

Me Si

Me Me O O Me Si Si CH-CH2 Si O O Me Me Si Me Me

Variation of the ratio of reagents for hydrosilylation gives an opportunity to obtain both high-mo-lecular products and oligomers with defined chain length, which is very important for synthesis of block-copolymer and polymer networks. After polymer treatment by heptamethylvinylcyclotetrasiloxane, heat resistance of silarylenecarbo-organocyclosiloxanes is slightly increased. The reason is that residual end ≡Si-H groups promoting high-temperature polymer degradation are substituted by higher heat resistant heptamethylcyc-lotetrasiloxane fragments, which causes an increase of thermal stability of the polymer. Estimation of the glass transition temperature of silarylene carboorganocyclosiloxanes and its varia-tion with regard to the origin of substituting agents at atoms of silicon in cyclic rings and introduc-tion of disilphenylene unit into the polymer backbone has indicated that at quite high molecular mass (up to 5.0×105) no high elasticity plateau on thermomechanical curves of the samples is pre-sent. This is probably associated with higher rigidity of silarylene carboorganocyclosiloxanes com-pared with linear poly(organosiloxanes). For the purpose of carbosiloxane network synthesis, at the first stage in accordance with scheme (2.25), silarylene carboorganocyclosiloxanes with 1,4-bis(dimethylsilyl) benzene excess and narrow MMD were obtained [116]. Hence, synthesized oligomers of the structure XV are transparent, colorless and viscous products with MM = 800 - 2,500. At the second stage, polyaddition of reaction (2.23) product with tetramethyltetravinylcyclotetrasiloxane is performed in accordance with the scheme as follows: R' R" Me H Si Me

Me

Me

SiCH2CH2 Si Me

OSiO Me

Me

SiCH2CH2 Si Me OSiO n R' R" Scheme 25

Me

H2PtCI6 Crosslinking Si H [Me(CH =CH)SiO] Croslinking polymer 4 polymer 2 Me

Where: R’ = R” = Me, Ph; R’ ≠ R”. Polymer networks depending on the structure of initial monomers and oligomers are characterized by different framing at atom of silicon and different regulated distance between network points. For the purpose of studying some physical and chemical properties, formation of a network structure directly during film formation from the solution is the unique method of obtaining film samples of polymer networks. Table 18 shows values of strength at break, σb, deformation at break, εb, and elasticity coefficient, E, of studied polymer networks. The data indicate that substitution of methyl groups by phenyl ones and variation of the distance between chain branching centers is accompanied by a significant chan-ge of deformation and strength properties of studied polymers. Note that substitution of both methyl groups by phenyl ones is accompanied by the

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

207

increase of the elasticity parameter from ~3 to ~600 MPa and the strength from ~1 to ~20 MPa. Besides the possibility of broad variation of mechanical properties, in some cases high mechanical properties may be realized, for example, for a polymer with R' = R" = С6Н5 groups at atoms of silicon (n = 2), which displays high strength (~20 MPa) and elasticity parameter (~600 MPa) combined with quite high deformability (~30%). Table 18. Deformation and strength parameters of films based on silarylene carboorganocyclosiloxanes of the structure XV [117] №

1 2 3 4 5 6 7 8 9

R’

R”

n

σр, MPa

εp, %

E, MP

Me Me Me Me Me Me Ph Ph Ph

Me Me Ph Ph Ph Ph Ph Ph Ph

1 2 1 2 3 4 1 2 3

1,1 0,6 10,8 0,9 0,8 0,6 21,3 19,3 9,5

36 52 158 164 209 234 9 30 50

3,1 1,5 43,0 6,8 0,6 0,3 610 570 350

For the purpose of estimating conformational parameters of silarylene carboorganocyclosiloxanes of the structure XV, two approaches were used [117]: computerized mathematical simulation using the Monte-Carlo method and experimental estimation of the flexibility parameters in solution under natural conditions. In the first case, mathematical simulation has determined the skeletal flexibility of the molecule in the absence of substituting agents at atoms forming the backbone. In the second case, all fragments of the chain, possible interactions with the solvent and temperature effect have been taken into account in the flexibility estimation. For the purpose of experimental estimation of the flexibility parameters in solution, silarylenecarbo-organocyclosiloxanes copolymer 2 (Table 18) with structure XV was fractioned from the benzene (solvent) – ethanol (coagulant) system into 14 fractions. At 25°C in toluene, characteristic viscosity values, [η], of these fractions fall within the range of 5.1 – 0.07 dl/g in toluene. For nine fractions, sufficient quantity of which was obtained, by the light scattering method, values of Мω at the angle of 90° in chloroform (dn/dс ≈ 0.95) on Fika photogoniodiffusometer were measured. For four most high-molecular fractions (Table 19), Мω and (R2)1/2 values at different angles were measured. Polydispersity coefficient of the copolymer was estimated by the GPC method (on KhZh1302 gel chromatograph). For silarylene carboorganocyclosiloxane copolymer 2, GPC data displayМω/Мn =1.34. Table 19 shows values ofМω and (R2)1/2 for silarylene carboorganocyclosiloxane fraction, measured by the light scattering method. As for fractions 4-9Мω values are high, they are measur-ed in non-polarized and polarized light. As these values are close, Table 19 shows the average one for these fractions. Small differences inМω values, measured in polarized and non-polarized light, as well as low scat-tering asymmetry values close for different fractions testify about low polydispersity of the fractions and coil like conformation of macromolecules, which is of

208

O. Mukbaniani, G. Zaikov and T.Tatrishvili

importance for experimental estimation of flexibility parameters by data on [η] and molecular mass of the fractions [117]. Table 19. Values of Мω, scattering asymmetry and the second virial coefficient, A2, for silarylene carboorganocyclosiloxanes fraction [117] № 1 2 3 4 5 6 7 8 9

Мω·10-2

〈R 2〉 z 1/2

206 252 400 883 1072 1381 1866 644.8 12500

298.6 405,7 644.8 1221.4

Scattering asymmetry 1.03 1.06 1.03 1.09 1.05 1.07 1.06 1.20 1.20

А2х10-5, cm2·mol/g2 0.940 0.281 0.221 0.264 0.236 0.202 0.140 0.135 0.093

The dependence of [η] and Мω values in lg[η] – lgМω coordinates, shown in Figure 15, indicates that the following Mark-Kuhn-Hauvink equations are corresponded to silarylene carboorganosilo-xane copolymer: [η] = 0.908·10-3 M0.506 ± 0.049 (toluene, 20°С); [η] = 0.383·10-3 M0.588 ± 0.084 (toluene, 25°С). Values of parameter α in the Mark-Kuhn-Hauvink equation, close to 0.5, which were obtained for silarylenecarboorganosiloxane fractions, allow correspondence of the polymer molecules to the coil- like type and toluene at 20 and 25°C to θ-solvents. As a consequence, extrapolation data of the Mark-Kuhn-Hauvink equation, silarylenecarboorganosiloxane molecules display the coil-like conformation, which is slightly disturbed in toluene at 20 and 25°C by interaction with the solvent.

Figure 15. Dependence of lg[η] on lg Мω for silarylenecarboorganosiloxane in toluene at 25°C (1) and 20°C (2)

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

209

True value of macromolecule flexibility was calculated from [η], А2 andМω of the fractions using some theoretical equations. Calculation of flexibility parameters at free rotation by the Monte-Carlo method indicates that free rotation of the molecule is possible in four cases only (l2, l4, l5, l6); in three cases it is hindered (l1, l3, l7), which is observed from Table 21 of the schematic presentation of the chain unit (scheme 1). Table 20. Conformational parameters of several organosilicon polymers №

Repeated unit of the Polymer

(〈h2〉 0 /M)x x10 -16

А, Å

Аfr, Å

Sfr= Аfr/l0

S=A/l0

σ

М0/l0 (l0, Å)

Ref.

1

Silarylene carboorganocyclosiloxane

18.91 19.92

19.2

1.04

1.03 1.08

1.02

638/18.4

-

2

~Ме2SiO~

9.4-10

6.0

2

3.2-3.4

1.26

74/2.96

129

3

-CH2CH2SiMe2SiMe2-

0.5461 0.5752 (〈h2〉 fr /M)= 0.555 0.42-0.43 (〈h2〉 fr /M)= 0.24 1.173 0.962

26.5 21.8

5.44

1

4.2 4.8

2.21 2.0

144/6.34

129

5.43 nm2

54

-

-

-

-

198/2.35

116

(〈h2〉 cв /M)= 0.28

-

15

1.3

-

-

618/11.5

112

(CH2)5CH3

4

Si (CH2)5CH3 R R

5

Me

Me

O (SiMe2O)k R R 6

R=Ph, k=1 R=Ph, k=5

0.303

16

10

-

1

1.12

914/21.9

112

7

R=Me, k=0

0.603

233

-

-

4.5

-

283/6.4

58

Note: Calculations have been executed by the following equations: 1 – Curata-Yamakawa; 2 – Stockmayer-Fixman; 3 – Yamakawa-Fudgi.

l1

l2 θ1

CH2 θ2 l3

H 2C

l4 Si

θ4 l 5

θ3

θ6

H 2C l6

Si

l7 θ5

H2C

Si θ7

Scheme 1 In accordance with calculations, current flexibility parameter (〈 h2〉 〈 h2〉

fr

fr/M),

where

is the mean-square distance between macromolecule chain ends at free rotation,

equals 0.555×10-6. If molecular mass of the chain unit equals M0=638 and length of the unit

210

O. Mukbaniani, G. Zaikov and T.Tatrishvili

l0=18.41×10-8 cm, the flexibility para-meter in terms of the Kuhn segment, A, at free rotation equals: Afr = (〈 h2〉

fr/M)Ml

= 19.2 Å.

Specified data show (Table 20) that the Kuhn segment, Afr, and A of silarylenecarboorganosiloxane are comparable with the molecule unitlength (l0 = 18.4 Å). Table 20 shows that for the sequence of silicon-containing high-molecular compounds, this takes place for Afr of poly(ethylenetetramethyl-disilane) (compound 3) and polyorganocyclosiloxane (compound 5), the repeated units of which contain -СН2СН2groups [129] and cyclic fragment, respectively. For the studied silarylene carboorganosiloxane rotation is prohibited both around -СН2СН2- (l3 and l7 bond lengths) and cyclic frag-ments (l1) (Table 21). For estimation of silarylene carboorganosiloxane macromolecules under natural conditions, when the coil is “perturbed” by interaction with the solvent, authors of the work [117] have used the fol-lowing prerequisites observed in the current case: L>>α, i.e. the macromolecule is of the coil-shaped type (α=А/2); low concentrations of solutions, in which the Einstein equation is active; the selected solvent is close to the θ-solvent. Table 21. Bond lengths and unit rotation angles in silarylene carboorganocyclosiloxane chain Bond length, Å

l1=4.25 l2=1.86 l3=1.54 l4=1.87 l5=6.51 l6=1.87 l7=1.54

Angles between bonds (θ ), deg

Type of rotation

54.5 66.0 66.0 68.0 68.0 66.0 66.0

Prohibited (trans) Free Prohibited (trans) Free Free Free Prohibited

For silarylene carboorganocyclosiloxane, (〈 h2〉

-16 0/M)=0.575×10

(Table 20), hence,

the Kuhn seg-ment A equals Kθ=19.9 Å. By the authors [117] it was shown, that (〈 h2〉 value, obtained by [η]/ Μ1/2 extrapolation, coincides with (〈 h2〉

fr/M),

0/M)

which is typical of

Gaussian impermeable coil. On the example of silarylene carboorganocyclosiloxane, the authors of the present work [117] have made an attempt to estimate the value of ML basing on the data on [η] and molecular mass of the studied polymer fraction. Table 21 shows assessment data on conformational parameters, persistent length (α), the Kuhn seg-ment (A) and structural parameter (ML) for silarylene carboorganocyclosiloxane fractions. Average values of α, А and ML, deduced from [η] andМω of silarylene carboorganocyclosiloxane fracti-ons, equal 9.6 Å, 19.2 Å and 34.45×108, respectively. Thus, the structural parameter, ML, calculated fromМω and [η] values, and the one given by chemical structure (ML=34.65×108) of molecules are practically coincident. As a consequence, the above considered Afr really equals 19.2 Å. Under natural conditions, the

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

211

value of A in solution is close to Аfr; that is why rotation dormancy factor σ = (А/Аfr)1/2=(19.9/19.2)1/2 =1.02. Thus, according to data of mathematical modeling and hydrodynamic studies, obtained by the Shtockmayer-Fixman equation [118], rotation around valence bonds in silarylene carboorganocyc-losiloxane chains is practically free (rotation is possible around l2, l4, l5 and l6 bonds (Table 21). This conclusion was proved by calculations of flexibility parameters of silarylene carboorganocyc-losiloxane molecules, executed by the authors of the present monograph usingМω and A2 values, measured by the light scattering method. The calculations were performed by Krigbaum [119] and Kurata-Yamakava [120] equations. A wide complex of investigations for assessment of conformational parameters of silarylene carbo-organocyclosiloxane macromolecules using hydrodynamic and molecular parameters allowed the authors of the present monograph to make some conclusions. The length of silarylene carborgano- cyclosiloxane macromolecule segment is comparable with the unit length, l0. At free rotation, the Kuhn segment value equals Аfr= 19.2 Ǻ. Under natural conditions, value of the Kuhn segment in so-lution is practically coincident with Afr, and the dormancy parameter of rotation around virtual bond is close to one, i.e. rotation is practically free. This is also proved by the value of characteristic ratio С∞, which is close to one. The chain rotates due to the presence of connective junctions. Thus, as follows from the abovesaid, the “flexibility mechanism” gives silarylene carboorganosiloxane mo-lecules the opportunity to form a dense coil, which approaches the Gaussian impermeable one for high molecular masses and semi-permeable as molecular mass is reduced.

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[59] Vitovskaya M.G., Astapenko E.P., Bushin S.V., Skazka V.S., Yamshchikov V.M., Makarova N.N., Andrianov K.A., and Tsvetkov V.N., Vysokomol. Soedin., 1973, vol. 15A(11), p. 2549. (Rus) [60] Tsvetkov V.N. and Andrianov K.A., Eur. Polym. J. 1973, vol. 9, p.27. [61] Tsvetkov V.N., Frisman E.V., and Boitsova N.M., Vysokomol. Soedin., 1960, vol. 2(7), p. 1001. (Rus) [62] Aleksandrova Yu.A., Nikitina T.S., and Pravednikov A.N., Vysokomol. Soedin., 1968, vol. 10A, p. 1078. (Rus) [63] Tomas T.H. and Kendrik T.C., J. Polym. Sci., 1969, vol. 27A, p. 537. [64] Plate N.A. and Shibaev V.P., Comb-Like Polymers and Liquid Crystals, Khimia, Moscow, 1980, p. 303. (Rus) [65] Liquid Crystalline Order in Polymers, Ed. Blumshtein A., Academic Press, New York, 1978. [66] Beatty C.L., Pochan J.M., Froix M.F., and Hinman P.P., Macromolecules, 1975, vol. 8, p. 547. [67] Papkov V.S., Godovski Yu.K., Litvinov V.M., Svistunov V.S., and Zhdanov A.A. International Conference of Socialist Countries on Liquid Crystals, Tbilisi, 1981, vol. 2, p. 201. (Rus) [68] Liquid Crystalline Order in Polymers, Ed. Blumshtein A., Academic Press, New York, 1978, Chapter 9. [69] Pomerantseva M.G., Belyakova Z.V., and Golubtsov S.A., Synthesis of Carbofunctional Organosilanes by Polyaddition Reaction, Moscow, 1971. (Rus) [70] Reikhsfeld V.O., Vinogradova V.N., and Fillipov N.A., Zh. Obshch. Khim., 1973, vol. 43(10), p. 2216. (Rus) [71] Fillipov N.A., Reikhsfeld V.O., Zaslavskaya T.N., and Kuzmina T.A., Zh. Obshch. Khim., 1977, vol. 47(6), p. 1374. (Rus) [72] Andrianov K.A. and Magomedov G.K., Doklady AN SSSR, 1973, vol. 228(5), p. 1094. (Rus) [73] Andrianov K.A., Gavrikova L.A., and Radionov E.F., Vysokomol. Soedin., 1971, vol. 13A(4), p. 937. (Rus) [74] Watanabe H., Kitahara T., Motegi X., and Nagai H., J. Organomet. Chem., 1977, vol. 139(2), p. 215. [75] Souchek I., Andrianov K.A., Khananashvili L.M., and Myasina V.M., Doklady AN SSSR, 1975, vol. 222(1), p. 128. (Rus) [76] Andrianov K.A., Petrashko A.N., Asnovich L.Z., and Gashnikova N.P., Izv. AN SSSR, Ser. Khim., 1967, No. 6, p. 1267. (Rus) [77] Andrianov K.A., Zhdanov A.A., Rodionova E.F., and Vasilenko N.G., Zh. Obshch. Khim., 1975, vol. 45(11), p. 2444. (Rus) [78] Andrianov K.A., Souchek I., and Khananashvili L.M., Uspekhi Khimii, 1979, vol. 48, p. 1233. (Rus) [79] Andrianov K.A., Sidorov V.I., Zaitseva M.G., and Khananashvili L.M., Khim. Geterotsicl. Soed., 1967, No. 1, p. 32. (Rus) [80] Zhdanov A.A. and Astapova T.V., Vysokomol. Soedin., 1981, vol. 23A(3), p. 626. (Rus) [81] Akhrem I.S., Chistovalova N.I., Myisov E.I., and Volpin M.E., Zh. Obshch. Khim., 1972, vol. 42(8), p. 1868. (Rus)

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[82] Akhrem I.S., Chistovalova N.I., Myisov E.I., and Volpin M.E., Izv. AN SSSR, Ser. Khim., 1976, No. 9, p. 2069. (Rus) [83] Stober M.R., Musole M.C., and Speier J.L. J. Org. Chem. Soc., 1965, vol. 30(5), p. 1651. [84] Bulkin A.F., Papkov V.S., Zhdanov A.A., and Andrianov K.A., Vysokomol. Soedin., 1978, vol. 20B (1), p. 70. (Rus) [85] Mukbaniani O.V., Khananashvili L.M., Koyava N.A., Porchkhidze G.V., and Tolchinski Yu.I., Intern. J. Polym. Mater., 1992, vol. 17(3-4), p. 113. [86] Mukbaniani O.V., Doctor’s Dissertation on chemical sciences, I. Dzhavakhishvili Tbilisi State University, 1993, Tbilisi, Georgia. (Rus) [87] Koiava N.A, Candidate’s Dissertation on Chemistry, I. Dzhavakhishvili Tbilisi State University, 1983, Tbilisi, Georgia. (Rus) [88] Sobolevski M.V., Skorokhodov I.I., Ditsent V.E., Sobolevskaya A.V., and Efimov V.M., Vyso-komol. Soedin., 1969, vol. 11A(5), p. 1109. (Rus) [89] Andrianov K.A., Pavlova S.A., Zhuravleva I.V., Tolchinski Yu.I., and Astapov B.D., Vysoko-mol. Soedin., 1977, vol. 19A(4), p. 896. (Rus) [90] Andrianov K.A., Pavlova S.A., Zhuravleva I.V., Tolchinski Yu.I., Makarova N.N., and Mukba-niani O.V., Vysokomol. Soedin., 1977, vol. 19A(4), p. 1387. (Rus) [91] Andrianov K.A., Papkov V.S., Zhdanov A.A., and Yakushina S.E., Vysokomol. Soedin., 1969, vol. 11A(9), p. 2030. (Rus) [92] Pathnode W. and Wilcock D.F., J. Amer. Chem. Soc., 1946, vol. 68, p. 358. [93] Astapova T.V., Matukhina E.V., Petrovski P.V., Blagodatskikh I.V., Makarova N.N., and Go-dovski Yu.K., Vysokomol. Soedin., 1999, vol. 41A(4), p. 581. (Rus) [94] He Y., Lapp A., and Herz J., Makromol. Chem., 1986, Bd. 189(5), S. 1061. [95] Akhrem I.S., Chistovalova N.I., Myisov E.I., and Volpin M.E., Zh.Obshch. Khim., 1972, vol. 42(8), p. 1868. (Rus) [96] Astapova T.V. and Makarova N.N., Vysokomol. Soedin., 1996, vol. 38B(8),p. 1442. (Rus) [97] Levis L.N. and Lewis N., J. Amer. Chem. Soc., 1986, vol. 108(23), p. 7228. [98] Matukhina E.V., Boda E.E., Timofeeva T.V., Godovski Yu.K., Makarova N.N., Petrova I.M., and Lavrukhin B.D., Vysokomol. Soedin., 1996, vol., 38A (8), p.1545. [99] Makarova N.N., Petrova I.M., Lavrukhin B.D., Matukhina E.V., and Godovski Yu.K., Vyso-komol. Soedin., 1997, vol. 39A(10), p. 1616. (Rus) [100] Makarova N.N., Astapova T.V., Godovski Yu.K., Matukhina E.V., Lavrukhin B.D., and Yaku-bovich O.Ya., Vysokomol. Soedin., 1993, vol. 35A(2), p. 190. (Rus) [101] Makarova N.N., Astapova T.V., and Lavrukhin B.D., Izv. RAN, Ser. Khim., 1996, No. 4, p. 958. (Rus) [102] Achelashvili V.A., Mukbaniani O.V., Meladze S.M., and Khananashvili L.M., Abstr. Commun. VII Intern. Symp. Organosilicon Chemistry, Kyoto, Japan, 1984, p. 216. [103] Inaridze I.A., Candidate’s Dissertation on Chemistry, I. Dzhavakhishvili Tbilisi State University, 1993, Tbilisi, Georgia. (Rus) [104] Chizhova N.V., Makarova N.N., Godovski Yu.K., and Buzin A.I., Vysokomol. Soedin., 2000, vol. 42A(11), p. 1797. (Rus). [105] Tverdokhlebova I.I., Kyrginyan P.A., Larina T.A., Makarova N.N., and Mukbaniani O.V., Vysokomol. Soedin., 1981, vol. 23A(5), p. 995. (Rus)

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[106] Damewood I.K. and West I.K., Macromolecules, 1985, vol. 18(2), p. 159. 113. Sundarajian P.R., Macromolecules, 1988, vol. 21(5), p. 1256. [107] Shukla P., Cotts P.M., Miller Ro D., Kussel T.K., Smith B.A., Wallraff G.M., Baier M., and Thiyagarajan P., Macromolecules, 1991, vol. 24(20), p. 5607. [108] Cotts P.M., Ferline S., Dagli G., and Pearson S., Macromolecules, 1991, vol. 24(25), p. 673 [109] Buzin A.I., Sauter E., Godovski Yu.K., Makarova N.N., Rechold W., Vysokomol. Soedin., 1998, vol. 40A(5), p. 782. (Rus) [110] Mukbaniani O.V., Achelashvili V.A., and Sturua G.I., Thes. Rep. XXII All-Union Conf. High-Molecular Compounds, Alma-Ata, 1985, p. 89. (Rus) [111] Mukbaniani O.V., Karchkhadze M.G., Matsaberidze M.G., Achelashvili V.A., Khananashvili L.M., and Kvelashvili N.G., Intern. J. Polym. Mater., 1998, vol. 41, p. 103. [112] Matsaberidze M.G., Candidate’s Dissertation on Chemistry, I. Dzhavakhishvili Tbilisi State University, 2001, Tbilisi, Georgia. (Rus) [113] Nogaideli A.I., Tkeshelashvili R.Sh., Nakaidze L.I., and Mukbaniani O.V., Trudy Tbilisskogo Gos. Universiteta, 1976, vol. 167, p. 69. (Rus) [114] Mukbaniani O., Scherf U., Matsaberidze M., Karchkhadze M., and Khananashvili L., Proce-eding of the Georgian Academy of Science, 1999, vol. 25(1-2), p. 54. [115] Zhdanov A.A., Phyakhina T.A., Afonina R.I., and Kotov V.M., Vysokomol. Soedin., 1993, vol. 35(5), p. 475. (Rus) [116] Zhdanov A.A., Phyakhina T.A., Gritsenko O.T., Kotov V.M., Zhukov V.P., Afonina R.I., and Levin V.Yu., Vysokomol. Soedin., 1992, vol. 33(8), p. 45. (Rus) [117] Tverdokhlebova I.I., Kuznetsov D.V., Pertsova N.V., Kotov V.M., Pryakhina T.A., and Bragi-na T.P., Vysokomol. Soedin., 1993, vol. 35(8), p.1278. (Rus) [118] Stocmayer W.H. and Fixman M., J. Polym. Sci., 1963, No. 1, p. 137. [119] Krigbaum W.R., J. Polym. Sci., 1958, vol. 28(116), p. 213. [120] Kurata M. and Yamakava H., J. Chem. Phys., 1958, vol. 29(1), p. 311.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 217-262 © 2006 Nova Science Publishers, Inc.

Chapter 16

ORGANOSILICON COPOLYMERS WITH MONOCYCLIC FRAGMENTS IN THE MAIN DIMETHYLSILOXANE BACKBONE O. Mukbaniani1, G. Zaikov2 and T.Tatrishvili1 1

2

I. Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION It is known [1, 2] that introduction of different components or groups of different chemical origin or structure into the backbone is one of the effective methods for modifying linear organosiloxane olymers. Introduction of alien fragments is resulted in variation of the spiral-shaped structure of dimethylsiloxane polymers, which causes variation of their physical and chemical properties [3]. In particular, introduction of cyclic fragments to linear poly(organosiloxanes) [4, 5] hampers the chain transfer reaction accompanied by ring separation which, in its turn, increases stability of the mentioned polymers. There is some information in the literature about synthesis of polymers with alternating diorgano-siloxane and organosilsesquioxane units [6 – 10] in cyclolinear double-stranded macromolecule of the polymer [11]. The first series of works has used co-hydrolysis products of dimethyldichloro-silane with phenyltrichlorosilane [6, 7], dimethyldichlorosilane with methyltrichlorosilane [8] or methylphenyldichlorosilane with phenyltrichlorosilane [9] for synthesis of the polymers. As a result of anionic polymerization of co-hydrolysis products at equimolar ratio of diorga-osiloxane and organosilsesquioxane units, 3D-polymers were synthesized. Polymerization of bicyc-lodimethylsiloxanes with various lengths of dimethylsiloxane chain between two cyclotetrasiloxane rings has given spatially cross-linked polymers [10]; copolymerization of octamethylcyclotetra-siloxane with polyphenylsilsesquioxane leads to formation of soluble low-molecular polymers [11].

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However, all above-mentioned co-hydrolysis reactions lead to formation of lowmolecular com-pounds with statistical disposition of linear and cyclic fragments, in which statistical disposition of siloxane (D) and silsesquioxane (T) units is preserved. Reviewed in this paper is synthesis of cyclolinear copolymers with regular disposition of mono-cyclic fragments in dimethylsiloxane backbone using HFC and hydride polyaddition reaction as the methods for synthesis of polymers.

1. SILOXANE CYCLOLINEAR COPOLYMERS WITH ORGANOCYCLOTETRA(PENTA, HEXA)-SILOXANE FRAGMENTS IN DIMETHYLSILOXANE BACKBONE HFC reaction of difunctional organocyclosiloxanes with α,ω−dichloro(dihydroxy, dimethylamino)-dimethylsiloxanes of different length (n) proceeding with formation of cyclolinear copolymers pos-sessing regular disposition of cyclic fragments in dimethylsiloxane chain is discussed in the current Section. In HFC reaction study, organocyclotetrasiloxanes with different disposition (1,3- and 1,5positions by edge and diagonal) of functional groups in cyclotetrasiloxane were used [12 – 17]. The effect of substituting agents at silicon atom in difunctional organocyclotetrasiloxanes on reac-tivity of haloid and hydroxyl groups interacting with α,ω−dichloro(dihydroxy)dimethylsiloxanes was studied. Polycondensation of dichlorohexaorganocyclotetrasiloxanes were performed at room temperature in 70% solution of anhydrous toluene or benzene both with acceptor and without it.

Figure 1. Dependence of polycondensation degree between 1,5-dichloro-1,5diorganotetraphenylcyclotetrasilocane and α,ω−dihydroxydimethylsiloxanes: curves 1, 2, 3 – at R = Me, n = 2, 4, 6, respectively; curves 4, 5 – at R = Ph, n = 2, 4, respectively.

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When HFC reaction proceeded without acceptor, the run of hydrogen chloride liberation was searched for. Figure 3.1 shows dependence of hydrogen chloride liberation on time at 20°C, whence it follows that as the length of dimethylsiloxane unit increases (n = 2 – 6), conversion by hydrogen chloride decreases from 45% (n = 2, R = Me) to 33% (n = 6, R = Me) (Figure 1, curves 1 – 3). Substitution of methyl side group by phenyl one at silsesquioxane atom of silicon induces abrupt decrease of hydrogen chloride liberation rate from 20 –25% (n = 2, R = Ph) to 5% (n = 4, R = Ph), which is displayed by curves 4 and 5 in Figure 1. Gas-liquid analysis of the product obtained by polycondensation of 1,5dichlorohexaphenylcyclo-tetrasiloxane with 1,3-dihydroxytetramethyldisiloxane has shown that initial compounds are absent in it and octamethylcyclotetrasiloxane, which would be formed by homocondensation of disiloxane-diol in acidic medium is also absent, but products with higher boiling points, i.e. the products of partial intramolecular condensation are present. In the presence of pyridine, HFC reaction of 1,5-dichlorohexaphenylcyclotetrasiloxane with α,ω−dihydroxydimethylsiloxanes proceeds by analogy (at low values of n). Thus basing on data obtained in the study of HFC reaction between dichloro(dihydroxy)organo-cyclotetrasiloxanes with α,ω−dihydroxy(dichloro)dimethylsiloxanes, it has been shown [14] that the reaction is both intermolecular forming cyclolinear copolymer and intramolecular giving bicyclic structures (at low values of n). As a consequence, the current reaction proceeds in accordance with the following scheme: Ph Ph x

Ph Ph R

R

R O (SiMe2O)n H +

R 2xPy + x Y(SiMe2O)n-1SiMe2Y HO . - 2xPy HCI X

X Ph Ph

Ph Ph

x I

Me2Si O O

SiMe2

+ Ph Ph2 II

O

Ph2

Ph

Scheme 1

Where: Х=СI, OH; Y=OH, CI; R=Me, Ph; n=2÷101. Ph

Ph CI + x HO(SiMe2O)nH

x CI Ph Ph

Ph Ph

Ph

2xPy HO - 2xPy .HCI Ph

Ph

Ph O (SiMe2O)n H Ph Ph III

Scheme 2

x

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Where: n = 2÷70. Reactivity of functional groups at their different location in the ring (1,5-or 1,3-position) was estimated in the reaction with α,ω−dihydroxydimethylsiloxane with the polymerization level n = 25, 70 at 180°C in block. From experimental data a conclusion was made [18] that 1,3- and 1,5-po-sitions of chlorine atoms at silicon in dichlorohexaphenylcyclotetrasiloxane interacting with α,ω− dihydroxydimethylsiloxanes cause a negligible effect on their reactivity during polycondensation (Figure 2), which runs counter to the conclusion in the ref [19]. At room temperature, polycondensation of 1,5-dihydroxyhexaphenylcyclotetrasiloxane with α,ω− dichlorodimethylsiloxanes in 70% solution of anhydrous toluene proceeds at deeper level, and con-version by hydrogen chloride reaches 60%, whereas in HFC reaction of 1,5-dichlorohexaphenyl-cyclotetrasiloxane with α,ω−dichlorodimethylsiloxanes it is below 30% (Figure 3).

Figure 2. Dependence of hydrogen chloride liberation rate in polycondensation reaction of dichlorohexaphenylcyclotetrasiloxane with α,ω−dihydroxydimethylsiloxanes: curves 1 and 2 – with 1,5disposition of chlorine atoms and at n = 25,70, respectively; curves 1 and 2 - with 1,3-disposition of chlorine atoms and at n = 25,70, respectively.

Figure 3. Hydrogen chloride conversion in polycondensation of 1,5-dichloro-and 1,5dihydroxyhexaphenylcyclotetrasiloxanes with α,ω−dihydroxy(dichloro)-dimethylsiloxanes (n = 2, 4): curves 1 and 2 -for 1,5-dichlorohexaphenylcyclotetrasiloxane with n = 4, 2 respectively; curves 3 and 4 – for 1,5dihydroxyhexaphe-nylcyclotetrasiloxane with n = 4, 2 respectively.

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As the screening effect of substituting agents at silicon atoms is considered separately, they display equal values of it. Thus, for estimating reactivity of functional groups in current reactions [18], both the screening effect of substituting agents at silicon atoms linked to reactive groups and the inductive action of this radical on the reactive group are considered. Because maximal conversion by hydrogen chloride did not exceed 50 – 60%, the acceptor (pyridine) was introduced for the purpose of increasing the depth of HFC proceeding. It is shown that under experimental conditions at 23 – 25°C condensation of α,ω−dihydroxydime-thylsiloxanes by hydroxyl groups does not proceed, which correlates with the previous conclusions [20]. In this work it is indicated that homofunctional condensation of 1,3-dihydroxytetrame-thyldisiloxane does not proceed even in the presence of more basic amines. As HFC proceeds in 60 – 70% solution of anhydrous toluene in the presence of pyridine, the yield of copolymers is increased to 72 – 93%, and copolymers synthesized after reprecipitation represent colorless or light-yellow transparent solids of viscous substances, well soluble in usual organic solvents with ηspec = 0.1 - 0.5. Study of the reaction (1) has indicated that at short length of linear dimethylsiloxane unit the yield of copolymers after reprecipitation is much lower. After eliminating solvent from the mother solution, a viscous product with molecular mass of ~830 units was obtained. Such molecular mass can be displayed by the product of intramolecular condensation with the structure II only. To prove the possibility of forming compound with the structure II, direct synthesis of this compound was performed [21]. Results of the current synthesis were also used for estimation of cis- and trans-isomers’ contents in the initial 1,5dichlorohexaphenylcyclotetrasiloxane. Namely, HFC reaction of a mixture of cis- and transisomers of 1,5-dichlorohexaphenylcyclotetrasiloxane with 1,3-dihydroxytetramethyldisiloxane was studied (equimolar ratio of initial reagents, 5% anhydrous toluene so-lution, 0°C, in the presence of acceptor – pyridine). In the case of cis-isomer, formation of poly-cyclic structured compound is the most probable, whereas trans-isomers give polymeric products. The reaction proceeds in accordance with the scheme as follows:

Ph Ph R CI Ph Ph

2Py R + HO(SiMe2O)2H -2Py.HCI CI

O Ph2

Ph II

Ph

Ph

Ph2

Me2 Si O O SiMe2

Ph Ph2

+

O Me2 Si O Me2Si O Ph

O Ph2 SiMe2 O SiMe2 O

Ph2

Ph

IV

Ph2

Scheme 3

Composition and structure of the individual polycyclic compounds, synthesized by fractionation in high vacuum, were determined on the basis of the ultimate analysis by determination of the molecular mass, IR and 1H NMR spectral data. Based on this reaction, the authors have concluded that 1,5-dichlorohexaphenylcyclotetrasiloxane used in HFC reactions represents a mixture of cis- and trans-isomers. The cis-form promotes for structures

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II and IV formation, total yield of which equals ~50%; the rest 50% are represented by oligomeric structures, formed from trans-forms of 1,5-dichlorohexaphenylcyclotetrasiloxane. Spectral data of 1H NMR analysis have indicated the regular structure of cyclolinear copolymers, which correlates well with the data from the literature [22]. Some physical and chemical parameters of copolymers with cyclotetrasiloxane fragments in the backbone are shown in Tables 1 – 2. Table 1. Some physical and chemical parameters and yield of structure I cyclolinear copolymers with 1,5-disposition of cyclotetrasiloxane fragment in dimethylsiloxane backbone

x

HO

R

Ph2

Ph2

R

(SiMe2O)n H

№ Copolymer R nSiO Yield, % Тg,0С ηspec* 1 Me 2 72 -54 0.15-0.16 2 Me 4 83 -57 0.09-0.16 3** Me 5 86 0.20 4 Me 6 86 -71 0.10-0.22 5 Me 12 90 -94 0.24-0.27 6** Me 25 90 -117 - 0.33 7 Me 51 91 -123 - 0.40 8 Me 70 93 -123 0.42 O 9 Me 101 96 -123 - 0.49 10 Ph 2 72 0.06-0.11 -10÷-20 11 Ph 4 80 -34 0.10-0.14 12 Ph 6 93 -55 0.10-0.21 13 Ph 12 93 -83 0.19-0.26 14 Ph 25 95 -110 0.19-0.34 15 Ph 51 96 -123 - 0.40 16 Ph 70 92 -123 0.15 Ph 101 97 -123 - 0.42 17 * Hereinafter, second values of viscosity are obtained by high-temperature polycondensation of 1,5dihydroxyorganocyclohexasiloxanes with α,ω−bis(dimethylamino)dimethylsiloxanes. ** For these samples, viscosities in benzene are determined.

Table 2. Some physical-chemical parameters and yield of cyclolinear copolymers of the structure III № 1 2 3 4 5 6

Copolymer

Ph

Ph O (SiMe2O)n H

HO Ph Ph

Ph Ph

x

nSiO 2 4 6 12 25 70

Yield, % 83 90 91 92 93 92

Тg,0С -23 -35 -83 -107 -123

ηspec 0.06 0.10 0.11 0.31 0.37 0.49

For copolymers, thermomechanical studies were carried out in accordance with the technique, described in ref. [23]. Expectedly, based on the data from the literature [24, 25] the studies have shown that the presence of inclusions of any chemical origin in the polydimethylsiloxane backbone (framing groups different from methyl ones, rings of

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223

different structure, branching points) causes the loss of the ability of copolymers to crystallize, if the distance between neighboring inclusions equals ~30 siloxane units. Copolymers with n = 2 – 25 studied do not crystallize, and the ones with n = 70 behave as crystallizing poly(dimethylsiloxanes) (PDMS). The temperature range corresponded to glass tran-sition in copolymers regularly expands towards higher temperatures with decrease of n. Of special attention is the fact that disposition of cyclotetrasiloxane fragment in the poly(dimethylsiloxane) backbone (1,5- and 1,3-positions) causes a negligible effect on Tg of the copolymers (Figure 4).

Figure 4. Thermomechanical curves for copolymers with 1,3- and 1,5- disposition of cyclotetrasiloxane fragments in PDMS backbone: 1, 2, 3, 4, 5 for copolymers with 1,3-disposition of hexaphenylcyclotetrasiloxane fragment in the backbone at n = 2, 4, 12, 25, 70 respectively; 1I, 2I, 3I, 4I - for copolymers with 1,5-disposition of hexaphenylcyclotetrasiloxane fragment in the backbone at n = 2, 4, 12, 25, respectively (100 g load, 5 deg/min heating rate).

Of special importance is the fact that introduction of rings containing phenyl framing groups into the linear chain is accompanied by Tg increase, compared with cyclolinear carbosiloxane polymers containing methyl framing groups [26]. In the case of cyclotetrasiloxanes with phenyl groups, Tg increase is higher than under the action of network points, which do not change Tg of PDMS networks at n = 20 [27]. The latter is determined by a significant effect of bulky phenyl groups, the presence of which at any place of PDMS backbone significantly increases Tg [28]. Substitution of phenyl side group by the methyl one in organosilsesquioxane fragment of organocyclotetrasiloxanes decreases the glass tran-sition temperature by ~15 - 20°C. The effect of cyclotetrasiloxane fragment is detected at dime-thylsiloxane unit n = 25 long and lies above Tg of PDMS. Thermogravimetric studies of cyclolinear copolymers indicate that 1,3-and 1,5dispositions of hexa-phenylcyclotetrasiloxane fragment cause no difference in mass losses of copolymers. As a result, by HFC reaction of 1,5-dihydroxy-1,5-bistrimethylsiloxytetraphenylcyclotetrasiloxane with α,ω−dichloromethylsiloxanes in the presence of pyridine and in 60% anhydrous toluene so-lution at 20 - 25°C cyclolinear copolymers with regular disposition of 1,5-bistrimethylsiloxy-tetraphenylcyclotetrasiloxane in the dimethylsiloxane backbone, completely dissoluble in organic solvents, were synthesized [29]. The reaction proceeds in accordance with the general scheme as follows:

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x

HO

Ph2

Me3SiO Ph2

Ph2 OH

2xPy + x CI(SiMe2O)n-1SiMe2CI

-2xPyHCI

OSiMe3

O (SiMe2O)n H

HO OSiMe3

Me3SiO Ph2

x I

Scheme 4

Where: m = 1, 2, 3, 10. Depending on the length of dimethylsiloxane unit, copolymers represent crystalline (Tg=100°C, n= 1), rubbery (Tg =30°C, εelong=400%) and quite strong (δbreak=40 kg/cm2 at 24°C) products. Of interest is that dielectric constant of this polymer decreases linearly with the temperature increase. A suitable method has been suggested [12] for obtaining cyclolinear copolymers, which concludes in high-temperature HFC reaction of dihydroxyorganocyclotetra(penta, hexa)siloxanes with α,ω− bisdiamino(dimethylamino)dimethylsiloxanes. The method suggested is simpler than the above-dis-cussed reactions (1) and (3), because synthesized copolymers possess low molecular mass. More-over, obtaining of pure copolymers in accordance with the above-shown schemes (1) and (2) requ-ires application of an additional stage of polymer purification from secondary product which is ami-ne hydrochloride. For the purpose of synthesizing cyclolinear copolymers with regular disposition of organocyclotetra- organocyclopenta- and organocyclohexasiloxane fragments in linear the dimethylsiloxane backbone, HFC reaction of 1,5-dihydroxy-1,5dimethyl(diphenyl)phenylcyclotetra(penta, hexa)siloxanes and 1,7-dihydroxy-1,7dimethyl(diphenyl)octaphenylcyclohexasiloxane with α,ω−bis(dimethylamino)(dichloro)dimethylsiloxanes was studied [15 – 17]. In this case, the reaction proceeds in accordance with the general scheme as follows: R x

Z

O(SiPh2O)m Si

Si O(SiPh2O)l

R + x Y(SiMe2O)n-1 SiMe2Y

Z

R

O(SiPh2O) m R Si (SiMe2O)n

Si O(SiPh2O) l

x

Scheme 5

Where: Z = OH, CI; Y = Me2N, OH; R = Me, Ph; m = l = 1 - structure I; m = 1, l = 2 structure V; m = 1, l = 3 - structure VI; m = l = 2 - structure VII. HFC was studied at 20-150°C in anhydrous nitrogen or argon flow both in block and in solution. As the reaction proceeds in block, the reaction mixture is heated up to 50-60°C until a homogeneous mixture is formed; thereafter, the reaction is continued in vacuum at P =3–5 mmHg and temperature range of 120-150°C up to constant viscosity. Application of reactive α,ω−bis(dimethylamino)dime-thylsiloxanes allowed performance of the initial stage of the reaction in solution at 20-50°C until a homogeneous mixture is formed. For more complete elimination of amine, liberated in the reaction, the mixture is aerated by dry inert gas. Polymers synthesized by this technique require no purifica-tion, because amines obtained as secondary reaction products possess very low boiling point and are completely removed from

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the reaction mixture. In as much as the mixture of dichloro(dihydroxy)-organocyclosiloxanes isomers was used in HFC, atactic copolymers were synthesized. In the case of HFC of 1,5-dihydroxyhexaphenylcyclotetrasiloxane with α,ω−bis(diethylamino)di-methylsiloxanes, gel formation proceeds after diethylamine conversion reaching ~5%. Previously, it was informed about a possibility of siloxane bond break in trimethyltriphenylcyclotrisiloxane by diethylamine and formation of a complex with the charge transfer [30]. In accordance with the authors’ opinion [15–17], immediate removal of diethylamine produced in the reaction with α,ω−bis(diethylamino)dimethylsiloxanes could be hardly guaranteed. In its turn, dimethylamine interacts with the siloxane bond in the cyclic fragment and forms bipolar zwitter-ions [31]. The HFC reaction proceeding with α,ω−bis(diethylamino)(diamino)dimethylsiloxanes [12] forms copolymers completely dissoluble in organic solvents, because dimethylamine and ammonium liberated during synthesis cause no breakage of siloxane bonds in cyclic fragments of the polymeric backbone. It is proved that at short lengths of dimethylsiloxane unit, HFC reaction proceeds in two directions: intramolecular ring formation giving polycyclic products and intermolecular formation of cyclo-linear copolymers. Formation of polycyclic products is proved by the direct synthesis. To prove formation of copolymers with regular disposition of cyclic fragments in macromolecular backbone, some copolymers were fractionated into several fractions. Results of the ultimate analysis have indicated that the values detected for fractions coincide with the calculated ones, which rep-resents direct proof of the regular structure of copolymers. Many investigators have studied dissolved solutions of poly(organosiloxanes) with different side groups at silicon atoms in the macromolecule backbones [32 - 35]. These works show results of the studies of the effect of the side groups origin, their disposition and the influence of hydrodynamic and conformation parameters of macromolecules. Table 3. Bond lengths and angles between them in poly(organocyclosiloxanes) of the structure I (n = 1) Bond l1 l2 l3 l4 l5 *

Bond length, Å 4.25 1.63 1.63 1.63 1.63

θI*, deg 54.5 37.0 70.0 37.0 54.5

Rotation conditions Prohibited Free Free Free Free

For the polymer backbone, this coefficient is exclusively associated with the structure of macromolecules and potentials of internal rotation around internal bonds of the backbone. This dependence gives information about energy of the chain conformation and mutual transitions.

The effect of introduction of regularly disposed cyclic fragments into the macromolecular backbone on conformational and hydrodynamic parameters is also studied [30]. For this purpose, copolymers 3 and 4 (Table 1) were fractionated into twelve fractions from the benzene (solvent) – methanol (precipitator) system. The influence of cyclic groups, introduced into the polymer backbone, on rigi-dity parameters was determined by direct computer simulation of macromolecular coil with the help of the Monte-Carlo method.

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The process was simulated for the copolymer of the structure I with n = 1, 5 and 10 in the structural unit of dimethylsiloxane chain, and the Kuhn segment A and /nM0 were calculated, where M0 is the molecular mass of the structural unit, is the mean-square distance between chain ends at free rotation around virtual bonds1, n is the number of structural units. Structural unit of the copolymer was simulated on the basis of the data from the literature on the simplest molecules’ structure, close by the composition and structure to monomeric units. Shown below is the geometrical structure of repeated structural unit in poly(organosiloxane) at n=1. Table 3 shows values of bond lengths and angles between them. 1 By the term of virtual bond the area of the chain is meant, rotation around which is possible. In particular case, it may be a simple valence bond –(l2-l5); in the general case, it may contain not only valence bonds, but also rings, or may determine the distance between atoms in the ring as (l1) does.

Si

Si O l O 1

Si

l2 O Q 2 l3 Q1

l4 O Q 4 l5 Si Si Q3

O Q5

O

O Si

To avoid the ring twisting, rotation around virtual Si-------Si (l1) bond is prohibited. Table 4 shows calculation results, which represent theoretical values of the Kuhn segment (A) and /nM0 for polymers of the structure I (n=1; n=5; n=10) and, for comparison, analogous values for PDMS [37]. Table 4. Calculation values of the Kuhn segment (A) and /nM0 Polymer of structure I

Me

Ph2

HO Ph2 PDMS

Me O (SiMe2O)n H

nSiO

A=/nl0A

/nM0

1 5 10

15 10 10

0.28 0.24 0.22

10

10

0.24

x

These theoretical data show that the influence of the octatomic siloxane ring is observed at n=1 only. Saturation is observed already at transition from n=5 to n=10, and increase of the quantity of ≡SiO- groups causes no effect on the coil size. For the fraction of copolymer 3 of the structure I and n = 5, experimental values of the Kuhn segment and /nM0 are shown in Table 4. One of the methods for estimating experimental thermodynamic flexibility of the polymer backbone is determination of parameters, associated with the size of isolated

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macromolecule coil. At the pre-sent time, methods of macromolecular coil parameter estimation under ideal and non-ideal conditi- tions. In the first case, characteristic viscosity of the fraction, [η], with the known molecular mass in ideal θ-solvent was measured. This method is based on the known Flory-Fox relation [38]. The second method represents measurements of the fraction [η] in good thermodynamic solvents and extrapo-lation of experimental data in accordance with the known techniques [39 - 41]. Because in the cur-rent work [36] all measurements were performed in good thermodynamic solvent, unperturbed di-mensions of macromolecules, , were determined by graphical extrapolation in accordance with the Shtockmayer-Fixman, suggested by the authors for flexible macromolecules, in [η] М1/2-М1/2 coordinates (Figure 6).

Figure 6. Determination of unperturbed dimensions by extrapolation in accordance with the ShtockmayerFixman method for copolymers 3 (Table 1): 1 – at 25°C; 2 - 40°C; 3 - 50°C.

Table 5 shows mean-weight molecular masses,Мω, and [η] for the fraction of copolymer 3 (n = 5) (Table 1) of the structure I at 25, 40 and 50°C in toluene. Table 5. Molecular masses and characteristic viscosities of copolymer 3 fractions (Table 1, structure I) at different temperatures Fraction №

1 2 3 4 5 6 7 8 9 10 11 12

Μωх10-3

9.0 17.0 22.0 26.0 33.0 42.0 44.0 72.0 85.0 92.0 141.0 239.0

[η] in toluene (dl/g) at temperature, °C 25 40 50

0.04 0.06 0.07 0.08 0.09 0.12 0.11 0.15 0.16 0.19 0.26 0.33

0.07 0.09 0.10 0.11 0.13 0.13 0.15 0.17 0.20 0.23 0.38

0.13 0.11 0.15 0.12 0.14 0.15 0.12 0.18 0.21 0.38 -

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O. Mukbaniani, G. Zaikov and T.Tatrishvili Table 6. Experimental conformational parameters of copolymer 3 (structure I, Table 1) № 1 2 3

Т, 0С 25 40 50

Kθх103 0.46 0.58 0.67

/nM0 0.303 0.340 0.380

А, Å 16.0 18.0 20.0

σ=(/)1/2 1.12 1.18 1.25

Table 6 shows experimental values of conformational parameters for the Kuhn segment, А= /nl0 (where l0 is the structural unit length), hindrance factor of rotation around the single bond, σ=(/)1/2, and constants of the Mark-Kuhn-Hauvink equation, Kθ≈[η]/Μ1/2, at different temperatures. Experimental data on conformational parameters of copolymer 3 (Table 1), shown in Table 6, exce-ed these calculated in the supposition that rotation around virtual and valence bonds is free. Comparison of experimental and calculated values of the abovementioned parameters indicates the hindrance of rotation around valence bonds ≡Si-O- and ≡Si-Ph, due to their short lengths, because distances between neighboring atoms Si----Si and О----О are shorter or close to the sum of Vander-Waals radii of these atoms. Data from Table 6 indicate also that experimental values of the hind-rance factors are low. As shown by Flory, these low values of σ, i.e. a negligible increase of PDMS molecule dimension compared with dimensions, calculated in the supposition of free rotation, are associated with pre-dominant containing of the plane trans-chain type conformation rather than the absence of rotation hindrance, compared with coiled conformations. Hence, low у values for these chains may be realiz-ed at both low and high differences of energies of rotational isomers under the condition of energy gain of the trans-shape [42,43]. On the other hand, low у must be combined with positive teperatu-re coefficient of unperturbed dimensions of macromolecules2, because relative content of the trans-shape must decrease with temperature growth [42, 43]. For linear PDMS, studies of the temperature coefficient of unperturbed dimensions of macromolecules were carried out in the work [44], and the value obtained equaled (0.78 ± 0.06) х10-3deg-1. For the purpose of determination of the temperature coefficient for unperturbed dimensions of copolymer 3 (Table 1), [η] values were measured in the same solvent (toluene) at different tempe-ratures. In accordance with the Shtockmayer-Fixman method, Kθ=(/M)1/2xF0 values was deter-mined using the least-square technique. The temperature coefficient of unperturbed dimensions was calculated from the values obtained at different temperatures (Table 6) using the relation, suggested in the work [45]: dln/dT = 2/3xlnKθ/dT. The coefficient of unperturbed coil dimension (dln/dT), determined for copolymer 3 (Table 1), equals 0.85x10-3 deg-1 [44]. Thus, data shown in Table 6 indicate that thermodynamic rigidity, mean-square dimensions and hindrance of copolymer 3 chains (Table 1) are increased with temperature. These facts as well as positive temperature coefficient of unperturbed dimensions testify about predominance of coiled trans-shape, more energetically preferable for copolymer 3 chains, similar to PDMS, compared with isomers. As temperature increases, the fracture of plane trans-chains decreases, which, as a result of 2For polymeric chain, this coefficient is

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229

associated with the structure of macromolecules and potentials of internal rotation around internal bonds in the backbone. Such dependence gives infor-mation about energetic conformation of the backbone at mutual transitions. transition from trans- to gauche-state, proceeds with an increase of unperturbed dimensions [41]. Summing up all above-discussed, one may conclude that, compared with PDMS, introduction of octatomic cyclic fragments with symmetrically disposed phenyl side groups causes no change of internal rotation conditions, as it takes place for poly(methylphenylsiloxane) with asymmetrical side phenyl groups [43]. However, already for 1:5 ratio (1 cyclic group per 5 siloxane units), i.e. at the decrease of the distance between cyclic fragments in the backbone, their introduction into dimethyl-siloxane backbone induces a significant increase of thermodynamic rigidity of macromolecules. The rigidity increase of copolymer 3 is also displayed in thermomechanical properties of copolymers. For example, Tg of copolymer 3 (Тg = -50°С) is much higher than Tg of PDMS. The study of hydrodynamic behavior of copolymer 6 (Table 1) indicates that, apparently, macromo-lecules of this copolymer possess branched backbones. In the Mark-Kuhn-Hauvink equation, parameter α for copolymer 6 solution in toluene at 25°C equ-als 0.30, which is typical of branched macromolecules. For cyclolinear polymer 3 under the same conditions, this parameter equals 0.62 (Figure 7). Molecular masses vary within the range from 4x103 to 565x103.

Figure 7. Dependence of lg[η] on lg М: 1 – for copolymer 3 in toluene at 25°С, [η]=1.394x10-4М0.62; 2 – for copolymer 6 at 25°С, [η]=1.79x10-2М0.30; 3 – for copolymer 6 in isopropyl alcohol at 22°С, [η]=9.86x104 0.53 М .

Mean-weight molecular masses,Мω, were measured on Sofica device. Moreover, molecular masses below 104 were also determined by the ebullioscopy method (Мn). Good coincidence betweenМω andМn was obtained. The reason for branching may be the fact that initial oligomers α,ω−dichlo-rodimethylsiloxanes) for synthesizing cyclolinear copolymers [poly(organocyclotetrasiloxanes)] with n=5 and 10 were produced by partial hydrolysis reaction of dimethyldichlorosilane, and oligo-mers with n=25 were telomerized in autoclave [46], which may cause formation of copolymers containing units capable of branching. Additional proof of branching is the loss of copolymer 6 so-lubility with time. However, behavior of copolymer 6 under θ-conditions, different from the beha-vior of

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branched macromolecules was observed. Parameter α equaled 0.53, which exceeded α=0.25 typical of branched copolymers under θ-conditions. For copolymer 6, θ-conditions was set on a de-vice of temperature polymer precipitation. Isopropyl alcohol at 22°C was used as θsolvent (Figure 8). The attempt to prove correctness of θ-conditions selection for copolymer 6 by checking equality to zero of the virial coefficient, A2, has given interesting results. It has been found that purification of the polymer solution from dust by filtration via dense Shott filter (№ 5) causes a sharp increase of light scattering intensity, which does not allow measurement of molecular mass and A2. Repeated filtering induces much more sharp increase of light scattering intensity. The precipitation temperature of filtered solution is increased. This fact contradicts to the supposition that copolymer 6 represents a branched structure. Possible reason for this effect may be solution structuring during long-term filtration. To check this suggesting [36], copolymer solutions (filtered and non-filtered) were studied on optical microscope. Films obtained from 1% filtered solution displayed oriented chains and aggregates from them, which were not observed in the films from non-filtered solution. Studies carried out with the help of electron microscope have not allowed definite conclusions, because the technique requires dilution to 0.01-g/ml concentration of the solution, i.e. an order of magnitude lower than that, at which molecular mass is determined.

Figure 8. Dependence of critical precipitation temperature, T0cr, of copolymer 6 fractions (Table 1) on molecular mass.

Thermogravimetric studies of copolymers 2 and 4 (Table 1) have determined the influence of regu-larly disposed organocyclotetrasiloxane fragments in linear dimethylsiloxane chain on thermal sta-bility of the studied copolymers. Pyrolytic spectrum (Figure 9) indicates that thermal degradation of polymers 2 and 4 below 300 and 350°C, respectively, displays full absence of organosilicon and organic compounds in the pyrolysis products. At 350 - 400°C, thermal degradation rate is considerably increased, and the reaction proceeds with benzene isolation. In 380 - 440°C temperature range, degradation products display cyclosiloxane components of Dn composition, D4