Progress in Olefin Polymerization Catalysts and Polyolefin Materials: Proceedings of the First Asian Polyolefin Workshop, Nara, Japan, December

Studies in Surface Science and Catalysis 161 CATALYSTS PROGRESS IN OLEFIN POLYMERIZATION CATALYSTS MATERIALS AND POLYO...

Author: Takeshi Shiono | Kotohiro Nomura | Minoru Terano

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Studies in Surface Science and Catalysis 161

CATALYSTS PROGRESS IN OLEFIN POLYMERIZATION CATALYSTS MATERIALS AND POLYOLEFIN MATERIALS

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Studies in Surface Science and Catalysis and J.T. J.T. Yates Advisory Editors: B. Delmon and Series Editor: G. G. Centi

Vol. 161

IN OLEFIN PROGRESS IN CATALYSTS POLYMERIZATION CATALYSTS MATERIALS AND POLYOLEFIN MATERIALS Poiyoiefin Workshop, Nara, Japan, Proceedings of the First Asian Polyolefin December 7-9, 2005

Edited by Takeshi Shiono Graduate School of of Engineering, Hiroshima University Graduate Higashi-Hiroshima, Japan

Nomura Kotohiro Nomura of Science and and Technology Nara Institute of Nara, Japan Minoru Terano of Science and and Technology Japan Advanced Institute of Ishikawa, Japan

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Committee

Academic Lee, Dong-Ho (Kyunpook National University, Korea) Li, Bo-Geng (Zhejiang University, PR China) Noh, Seok Kyun (Yeungnam University, Korea) Nomura, Kotohiro (Chair, NAIST, Japan, General Secretary) Shiono, Takeshi (Chair, Hiroshima University, Japan) Sun, Wen-Hua (Institute of Chemistry, CAS, PR China) Terano, Minoru (Chair, JAIST, Japan) Woo, Seong Ihl (KAIST, Korea) Industry Aral, Toru (Denka Co.) Hujita, Takashi (Toho Catalyst Co., Ltd.) Imuta, Jun-iehi (Mitsui Chemicals Inc.) Kuramoto, Masahiko (Idemitsu Kosan Co., Ltd.) Miyatake, Tatsuya (Sumitomo Chemical Co., Ltd.) Takahashi, Mitsuru (Tosoh Fineehem. Corp.) Tayano, Takao (Japan Polypropylene Corp.) Watanabe, Harumi (Asahi Kasei Chemicals Corp.) Organized by Catalysis Society of Japan, Polymerization Catalysis Division Coorganized by The Chemical Society of Japan The Japan Petroleum Institute The Society of Polymer Science, Japan Nara Convention Bureau


Contents Committee

v

Preface

1

xv

Creation of New Polyolefm Hybrids on the Surface of Molded Polypropylene Sheet S. Matsuo, T. Matsugi, J. Saito, N. Kawahara, H. Kaneko, N. Kashiwa (R&D Center, Mitsui Chemicals, Inc., Japan)

1

2

Japanese National Project for the Innovation of Industrial Polypropylene Process Technology 7 M. Terano", K. Suehiroh, T, Sagae", E. Tobitad ("Japan Advanced Institute of Science & Technology,l'Mitsui Chemicals, Inc., "Japan Polypropylene, Co., Asahi Denka Co., Ltd., Japan)

3

Novel Energy and Cost Saving Polypropylene Stabilization via addition of Antioxidant into Polymerization System H. Yokotaa, K. Nomura", T. Horikoshi3, Y. Negishia, N. Kawamoto11, E. Tobitaa, M. Teranob ("Asahi Denka Co., Ltd., Japan Polypropylene, Co., Japan)

4

5

Polymerization Behavior with Metallocene Catalyst Supported by Clay Mineral Activator H. Nakano, T, Takahashi, H. Uehino, T, Tayano, T. Sugano (Polymerization Technical Center, Japan Polypropylene Corporation, Japan) Regulating the Structure of Ethylene-Propylene Copolymer for Polyolefin In-reactor Alloy with Improved Properties Q. Dong, N. Li, X. Wang, Z. Fu, J. Xu, Z. Fan (The Institute ofPolymer Science, Zhejiang University, China) VII

13

19

25

viii 6

7

8

9

Contents Application of High Resolution FTIR Spectroscopy in Structural Characterization of Polyethylene and Ethylene Copolymers Z. Sua, X. Zhanga, N. Kanga, Y. Xub, Y. Zhao", D. Wang,"" J. Wub, D. Xua ("State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, China) Microstructure Characterization of Polyolefins. TREF and CRYSTAF B. Monrabal (Polymer Char, Spain) Ultra-high Molecular Weight Polyethylene from Slurry INSITE™ Technology Koichi Hasebe, Akio Fujiwara, Takashi Nozaki, Koichi Miyamoto, and Harumi Watanabe {Polyolefins Development Dept, Polyethylene Division, Asahi Kasei Chemicals Corporation, Japan) Effects of Solvents in Living Polymerization of Propene with ^BuNSiMe2(3,6-^Bu2Flu)]TiMerMMAO Catalyst T. Shiono, Z. Cai, Y. Nakayama (Graduate School of Engineering, Hiroshima University, Japan)

10 Preparation of Ethylene/Polyhedral Oligomeric Silsesquioxane(POSS) Copolymers with rae-Et(Ind)2ZrCl2/MMAO Catalyst System D.-H Leea, K.-B. Yoona, M.-S. Junga, J.-K. Sungb, S. K. Nohc ("Department of Polymer Science, Kyungpook National University, Korea, b R&D Center, Korea Petrochemical Inc., Korea, cSchool of Chemical Engineering and Technology, Yeongnam University, Korea) 11 Norbomene and Ethylene Polymerization with Palladium and Nickel Complexes with Potentially Tri- or Tetradentate Ligands D. W. Leea, C. Kimb, I.-M. Leea ("Department of Chemistry, Inha University, Korea, ^Department of Fine Chemistry, Seoul National University of Technology, Korea) 12 Effects of Bridge Nature of Dinuclear Half-Titanocenes on Polymerization Properties Seok Kyun Noh\ Yong Rok Lee\ Won Seok Lyoob, Dong-Ho Leec ("School of Chemical Engineering and Technology, Yeungnam University, Korea, School of Textiles, Yeungnam University, Korea, ^'Department of Polymer Science, Kyungpook National University, Korea)

31

35

43

47

53

59

69

Contents

ix

13 Modification of Catalytic Properties of Homogeneous Metallocene Catalytic Systems in Propylene Polymerization under Action of Triisobutylaluminum and Lewis Bases 77 N.M. Bravaya, E.E. FalngoPd, EA. Sanginov, A.N. Panin, O.N. Babkina, S.L. Saratovskikh, O,N, Chukanova, A.G. Ryabenko, E.N. Ushakov {Institute of Problems of Chemical Physics, Russian Academy ofSciences, Russia) 14 Iron(II) Complexes Ligated with 2-Irnino-l,10-Phenanthroline for Ethylene Activation W.-H. Sun, S. Jie, S. Zhang, W. Zhang (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

87

15 Polymerization of 1 -Hexene and Copolymerization of Ethylene with 1-Hexene Catalyzed by Cationic Half-Sandwich Scandium Alkyls 95 Y. Luob, Z. Houa (fl Organometallic Chemistry Laboratory, RIKEN, Japan, b PRESTO, Japan Science and Technology Agency, Japan) 16 Stereoerrors Formation in the Polymerization of Deuterated Propylene 105 V. Volkis, A. Lisovskii, M, S. Eisen (Department of Chemistry and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology, Israel) 17 Vinylic Polymerization of Norbornene with Neutral Nickel(IT) Complexes Bearing P-Diketiminato Chelate Ligands 113 Y.-Q. Duan, X.-F. Li, Y.-S. Li (State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, China, and Graduate School of the Chinese Academy ofSciences) 18 Effect of Anionic Ancillary Ligand in Ethylene Polymerization Catalyzed by (Arylimido)vanadium Complexes Containing Aryloxide, Ketimide Ligand 123 K. Nomura, W. Wang, J. Yamada (Graduate School of Materials Science, Mara Institute of Science and Technology, Japan) 19 Computational Approach on the Interaction between CrO3 and Ethylene as a Model for the Understanding of Phillips Catalyst 129 B. Liu, W. Xia, M. Terano (School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

x

Contents

20 Olefin Polymerization by Bimetallic Zr Catalyst. Ligand Effect for Activity and Stereoselectivity 135 J. Kuwabara, D. Takeuehl, K. Osakada (Chemical Resources Laboratory, Tokyo Institute of Technology, Japan) 21 Synthesis, Characterization and Ethylene Reactivity of 2-Ester-6-iminapyridyl Metal Complexes W, Zhang, B. Wu, W.-H. Sun (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

141

22 Ligand Effect in Syndiospecific Styrene Polymerization and Ethylene/Styrene Copolymerization by Some Nonbridged Half-Titanoeenes Containing Anionic Donor Ligands H. Zhang, K. Nomura (Graduate School of Materials Science, Nara Institute of Science and Technology, Japan)

147

23 Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand: Synthesis and Olefin Polymerization Activity 153 P, Sudhakar, G. Sundararajan (Department of Chemistry, Indian Institute of Technology, India) 24 Stereoselective Polymerization of Styrene by FI Catalysts 159 K. Michiue8, M. Ondab, M. Mitanf, T. Fujita a f5 & D Center, Mitsui Chemicals, Inc., Japan, Mitsui Chemical Analysis & Consulting Service, Inc., Japan) 25 Synthesis of Bis(imino)pyridine Complexes of Group 5 Metals and Their Catalysis for Polymerization of Ethylene and Norbornene Y, Nakayama, N. Maeda, T. Shiono (Graduate School of Engineering, Hiroshima University, Japan) 26 Ethylene Polymerization with an Anilinonaphthoquinone-Ligated Nickel Complex M. Okada, Y. Nakayama, T. Shiono (Graduate School of Engineering, Hiroshima University, Japan) 27 Ring Opening Metathesis Polymerization of Norbornene Catalyzed by V(CH2SiMe3)a(N-2,6-Me2C6H3XN=C'Bu). In Situ Generation of the Vanadium-Alkylidene K. Nomura, J, Yamada (Graduate School of Materials Science, Nara Institute of Science and Technology, Japan)

165

171

175

Contents 28 Ethylene/2-Methyl-1 -Pentene Copolymerization Catalyzed by Half-Titanocenes Containing Aryloxo Ligand: Effect of Cyclopentadienyl Fragment K. Nomura, K. Itagaki (Graduate School of Materials Science, Nora Institute of Science and Technology, Japan) 29 Synthesis and Optical Properties of Cyeloolefm Copolymers K.-B. Yoon", H. Y. Lee8, S. K. Nohb, D.-H Leea {"Department ofPolymer Science, Kyungpook National University, Korea, bSchool of Chemical Engineering and Technology, Yeongnam University, Korea) 30 Effects of Temperature in Syndiospecific Living Polymerization of Propylene with [r-BuNSiMe2(3,6-f-Bu2Flu)]TiMe2-MMAO Catalyst Z. Cai, Y, Nakayama, T, SHono (Graduate School ofEngineering, Hiroshima University, Japan) 31 Copolymerization of Styrene Derivatives and Cycloolefin with Ni Compound/MAO Catalyst N. Nishimura, K. Maeyama, A. Toyota (Graduate School ofEngineering, Tokyo University of Agriculture and Technology, Japan)

xi

179

185

189

193

32 Additive Effects of Dialkylaluminum Hydrides on Propylene-1,3-Butadiene Copolymerization Using an Isospecific Zirconocene Catalyst 197 T. Ishihara", H. T. Bana, H. Hagihara\ T, Shionoe ("Japan Chemical Innovation Institute, Japan, * National Institute of Advanced Industrial Science and Technology, Japan,c Graduate School of Engineering, Japan) 33 Pd Complex-Promoted Cyclopolymerization ofDiallylmalonates 201 S. Park, D. Takeuchi, K. Osakada (Chemical Resources Laboratory, Tokyo Institute of Technology, Japan) 34 Synthesis of Polymeric Radical Scavengers via ROMP of Norbomene Derivatives and Their Antioxidation Activities K. Horikawa, K. Maeyama, A, Toyota (Graduate School ofEngineering, Tokyo University of Agriculture and Technology, Japan)

205

35 Vinyl Polymerization of Norbomene over Supported Nickel Catalyst 209 J. Hou, W. Zhang, S. Jie, W.-H. Sun (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

xii

Contents

36 Effect of Catalyst Loading in Olefin Polymerization Catalyzed by Supported Half-Titanoeenes on Polystyrene through Phenoxy Linkage

213

B. Kitiyanan, K. Nomura {Graduate School of Materials Science, Nara Institute of Science and Technology, Japan) 37

38

39

Theoretical Study on Active Site Formation of Olefin Metathesis and Olefin Polymerization in Phillips CrOx/SiO 2 Catalyst by PIO Analysis A. Shigaa, B. Liub, M. Teranob f LUMMOX Research Lab., Japan, h School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

219

Plausible Mechanism for the Formation and Transformation of Active Sites on Novel Phillips Type Catalyst with New Organo-siloxane Ligand W. Xia, B. Liu, Y. Fang, D. Zhou, M. Terano (School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

225

Influence of Polymer Morphology on Photo-stability of Polypropylene/SiO2 Nanocomposites K. Suminoa, K. Asukaa, B. Liua, M. Yamaguchf, M. Terano8, T. Kawamurab, K. Nittaa (a School of Materials Science, Japan Advanced Institute of Science and Technology, Japan, * Graduate School of Natural Science and Technology, Kanazawa University, Japan)

40

Photo-oxidation of Polyolefln/Clay Composites S. Zhang, H, Qin, M. Yang (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, P. R. China)

41

Effects of Silica Particles on the Transparency of Polypropylene Based Nanocomposites Kazuo Asukaa, Iku Kouzaf, Boping Liua, Minoru Teranoa, Koh-hei Nfttab ("School of Materials Science, JAISTJapan, hGraduate School of Natural Sci and Tech., Kanazawa University, Kakvma, Kanazawa, 920-1192, Japan)

42

Propene Polymerization by a/wa-Fluorenylamidodimethyltitanium Activated with SiO2-Supported Modified Methylalrninoxane Takeshi Shiono3*, Takashi Matsumaeb, Kef Nishiib, Tomiki Ikedab ("Graduate School of Engineering, Hiroshima University, Chemical Resources Laboratory, Japan)

229

233

237

241

Contents 43 Branched-PE/i-PP Reactor Blends Prepared through Ethylene Gas-Phase Polymerization Catalyzed by a-Diimine Nickel Supported on iPP Particles Chtmwen Giro", Hong Fan*, Bo-Geng Li", Shiping Zhub ("State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, China, Department of Chemical Engineering, McMaster University, Canada)

44 Kinetics of Propylene Bulk Polymerization with a Spherical Ziegler-Natta Catalyst Bogeng L i", Hong Fan a, Jijiang Htta, Shiping Zhub ("State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, China, bDepartment of Chemical Engineering, McMaster University, Canada) 45

Effect of a-Olefins on Copolymerization of Ethylene and a-Olefin with [t-BuNSiMe 2 Flu]TiMe 2 Catalyst $ Nawaporn Intaragamjona, Takeshi Shionob*, Bunjerd Jongsomjit""* Piyasan Praserthdam3* ("Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering Chulalonngkorn University, Thailand,bDepartment of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Japan)

xili

245

253

271

Author Index

275

Subject Index

279


Preface

More than a half-century has passed since the finding of Ziegler-Natta catalysts and a quarter-century from that of metallocene catalysts. The development of sophisticated production systems owing to the innovative catalyst technology has made polyolefm one of the most important polymer materials. Considerable research effort has been continuously paid on polyolefin technology in the world, and Asia has been growing up as one of the most active regions in this field. Asian Polyolefin Workshop (APO) was thus planned to provide a venue for Asian scientists and engineers identifying and exploring the areas of common interests. The 1 st APO was held in Nara on December 7th - 9th, 2005, with more than 100 participants from China, Israel, India, Japan, Korea, Russia, Spain and Thailand. The workshop concerned the following research topics with 34 oral and 37 poster presentations; 1) Heterogeneous olefin polymerization catalysts Traditional Ziegler-Natta, Phillips, heterogenized metallocene and post metallocenes 2) Homogeneous olefin polymerization catalysts Traditional Ziegler-Natta, metallocene and post metallocenes 3) Precise synthesis of new polyolefins 4) Structure and properties of polyolefins 5) Engineering aspects of olefin polymerization This book is a collection of the important papers presented at the Workshop, We believe that these works will stimulate further research as well as contribute to an understanding of the activity of Asia in this field. April, 2006 Takeshi Shiono Kotohiro Nomura Minoru Terano Editors xv


Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

1

Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet Shingo Matsuo*, Tomoaki Matsugi, Junji Saito, Nobuo Kawahara, Hideyuki Kaneko, Norio Kashiwa R&D Center, Mitsui Chemicals, Inc., 580-32, Nagaura Sodegaura, Chiba, 299-0265, Japan

Abstract Surface polymerization of 2-hydroxyethyl methacrylate (HEMA) at the initiation sites on the molded sheet of polypropylene macroinitiator (PP-MI) was performed by a CuBr mediated controlled radical polymerization (CRP). The obtained sheet was coated with poly(HEMA), then analyzed by attenuated total reflection infrared (ATR/1R) and transmission electron microscopy (TEM) to investigate the structure and the morphology. It was revealed that PP-graft-poly(HEMA) was successfully synthesized on the sheet and showed unique morphological features. 1. INTRODUCTION Polyolefins (POs) are the most widely used commercial polymers. On the other hand, it is becoming important to add new functions into POs in order to broaden the applications vis-a-vis certain highly valuable fields. One approach to develop this point that has been attracting much attention is the creation of hybrid materials having chemical linkage between PO and non-PO [1]. In order to produce these materials, it is necessary to apply either PO macroinitiator [2,3,4], PO maeromonomer [5,6] or reactive PO [7]. By doing so, it is possible to create a new class of PO/non-PO hybrid polymers possessing unique topologies, compositions and properties. Recently, some methods have been developed for introduction of functional groups into PO, for example, eopolymerization of olefin and polar monomers [2,8,9]. This functional PO was useful to create PO macroinitiator for controlled radical polymerization (CRP). It has already been reported in our

1

S, Matsuo et al.

previous paper [3] that the method to produce polyethylene-block-poly(methyl methacrylate) block copolymers under solution conditions is by using terminally esterified polyethylene as a PO macroinitiator. But to produce POblock or graft-non-PO copolymers like that on molded sheet has not yet been reported. In this paper, we would like to report the CRP of 2-hydroxyethyl methacrylate (HEMA) to prepare PP-graft-poly(HEMA) on a molded sheet of PP-MI by using PO macroinitiator techniques and the results of surface observations. 2. EXPERIMENTAL Typical example for synthesis of polypropylene macroinitiator (PP-MI) Toluene (1 500 mL) was introduced into 2 000-mL glass flask equipped with a mechanical stirrer, a condenser, and a thermometer under nitrogen. After the solvent was thermostated to 40°C, then propylene gas was fed (100 L/h) for 20 min, triisobutylaluminium (44 mmol) and 10-undecen-l-ol (40 mmol) were added to the reactor. Pretreated solution of rac-ethylenebis(indenyl)zirconium dichloride (Et(Ind)2ZrCl2, 0.020 mmol) and methylaluminoxane (MAO, 4.0 mmol) in 10 ml toluene for 5 min was added to start polymerization. The polymerization was conducted for 20 min under vigorous stirring (600 rpm). Isobutyl alcohol (10 mL) was added to terminate the polymerization. The resulting solution was poured into methanol (3 000 mL) with concentrated HCl (5 mL) to precipitate the copolymer. The resulting polymer was collected by filtration, washed with methanol (300 mL x3), and dried under vacuum. Thus 53.6 g of isotactic poly(propylene-eo- 10-undecen-l-ol) was obtained as white powder (Mn: 15 400). lR NMR analysis revealed that 1.0 mol% of 10-undecenl-ol was incorporated into the copolymer. The resulting poly(propylene-eo- 10-undecen-l-ol) (50 g, 12 mmol of OH group), triethylamine (72 mmol), 2-bromoisobutyryl bromide (60 mmol), and hexane (600 mL) were added to a 1 000 mL-glass flask equipped with a mechanical stirrer, a condenser, and a thermometer under nitrogen. The mixture was heated to 80 °C and stirred for 80 min. Then, the reaction mixture was cooled to room temperature. The precipitated polymer was collected by filtration, washed with methanol, IN HCl (aq), and dried at 50 °C under vacuum. Thus, esterified PP as a macroinitiator was obtained in quantitative yield. Typical example for controlled radical polymerization (CRP) on the surface of PP-MI sheet A typical CRP was performed as follows, A PP-MI sheet (ca. 1 mm of thickness) prepared by hot-pressing method at 180 °C (10 Mpa, 1 min) was set into 500-mL flat-bottomed glass flask equipped with a

1, Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet 3

magnetic stirrer. Dried ethanol (250 mL) and 2-hydroxyethyl methacrylate (HEMA, 50 mL) were added to the flask under nitrogen atmosphere and stirred for 20 min at 25 °C. Ethanol and HEMA were degassed by bubbling with nitrogen for 30 min prior to use. CuBr (5,3 mmol) and N,N,N',N",N"pentamethyldiethylenetriamine (PMDETA, 10.6 mmol) were dissolved in ethanol (5 mL) and stirred for 5 min, then the solution was added into the flask to initiate the polymerization. The polymerization was conducted with stirring at 25 °C. After the desired polymerization time, the polymerization was stopped, and the resulting sheet was washed in excess methanol. The sheet was dried at 80 °C under vacuum. 3. RESULTS AND DISCUSSION 3.1. Preparation of polypropylene macroinitiator A synthetic route for preparation of polypropylene macroinitiator (PPMI) is shown in Scheme 1. Hydroxylated PP was prepared by copolymerization of propylene and 10-undecen-l-ol with Etflnd^ZrCla/MAO at 40 °C. Triisobutylaluminium was used as a reagent for masking hydroxyl group of 10undecen-l-ol. The resulting polymer solution was treated with acidic methanol to remove catalyst residues and aluminum moiety which caused gel formation. The thus obtained hydroxylated PP was treated with 2-bromoisobutyrylbromide and triethylamine in hexane at 80 °C to produce esterified PP, which was able to work as a macroinitiator (i.e. PP-MI) for CRP. This PP-M1 was molded by hotpressing (ca. 1 mm of thickness) at 180 °C, Scheme 1. Preparation of PP Macroinitiator C'BukAl

n AI /Q

Toluene

»

Propylene Metallocene/ MAO

MeOH

Toluene/4CTC O B r

-^

B r

/Et 3 N

Hexane OH

OH

n

= PP Macroinitiator (PP-MI)

4

S, Matsuo et al,

3.2. Controlled radical polymerization on the surface o/PP sheet The presence of initiation sites exposed on the surface was confirmed by attenuated total reflection infrared (ATR/IR) analysis. CRP of HEMA on the surface of PP-MI sheet was conducted at 25 °C in ethanol for 24 h. The surface of the sheet was obviously changed to rough and opaque after CRP, then it was analyzed by ATR/IR and transmission electron microscope (TEM) in detail. Polymerization Time Oh (PP-MI) Ester G=O of Foly(HEMA) |

3h

9h

24h vO-H

vC-H

vC=O(1?30) 4000

3B0D 3200

2800 2400 2000 1800 1200 800 WavenumberCerrr1)

400

Figure 1. ATR/IR spectra on the surface of PP-MI sheet

4000 3MD 3200 2800 2400 2000 1600 1200 BOO 400 Wavenumbers (em )

Figure 2. ATR/IR spectrum on the surface of homo PP sheet after treated under the same conditions as CRP

Figure 1 shows the change of ATR/IR spectra on the surface of the sheet. As the polymerization advanced, the absorption of the hydroxyl group and the carbonyl group derived from the poly(HEMA) became stronger with

1, Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet 5

lowering that of the alkyl group of the PP main chain. Meanwhile, the same absorption of the hydroxyl group and the carbonyl group was not observed on the surface of the commercially available homo PP sheet treated under the same conditions as the control (Figure 2). These results suggest that poly(HEMA) was propagated from the initiation sites on the sheet like the image in Figure 3. initiating site

Surface of PP-MI press-sheet Figure 3. Image of CRP on the surface of PP-MI press sheet

Moreover, Figure 4 showed the spectra of the cross section of the sheet after 24h polymerization in 2 um depth at each point (a-c). There was little absorption derived from the hydroxyl group and smaller absorption derived from the carbonyl group on the inside of the sheet (c), compared to the surface (a). These data also confirmed that the CRP of HEMA successfully occurred on the surface of the sheet. C u t t i n g bv tbc d i a m o n d knife

4000

3SO0

3200

2SO0 £400 2000 VVavenumbeitcnr 1 )

1600

1200

800

Figure 4. ATR/IR spectra, of the cross section of PP-graft-poly(HEMA) sheet

S. Matsuo et al.

(a)

Poly(HEMA)

(b)

PP-MI phase Figure 5. TEM image of the section nearby the surface of PP-graft-poly(HEMA) sheet at a magnification of (a) x 5 000 and (b) x 60 000

Furthermore, TEM observation was also examined in order to observe the change of the morphology of the surface on the sheet. Figure 5 shows the TEM images of the surface section of the same sheet in Figure 4. The thickness of the poly(HEMA) layer was in the range of about 5-20 um. The interface between PP and poly(HEMA) phase was not clear in the magnified image (b), probably derived from the chemical linkage. These TEM images support the results of ATR/IR in Figure 4 well. 4. Conclusions PP-graft-poly(HEMA) hybrid polymer on the surface of PP was successfully produced by the combination of metallocene catalyzed olefin polymerization followed by CRP. This technique should be applied to introduce polar polymer segments onto the surface of the various molded parts based on POs. Another kind of PO hybrid modified on the surface is now under investigating and will be reported soon. References [1] For recent review: T.C. Chung, Prog. Polym. Sci. 27 (2002) 39-85. [2] N. Kashiwa, T. Matsugi, S. Kojoh, H. Kaneko, "N. Kawahara, S. Matsuo, T. Nobori, J. Imuta, J. Polym. Sci. Part A: Polym. Chem. 41 (2003) 3657-3666. [3] T. Matsugi, S. Kojoh, N. Kawahara, S. Matsuo, H. Kaneko, N. Kashiwa, J. Polym. Sci. Part A: Polym. Chem. 41 (2003) 3965-3973. [4] Y. Inoue, T. Matsugi, N. Kashiwa, K. Matyjaszewski, Macromoleeules 37 (2004) 3651-3658. [5] H, Kaneko, S. Kojoh, N. Kawahaia, S. Matsuo, T. Matsugi, "H. Kashiwa, J. Polym. Sci. Part A; Polym. Chem. 43 (2005) 5103-5118. [6] H. Kaneko, S. Kojoh, N. Kawahara, S. Matsuo, T. Matsugi, N. Kashiwa, Macromol. Symp. 213 (2004) 335-345. [7] N. Kashiwa, S. Kojoh, N. Kawahara, S. Matsuo, H. Kaneko, T. Matsugi, Macromol. Symp. 201(2003)319-326. [8] J. Imuta, Y. Toda, N. Kashiwa, Chem. Lett. (2001) 710-711. [9] J. Imuta, N. Kashiwa, Y. Toda, J. Am. Chem. Soc. 124 (2002) 1176-1177.


7

Japanese National Project for the Innovation of Industrial Polypropylene Process Technology Minora Terano8"*, Keigo Suehiro\ Takehiro Sagaec, Etsuo Tobitad a

Japan Advanced Institute of Science & Technology, Nomi, Ishikawa, 923-1292, Japan Mitsui Chemicals, Inc., Minato-ku, Tokyo, 105-7117, Japan c Japan Polypropylene, Co., Yokkaichi, Mie, 510-0848, Japan Asahi Denka Co., Ltd., Shimhata, Minami-ku, Saitama, 336-0022, Japan

Abstract Japanese national project relating to the innovation of industrial polypropylene process technology has been conducted in order to depress the CO2 emission. Various new technologies including highly active catalyst with large particle size and effective stabilizer for polymerization stabilization have been successfully developed for the purpose. 1. INTRODUCTION The Kyoto Protocol came into force on February 16,2005 with 141 countries in order to reduce the emission of green house gases (mainly CO2). Japanese national project relating to the innovation of industrial polypropylene (PP) process technology named Simple Plastic Manufacturing (SPM) project has been conducted for 3 years using totally about 15 million US dollars. The main target of the project was to reduce the energy consumption of the industrial PP process in order to depress the CO2 emission [1,2]. Pelletizing step has been known to consume about 40% of total production energy in the process [1,2]. Therefore, SPM project was tried to establish the technologies to omit the pelletizing step. PP powder having good morphology, mechanical strength and high stability should be produced without pelletizing. Highly advanced catalyst and stabilization technologies were mainly required for the purpose.

M. Terana et al.

2. RESULTS AND DISCUSSION 2,1. Outline of SPM project SPM project was consisted of 2 groups aiming to develop the technologies for 2 PP grades, mjection and film. Amount of PP for injection molding grade used in Japan for various products from small-sized daily necessities to large-sized industrial materials is 1.55 million tons per year, which corresponds to ca.52 % of total PP production in Japan. Therefore, if the pelletizing step can be omitted, a great amount of energy can be saved. Fig. 1 shows the schematic diagrams of current and SPM processes for injection grade. Not only pelletizing step but compounding step can be skipped by establishing the direct compounding technology.

Current (a) Current propylene catalyst

PP Plant

propylene ethylene

Injection Plant

powder

Polymerization

(b) SPM propylene catalyst

filler pigment

stabilizer pellet

Pelletizing

product pellet

Compounding V

PP Plant propylene ethylene

Injection Injection

,

Injection Plant stabilizer filler pigment

powder

product

Compounding Direct Compounding

Polymerization

Injection Injection

Fig.l Schematic diagrams of Current and SPM processes for injection grade

2, Japanese National Project for the Innovation of Industrial PP Process Technology 9 (a) Current 1

'

FilmPlaat

Film

\

Polymerization

Extrusion & Stretching

Pelletizinn

(b) SPM

PP& Film Plant

Direct Powder Extrusion Film

Polymerization

Film Plant w connected-with PP plant.'

Extrusion & Stretching

Fig,2 Schematic diagrams of Current and SPM processes for film grade

More than 0.5 million tons of film grade PP have been produced per year in Japan. Thus, large energy saving effect was expected to achieve by SPM project. Fig. 2 shows the schematic diagrams of current and SPM processes for film grade. In SPM process, polymerization vessel and processing machine are directly connected in one factory, by which transportation of PP between the factories can be omitted in addition to the pelletizing step. It will highly contribute to reduce the energy consumption. 2.2. Catalyst technologies In order to omit the pelletizing process, highly advanced catalyst technology must be applied to generate PP powder having the same level of morphology and particle size as pellet. Impact copolymer made by in situ mixing of homo-PP and ethylene-propylene rubber in the reactor is quite important for the recent injection molding applications. When the conventional Ziegler-Natta catalysts are applied for the impact copolymer production, the producible amount of rubber is limited because of poor powder morphology and fouling in the reactor. Metallocene catalyst system discovered by Kaminsky in 1980 [3] can solve the problem by producing the polymers having narrow molecular weight and composition distributions without generating the low molecular weight and low temperature

10

M. Terano et al.

extracted components. For SPM project, the metallocene compound was combined with unique clay support-activator to produce spherical polymer. It became possible to control the morphology and particle size of PP powder by controlling the clay morphology and particle size [4]. Fig.3 shows the polymer with 2-3mm diameter produced using the clay supportactivator with 50-70 fi m in diameter.

Support-Activator Dp=50-70^.m

Polymer Dp=2-3mm

Fig.3 Morphology control for injection grade with metallocene catalyst

In the case of film grade, existing highly active Ziegler-Natta catalyst technology was applied to achieve the target morphology. Catalyst support was mechanically classified to get larger and more uniform particles. (Fig.4) 100 90

Accumulated Volume(%)

80

Original

70 60 50

Classification, 60 % recovery

40

Classification, 75%revovery

30 20 10 0 20

40

60

80

100 100

120

140

160

180

200

Support Diameter ((/an) µ m)

Support Dp=80-90/im

Polymer Dp=2-3mm

Fig.4 Morphology control for film grade with Ziegler-Natta catalyst

2. Japanese National Project for the Innovation of Industrial PP Process Technology 11 2.3. Stabilization

technology

PP is known to degrade easily via thermo- or photo-oxidation [5] . Therefore, stabilizers have to be added to PP typically in the pelletizing process in order to prevent the degradation. The palletizing is very important from this viewpoint, but the process consumes huge energy. In order to stabilize PP without pelletizing, new technology with low energy consumption should be developed. Several attempts for the stabilizer addition have been made for simplifying the production process or lowering energy consumption [6,7] . However, a direct stabilizer addition to the polymerization system has been regarded to cause a drastic decrease in the catalyst activity. In this study, the stabilizer was tried to add during polymerization, because the method is believed to be quite effective for energy saving. In addition, the cost reduction of PP production may be achieved at the same time by the method. Ziegler-Natta and metallocene catalysts are known to deactivate easily by various compounds having polar group. Masking of polar group seemed to be a key technology to realize the direct stabilizer addition. Antioxidant containing phenolic OH was chosen as an adequate stabilizer for this study. Phenols react with alkylaluminum to generate phenoxides, which can reproduce original phenols by hydrolysis after polymerization. Market available phenolic antioxidants were examined first, but they were found to decompose during hydrolysis. Therefore, new antioxidant, 3-(3,5-di-t-butyl-4-hydroxyphenyl)-Noctadecylpropionamide (AO-1), was developed and confirmed as a suitable compound in order to avoid the phenomenon. Tab.l summarizes the polymerization results with Ziegler-Natta and Metallocene catalysts in the presence of AO-1 phenoxide (Fig.5) made by the reaction of AO-1 with triethylaluminum.

o Fig.5 AO-1 phenoxide

No differences are found in catalytic activity and polymer characteristics such as molecular weight, polydispersity and meso pentad fraction as shown in Tab.l. It becomes obvious that the masking of OH group by alkylaluminum is quite effective to prevent the catalyst deactivation. PP powder obtained using AO-1 phenoxide was confirmed to be as stable as pellet.

12

M, Terano et at Tab.l Polymerization results with AO-1 phenoxide M

[mmmm] e '

Cat. system

Additives

Yield c>

Ziegler-Natta a*

Non

9400 7100 9100

40 39 40

4.8 5.1

97.1 97.0 97.2

24000 8000 23000

4.6 4.4 4.6

2.0 1.9 2.0

86.9 87.8 86.6

AO-1 AO-1 phenoxide Metalloceneb^

Non AO-1 AO-1 phenoxide

Mw- 1C

% 5.1

) heptane slurry, Tp=70aC, Pp= O.SMPaG, 1h b> toluene slurry, , Pp= O.SMPaG, 1h > g-PP/g-cat. for Ziegler-Natta, kg-PP/mol-Zr-h for metallocene "' measured by GPC ' rneso pentad fraction by "C-NMR

c

3.CONCLUSIONS New catalyst and stabilization technologies were successfully developed to omit the pelletizing step, which will contribute to the innovation of industrial PP process with low energy consumption leading to depress the CO2 emission. Acknowledgements This work was supported by NEDO (New Energy and Industrial Technology Development Organization). References [1] Simple Plastic Manufacturing (SPM) Project, 2005: http://www.nedo.go.jp/ iinkai/kenkyuu/bunkakai/17h/jigo/4/l/index.html [2] M. Terano, E. Tobita, O. Segawa, T. Sagae, M. Ohgizawa, Expected Materials for the Future, 4 (2004) 28-35. [3] T. Tayano, M. Sugawara, MetCon2000 (Jun. 8-9,2000, Houston). H. Uchino, Polypropylene 2001, (Sep.l 1-13,2001, Zurich). [4] H. Sinn, W. Kaminsky, Adv. Organomet. Chem.18 (1980) 99-149. [5] H. Zweifel, Stabilization of Polymeric Materials, Springer, Berlinl (1998) pp.10. [6] for example, EP0254348 A2, Enichem, JP 2991751, Himont. [7] N. Kawamoto, T, Horikoshi, K. Nomura, H. Yokota, Y. Negish, E. Tobita, M. Terano, J. Appl. Polym. Sci. 99 (2006) 1350-1358.


13

Novel Energy and Cost Saving Polypropylene Stabilization via Addition of Antioxidant into Polymerization System Hideyuki Yokota,a Kazukiyo Nomura,8 Takahiro Horikoshi,a Yoshinori Negishi,a Naoshi Kawamoto/ Etsuo Tobita,*a Minoru Teranob "Polymer Additives R&D Laboratory, ASAHIDENKA Co., Ltd, 5-2-13, Shirahata, Minami-ku, Saitama City, Saitama, 336-0022, Japan b Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi City, Ishikawa, 923-1292, Japan

Abstract Polypropylene powder stability was evaluated by means of biaxially-oriented film processing, where the powder were prepared by using Ziegler catalyst in the presence of aluminum phenoxide derived from 3-(3,5-di-f-butyl-4hydroxyphenyl)-N-octadeeylpropionamide (AO-1) and triethylaluminum. Despite the lower concentration of antioxidant (ca. 560 ppm), the powder exhibited excellent stability compared with commercial film grade pellet including antioxidants of over 1000 ppm. Half amount of loading was found to be sufficient in the case of AO-1 phenoxide added into polymerization system. This indicates that cost saving of antioxidant due to the reduction of loading level can be achieved by the method. Thus, the method used the AO-1 phenoxide in the polymerization system is effective and economical technology. 1. INTRODUCTION Since the PP production energy savings was considered to contribute to the reduction of carbon dioxide emission, NEDO (New Energy and Industrial Technology Development Organization, Japan) promoted the energy reduction project on PP production technology via excluding pelletizing process, which was named as SPM (Simple Plastic Manufacturing) project [1], In the course of

14

H. Yokota et at

our studies, it was demonstrated that the stabilization via the phenolic antioxidant addition as an aluminum phenoxide into slurry and bulk polymerization instead of pelletizing was quite effective [2-5]. AO-1 (3-(3,5di-f-butyl-4-hydroxyphenyl)-N-octadecylpropionamide) was designed as a suitable phenolic antioxidant for the use in the polymerization system from the standpoint of avoiding the decomposition via masking with aluminum alkyls. Thus, excellent additive-dispersion throughout the PP powder by the method enables us the superior stability. From the viewpoint of industrialization of this method, it is important whether cost saving can be achieved via this method or not. Since this method provides superior stability of PP powder, there is a possibility of the reduction of the additives-loading amount, resulted in cost saving of additives even with pelletizing process. In this study, the powder stability via the method was evaluated in comparison with that of commercial standard PP pellet. Biaxially-oriented film processing was conducted in this study, where PP encounters higher processing temperature and higher shear under the atmosphere, since the reduction possibility of additives-loading was considered to be actually estimated under severe conditions, 2. EXPERIMENTAL Sample was prepared by bulk polymerization with a supported Ziegler catalyst in combination with triethylaluminum and cyclohexylmethyldimethoxysilane (Al/Si/Ti=250/4/l) at 70 °C for 1 h in the presence of AO-1 phenoxide [1]. Additionally, AO-1 of 560 ppm was dry-blended under nitrogen atmosphere to powder polymerized without phenoxide under the same above conditions. These samples were extruded at 230 °C under nitrogen atmosphere, followed by sheeting and drawing, and then changes in molecular weight of the biaxiallyoriented films (BOPP) were evaluated by size exclusion chromatography (SEC) [1,4], Commercial film grade pellet containing conventional antioxidants of over 1000 ppm was also processed and evaluated. 3. RESULTS AND DISCUSSION The stability of PP powder via the addition of AO-1 phenoxide into polymerization system was evaluated in order to estimate the possibility of cost saving via the method using AO-1 phenoxide. Two powder samples were prepared by bulk polymerization. One powder sample was prepared by traditional method, in which AO-1 was dry-blended under N2 after polymerization. Another one was prepared by the method, where AO-1 phenoxide was added into polymerization system. Stability during film processing as BOPP was evaluated by SEC as changes in molecular weight.

3, Novel Energy and Cost Saving PP Stabilization via Addition ofAntioxidant

15

Figure 1 shows the changes in molecular weight of bulk-polymerized samples at each processing stage. Here, both samples contained AO-l of 560 ppm, respectively. The molecular weight of the sample prepared by dry-blend was slightly decreased by extrusion as a first step of processing, but the magnitude was minimal. Drastic decrease in molecular weight (over 7 %-decrease) was observed during sheeting. Molten polymer encountered higher shear rate and was exposed by oxygen in atmosphere at higher temperature. This was considered to lead to drastic degradation of the sample. At drawing stage, further decrease in molecular weight was found to proceed with drawing resulting in over 10 %-decreasing. Since the drawing was conducted at a temperature of below melting temperature of polymer, i.e., the moderate conditions, the magnitude in the decrease during drawing was considered to be lower than that during sheeting. 6.0 X I 0 s

4.0 X 10 s Initial Extrusion Sheeting Drawing Figure 1 Changes in Mw of samples in each processing stage. : by developed method (AO-l of 560 ppm), (o): by dry blend (AO-l of 560 ppm)

On the other hand, the sample polymerized with AO-l phenoxide (by developed method) exhibited excellent stability throughout the BOPP processing. No degradation was observed for the samples by the developed method during extrusion and drawing. Despite the cruel conditions of sheeting, degradation of the sample by the developed method was prevented effectively, and the decrease in molecular weight throughout the BOPP processing was estimated to be minimal as below 2 %. Thus, excellent stability can be achieved by the developed method even under cruel processing conditions, and the method was superior to the conventional dry-blend one in stabilization. As reported previously, superior dispersion of antioxidants throughout the PP powder was considered to give rise to the advantage in stability [1-7]. In contrast, the

16

H. Yokota et al.

antioxidant dispersion of the sample extruded by dry-blend was indicated to be insufficient. This was thought to cause the depression of the efficient and effective inhibition of degradation triggered with oxygen/heat during sheeting. Figure 2 shows the changes in molecular weight of the sample by the developed method (560 ppm as AO-1) and commercial pellet having over 1000 ppm of conventional phenolic antioxidant. Additionally, commercial pellet contained phosphite as a secondary antioxidant as well as phenolic antioxidant. Phosphite is known to provide good stability in particular during processing, and to add generally to PP together with phenolic antioxidant [6]. The commercial one degraded in particular at the sheeting stage and the magnitude in the decrease of molecular weight was estimated to be ca. 3 %. This was not so significant and was acceptable degradation levels in practical use.

O.U 1U

is

5.5 X I 0s

u

5.0 X 10s

J

4.5 X10 5

a

_,

4.0 X 10s

Initial Extrusion Sheeting Drawing Figure 2 Changes In Mw of samples obtained by the developed method and standard pellet in each processing stage. : by developed method (AO-1 of 560 ppm), (o): commercial pellet (conventional antioxidant of over 1000 ppm)

As mentioned above, the decrease in molecular weight of the sample by the developed method was estimated to be less than 2 %. It should be noted that the stability of the sample by the developed method was superior to that of commercial one, because the sample contained only phenolic antioxidant of 560 ppm: the content was about half of that of commercial one and without phosphite. This indicates that excellent stability can be achieved by the developed method with lower-loading level compared with conventional dry blend method. Considering these results, half amount of phenolic antioxidant is at least suggested to be sufficient for stabilization of PP in the case of the use of the developed method. In addition, suitable usage of phosphite and calcium

3. Novel Energy and Cost Saving PP Stabilization via Addition ofAntioxidant

17

stearate in combination of AO-1 phenoxide by the developed method is believed to promote the further reduction of total loading-amount of additives. Thus, the cost saving concerning additives via the developed method is estimated to be above 30 % including of cost of aluminum alkyls as masking agent for phenolic antioxidant, AO-1. Furthermore, no additional installation of heavy equipment was necessary for the existing PP plant because the additives can be fed into reactors via cocatalyst feeding system or vessels, and then no investment for expensive equipments was necessary to apply the developed method to the existing plant. In other words, the developed method has an excellent retrofitability. The developed method enables us not only to reduce the carbon dioxide emission due to excluding the pelletizing process but also to minimize the loading-amount of additives resulting in saving PP production cost. The method is believed to be competitive technology instead of pelletizing, and to contribute further progress of polypropylene industry. 4. CONCLUSIONS Polypropylene obtained by the developed method with AO-1 phenoxide exhibited excellent stability under cruel processing conditions as biaxiallyoriented film processing. Below half loading-amount was suggested to be sufficient for stabilization by using the developed method, that is, the significant reduction in additives-loading amount was indicated to be achieved by the method. The estimated cost saving of additives loading is over 30 %-reduction of conventional dry-blend method with pelletizing. Thus, the method is competitive stabilization technology. Acknowledgements The study was supported by Grand-in-aid for the Simple Polymer Manufacturing (SPM) Project (2002-2004) of New Energy and Industrial Technology Development Organization (NEDO), Japan, References [1] Simple Plastic Manufacturing (SPM) Project, 2005: http://www.nedo.go.ip/ imkai/kenkvuu/bunkakai/17h/iigo/4/l /index.html [2] M. Terano, E. Tobita, O. Segawa, T. Sagae, M. Ohgizawa, Expected Materials for the Future 4 (2004) 28-35. [3] N. Kawamoto T. Horikoshi, K. Nomura, H. Yokota, Y. Negishi, E. Tobita, M. Terano, J. Mater. Life Soc. 17 (2005) 61-66. [4] N. Kawamoto, T. Horikoshi, K. Nomura, H. Yokota, Y. Negishi, E. Tobita, M. Terano, J. Appl. Polym. Sci. 99 (2006) 1350-1358.

18

H. Yokotaetal,

[5] M. Terano, N. Kawamoto, T. Horikoshi, K. Nomura, H. Yokota, Y. Negisbi, E. Tobita, J. Mater. Life Soc. Symposia 2005, 67-68. [6] K. Schwarzenbach, B. Gilg, D. Mueller, G. Knobloch, J.-R. Pauquent, P. Rota-Graziosi, A. Schmitter, J. Zingg, E. Kramer in: H. Zweifel (Ed.), Plastics Additives Hanser, Munich 2000, p. 14.


19

Polymerization Behavior with Metallocene Catalyst Supported by Clay Mineral Activator Hiroshi Nakano,* Tadashi Takahashi, Hideshi Uehino, Takao Tayano, and Toshihiko Sugano Polymerization Technical Center, Japan Polypropylene Corporation 1, Toho-cho Yokkaieki, Mie, 510-0848 JAPAN, email:[email protected]

Abstract Acid treated clay (montmorillonite) was reacted with AlEt3 (TEA) to give TEA-treated montmorillonite (TEA-Montmorillonite). Various amounts of 2,6-dimethylpyridine (26DMP) was added to TEA-Montmorillonite in order to control the acid strength of TEA-Montmorillonite, then the reaction mixture was reacted with triisobutylaluminum (TiBA) (O.fimmol) and 0.3mmol of racMe2Si(2-Me-4-Ph-l-Ind)aZrCl2 (1) to prepare the catalyst. The catalysts were characterized by using solid state UV-vis spectrum spectroscopy. Ethylene polymerizations and propylene-ethylene (1:1 molar ratio) copolymerizations were carried out in heptane at 75 °C-0.8 MPaG for 0.5 h after prepolymerization. The effect of acid strength and propylene prepolymerization on the olefin polymerization behaviors were studied in this catalyst system. 1. INTRODUCTION Since the discovery of MAO-metallocene catalyst system by Sinn and Kaminsky, metallocene catalysts have given to the chemist the opportunity to control the catalytic features by the design of metallocene complex. [1] The cocatalysts have also been developed to control the catalytic features such as activity, selectivity, and molecular weight. [2-5] Clay mineral is one of the most attractive cocatalyst for the olefin polymerization because of its abilities of activating metallocene without MAO.[6-12] From the other view point, this

20

H. Nakano et al

material has attracted much attention as a modifier of the polyolefin to make clay-polymer nanocomposite.[13-20] As a co-catalyst, the clay mineral has superior characteristics such as stability and inflammability, in contrast to MAO which is reactive to air and moisture. In addition, clay mineral could be used as a catalyst support for the production of polyolefins, therefore the clay mineral cocatalyst is called "Support Activator." In this paper, we will show the preparation and characterization of metallocene catalyst supported by clay mineral activator and discuss the results of the ethylene polymerization and ethylene-propylene co-polymerization, 2. EXPERIMENTAL Acid treated clay was prepared by the treatment of clay (montmorillonite) with the solution of sulfuric acid. Treated clay was washed with water to pH>3 and dried in vacuum at 200 °C. The clay was reacted with heptane solution of AlEtj (TEA) under nitrogen, and then rinsed with heptane to give TEA-treated montmorillonite (TEA-MontmoriEonite). Various amounts of 2,6dimethylpyridine (26DMP; Oumol/g-clay for Cat.l, 80 umol/g-clay for Cat.2, and 200 umol/g-elay for Cat.3) was added to the slurry of TEAMontmorillonite (20 g) in order to control the acid strength of TEAMontmorillonite, then the mixture was reacted for lh with triisobutylaluminum (TiBA) (0.6 mmol) and 0,3 mmol of rac-Me2Si(2-Me-4Ph-l-indenyl)2ZrCl2 (1) to give the catalyst (Cat.1-3). The Cat.1-3 were treated with propylene monomer (C3He/Cat.=2.0wt/wt) in heptane, and then the solvent was removed to give Pcat.1-3, respectively. Ethylene polymerizations and propylene-ethylene (1:1 molar ratio) copolymerizations were carried out in heptane at 75 °C-0,8 MPaG for 0,5 h after prepolymerization. 3. RESULTS AND DISCUSSION 3.1. Acid strength and catalysis feature Acid strength of clay mineral, in this article this means the acid strength of the strongest acidic sites on each clay mineral, should be controlled by amount of the added base, 26DMP. The base would react with strongest acidic sites to poison the acidic site. Therefore addition of smaller amount of base should retain stronger acidic site and the resultant acid strength will be in the order of Cat.1 (strong) >Cat.2 (intermediate) >Cat.3 (weak). The TEAMontmorillonite with no 26DMP, which is used for the synthesis of Cat.1, exhibits an acidic coloration by addition of benzeneazodiphenylamine as acid-

4. Polymerization Behavior with Metallocene Supported by Clay Mineral Activator

21

Absorbance

base indicator. This means that this clay mineral has an acidic site of pKa less than 1.5. Addition of 80umol/g-elay of 26DMP, which amount corresponds to that for Cat.2, makes disappearance of the acidic coloration. This indicates that Cat.2 has an acidic site of pKa equal to about 1.5. Figure 1 shows solid state UV-vis spectrum of catalyst, indicating that the Cat.1 with strong acidic site has two peaks. The calculation by density function theory result[21,22] shows that the peak with shorter wavelength is assigned to a neutral zirconium species, such as "ZrCl2" or "ZrR2", and the peak with longer wavelength is assigned to a 0.5 cationic Zr species. These Cat.1 0.4 Cat.2 results indicate that strong Cat.3 acidic site of pKa99

1.01

2

2a

500

40

2.12

0.64

>9S

1.56

3

2a

1000

40

4.91

0.62

>94

14.6

4

2a

1500

40

2.55

0.62

>97

9.13

5

2a

2000

40

0.75

0.64

>98

1.25

6

2a

1000

20

1.64

0.49

>96

10.1

7

2a

1000

30

2.14

0.55

>95

26,3

g

2a

1000

50

3.55

0.61

>93

5.87

9

2a

1000

60

1.44

0.44

>95

4.88

10

la

1000

40

3.89

0.67

>96

102

11

3a

1000

40

0.94

0.50

>9S

0.21

12

4a

1000

40

2.37

0.37

>79

trace

13

Sa

1000

40

3.51

0.52

>79

trace

14

6a

1000

40

4.06

0.61

>80

65.5

15

7a

1000

40

1.33

0.58

>94

48.6

16

8a

1000

40

0.16

0.54

>99

trace

17

9a

1000

40

0.90

0.48

>97

0.88

18

10a

1000

40

1.27

0.57

>91

304

19

lla

1000

40

2.30

0.52

>95

3.25

20

12a

1000

40

0.13

0.50

>98

3.18

E

General conditions: 2 junol cat.; reaction time: 1 h; solvent: 100 mL toluene; ethylene pressure: 10 atm. * Reaction temperature. c Activity for oligomers: 107 g mor'(Fe) h"1. 4 Activity for lowmolecular-weight waxes: 10s g mof^Fe) h"1. B% a-olefm content determined by GC and GC-MS.

3.2.2. Effect of the iigand environment. Note that the variation of the R substituent on the imino-C of ligands, 2(ArN=CR)-l,10-phen, resulted in tuning the catalytic performance. Aldimine (R=H) and phenyl-ketimine (R=Ph) complexes showed relatively lower catalytic activities than the corresponding methyl-ketimme (R=Me) complexes.

91

92

W.-H. Sun et al.

Furthermore, the R substituent had different influences on the catalytic performances of methyl- or phenyl-ketimine and aldimine analogues. For the 2,6-dialkyl-substituted ketimine and aldimine complexes, both the methylketimine complex 2a and the phenyl-ketimine complex l l a containing 2,6diethyl groups on the phenyl ring of the imino nitrogen, showed the highest activity among their analogues. However, the aldimine complex 8a showed much lower activity under the same reaction conditions (entry 3, 19 and 16 in Table 1). Comparing the complexes containing ketimine or aldimine ligand which possesses 2,6-diisopropylphenyl group on the imino nitrogen, both 3a and 9a (entries 11 and 17 in Table 1) showed much higher catalytic activity than 12a (entry 20 in Table 1), which also showed lower activity than its analogues (entries 18 and 19 in Table 2), perhaps due to the bulky phenylketimine ligand. In general, all methyl-ketimine complexes bearing electrondonating alkyl groups showed high catalytic activity and good selectivity for aolefins. On the contrary, relatively lower selectivity was observed with the complexes containing electron-withdrawing halogen groups, such as complexes 4a - 6a, although these complexes showed high activities. The substituents on the imino-N aryl ring were found to show great influence toward the catalyst performances of both the ketimine and aldimine complexes. For instance, the 2,6-dialkyl-substituted methyl-ketimine complexes la-3a, decrease in the catalytic activity was observed upon increasing the steric bulk on R1, and this could be demonstrated by comparing the 2,6-diisopropylsubstituted 3a with the 2,6-dimethyl-substituted la or 2,6-diethyl-substituted 2a (entry 11 vs. entry 10 or 3 in Table 1). The steric bulk of the isopropyl groups at the o?ffe-positions of imino-N aryl ring of complex 3a may prevent the access (coordination) of ethylene to the active center in the catalytic system, therefore leading the decrease in the catalytic activity. Furthermore, the bulkier the substituents, the smaller a value and a smaller amount of low-molecular-weight waxes were produced. Complexes 4a-6a, containing halogen groups, exhibited comparable catalytic activity and relatively lower selectivity of a-olefins in the oligomerization of ethylene than complexes bearing only alkyl groups. In the catalytic systems of 2,6-dihalogen-substituted complexes 4a-6a, the bulkier substituents at the or^o-positions of imino-N aryl ring resulted in higher catalytic activities as well as higher a value (bromo- > chloro- > fluoro-, entries 12-14 in Table 1). For the aldimine complexes 7a~9a, 2,6-dimethyl-substituted complex 7a displayed the higher catalytic activity of 1.33xlO7 g mol'l(Fe) h"1 (entry 15 in Table 1), while a much lower catalytic activity was obtained for 2,6-diethylsubstituted complex 8a (entry 16 in Table 1) under the same reaction conditions. For the phenyl-ketimine complexes, complex 12a bearing bulkier isopropyl groups at the ortte-positions of the aryl ring had much lower oligomerization

14. Fe(II) Ligatedwith 2-lmmo-l,10-Phenanthroline for Ethylene Activation

93

activity than the 2,6-dimethyl-substituted 10a and the 2,6-diethyl-substituted l l a , probably because of the cooperative interaction of bulkier isopropyl groups on the imino-N aryl ring and bulkier phenyl on the imino-C. 3.2.3, Characterization for low-molecular-weight waxes. In many cases, some low-molecular-weight waxes were obtained as higher oligomers in addition to lower oligomers. Characterized by IR spectra recorded using KBr disc in the range of 4000-400 cm"1, the waxes can be confirmed to be mainly linear a-olefins from the characteristic vibration absorption bands of C=C and various C-H bonds. ! H and 13C NMR spectra of the waxes obtained by complex la/MAO were recorded in o-dichlorobenzene-rf4 using TMS as the internal standard. The NMR spectra of the waxes were shown in Figure 2 and the assignments were determined according to the literatures [8,9]. The 13C NMR spectra further demonstrated that linear a-olefins of the waxes absolutely predominantly existed in the waxes and the single peaks at S 139.14 and 114.17 ppm showed the property of vinyl-unsaturated chain end. The obtained average molecular weight from lH NMR indicated that the carbon number of the waxes was about 40. -CH,-

-CH-

(a) (b)

JL

VJ

Figure 2. NMR spectra of the waxes obtained by complex la/MAO. (a) I3C NMR; (b) JH NMR.

4. CONCLUSIONS A series of tridentate iron(II) complexes bearing 2-imino-l,10phenanthrolinyl ligands have been synthesized and fully characterized. Upon treatment with MAO, these iron(ll) complexes showed high catalytic activities of up to 4.91 xlO7 g moF'CFe) h"1 for ethylene oligomerization with high selectivity for a-olefins. Both the R on the imino-C and the substituents on the N-aryl rings strongly affect the catalytic activity, distribution of oligomers, and selectivity for a-olefins due to their different steric and electronic properties.

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The methyl ketimine complexes were proved to be relatively more active catalysts than either the corresponding aldimine or phenyl ketimine complexes under the same reaction conditions. Electron-donating groups placed on the Naryl rings increased the selectivity for ct-olefins. The placement of bulkier oalkyl groups on the N-aryl rings led to the reduced activity because of steric interaction, however, bulkier halogen groups gave the reverse effect. Acknowledgements The project was supported by NSFC 20473099 along with National 863 Project (2002AA333060), and partly sponsored by CNPC Innovation Fund (04E7054). References [1] B. L. Small, M. Brookhart, and A. M. A. Bennett, J. Am. Chem. Soc. 120 (1998) 4049-4050. [2] G. J. P. Britovsek, ¥ . C. Gibson, B. S. Kimberley, P. J. Maddox, S. J. MeTavish, G. A. Solan, A. J. P. White, and D. J. Williams, Chem. Commun. (1998)849-850. [3] B. L. Small, and M. Brookhart, J. Am. Chem. Soc. 120 (1998) 7143-7144. [4] L. Wang, W. -H. Sun, L. Han, H. Yang, Y. Hu, and X. Jin, J. Organomet. Chem. 658 (2002) 62-70. [5] G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson, D, F. Wass, A. J. P. White, and D. J. Williams, Inorg. Chim. Acta 345 (2003) 279-291. [6] S. Ameerunisha, J. Schneider, T. Meyer, P. S. Zacharias, E. Bill, and G. Henkel, Chem. Commun. (2000) 2155-2156. [7] (a) G. V. Z. Schulz, Phys. Chem., Abt. B 30 (1935) 379-398. (b) G. V. Z. Schulz, Phys. Chem., Abt. B 43 (1939) 25-46. (c) P. J. Flory, J. Am. Chem. Soc. 62 (1940) 1561-1565. (d) G. Henrici-Olive, and S. Olive, Adv. Polym. Sci. 15 (1974) 1-30. [8] G. B. Galland, R. F. De Souza, R. S. Mauler, and F. F, Nunes, Macromolecules 32 (1999) 1620-1625. [9] G. B. Galland, R. Quijada, R. Rojas, G. C. Bazan, and Z. J. A. Komon, Macromolecules 35 (2002) 339-345.


95

15 Polymerization of 1-Hexene and Copolymerization of Ethylene with 1-Hexene Catalyzed by Cationic Half-Sandwich Scandium Alkyls Yunjie Luof and Zhaomin Hou* Organometallic Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198 Japan, and PRESTO, Japan Science and Technology Agency (JSI), Japan

Abstract The combination of half-sandwich scandium bis(alkyl) complexes, such as (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) (1), with 1 equiv of [Ph3C][B(C6Fs)4] showed high activity for the polymerization of 1-hexene. Such complexes could also promote the copolymerization of ethylene and 1-hexene with high activity to produce ethylene/1 -hexene copolymers containing isolated butyl branches in the chain backbone. The copolymerization activity of the present catalyst is much higher than that of the homopolymerization of either monomer, thus constituting a rare example of a homogeneous catalyst system that shows significant positive "comonomer effect" in the copolymerization of two different monomers. 1. INTRODUCTION The development of efficient homogeneous catalysts for the polymerization and copolymerization of ethylene and a-olefins to synthesize high performance polymer materials has been the subject of intense scrutiny in both academic and industrial researches [1]. Over the past two decades, organo rare earth metal complexes have received much attention for application as homogeneous polymerization catalysts [2,3]- Generally, neutral organo rare earth metal complexes can show high activity for the polymerization of ethylene and polar monomers without requirement of a eoeatalyst. However, most of these

96

Y. Luo and Z, Hou

complexes usually show no or very low activity for the polymerization of higher olefins such as cc-olefins, conjugated dienes, cyclic oleflns, and styrene [4,5], In particular, the copolymerization of ethylene with an a-olefm by a rare earth metal catalyst remained scarce [4a,k,n]. Recently, more attention has been directed to cationic rare earth metal alkyl complexes because of their high potential as catalysts for olefin polymerization [3,6,7]. Recent work in our group has demonstrated that cationic half-sandwich rare earth metal alkyls, such as [(CsMe4SiMe3)Sc(CH2SiMe3)]+ and [Me2Si(C5Me4)C"-PCy)YCaCH2SiMe3)Y(/^PCy)(C5Me4)SiMe2]+, which are generated by treatment of the corresponding neutral dialkyl precursors with 1 equiv of [Ph3C][B(C6Fs)4], can serve as unique catalysts for polymerization and copolymerization of various olefins, such as syndiospecific copolymerization of styrene with ethylene [6a], alternating copolymerization of ethylene with norbomene (or dicyclopentadiene) [6b,e], terpolymerization of ethylene, dicyclopentadiene, and styrene [6c], and isospecific 3,4-polymerization of isoprene [6d]. We wish to report here that such cationic half-sandwich scandium alkyl species can also act as a highly active catalyst for the polymerization of 1-hexene and the copolymerization of ethylene with 1-hexene [8]. In particular, the activity for the copolymerization of ethylene with 1-hexene is the highest ever reported for a rare earth metal catalyst, and could be compared with those reported for the most active group 4 metal-based catalyst systems [9]. 2. EXPERIMENTAL General Considerations. All the manipulations were performed under pure argon with rigorous exclusion of air and moisture using standard Sehlenk techniques and an Mbraun glovebox. Ethylene (Takaehiho Chemical Industrial Co., Ltd.) was purified by passing through a Dryclean column (4 A molecular sieves, Nikka Seiko Co.) and a Gasclean CC-XR column (Nikka Seiko Co.). [Ph3C][B(C,jF5)4] was purchased from Tosoh Finechem Corporation and used without purification. 1-Hexene (Kanto Chemical Co., Ltd.) was dried by stirring with CaH2 for 24 hours, and distilled under reduced pressure prior to polymerization experiments. Cp'Se(CH2SiMe3)2(THF) (1-7) were prepared according to literature [6a,b,10,l 1]. 'H, 13C NMR spectra of polymer samples were recorded on a JEOL INM-EX 270 spectrometer (FT, 300 MHz for ! H; 75.5 MHz for 13C). The spectra of ethylene-1-hexene copolymers were measured in lsl,2,2-tetrachloroethane-rf2 at 120 °C, while the spectra of poly(l-hexene)s were recorded in CDC13 at 25 °C. Molecular weights and molecular weight distributions of poly(l-hexene)s were determined against polystyrene standard by gel permeation chromatography (GPC) on a HLC-8220 GPC apparatus (Tosoh Corporation). THF was used as

15. Homo- and Capofymerization of 1-Hexene with Ethylene

97

an eluent at a flow rate of 0.35 mL/min at 40 °C. Molecular weights and molecular weight distributions of ethylene/1-hexene copolymers were determined against polystyrene standard by high temperature gel permeation ehromatography (HT-GPC) on a HLC-8121 GPC/HT apparatus (Tosoh Corporation). 1,2-Dichlorobenzene was used as an eluent at a flow rate of 1.0 mL/min at 145 °C. 1-Hexene Hamopolymerization. A typical polymerization reaction is given below (Table 1, run 1). In a 100 mL round-bottom glass flask with a stirring bar, 10 mg (21 /anol) of (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) in toluene (5 mL), and 19 mg (21 /flnol) of [Ph3C][B(C6F5)4] in toluene (8 mL) were introduced sequentially at room temperature. A few minutes later, 1.736 g (21 mmol) of 1hexene was added under vigorous stirring. The polymerization reaction was carried out at room temperature for 15 minutes, Methanol (60 mL) was poured into the flask to precipitate the polymer, which was then separated and dried under vacuum at 60 °C to a constant weight (1.68 g, 97%). Ethylene and 1-Hexene Copolymerization. A typical eopolymerization reaction is given below (Table 2, run 3). In a glove box, 15 mL of toluene, 1.736 g (21 mmol) of 1-hexene were mixed together in a 100 mL two-necked round-bottom glass flask with a stirring bar. The flask was taken outside and attached to a Schlenk line, a well-purged ethylene line, and a mercury-sealed stopper. The flask was placed in a water bath at 25 °C, and ethylene was then introduced under rapid stirring, A reaction mixture of 21 /flnol (10 mg) of (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) and 21 /anol (19 mg) of [Ph3C][B(C6F5)4] in 15 mL of toluene was quickly added into the flask via a syringe under an ethylene counter flow. The polymerization reaction was carried out for 5 minutes, and was then terminated by addition of 2 mL of methanol. The resulting mixture was poured into methanol (400 mL) to precipitate the polymer. The white polymer product was collected by filtration, dried under vacuum at 60 °C to a constant weight (2.26 g). 3. RESULTS AND DISCUSSION J. 1. Polymerization of 1-Hexene The neutral half-sandwich scandium bis(alkyl) complexes Cp'Sc(CH2SiMe3)2(THF) (Cp' = C5Me4SiMe3 (1), CsMes (2), l,3-(SiMe3)2C5H3 (3)) were inert for 1-hexene polymerization. However, on treatment with 1 equiv of [Ph3C][B(CgF5)4] in toluene, these complexes showed high activity for the polymerization of 1 -hexene, with an activity order of 1 > 2 > 3 (Table 1, runs 1, 6 and 7). The average number molecular weight (Mn) of the polymers

Y, Luo and Z, Hou

98

Table 1 Polymerization of 1-Hexene Catalyzed by Cp'Sc(CH2SiMe3)2(THF)/[Ph3C][B(C6F5)4]E

Cp'Sc(CH2SiMe3)2(THF) + [Ph3C][B{C8F6)4] »

toluene

(pp' = C5iyie4SiMe3 (1), C s Me s (2), 1,3-(SiMe3)2CsH3 (3)] run

oat.

[M]/[Sc]

Tv

t

cam.

activity

Mnb

(°C)

(min)

(%)

kg/(mol-Sc-h)

(xlO"3)

MJMnh

1

1

1000

25

15

97

322

5.8

1.65

2

1

1500

25

30

90

446

5.7

1.67

3

1

1000

0

30

85

140

27,7

1.58

4

1

1000

-15

60

87

71

144.1

1.43

5

1

1000

-40

150

78

26

332.5

1.48

6

2

1000

25

15

64

213

5.6

1.58

7

3

1000

25

15

26

86

4.8

1.51

* Polymerization conditions; in toluene; Sc, 21 /anol; [Sc]/[B] = 1/1 (molar ratio); solvent/monomer = 5:1 (v/v). h Determined by GPC against polystyrene standard.

obtained at room temperature was rather low (Mn = 4800-5800), and was independent of the amount of monomer consumed (Table 1, runs 1, 2, 6 and 7). However, when the polymerization was carried out at low temperatures (Table 1, runs 3-5), the molecular weight of the resulting polymers increased dramatically, and reached as high as 332.5 x 103 at -40 °C. These results suggest that a chain transfer reaction must occur rapidly at room temperature but could be suppressed efficiently at lower temperatures. The ! H NMR analysis of an oligomer product (Mn = 3000, MJMn = 1.34) obtained at room temperature revealed the presence of two types of olefinic end groups. One is terminal vinylidene at S4.61 (br s) and 4.73 (br s), which could be formed by fihydrogen elimination after 1,2-insertion, and the other is a internal vinylene unit (£5.37, multiplets), which must result from ^-hydrogen elimination after 2,1insertion [12]. These results indicate that the present polymerization reactions should proceed in both 1,2- and 2,1-insertion fashions, with /J-hydrogen elimination as a chain termination reaction. The GPC curves of the resulting polymers were all unimodal with relatively narrow molecular weight distributions {MJMn - 1.43-1.67), indicative of single-catalyst behavior. Under the same conditions, the analogous complexes of larger metal ions such as (CsMe4SiMe3)Ln(CH2SiMe3)2(THF) (Ln = Y (4), Gd (5), Dy (6), Lu (7)) did not show activity for 1-hexene polymerization, suggesting that the activity of this type of complex is metal dependent. Similar metal dependence was

15. Homo- and Copolymerization of 1-Hexene with Ethylene

99

observed previously in sryrene polymerization and ethylene-norbomene copolymerization [6a-c], Table 2 Ethylene (E) and 1-Hexene (H) Copolymerization Catalyzed by

1 o r 2 + [Ph3e][B(C8F5)4]

toluene, 25 °C

cat.

H

E

t

yield

(mmol)

(atm)

(min)

(g)

activity*

Hcont. c

Mnd

(mol%)

MJMnd

^

1 2

1 1

0 21

1 0

5 15

1.13 1.33

658 258

0 100

21.35 0.49

1.75 1.49

3

1

21

1

5

2.26

1291

13

2.37

2.89

4

1

42

1

5

3.38

1932

23

1.37

2.74

5

1

S4

1

5

3.98

2274

32

1.09

2.16

6

2

21

1

5

0.99

565

2

20.62

2.59

b

Conditions: toluene, 30 mL; Se, 21 /anol; [Sc]/[B] = 1/1 (mol/mol). Given in kg/(molSc-h-atm).c Determined by ! H NMR. Determined by GPC against polystyrene standard,

3,2. Copolymerization of Ethylene with 1-Hexene The combination of (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (1) with [Ph3C][B(C6Fs)4] also showed high activity for the copolymerization of 1hexene and ethylene at room temperature, yielding the corresponding ethylene1-hexene copolymer, or the so-called linear low density polyethylene (LLDPE) (Table 2). The 1 -hexene content in the copolymer products could be controlled by changing the 1-hexene monomer feed under 1 atm of ethylene. As 1-hexene feed was raised, the incorporation of 1-hexene increased significantly (Table 2, runs 3-5), It is also noteworthy that the polymerization activity of the present catalyst was also increased significantly with the increase of 1-hexene feed, which thus constitutes a rare example of a homogeneous polymerization catalyst system that shows significant positive "comonomer effect" in the copolymerization of ethylene with an o-olefm [13,14]. The activity of the present caMyst system for the copolymerization of ethylene with 1-hexene could reach as high as ca, 2.3 x 103 kg/(mol-Sc-atm-h) at room temperature (Table 2, run 5), which ranks the highest ever reported for a rare earth metal

Y. Luo and Z. Hou

100

catalyst for ethylene/1-hexene copolymerization [4], and could be compared with those reported for the most active group 4 metal catalysts [9]. In the case of 2, the incorporation of 1-hexene was very low (2 mol%) (Table 2, run 6), while with 3-7, no incorporation of 1-hexene was observed under the same conditions. These results are in consistence with the activity of these complexes for 1-hexene homopolymerization. 13C NMR analyses revealed that the resulting ethylene- 1-hexene copolymers contain isolated butyl branches in the polymer chain backbone (Figure 1). No hexene-hexene sequence was formed as evidenced by the absence of <mmethylene carbon peaks ($40—41 ppm) [15], γδ+

δδ+

δδ+

αδ+

βδ+

αδ+

γδ+

βδ+ 4B4

δδ+

3B4 2B4 1B4 + αδ oc8+ 4B 4 B 44

methine methine

γδ y8++ 3B 3 B 44

+ βδ P8 +

1B4

2B44

v»v»*^*^m-A-wv

42

40

38

Figure 1

36

34

32

30

-rp-r

28 28 δ (ppm) 8 (ppm)

26

24

22

20

18 18

16

T 14 14

T3

C NMR spectrum of an ethylene-1 -hexene copolymer (Table 2, run 5).

CONCLUSION We have demonstrated that the combination of a half-sandwich scandium bis(alkyl) complex such as (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) (1) with 1 equiv of [Ph3C][B(C6Fs)4] can act as a highly active catalyst not only for the homopolymerization of 1-hexene but also for the copolymerization of ethylene with 1-hexene. The copolymerization activity of the present catalyst is much higher than that of the homopolymerization of either monomer, thus constituting a rare example of a homogeneous catalyst system that shows significant positive "eomonomer effect" in the copolymerization of two different monomers. This is the first example of efficient ethylene/a-olefin copolymerization catalyzed by a rare earth metal catalyst. The difference in catalytic activity observed among complexes 1-7 suggest that the activity of this type of complex could be tuned by changing the cyclopentadienyl ancillary ligands or the central metal ions in rare earth metal series. Acknowledgements This work was partly supported by a Grant-in-Aid for Scientific Research on Priority Areas (No. 14078224, "Reaction Control of Dynamic Complexes")

15. Homo- and Copofymerization qfl-Hexene with Ethylene

101

from the Ministry of Education, Culture, Sports, Science and Technology of Japan. References and Notes [1] (a) H. H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R. M. Waymouth, Angew. Chem. Int. Ed. 34 (1995) 1143-1170. (b) A. L. MeKnight, R. M. Waymouth, Chem. Rev. 98 (1998) 2587-2598. (c) G. W. Coates, Chem. Rev. 100 (2000) 1223-1252. (d) G. W. Coates, P. D. Hustad, S. Reinartz, Angew. Chem. Int. Ed. 41 (2002) 2236-2257. (e) V, C. Gibson, S. K, Spitzmesser, Chem. Rev, 103 (2003) 283-315. [2] (a) C. J. Schaverien, Adv. Organomet. Chem. 36 (1994) 283-362. (b) F. T. Edelmann, In; Comprehensive Organometallic Chemistry II (Edited by E. W. Abel, F. G. A. Stone, G. Wilkinson, M. F. Lappert), Pergamon, Oxford, 1995, Vol. 4, pp. 11-212. (c) H. Schumann, J. A. Meese-Marktscheffel, L. Esser, Chem. Rev. 95 (1995) 865-986. (d) R. Anwander, In Applied Homogeneous Catalysis with Organometallic Compounds, (Edited by B. Cornils, W. A. Hermann), VCH, Weinheim, 1996, Vol. 2, pp. 866-892. (e) M. Ephritikhine, Chem. Rev. 97 (1997) 2193-2242. (f) H. Yasuda, E. lhara, Bull. Chem. Soc. Jpn. 70 (1997) 1745-1767. (g) Z. Hou, Y. Wakatsuki, In Science of Synthesis (Edited by R. Noyori, T. Imamoto), Thieme, Stuttgart, 2002, Vol. 2, pp. 849-942. (h) Z. Hou, Y. Wakatsuki, J. Organomet. Chem. 647 (2002) 61-70. [3] (a) Z. M. Hou, Y. Wakatsuki, Coord. Chem. Rev, 231 (2002) 1-22. (b) W. E. Piers, D. J. H. Emslie, Coord. Chem. Rev. 233-234 (2002) 131155. (c) S. Arndt, J. Okuda, Chem. Rev. 102 (2002) 1953-1976. (d) J. Okuda, Dalton Trans. (2003) 2367-2378. (e) Z. Hou, Bull. Chem. Soc. Jpn. 76 (2003) 2253-2266. (f) J. Gromada, J. F. Carpentier, A. Mortreux, Coord. Chem. Rev. 248 (2004) 397-410. (g) Y. Nakayama, H. J. Yasuda, Organomet. Chem. 689 (2004) 4489-4498. (h) S. Arndt, J. Okuda, Adv. Synth. Catal. 347 (2005) 339-354. (i) Z. Hou, J. Synth. Org. Chem. Jpn. 63 (2005) 1124-1136. (j) Z. Hou, Y. Luo, X. Li, J. Organomet, Chem. in press. [4] (a) For examples of polymerization and oligomerization of a-olefins catalyzed by neutral organo rare earth metal complexes, see: G. Jeske, L. E. Schock, P. N. Swepston, H. Schumann, T, J, Marks, J. Am, Chem, Soc. 107 (1985)8103-8110.

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[7] (a) For examples of polymerization catalysts based on cationic rare earth metal alkyl species bearing non-cyclopentadienyl ligands, see; B. D. Ward, S. Bellemin-Lapormaz, L. H. Gade, Angew. Chem., Int. Ed. 44 (2005) 16681671. (b) C. S. Tredget, F. Bonnet, A. R. Cowley, P. Mountford, Chem. Commun. (2005) 3301-3303. (c) S. Amdt, K. Beckerle, P. M. Zeimentz, T. P. Spaniol, J. Okuda, Angew, Chem. Int. Ed. 44(2005) 7473-7477. (d) S, Bambirra, M. W. Bouwkamp, A. Meetsma, B. Hessen, J. Am, Chem, Soc 126(2004) 9182-9183. (e) S. Arndt, T. P. Spaniol, J. Okuda, Angew. Chem., Int. Ed. 42 (2003) 5075-5079. (!) S. C. Lawrence, B. D. Ward, S. R. Dubberley, C. M. Kozak, P. Mountford, Chem. Commun. (2003) 2880-2881. (g) P. G. Hayes, W. E. Piers, R. McDonald, J. Am. Chem. Soc. 124 (2002) 2132-2133. (h) S. Bambirra, D. van Leusen, A. Meetsma, B. Hessen, J. H. Teuben, Chem. Commun. (2001) 637-638. (i) S. Hajela, W. P. Schaefer, J. E. Bercaw, J. Organomet. Chem. 532(1997) 45-53. [8] During the preparation of this work, homopolymerization of 1-hexene catalyzed by di-cationic scandium alkyl species was reported independently by Gade [7a] and Mountford [7b]. Copolymerization of ethylene with an otolefin by a cationic rare earth metal species has not been reported previously. [9] (a) For examples of copolymerization of ethylene with 1-hexene catalyzed by group 4 metal catalysts, see: K. Nomura,; K. Oya,; Y. Imanishi, J. Mol. Catal. A: Chem. 174 (2001) 127-140. (b) T. N. Choo, R. M. Waymouth, J. Am. Chem. Soc. 124 (2002) 4188-4189. (c) J. Huang, B. Lian, Y. Qian, W. Zhou, W. Chen, G. Zheng, Macromolecules 35 (2002) 4871-4874. (d) I. Bruaseth, E. Rytter, Macromolecules 36 (2003) 3026-3034. (e) M. Dankova, R. M. Waymouth, Macromolecules 36 (2003) 3815-3820. (f) M, K, Mahanthappa, A. P. Cole, R. M. Waymouth, Macromolecules 23 (2004) 836-845. (g) W. Q. Hu, X. L. Sun, C. Wang, Y. Gao, Y. Tang, L. P. Shi, W. Xia, J. Sun, H. L. Dai,; X. Q. Li, X. L. Yao, X. R. Wang, Organometallics 23 (2004) 1684-1688. (h) S. E. Reybuck, R. M. Waymouth, Macromolecules 37 (2004) 2342-2347. (i) R. Furayama, M. Mitani, J. Mohri, R. Mori, H. Tanaka, T. Fujita, Macromolecules 38 (2005) 1546-1552. [10] D. Cui, M. Nishiura, Z. Hou, Macromolecules 38 (2005) 4089-4095.

104

Y. Luo andZ. Horn

[11] O. Tardif, M, Nishiura, Z. Hou, Organometallics 22 (2003) 1171-1173. [12]L. Resconi, F. Piemontesi, G. Franciscono, L. Abis, T, Fiorani, J. Am. Chem. Soc. 114(1992)1025-1032. [13] Homogeneous polymerization catalyst systems usually show no or negative "comonomer effect" in the copolymerization of ethylene with a-olefins, although positive "comonomer effect" was known in heterogeneous ZieglerNatta catalysis. For examples, see: J. C. W. Chien, T. Nozaki, J. Polym. ScL, Part A: Polym. Chem. 31 (1993) 227-237. See also ref. [14]. [14] L. J. Irwin, J. H. Reibenspies, S. A. Miller, J. Am. Chem. Soc. 126 (2004) 16716-16717. [15] (a) E. T. Hsieh, J. C. Randall, Macromolecules 15 (1982) 1402-1406. (b) W. X. Liu, D. G. Ray in, P. L. Rinaldi, Macromolecules 32 (1999) 38173819.


105

16 Stereoerrors Formation in the Polymerization of Deuterated Propylene Victoria Vollds, Anatoli Lisovskii and Moris S. Eisen* Department of Chemistry and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology Haifa 32000 Israel

Abstract The influence of the number of ancillary ligations and the corresponding structural features of three titanium benzamidinate complexes 1-3, in the polymerization of propylene, has been investigated. These complexes produce similar polymers indicating the formation of similar active species. The activation process was followed via 29Si-NMR spectroscopy. 1. INTRODUCTION The polymerization of propylene by single site catalyst has experienced a phenomenal growth in the last two decades, from academic to industrial research groups engaged in the design of new coordinative unsaturated catalysts for the controlled polymerization [1, 2]. The flourishing application of the "well-defined" single-site group 3 and 4 metallocene catalysts for the polymerization of a-olefins [3], together with sophisticated investigations on the role of the ligands composition and structure in the stabilization of the active centers in the mechanism for the activation of these metallocene catalysts has facilitated the search of the non-metallocene systems as alternative catalysts for this polymerization processes [4]. Among the various organometallic compounds synthesized during the last decade, the complexes of early transition metals with the bidentate JVjJV'-feftrimethylsilyl) benzamidinate ligations [TJRC(NR') 2 r (where R = C6H5 or substituted phenyls, R' = alkyl, aryl or SiMe3) have been widely described as promising alternative to the cyclopentadienyl

106

V. Volkisetal

complexes [5, 6]. The catalytic properties of several group 4 benzamidinate complexes in the polymerization of a-olefins have been previously investigated [7, 8]. 2. RESULTS AND DISCUSSION Our main goal was to investigate the influence of the compositional and structural features of the benzamidinate- titanium complexes 1, 2 and 3, having a similar chemical nature, but differing by the space symmetry and number of the ligations around the metal center, on their polymerization activity. Complexes 1-3 activated with MAO were found to be active in the polymerization of propylene only at high pressure, producing an elastomeric polypropylene with a wide polydispersity, as shown in Table 1.

Table 1. High pressure propylene polymerization results for complexes 1-3. yield of activity0 properties of polypropylene polymer mwdd Mw mtntnm 5 A-10" % 9 complex 1 1 0.043 16.0 500 CH2CI2 0.20 51000 2.83 12.8 0.40 2 1000 16.0 1.93 47000 3.13 14.9 3 2000 0.84 CHZCIZ 17.0 4.28 29000 5.81 15.7 1000 4 toluene 0.69 16.0 3.23 59000 3.70 10.9 Comdex 2 0.24 3.20 34.1 500 CHZCIZ 1.69 5 23.9 80000 6 0.38 1000 GH2GI2 3.10 25.1 51000 3.76 20.6 7 0.71 18.4 2000 CH2CI2 5.31 25.1 38000 6.33 1000 4.73 8 toluene 11.9 25.1 58000 3.97 0.63 complex 3 0.38 1000 9 2.30 GHzCIz 14.7 20.4 55000 3.77 1000 3.37 0.55 10 toluene 9.9 20.4 62000 3.26 1 23°C, 10.2 atrn, 6 ml of solvent, 40 ml C3H6,180 mm; mol Ti x 10: g PP x mol Ti"1 x h"1;d molecular weight distribution. entry

process conditions8 solvent eatb AI:Ti ratio

16. Sterreoerrors Formation in the Polymerization afDeutemtedPropylem

107

As may he seen, at AhTi ratios greater than 500, the polymerization activities of the complexes in each solvent differs insignificantly. These results induce us to consider that possible similar active species are operative in the polymerization process regardless of the starting materials. For all the complexes, the elastomeric polypropylene produced in toluene has somewhat higher molecular weight than the polymers formed in dichloromethane. Raising the MAO concentration in the catalytic mixture decreases the molecular weights of the polymers and increases their molecular weight distribution. This result normally indicates that the aluminum transfer chain termination mechanism is operative inducing the lower molecular weights. However, according to the 13C NMR analysis of the end groups of the polymers, the chain termination was found to be (3-hydrogen elimination. Taking into consideration that the resulted polymers have a wide MWD, which increases with an increasing of Ti:Al ratio, the assistance of MAO in the formation of different active species from pre-catalysts 1-3 may be assumed. Interestingly, in spite of the different structural features of the used precatalysts, the molecular weights of the polymers created under the same conditions, were unexpectedly found to be alike. As regards to the stereoregularity of the monomer insertion, the isotacticities of the polymers are also similar, although a slight increase in the mmmm of the polymer only produced by complex 2 in CH2C12 is observed. The high polydispersity of the obtained polypropylenes is a consequence of the presence of various active species producing polymers with a wide spectrum of molecular weights and different tacticities. Such polymers can be fractionalized in hexane into a solid hexane-insoluble (HI), and elastomer hexane-soluble (HS) fractions, and the representative results for complexes 1 and 2 are given in Table 2. Table 2. Results of the fractionalization for polymers PP1 and PP2 produced by complexes 1 and 2 correspondingly in hexane.

samples PP1 (whole) PP1-HS PP1-HI PP2 (whole) PP2-HS PP2-HI

%wt 100 98.2 1.8 100 96.7 3.3

M« 59000 55000 238000 58000 56000 216000

mwd 3.1 3.2 3.3 3.8 3.1 3.6

mmmm, % 10.9 10.0 74.4 11.9 10.0 74.5

Interestingly, the major part (97-98%) of the polypropylenes PP1 and PP2 were the soluble hexane fraction obtained as an elastomeric (not atactic) polymer. For each of the polymers, in each fraction the molecular weights and isotacticities of the polymers were found to be unexpectedly identical Property-

108

V.VoMsetal.

wise, the hexane soluble elastomers were found to be closed by its tacticities to the elastomers described by Resconi [9]. However, the MW was noticeably lower. One possible reason for the elastomeric behavior of such low tacticity and low MW polymers is the presence of comparatively large amounts of ethane and butane fragments, formed as the result of misinsertions. The hexane insoluble solids were high molecular weight polymers with larger isotacticities. To shed some light on the mechanism for the formation of elastomeric polypropylene by different benzamidinate complexes, it was necessary to clarify two conceptual questions: how the different fractions are formed and how the elastomeric fraction is produced It seems that during the polymerization process, the complexes undergo rearrangements, forming similar number of structural alike species proposed to be active for the polymerization. To corroborate this hypothesis, one of such active species was postulated to be the corresponding Al benzamidinate that can be formed as a result of interaction of the studied Ti benzamidinates with methylalumoxane. To confirm experimentally such supposition, the aluminum benzamidinate complexes [Ti-C6H5-C(NSiMe3)2AlX2] (X = Cl (4), Me (5)), were synthesized by the reaction of the lithium benzamidinate ligand [ri-CfiHsC(NSiMe3)2Li] with AICI3 or the reaction of the neutral benzamidinate ligand [C6H5-C(=NSiMe3)(NSiMe3)2] with AlMe3, correspondingly. We have investigated the features of activation of complexes 1 and 2 with methylalumoxane using the 29Si NMR technique allowing discriminating various species formed on different steps of the activation. The spectra obtained were compared to the spectrum of Al benzamidinates 4 and 5 taken as a reference. Figure 1 illustrates the monitoring of the activation of complex 1. The spectrum (a) is of the pure complex 1 whereas spectrum (b) is of complex 1 activated with MAO. One of the signals in spectrum (b) matches the signals in the spectra (c) for Al benzamidinate dichloride 4 and (d) for Al benzamidinate dimethyl 5. A similar result was obtained for complex 2. These results indicate that upon the reaction of either complex 1 or 2 with MAO, the monobenzamidinate aluminium complex is obtained. The formation of the aluminium complex involves the metathesis of the benzamidinate ligand from Ti to Al. The activities in the polymerization reaction of complexes 4 and 5 at high propylene pressure were found to be about 10 times lower as for the corresponding titanium precatalysts 1 and 2 (~ 0.5 x 104 g PP x mol Al"1 x h"1) producing an atactic polymer, therefore not being the major player in the polymerization process. The formation of two additional signals (Figure lb) is representative of two different complexes, each of one probably responsible for the different fraction. If we assume that the formation of a bis(benzamidinate) titanium methyl complex with a C^-symmetry is responsible for the small isotactic fraction, a second monomeric mono(benzamidinate) titanium complex

16. Sterreoerrors Formation in the Polymerization of Deuterated Propylene

109

must be responsible for the formation of the elastomeric polymer. Hence, complexes 1 and 2 rearranges upon their reaction with MAO, Plausible mechanism for the rearrangement of complex 2 is described in Scheme 1.

.

It

1:

L2

]L

11

13

1!

LI

ID

13

B

II

II

3

1

t

^

S

7

I

T

s

! !

s

i

1 2

t

I

3

4

1

2

I

1

c

-1

-1

-3

1

I

-1

-»

-3

1

d

-J

- 1 - S - 4 mrr

1

I

-1

-2

-1

- * wrr

-1 in

Figure 1, Si NMR monitoring of the aetive specie formation from complex 1 in toluene-' complex 1, b — complex 1 + MAO at Ti:A 1 ratio 1:20, c — complex, 4, d — complex 5,

Hexane soluble elastomer

He&ane Insoluble f

Scheme 1. Plausible scheme for the rearrangement of complex 2.

110

V, Valkisetal

As regarding to the elastomeric behavior of the polymers produced by benzamidinate complexes, which is related to the stereoregularity of the polymer, it is usually considered to be a result of the two competing reactions: a) stereoregular polymerization inducing isotactic material, b) an intramolecular epimerization of the growing polymer chain that induces stereo-errors. For the latter two possible epimerization mechanisms have been reported: the first one proposed by Busico [10,11] leads to the formation of single errors in the polymer chain; the second mechanism proposed by Resconi [12] includes in addition, the formation of exo-double bonds at the polymer chain and particular chain-ends. To discriminate between the two possible pathways, the polymerization was carried out with 2-D-propene at low and high pressures and compared to the polymerizations with non-labelled propene. The polymerization data is presented in Table 3. Table 3 indicates three unexpected effects. First, the rate of insertions is much faster for the polymerization with deuterated propylene. This inverse isotopic effect rests on the fact that deuterium is an electron releasing atom as compared to hydrogen. Second, there is a trend of higher isotacticity for the deuterated polymers relatively to non-deuterated analogs. We presumably could assume here better stereoselective interactions for the incoming deuterated monomer as compared to its non-deuterated analog. Finally, larger MW are obtained for the deuterated polypropylene as comparing to the non-deuterated. We have found that the use of the deuterated substrate leads to increasing of both rates of insertions and terminations, but the effect on the rate of insertions was measure to be stronger than on the rate of terminations. Table 3. Results of the polymerization of deuterated and non-deuterated propylene catalyzed by benzamidinate complexes Run

Cat

Substrate

Pressure atm

Time h

Activity"

Mw xlQ" 3

MWD C

mmmm , %

1

1

H2C=CD-CH3

1.5-2.0

22

0.58

99000

1.77

12.5

2

1

H2C=CH-CH3

1.5-2.0

22

0.26

8B000

2.26

9.4

3

1

H2C=CD-CH3

9.0

3

0.54

143000

1.70

58.9

4

1

H2C=CH-CH3

9.0

3

0.48

19000

2.48

10.9

a Ti:Al = 1:800, 3 ml of toluene, 5 mg catalyst; distribution Mw/Mn; d isotactic pentad content.

g PP- mol Ti~l- h"l;

c

molecular weight

In order to clarify the pathways for the possible formation of stereoerrors during the polymerization, the 13C{2H}-NMR shows no deuterium incorporation into the methyl group (Busico or Resconi epimerization

16. Sterreoerrors Formation in the Polymerization ofDeuteratedPropylene

111

pathways). However we have observed a deuterium-hydrogen exchange between -CD- and -CH 2 - groups, given -CH- and -CHD- fragments on the skeleton chain. This exchange can be explained by the mechanism, presented on Scheme 2,

Ti reinsertion

fS-D elimination

reinsertion

y-H elimination

D-reinsertion

H-reinsertion

j-D

elimination

I

Scheme 2. The exchange of CH(CH3)- and CF^-hydrogens

3. CONCLUSIONS Here we have presented a totally new epimerization pathway for the formation of stereoerrors using octahedral complexes in the polymerization of propylene.

Acknowledgment!. This research was supported by the Israel- USA Binational Science Foundation under Contract 2004075. Reference! [1] W. Kaminsky, In: Advances in Catalysis; eds: B. C. Gate, H. KnSzinger,; Academic Press: San Diego, 46 (2002) 89, [2] P. Corradini, J. Polym. Sci., Part A: Poly. Chem. 42(3) (2004) 391. [3] H. G, Alt, A. Kfippl. Chem. Rev. 100 (2000) 1205, and references therein. [4] V. C. Gibson, S. K. Spitzmesse, Chem. Rev. 103 (2003) 283. [5] F. T. Edelmann, Coord. Chem. Rev. 137 (1994) 403, and references therein. [6] K. C. Jayarante, L. R. Sita, J. Am. Chem. Soc. 123 (2001) 10754. [7] J. C. Flores, J. C. W. Chien, M. D. Rausch, Organometallics 14 (1995) 1827. [8] (a) D. Herscovics-Korine, M. S. Eisen, J. Organomet. Chem. 503 (1995) 307. (b) V. Yolkis, E. Nelkenbaum, A. Lisovskii, G. Hasson, R. Semiat,

112

Y.VoMsetaL

M. Kapon, M. Botushansky, Y. Eishen, M. S. Eisen J. Am. Chem. Soc, 125 (2003) 2179. [9] L. Resconi, R. L. Jones, A. L. Rheigold, Organometallics, 15 (1996) 998. [10] V. Busico, R. Cipullo, J. Am. Chem. Soc. 116 (1994) 9329. [11] V. Busico, L. Caporaso, R. Cipullo, L. Landriani, J. Am. Chem. Soc. 118 (1996), 2105, [12] L. Resconi, J. of Mol. Catal, A: Chemical 146 (1999) 167.


113 113

17 Vinylic Polymerization of Norbornene with Neutral Nickel(II) Complexes Bearing p-Diketiminato Chelate Ligands Yi-Qun Duan, Xiao-Fang Li, Yue-Sheng Li* State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China, and Graduate School of the Chinese Academy of Sciences

Abstract A series of neutral nickel(II) complexes la-c bearing asymmetric bidentate Pdiketiminato ligands have been investigated as catalysts for vinyl-addition polymerization of norbornene (NBE) in the presence of modified methylaluminoxane (MMAO) cocatalyst. The highest catalytic activity up to 4.5 lxl0 4 kg FNBE/mol-Ni-h and viscosity-average molecular weight (Mv) of polymers up to 1,07x106 g/mol were observed under optimal conditions, and lac exhibited higher catalytic activities, afforded higher molecular weight polymers than the corresponding bis(P-diketiminato)mekel(II) complexes, 2a-c. 1. INTRODUCTION The research on the vinyl-addition polymerization of norbornene (NBE), which emerges with the exploitation of Ziegler-Natta catalysts since 1950's [1,2], has been greatly developed with the upsurge of metallocene-MAO based catalysts in the field of transition-metal-catalyzed olefin polymerization [3-6]. Unlike ring-opening metathesis and cationic or radical polymerization, the vinyladdition polymerization yields PNBE as a saturated polymer with the bicyclic structure of the monomer left intact [7]. This unique microstructure gifts the PNBEs with many excellent physical properties, such as high density, high glass-transition temperature, corrosion resistance, optical transparency, low

114

Y.-Q. Duan et al.

birefringence and dielectric properties, which has attracted increasing attention from both of the academic and industrial world [8,9], Besides the zirconocene catalysts for the vinyl-addition polymerization of NBE originally introduced by Kaminsky, late transition metal such as nickel [10-16], cobalt [17-19] and palladium [20-28] catalysts have also been developed to catalyze the polymerization of NBE with much higher catalytic activity. Compared with the highly stereo-regular PNBEs produced by zirconocene catalysts, which do not appear to dissolve in any organic solvent [9], the amorphous PNBEs obtained with late transition metal catalysts own good solubility especially in aromatic halide, which indicates their unique potential in solution-processing. In 2000, Grubbs reported the potential application of neutral Ni complexes bearing salicylaldiminato ligands to catalyze the copolymerization of ethylene and NBE derivatives, while detailed catalytic data for NBE homopolymerization were not given [29]. Later, we found that Grubbs' neutral nickel catalysts activated with modified methylaluminoxane (MMAO) were a powerful catalytic system for the vinyl-addition polymerization of NBE, producing high molecular weight and amorphous PNBEs with good thermal stability [30]. Recently, our exploration on bis(P-diketiminato)nickel(II) complexes revealed that this series of catalysts also were efficient for the NBE polymerization and can be easily modified by varing substituents on the complex backbones [31]. We wonder if the neutral Ni(II) complexes bearing single P-diketiminato ligands are more active towards vinyl-addition polymerization of NBE and produce higher molecular weight polymers. Here we report NBE polymerization behaviors of a series of the neutral mckel(II) catalysts with P-diketiminato ligands activated with MMAO under mild conditions. Further 13C NMR spectra suggested the vinyl addition nature of the produced PNBEs, in which no ring-opened product was observed. 2. EXPERIMENTAL Materials. The details of synthesis and characterization of the catalysts la-c (Scheme 1) have been reported elsewhere [32]. NBE was dried over sodium, vacuum-transferred, and degassed by repeated freeze-pump-thaw cycles, oC6D4CI2 was obtained from Aldrich and used without further purification. Modified methylaluminoxane (MMAO, 7% Al in heptane solution) was purchased from Akzo Nobel Chemical Inc. Polymerization Procedure. All work involving air and moisture sensitive compounds was carried out using standard Schlenk techniques. 2.0 ml of a fresh catalyst solution (chlorobenzene, 0.5 pjnol catalyst), 3.0 ml of NBE in chlorobenzene, and 14.0 ml of chlorobenzene were added under inert gas

17. Vinylie Polymerization ofNorbornene with Neutral Ni (II) Complexes

115

atmosphere into a Schlenk flask with a mechanical stirrer. The reaction was started by the addition of 0,5 ml of a MMAO solution (1.0 mmol in heptane) at 30 °C. Total reaction volume was 20 ml, unless otherwise stated. This was achieved by the variation of the amount of chlorobenzene if necessary. After 5 min, the reaction mixture was poured into 200 ml of acidic ethanol (ethanol/HClcorre = 50/1). The polymer was isolated by filtration, washed with methanol, and vacuum dried at 80°C for 24 h. Analytical Procedures. NMR analyses of polymers were performed on a Varian Unity 400 MHz spectrometer at 135°C, using o-C6D4Cl2 as solvent. DSC measurements were performed with a Perkin-Elmer Pyris 1 Differential Scanning Calorimeter. Viscosity-average molecular weights (Ms) were calculated from the intrinsic viscosity by using the Mark-Houwink coefficients: a = 0.56, K= 5.97X10"4 dyg [33]. 3. RESULTS AND DISCUSSION Preliminary research in our group had indicated that single component bis(chelate) Ni(II) complexes were not able to polymerize NBE without MMAO as a cocatalyst [31]. In this research, the neutral nickel(II) complexes la-c, bearing the single corresponding ligands were also found to be inefficient for NBE polymerization in the absence of MMAO, with trace polymer obtained. However, when subsequent experiments were carried out in the presence of MMAO, all of the nickel(II) complexes la-c exhibited high catalytic activity for the NBE polymerization.

a:

R i =Ph,R 2 =CF 3

b: R,= Ph, R2= CH3

^ \__

c: R,= CF3> R2= CHS

la-c

2a-c

Scheme 1. Nickel(II) complexes la-c and 2a-c

The ratio of MMAO/la, which is expressed as Al/Ni molar ratio here, has significant effects on polymer yields, catalytic activities and the molecular trace weights of the polymers obtained. In the absence of MMAO, a trace amount of polymer could be obtained. However, as shown in Figure 1, with the increase of the Al/Ni molar ratio at a constant Ni concentration, polymer yield gradually increased. Within 5 min polymerization, PNBE yield rised up to 93.6% at the

Y.-Q, Duan et al.

116

Al/Ni ratio of 3000/1; the yield of PNBE could reach up to 99.8% upon the further increase in the Al/Ni molar ratio (5000/1). It is interesting to note that 12 100 100Yield after an initial ascent with the M increase of Al/Ni ratio from 500 90 10 to 2000, Mv of PNBE increased up 6 80 to a summit of l.OlxlO g/mol, then began to decrease upon the 70 8 continued increase of Al/Ni ratio, 60 6 and finally reached to 0.56x10 50 g/mol. The subsequent decrease 6 of My is probably due to the faster 40 chain transfer reaction to Al 0 1000 2000 3000 4000 5000 compounds than the chain AIM Al/Ni (molar ratio) propagation reaction, when Al/Ni Figure 1. Plot of yield and Mv versus Al/Ni ratio exceeded 2000. (molar ratio). 0.50 ^mol la, 1.88 g NBE, V M = Sufficient reaction time 20 ml, polymerization reaction at 30°C for 5 min. assured the high yield of PNBE, As shown in Figure 2, initial yield of polymer was only 80.9% in 5 min, but 120 the yield of PNBE kept increasing, 100 and reaches up to 99.8% in 120 min. 80 Reaction temperature also had 60 considerable effects on both the 40 catalytic activity and molecular 20 weights of polymers. 0 As shown in Figure 3, nickel(II) 5 min 30 min min 120 120 min mm min complex la exhibits high activity of 2.47X104 kg PNBE/mol-Ni-h at 0°C, Yield(%) Yield % Mv Mv (10000 10000 g/mol) g/mol and the catalytic activity reached to 3.67x104 kg PNBE/mol-Ni-h at 50°C. Figure 2, Plot of reaction time vs. PNBE yield. The activity slightly decreased but still 0.50 |X mol la, 1.88 g NBE, V t^, = 20 ml, remains at 3.42x10 kg PNBE/mol- Al/Ni = 2000, 30°C. Ni-h at 70°C. Nevertheless, for the corresponding bis(chelate) Ni(II) complexes, the activity increases to a summit around 20 °C, but decreased dramatically with ascending temperature and finally drops down at the lowest value at 50 °C [31]. Therefore, compared with the corresponding bis(chelate) complexes, nickel(II) complexes la-c bearing single P-diketiminato ligands proved to be robust catalysts for the NBE polymerization at high temperature, which indicates their potential as excellent catalysts for NBE polymerization. (Mv (106 g/mol)

Yield (%)

v

17. Vinylic Polymerization ofNorbomene with Neutral Ni (11} Complexes

117

Mv (105 g/mol)

Activity (104 kg PNBE/molNih)

In contrast, reaction temperature 3.8 12 influences molecular weights of 3.6 polymers in a different style. No Activity 10 distinct changes of the molecular 3.4 Mv weight for the resultant PNBE was 3.2 8 observed between 0 and 30 °C, but the 3.0 Mv value notably decreased upon increasing the temperature till 70 °C: 2.8 6 Mv value became half from 30 to 70 °C. 2.6 This may be due to the fact that fast 4 2.4 chain propagation, indicated by the high catalytic activity, is always 23 30 4 40 -10 0 10 20 0 50 60 70 80 o Q Temperature ( C) accompanied by faster chain transfer reaction, finally leading to the decrease Figure 3. Plot of activity and M vs. reaction v of molecular weight of polymers. temperature. 0.50 |imol la, 1.88gNE, Ftatai= To understand a relationship 20 ml, Al/Ni=2000, polymerization, for 5 min. between structures of the complexes la-e and catalytic activities and molecular weights of PNBE, corresponding data were tested and summarized in Table 1. Generally, catalyst performances are influenced in the way of both steric hindrance and electronic effect. As it is well known, steric hindrance that bulky substituents bring into late transition metal catalyzed polymerization system is propitious to control chain transfer reaction and increase the molecular weight of polymers. Compared with the other complexes, catalyst la, with a phenyl group and a CF3 group both as bulky substituents, produces PNBE with the highest molecular weight, 10.7x105 g/mol, while complex lc, bearing a CH3 group and a CF3 group, produces PNBE with the lowest Mv, 5.6xlO5 g/mol. Complex l b supported by a CH3 group and a phenyl group polymerizes NBE with a medium Mv of 7.5x10s g/mol. On the other hand, electronic effect of different substituents plays an important role in adjusting catalytic activities of Ni(II) complexes polymerization system. As seen from Table 1, complex l b , with a phenyl group and CH3 group as electron donating substituents, polymerizes NBE with the lowest activity (1.06 xl04kgPNBE/mol-Ni-h); while complex lc, bearing a CF3 group and a CH3 group, owns higher catalytic activity (2.11xl04kgPNBE/ mol-Ni-h). This indicates that CF3 group with stronger electron-withdrawing ability than the phenyl group could efficiently mcrease catalytic activities of single chelate (3-diketiminato nickel(II) complexes towards NBE polymerization, which acts in the same fashion of the corresponding bis(chelate) nickel(II) complexes [31]. Noticeably, complex la, with a phenyl group and a CF3 group, exhibited the highest activity for NBE polymerization up to 3.65x104 kg PNBE/

Table 1, The results of the vinyl-addition polymerization of norbomenea Entry

AI/Ni

Norbomene

(mol ratio) -

(g) 1,88

la

soo

la la

1000

1.88 1.88

ib

la

2 3 4 5 6

la

1500 2000

la

3000

7 8

Temperature

(min)

fC)

60 5

30 30 30

1.88

5

30

1.88 1.88

5 5

30 30

1.SS 1.88

la

5000

9

2000 2000

10

la

2000

11

la la

2000

1.88

lb

2000 2000

1.88 1.88

lc 2a"

2000

IS

2500

16 17

»' 2c*

2S00 2S00

14

Time

5

la la

12 13

a

Catalyst

Polymer

Yield (%) .

Activity 4

(10 kgPNBE/mol-M-h) -

(lO'gm -

(B) trace 0.771

41.0

1.85

0.889 1.401

47.3 74.S

2,14

9,5

3.36

10.

1.521 1.760 1.876 1.720

80.9 93.6

3,65 4.22

10. 8.1

99.8

4.51

91.5 99.8 54.8

0.23 0,19 2.47

5.6 5.8

7.7

5

30

30 120

30 30

5 5

0 SO

1.530

81.4

3.67

10. 6.2

5 5

70 30

1.350 0.440

71.8 234

3.42 1.06

3.7 7.5

1.88

5

30

0.880

5.6

15

30

0.S90

46.8 98

2.11

0.6 0,6 0.6

15 15

30 30

0,350 0.580

$8 97

1.18 0.70 1.16

5.5 6.4

1.S8 1.88

1,876 1.030

6.7

5.9

0.5/flnol of nickel complex, Vum — 2Qml (ehlorabenzene). b NBE polymerization with complex a as a single component E0.2/ffnol of nickel complex, Ktmai — 15ml polymerization reaction for 15 min at 30 °C. For polymerization data of entry 16 and 17, see [32].

17. Vinytic Polymerization ofNorbornene with Neutral Ni (II) Complexes

119

mol-Ni-h. Typically, bulky substituents always go against inserting olefin into metal-carbon bonding, which decreases the rate of polymerization and hence the catalytic activity. But why complex la, with much steric hindrance possesses higher activity than complex lc? This may be due to the fact that the phenyl group is not only a bulky substituent, but also an electron-withdrawing group. So when electronic effect acts as the leading factor for polymerization activities, phenyl group could increase catalytic activities more than CH3 group, although the latter possesses smaller hindrance for olefin insertion. Interestingly, comparing with the corresponding bis(chelate)complexes, the single chelate Ni(II) complexes la-c all exhibited higher activities towards NBE polymerization (3.65, 1.06 and 2.11xl0 4 kg PNBE/mol-Ni-h vs 1.18, 0.7 and 1.16xl0 4 kg PNBE/mol-Ni-h, Table 1). To explain this phenomena, possible mechanism for NBE polymerization catalyzed by Ni(II) complexes bearing single or bis(p-diketiminato) ligands is supposed as shown in Scheme 2. For nickel (II) complexes la-c with single chelate ligands, the function of MAO as a cocatalyst is to withdraw the PPh3 ligand and generate a three coordinating neutral complex la'-c' occupied by the N, O atoms and a phenyl group, with a coordination vacancy left for the further coordination of NBE monomer and the enchainment of coordinating monomers. Then this initial active site is transferred into the three coordinating neutral complex a"-c"as major active centers of polymerization [34].

2a-c

2a'-c'

3a-c

Scheme 2. Proposed Mechanism for vinyl-addition polymerization of NBE.

However, for the bis(P~diketiminato)Ni(II) complex 2a-c, one MAO can only snatch one (p-diketiminato) ligand from the original complex, in order to form a three coordinating neutral complex a"-c" as an active center. Since the resulted Al complex 3a-c with one chelate ligand may not be stable as MAO, this MAO snatching [NO] ligand reaction could be reversible. Then only part of the initial complexes could be transformed into active Ni centers (a"-c") for

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polymerization by MAO and the number of the latter would be much fewer, which finally leads to the lower catalytic activity of bis(chelate) complexes than the corresponding single chelate catalysts. 13 C NMR spectrum of typical PNBE obtained by complex la (Entry 5) is presented in Figure 4. Resultant polymer is vinyl addition in nature since no olefinic resonances are observed in the isolated polymer (e.g., no ROMP polymer was formed). Assignment of methylene and methine resonances are listed as follows, signals at 29.5-34.0 ppm are from carbon-5 and carbon-6; the ones at 35.3-37.5 ppm originate from carbon-7; the ones at 38.4-42.5 ppm are for carbon-1 and carbon-4; and the ones at 46.7-54.5 ppm are for carbon-2 and carbon-3. In addition, since the resonance in the 20-24 ppm region is considered as evidence of endo enchainment on the basis of model studies, the absence of such resonances in Figure 4 indicates the exo enchainment nature of the PNBE [35]. The 13C-NMR spectrum is similar to that reported by Greiner's and Wu's groups [36,37]. C1.C4 C7 C5, C6

C2,C3

HO

120

100

(?'c

60

JO

20

Figure 4. "C NMR spectra of PNBE recorded in o-CsD4Cl2 at 135°C

The r g 's of the PNBEs range from 360.1 to 415.8 °C, suggesting good thermal stability of the polymers. All polymers are soluble at room temperature in chlorobenzene and o-dichlorobenzene» which indicates low stereoregularity. 4. CONCLUSIONS Neutral nickel (II) complexes la-c bearing single (p-diketiminato) ligands activated with MMAO proved to be highly efficient catalysts for the vinyl addition NBE polymerization. Under optimal conditions, complex la exhibits the highest catalytic activity up to 4,5lxl 04 kg PNBE/mol-Ni-h and produces polymer with high viscosity-average molecular weight up to 1.07X106 g/mol. The catalytic activities, yield and molecular weight of polymers were adjusted effectively by Al/Ni ratio, reaction time, reaction temperature and the structure

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of complexes, with steric effects and electron-withdrawing effects of substituents on the catalyst backbone. The PNBEs obtained here exhibit good thermal stability, are amorphous and soluble at room temperature in halogenated aromatic hydrocarbons, A discussion and comparison between performances of (p-diketiminato)Ni (II) complexes la-c and the corresponding Ms(ehelate) complexes 2a-e, derived from a serial experiments under similar conditions, were presented to help the understanding of NBE polymerization mechanism with neutral nickel (II) complexes bearing (p-diketiminato) ligands. References [1] G. Sarttori, F, C. Ciampelli, N. Cameli, Chim. Ind. (Milan) 45 (1963) 1478-1482 [2] T. Tsujino, T. Saegusa, J, Furukawa, Makromol. Chem. 85 (1965) 71-79. [3] W. Kaminsky, A. Noll, Polym. Bull. 31 (1993) 175-182. [4] W. Kaminsky, A. Bark, Polym. Int. 28 (1992) 251-253. [5] W. Kaminsky, A. Bark, R. Steiger, J. Mol. Catal. 74 (1992) 109-119. [6] M. Arndt, R. Engehausen, W. Kaminsky, K. Zoumis, J. Mol. Catal. A: Chemical 101 (1995) 171-178. [7] N. Seehof, Ch. Mehler, S. Braining, W. Risse, J. Mol. Catal. 76 (1992) 219-228. [8] C. Janiak, P.G. Lassahn, Macromol. Rapid Commun. 22 (2001) 479-493. [9] S. Ahmed, S. A. Bidstrup, P.A. Kohl, P. J. Ludovice, J. Phys. Chem. B 102 (1998) 9783-9790. [10] T. J. Deming, B. M. Novak, Macromolecules 26 (1993), 7089-7091. [11] W. Massa, N. Faza, H. C. Kang, C. Focke, W. Heitz, Acta. Polym. 48 (1997) 432-437. [12] M. Arndt, M. Gosmann, Polym. Bull. 41 (1998) 433-440. [13] F. Peruch, H. Cramail, A. Deffieux, Macromol. Chem. Phys. 199 (1998) 2221-2227. [14] C. Mast, M, Krieger, K. Dehnicke, A. Greiner, Macromol. Rapid. Commun. 20 (1999) 232-235. [15] S. Brorkar, P. K. Saxena, Polym. Bull. 44 (2000) 167-172. [16] D. Zhang, G. X. Jin, L. H. Weng, F. S. Wang, Organometallics 23 (2004) 3270-3275. [17] F. P. Alt, W. Heitz, Macromol. Chem. Phys. 199 (1998) 1951-1956. [18] F. P. Alt, W. Heitz, Acta. Polym. 49 (1998) 477-481. [19] F. Pelascini, F. Peruch, P. J. Lutz, M. Wesolek, J. Kress, Macromol. Rapid Commun. 24 (2003) 768-771.

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[20] C. Tanielian, A. Kiennemann, T. Osparpueu, Can. J. Chem. 57 (1979) 2022-2027. [21] A. Sen, T. W. Lai, R. R. Thomas, J. Organomet. Chem. 368 (1988) 567588. [22] C. Mehler, W. Risse, Macromolecules 25 (1992) 4226-4228. [23] T. F. A. Haselwander, W. Heitz, S. A. Krugel, J. H. Wendorff, Macromol. Chem. Phys, 197 (1996) 3435-3453. [24] B. S. Heinz, F. P. Alt, W. Heitz, Macromol. Rapid Commun. 19 (1998) 251-256, [25] A. S. Abu-Surrah, K. Lappalainen, T. Repo, M. Klinga, M. Leskela, H. A. Hodali, Polyhedron 19 (2000) 1601-1605. [26] A. S. Abu-Surrah, K. Lappalainen, M. Kettunen, T. Repo, M. Leskela, H. A. Hodali, B. Rieger, Macromol. Chem. Phys. 202 (2001) 599-603. [27] J. Lipian, R. A. Mimna, J. C. Fondran, D. Yandulov, R. A. Shick, B. L. Goodall, L. F. Rhodes, Macromolecules 35 (2002) 8969-8977. [28] P. G. Lassahn, V. Lozan, C, Janiak, J. Chem. Soc, Dalton Trans, (2003) 927-935. [29] T. R.Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H. Grubbs, D. A. Bansleben, Sciences 287 (2000) 460-463. [30] X. F. Li, Y. S. Li, J. Polym. Sci. Part A: Polym. Chem. 40 (2002) 26802685. [31] Y. Z. Zhu, J. Y. Liu, Y. S. Li, Y. J. Tong, J. Organomet. Chem. 689 (2004) 1295-1303. [32] X. F. Li, Y. G. Li, Y. S. Li, Y. X. Chen, N. H. Hu, Organometallics 24 (2005)2502-2510. [33] D. A. Barnes, G. M. Benedikt, B. L. Goodall, S. S. Huang, H. A. Kalamarides, S. Lenhard, L. H. Mclntosh, K. T. Selvy 111, R. A. Shick, L. F. Rhodes, Macromolecules 36 (2003) 2623-2632. [34] Corresponding aluminium complex bearing Ph and CH3 groups have been tested and proved to be inactive to catalyze NBE polymerization. [35] C. Mast, M. Krieger, K. Dehnicke, A. Greiner, Macromol. Rapid Commun. 20(1999)232-235. [36] Q. Wu, Y. Y. Lu, J. Polym. Sci. Part A: Chem. 40 (2002) 1421-1425. [37] T. F, A. Haselwander, W. Heitz, Macromol. Rapid Commun. 18 (1997) 689-697.


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18 Effect of Anionic Ancillary Ligand in Ethylene Polymerization Catalyzed by (Arylimido)vanadium Complexes Containing Aryloxide, Ketimide Ligand Kotohiro Nomura,*, Wei Wang, and Junji Yamada Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Factors affecting the catalytic activity in ethylene polymerization using (arylimido)vanadium dichloride complexes containing anionic ancillary donor ligand of the type, (ArN)VCl2(X) [X: O-2,6-Me2C6H3, O-lfi-^tzCsHi, N=C'Bu2, N=C('Bu)(CH2SiMe3)], have been explored. These complexes exhibited high catalytic activities in the presence of MAO cocatalyst and the activities at 25 °C by the aryloxide analogues were higher than those by the ketimide analogues. In contrast, the activities by the ketimide analogues (X = N=C'Bu2) increased at higher temperature (50 °C), whereas the significant decrease in the activities was observed by the aryloxide analogues. Although the aryloxide analogues showed especially high catalytic activities in the presence of EtaAlCl, the observed activities by the ketimide analogues in the presence of Et2AlCl were lower than those in the presence of MAO. 1. INTRODUCTION Topics concerning precise synthesis of polyolefins by new generation of transition metal catalysis attract considerable attention [1], because the evolution of new polyolefins that can not be prepared by ordinary catalysts is highly expected. Since the classical Ziegler type vanadium catalyst systems displayed the unique characteristics such as synthesis of high molecular weight polymer with narrow polydispersity, synthesis of ethylene/a-olefin copolymer with high a-olefm content, and others [2], therefore, the design of new

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vanadium complex catalyst for the controlled olefin polymerization has been one of the most attractive targets. We reported recently that (arylimido)(aryloxo)vanadium complexes of type, VCl2(^-2,6-Me2C6H3)(OAr) [Ar = 2,6-Me2C6H3 (1), Ifi-^C^ (2), Chart 1], exhibited high catalytic activities in ethylene polymerization [3,4], and the activities in the presence of Et2AlCl was higher than that in the presence of MAO [3,4]. We also demonstrated that these complexes are also effective for synthesis of ultra high molecular weight poly(ethylene-co-norbornene)s, and the norbornene incorporation as well as the Mn values were dependent upon the cocatalyst employed [4]. Since we recently reported the synthesis of various (arylimido)(ketimide)vanadium complexes of the type, VCl2(NAr')[N=C('Bu)R] [Ar' = 2,6-Me2C6H3 and R = (Bu (3), CH2SiMe3 (4); Ar' = 2,6s and R = 'Bu (5), Chart 1], and isolated a vanadium-alkylidene complex which showed remarkable catalytic activity for ring-opening ci metathesis polymerization of Cl norbornene [7], we thus studied these R3 complexes as the olefin coordination 3 R*;R = Me; f Bu PIO-1 (A) = 0.983 LUMOA PIO-1(B) = - 0.996 H0M0 B

(1) (2) (3) (4)

Minor contributions from various atomic orbitals were omitted in these equations, from which the main components (Cr 3Dx ~y , Cr 3 D g 2 , Cr 4S and C 2Py) of atomic orbitals can be observed to form the attractive interaction between A and B at GO-3. PIO-1 orbital could also be expressed in terms of a linear combination of molecular orbitals (LCMO) calculated from molecular A and B, respectively, as shown in Eqs. (3) and (4). In Eqs.(3) and (4), those minor contributions from various molecular orbitals were omitted. The main components of molecular orbitals for PIO-1 orbitals of GO-3 for the formation of the attractive interaction between A and B at GO-3 can be observed to be LUMOA and H0M0 B . It is noticeable to see that the intermolecular orbital interaction at GO-3 is mostly derived from LUMO and HOMO of CrOa and ethylene, respectively.

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Extended Hiickel calculations were also used to obtain the canonical molecular orbitals for the combined interacting system C at GO-4. Similar LCAO and LCMO results were obtained. Only the contour maps of PIO-1 of the interacting system C at the intermolecular orientation GO-4 are shown in Fig. 3 ((c) and (d)). It was further confirmed that PIO-1 orbitals at GO-1, GO-2, GO-5 and GO-6 all show repulsive intermolecular interaction between A and B. Calculation results here demonstrated that a similar reduction of GO} by ethylene into CrO and formaldehyde (reaction (2) in Scheme 1), which requires an intermolecular orientation of GO-2, seems not plausible indicating the importance of supporting bulky CrO3 onto SiO2 for ethylene polymerization activity. Moreover, the formation of stable Jt-bonded molecular complex between CrO3 and ethylene can be expected. 4. CONCLUSIONS Interaction between CrO3 and ethylene was investigated in a molecular orbital level using DFT and PIO methods as a model for the mechanistic understanding of Phillips CrOx/SiO2 catalyst. It was demonstrated that bulky CrO3 without supporting onto S1O2 surface is difficult to achieve activity for ethylene polymerization because formation of stable ji-bonded molecular complex between CrO3 and ethylene monomer could block the whole activation process. References [I] M. McDaniel, Adv. Catal. 33 (1985) 47-98. [2] B. Liu, P. Sindelaf, Y. Fang, K. Hasebe, M. Terano, J. Mol. Catal. A: Chem. 238 (2005)142-150. [3] Y. Fang, B. Liu, K. Hasebe, M. Terano, J. Polym. Sci. Part A: Polym. Chem. 43(2005)4632-4641. [4]B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 184 (2002) 387398. [5]B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 201 (2003) 189197. [6] E. Groppo, C. Lamberti, S. Bordiga, G. Spoto, A. Zeechina, Chem. Rev. 105 (2005)115-183. [7] B. Liu, Y. Fang, M. Terano, J. Mol, Catal. A: Chem, 219 (2004) 165-173. [8] Y. Fang, B. Liu, M. Terano, Appl. Catal. A: Gen. 279 (2005) 131-138. [9] B. Liu, Y. Fang, M. Terano, Mol. Simula! 30 (2004) 963-971. [10] B. Liu, Y. Fang, W. Xia, M. Terano, Kinet. Catal. 47 (2006) 234-240. [II] A. Shiga, H. Kawamura, T. Sasaki, J. Mol. Catal. A: Chem. 77 (1992) 135152, [12] H. Fujimoto, Ace. Chem. Res. 20 (1987) 448-453.


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Olefin Polymerization by Bimetallic Zr Catalyst. Ligand Effect for Activity and Stereoselectivity Junpei Kuwabara, Daisuke Takeuehi, and Kohtaro Osakada* Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, 226-8503, Japan

Abstract Bimetallic Zr complexes are synthesized by olefin metathesis reaction of vinyl group of monometallic complexes. The Si bridged zirconocene {rfC5Me4-SiMe2-ri5-C5H3CH2CH=CH2}ZrCl2 is transformed by metathesis reaction to the novel bimetallic complex with arasa-strueture. Ethylene and propylene polymerization was conducted by bimetallic complexes. The activity of the bimetallic complex depends on the steric hindrance of the ligand. The bimetallic complex with aasa-structure gave isotactic polypropylene with a similar high selectivity to that of the monometallic analog. Bimetallic complexes catalyzed cyclopolymerization of 1,5-hexadiene to give poly(methylene-l ,3-cyclopentane). 1. INTRODUCTION Group 4 metallocene catalysts have been widely investigated for olefin polymerization]!]. Recent progress of metallocene catalyst is led to stereospecific polymerization of a-olefm[2]. Design of new catalysts with bimetallic structure would exhibit a unique performance originated from cooperative effect of the two metal centers. During the last decade, several groups reported preparation of the bimetallic complexes of Ti and Zr, and their olefin polymerization[3]. Since the catalytic behavior strongly depends on bridging ligand, we have investigated the relationship between catalytic activity and structure of bridging chain[4]. Herein, we report the effect of ligand structure around metal center of bimetallic Zr complexes for ethylene and

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propylene polymerization. Since nietallocene catalyst promotes polymerization of non-conjugated diene such as 1,5-hexadiene as well as olefln polymerization[5], cyclopolymerization of 1,5-hexadiene by bimetallic catalyst were also investigated. 2. EXPERIMENTAL Materials. All the manipulations of the air-unstable complexes were carried out under nitrogen or argon using standard Schlenk techniques. Toluene, hexane, and EtaO were distilled from sodium benzophenone ketyl and stored under nitrogen or argon. MAO was purchased from TOSOH-FiNECHEM and stored under nitrogen or argon. 1, 2,3, 4 and 5 were prepared according to the method reported previously[4]. 6 was prepared in similar manner to the previous report[4]. 'H NMR (300 MHz, C6D6): 6 (major) : 8 6.75 (t, 2H, J=2 Hz, cyclopentadienyl), 5.79 (m, 2H, olefmic), 5.39 (t, 2H, J=3 Hz, eyclopentadienyl), 5.13 (t, 2H, J=3 Hz, cyclopentadienyl), 3.5-3.7 (m, 4H, CH2), 2.03, 2.00, 1.76, 1.66 (s, 24H, C5Me4), 0.39, 0.38 (s, 12H, SiMea). 6 (minor): 5 6.80 (t, 2H, J=2 Hz, cyclopentadienyl), 5.83 (m, 2H, olefinic), 5.41 (t, 2H, J=3 Hz, cyclopentadienyl), 5.16 (t, 2H, J=3 Hz, cyclopentadienyl), 3.5-3.7 (m, 4H, CH2), 2.03,2.00,1.76, 1.65 (s, 24H, C5Me4), 0.39, 0.37 (s, 12H, SiMe2). Polymerization Procedure. Typical experimental procedure for ethylene polymerization is as follows. To a solution of 1 (4.3 mg, 0.01 mmol) in toluene (6.4 niL) was added a toluene solution of MAO (2.79 M-Al, 3.6 mL, 10 mmolAl). The catalyst solution (1.0 mM-Zr) was stirred at room temperature for 15 min for the pre-activation. To a toluene (30 mL) saturated with ethylene (1 atm) was added the solution of the catalyst (0.50 mL, 0.50 pmol). The solution was stirred for 5 min under atmospheric ethylene at 15 °C. The reaction was quenched with MeOH and 5 M HCl-MeOH. Separated polyethylene solid was filtrated, washed with MeOH, H2O, and hexane, and dried in vacuo. In the case of Zr bimetallic catalyst, 0.25 (jmol catalyst was used. Analytical Procedure. Gel permeation chromatography (GPC) was performed on a TOSOH HPLC-8121GPC/HT using orthodichlorobenzene (152 °C) as eluent for polypropylene and on Waters 150CV using orthodichlorobenzene (135 °C) as eluent for poly(methylene-l,3-cyclopentane). NMR spectra ('H and 13 C{'H}) were recorded on JEOL JNM LA-500 or Varian Mercury 300 spectrometers. Sample solutions of polyethylene were prepared in 1,1,2,2tetrachloroethane-rf2 and the central peak of the solvent (74.0 ppm) was used as an internal reference. Sample solutions of polypropylene and poly(methylene1,3-cyclopentane) were prepared in CDCI3 and the central peak of the solvent (77.0 ppm) was used as an internal reference.

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3. RESULTS AND DISCUSSION 3,1. Synthesis of bimetallic complexes Ru catalyst promotes olefin metathesis reaction of vinyl group of 1-3 to give bimetallic Zr complexes 4-6, respectively, according to the previous report[4]. The coupling reaction of 3 gives bimetallic complex 6 as a mixture of meso and racemic diastereomers because of the planar chirality on the cyclopentadienyl complex. ] H NMR spectrum of the reaction mixture shows 3:4 molar ratios of the isomers. Recrystallization changed the ratio to 9:1 due to a difference of solubility between the isomers. "iSi. , Zr^

•ci

*

4

5

«C1

01/,,.

6

3,2. Olefin polymerization by bimetallic Zr complexes. The monometallic and bimetallic complexes catalyze polymerization of ethylene in the presence of MAO ([Zr] = 16.7 uM and [Al]/[Zr] = 1000 in toluene). Activities of the catalysts are estimated from the polymer yield of the reaction for a short period (5 min) at 15 °C in order to avoid the mass transfer effect[6]. Bimetallic complex 4 exhibits higher catalytic activity (3020 g mmol"'h"') than that of mononuclear precursor 1 (2350 g mmor'h"1). On the other hand, S has a slightly lower activity 4000 (3600 g mmor'h"') than that of 2 (3730 g mmol"'h"'). The catalytic activity of 6 (426 g -_ 3000 mmol"'h"') is significantly lower than that of 3 o (1420 g mmor'h 4 ). We proposed that E enhancement of dissociation of the active Zr 3 2000 cation and the MAO-derived anion due to the 1000 bimetallic structure resulted in higher activity of 4 than 1[4]. Low activity of S can be Monometallic Bimetallic attributed to steric hindrance of fluorenyl catalyst catalyst group. Since two metallocene groups are close to each other, fluorenyl ligand on a Figure 1. Ethylene polymerization metal center probably retards smooth activity of Zr complexes.

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polymerization on the other metal center. The effect of steric hindrance in 6 is larger than that of fluorenyl group in 5 because methyl groups on eyclopentadienyl ligand are orientated to the Zr center. These results indicate that the position of substituent on the ligand affects the activity of bimetallic complex. Low catalytic activity has been reported for the bimetallic complex having bulky ligand such as CsHMe4[7]. In propylene polymerization, 6 has low catalytic activity than that of 3, which is similar to the ethylene polymerization (Table 1). Si-bridged catalyst 3 has an allyl group at ^position. This C\ symmetric catalyst produced isotactic polypropylene (mmmm=88%) via back-skip mechanism as reported by Marks et a/[8]. 6 also gives highly isotactie polypropylene (mmmm=86%). The isotacticity was independent of monomer pressure. The isospecific bimetallic catalyst is rare example [9]. The metathesis method constructs bimetallic structure without loss of catalytic property of monometallic precursor. Table 1 Propylene polymerization3. m pentad Propylene Cat. Activity Entry (atm) (g mmorV1) (%) 1 29 88 1 3 2.5 2 86 3 181 1 18 86 6 3 87 86 6 2.5 4 a [Zr] = 187 JIM, [AI]/[Zr] = 1000, 1 h, 30 m L toluene, r.t.

Mn 2600 5000 2600 4800

1.5 2.2 2.1 2.0

3.3. Cyclopolymerization ofl,5-hexadiene by bimetallic Zr complexes. Zr complexes in combination with MAO catalyze polymerization of 1,5hexadiene to give poly(methylene-l,3-cyclopentane) (PMCP). Table 2 shows results of polymerization by various Zr complexes. These polymers contain negligible amount of acylic unit, which are confirmed by 13C{'H} NMR. spectra. Bimetallic complexes 4-6 gave high molecular weight polymer in comparison with monometallic 1-3. Especially, molecular weight of the polymer formed by 5 is approximately two times larger than that by 2. Figure 2 shows 13C{'H} NMR spectra of aliphatic region and expansion of the spectra from 31 ppm to 34 ppm. The spectrum of the polymer obtained by 4 indicates trans-rich structure based on the strong signals around 33.3 ppm (Figure 2a). Figure 2b shows signals of methyl end group at 21.3 ppm (trans) and 21.1 ppm (cis) as well as signals of cyclic structure of main chain. The spectrum of the polymer formed by 4 shows =CH2 signals of the terminal group at 153.2 and 104.6 ppm instead of that of methyl end group. Thus, the polymer formed by 4 has methylenecyclopentyl end groups. On the other hand, 5 affords the polymer with both methylcyclopentyl and methylenecyclopentyl end group. The content

20. Olefin Polymerization by Bimetallic Zr Complex

139

of methyl end group increases with the increase of the steric hindrance of the ligand around metal center. Waymouth et al reported cyclopolymerization of 1,5-hexadiene by (CsMe5)2ZrCl2 to give methyl terminated polymer[10]. Catalyst with bulky ligand undergoes chain transfer of the growing chain from Zr center to Al compounds in preference to pl-H elimination as termination of propagation. Signals of 4 and 5 positions of cyclopentane ring provide information for tacticity of the polymer[5]. The spectrum shows signals at 31.78, 31.82 and 31.96 ppm for cis rings and signals at 32.28, 34.32 and 34.39 ppm for trans ring (Figure 2c). These results indicate that 4 gave ataetie PMCP. On the other hand, Figure 2d has very small signals at 31.86 and 34.32 ppm, suggesting that 6 affords isospecific PMCP. Both the bimetallic and monometallic complexes show similar trans-selectivity and tacticity in the polymerization. Me

4

5

4

5 /M

(a)

4,5 trans

1,3 t

4,5 t

4,5 cis

1,3 c 4,5 c

2c 2t _JA.

^

.P, il

(d)

Me end group tc I

45

40

35

30

25

20

34

{

J \ 33

32

31

Figure 2. 13C{'H} NMR spectra of PMCP produced by (a) 4 and (b)6. The extended the spectra of PMCP by (c) 4 and (d) 6. Table 2 Polymerization of 1,5-hexadienea. Entry Yield Mn Cat. MwtMn

a

trans:cis

Tacticity

77:23 1 12800 1.7 1 41 Ataetic 2 2 21 45:55 Atactic 12000 1.6 59:41 3.6 10300 40 3 3 Isotactic 4 4 44 1.7 78:22 Ataetic 13700 S 3.2 5 31 44:56 Atactic 22700 1.9 6 35 58:42 Isotactic 13200 e [Zr] = 200 yM, [monomer]/[cat.] = 2000, [AI]/[Zr] = 1000, 3 h , 25 mL toluene, r.t.

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4. CONCLUSIONS The catalytic activity of bimetallic Zr catalyst strongly depends on the steric hindrance of the ligand. The bimetallic complex with oara-structure undergoes isospecific propylene polymerization, which is similar to monometallic analog. This result indicates that the metathesis coupling reaction constructs bimetallic structure without loss of catalytic property of monometallic precursor. The ansa-type bimetallic catalysts also catalyze isospecific polymerization of 1,5hexadiene. Acknowledgements This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan and by the 21st Century COE program. J. K. acknowledges JSPS Research Fellowship for Young Scientist. The authors thank Prof, Takeshi Shiono, Dr. Kei Nishii and Mr. Mitsuhiro Okada for GPC measurement. References [1] H. H, Brintzinger, D. Fischer, R, Mulhaupt, B. Rieger, R. M. Waymouth, Angew. Chem., Int. Ed. Engl. 34 (1995), 1143-1170. [2] L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 100 (2000) 1253-1345. [3] (a) S. Jttagling, R. Mulhaupt, J. Organomet. Chem. 460 (1993) 191-195. (b) S. K. Noh, J. Kim, J. Jung, C. S. Ra, D. Lee, H. B. Lee, S. W. Lee, W. S. Huh, J. Organomet. Chem. 580 (1999) 90-97. (c) L. Li, M. V. Metz, H. Li, M. Chen, T. J. Marks, L. Liable-Sands, A. L. Rheingold, J. Am. Chem. Soc. 124 (2002) 12725-12741, and references therein. [4] J. Kuwabara, D. Takeuchi, K. Osakada, Organometallics 24 (2005) 27052712. [5] (a) L. Resconi, R. M. Waymouth, J. Am. Chem. Soc. 112 (1990) 4953-4954. (b) G. W. Coates, R. M. Waymouth, J. Am. Chem. Soc. 115 (1993) 91-98. [6] Y.-X. Chen, M. V. Metz, L, Li, C, L, Stern, T. J, Marks, J. Am, Chem. Soc. 120(1998)6287-6305. [7] G. Tian, B. Wang, S. Xu, X. Zhou, B. Liang, L. Zhao, F. Zou, Y. Li, Macromol. Chem. Phys. 203 (2002) 31-36. [8] M. A. Giardello, M. S. Eisen., C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 117(1995)12114-12129. [9] W. Spaleck, F. Kiiber, B. Bachmann, C. Fritze, A. Winter, J. Mol. Catal. A: Chem. 128 (1998)279-287. [10] A. Mogstad, R. M. Waymouth Macromolecules 25 (1992) 2282-2284.


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21 Synthesis, Characterization and Ethylene Reactivity of 2-Ester~6-iminopyridyl Metal Complexes Wenjuan Zhang, Biao Wu, Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China

Abstract A series of late-transition metal complexes such as iron (L)FeCl2 (3a-f), cobalt (L)CoCl2 (4a-f), nickel (5a-f) and palladium(6a-f) complexes have been prepared by the reaction of 2-carboxylate-6-iminopyridine 2a-f [2-COOEt-6(2,6-R2CfiH3N=CCH3)CsH3N (2a: R = CH3, 2b; R = Et, 2c: R = i-Pr, 2d: R = F, 2e: R = Cl, 2f: R = Br)] with MC12 (M = Fe, Co, Ni or Pd). These complexes were characterized by elemental analysis, IR spectroscopy and X-ray crystallography. These complexes were tested for ethylene oligomerization and polymerization in the presence of MAO under various reaction conditions. The iron complexes exhibited high catalytic activities for ethylene polymerization/ oligomerization, whereas the cobalt complexes showed moderate activities for the polymerization and high activities for the oligomerization. In addition, the iron catalysts predominantly produced linear oligomers and polyethylene with vinyl group. Nickel complexes showed remarkably high catalytic activities for the ethylene oligomerization affording C4-C8 olefins as the main products, although the selectivity of a-olefm was very low. Palladium complexes showed moderate activity for the ethylene oligomerization and polymerization, and the oligomer product was only C4. These facts indicated that the nature of the metal core strongly affects toward the catalyst behavior in these catalyses.

142

W. Zhang etal

1. INTRODUCTION Olefin polymerization catalyzed by late transition metal complexes has received great prominence over the past decade especially since Brookhart's report on Pd (II) and nickel(II) diimine catalyst systems which showed notable catalytic activity for both ethylene and a-olefin polymerization [1]. Following this pioneering work, various modified bidentate nitrogen ligands, such as bipyridine ligands, imino-pyridine compounds were reported [2]. During the course of synthesis of diaeerylpyridine, we established the synthetic procedure for 2-ethylcarboxylate-6-acetylpyridyl. We thus prepared various late transition metal complexes containing a series of ligands of this type and tested these complexes for ethylene oligomerization/polymerization [3]. In this paper, we present that nature of the centered metal directly affected the catalytic behavior, 2. EXPERIMENTAL Ethyl 6-acetylpyridine~2-carboxylate was initially synthesized by the reaction of 2,6-dicarbethoxypyridine with ethyl acetate in the presence of CaH5ONa using the modified procedure for the synthesis of 2,6-diaeetylpyridine [3b]. The optimal molar ratio of QjHsONa to 2,6-dicarbethoxypyridine was determined to be 1.1-1.5 in order to obtain compound 1 in an acceptable yield, whereas 2,6-diacetylpyridine was produced with the molar ratio (4.5:1) of CaHjONa to 2, 6-diearbethoxypyridme. The pyridylimine ligands 2a-c were easily prepared in satisfactory yields (68.2-73.0 %) through the Schiff-base condensation of 1 with anilines in the presence of catalytic amount of ptoluenesulfonic acid (p-TsOH) under refluxing toluene [3b]. The complexes were obtained by treating ligands with corresponding MCI2CM = Fe, Co, Ni, Pd). 3. RESULTS AND DISCUSSION J. 1. Syntheses and characterization of complexes. Scheme 1 shows synthesis of the ligands and complexes. Comparing the IR spectra of the ligands with corresponding complexes, the C=N stretching frequencies were shifted due to the coordination interaction between the imino nitrogen atom and the metal center. Most structures of these complexes were confirmed by X-ray crystallography, and Figure 1 shows the selected examples. The structure indicated that the different geometry of coordination was strongly dependent upon the centered metal employed. For the iron and cobalt complexes, the coordination geometry was similar, and two nitrogen atoms coordinated metal cores. The nickel atom was coordinated by two nitrogen

21. Synthesis and Ethylene Reactivity of2-Ester-6-iminopyridyl Metal Complexes

143

atoms and one oxygen atom. The structure by palladium possessed square planar around the metal center coordinated by two nitrogen atoms

HOOC

N

"COOH

EtOH reflux

CH3COOEt EtOOC

N

COOEt 1-1 equivof EtONa 2a: R = Me; 2b: R = Et; 2c: R = i-Pr; 2d: R = F; 2e: R = Ci; 2f: R = Br.

EtOOC

EtO. Fe Co Ni Pel

Me

Et

i-Pr

F

CI

Br

3a 4a Sa 6a

3b 4b

3c 4c 5c 6c

3d 4d 5d 6d

3e 4e 5e 6e

3f 4f 5f 6f

Sb 6b

Scheme 1, Reagents and conditions: i) toluene, p-TsOH, ii) toluene, /?-TsOH, silica-alumina catalyst support, 4 A molecular sieves, iii) FeClj, CoCl2 and NiClz in ethanol; PdCl2 in CH2C12.

Figure 1. Structure of MC12(L) (M= Fe, Co, Ni, Pd)

3.2. Ethylene oligomerization and polymerization in the presence of MAO. These complexes were investigated in detail as the catalyst precursor for ethylene oligomerization/polymerization (ethylene 1 or 10 atm). In general, complexes 3a-f showed considerable activity for ethylene oligomerization to produce butenes and hexenes (with a little of high oligomers) at 1 atm ethylene

144

W. Zhang et al

pressure. Simultaneously, the catalyst systems of 3a and 3b produced some polyethylene. However, complexes 3d-f showed higher activity for oligomerization than 3a-3b, which indicated that the ligand environment significantly affected the catalytic activity. The cobalt complexes 4c, 4f showed higher activity for oligomerization. The nickel complexes 5c, 5f showed notable activity for ethylene oligomerization and polymerization. However, the palladium analogues were inactive at 1 atm. The effect of auxiliary ligand toward the catalyst activity was also investigated. However, as shown in Table 1, only a slight increase in activity was observed relative to the catalytic system of 3i/MAO (entries 6, 7 in Table 1). The results show that addition of PPhato the reaction led to the increase of the oligomerization activity of 4f/MAO. For nickel complexes, the ethylene oligomerization activities of 5c, 5f were significantly improved in the presence of PPh3as auxiliary ligands (entries 11,12,13,14 in Table 1). Table 1 Ethylene oligomerization and polymerization with 3 a - 6 f / MAO at 1 atm a Entry

Complex

Al/Fe

Temp

(mol)

C°c)

Oligom distribution11(%) C4/ZC

Activity

Cfi/IC

Linear

lff^g-mol-Mf'-h"1 aHgora13

Polym

3.35

aolefin >99

2.17

9.44

1

3a

1OOO

15

92.40

4.25

2

3b

1000

15

71.15

28.84

-

97.1

1.61

0.91

>99

3

3c

1000

15

98.20

1.50

0.3

1.39

trace

4

3d

1000

15

84.04

0.90

15.06

94.6

2.60

no

5

3e

1000

15

35,42

57.74

6.84

97.7

6.04

trace

S

3f

1000

15

77.96

2.89

19.15

93.3

1.80

trace

7C

3f

1000

15

100

-

-

>99

2.45

no

8

4c

1000

15

55.34

27.17

17.49

98.1

5.32

3.50

9

4f

1000

15

72.11

23.78

4.10

95.6

18.90

trace

10e

4f

1000

15

71.28

23.28

5.23

92.2

31.70

no

11

Sc

1000

15

48.53

8.73

42.74

7.9

5.47

1.37

C

12

Sc

1000

15

76.49

21.62

8.8

65.2

no

13

Sf

1000

15

70.15

21.89

51.0

9.04

0.30

14C

Sf

1000

15

81.68

17.09

8.7

79.2

no

7.96

"General conditions: 5 nmol precatalyst; 30 m L toluene; reaction time 30 m i n ^ D e t e r m i n e d by GC, £ C means the total amounts of oligomers. C2 equiv of PPhj as auxiliary ligand

21, Synthesis andEthylene Reactivity of2-Ester-6-iminopyridyl Metal Complexes

145

The complexes were also investigated for ethylene polymerization at 10 atm ethylene pressure. The results were listed in Table 2, Comparing the data in Table 2 with that in Table 1, the iron complexes containing less bulky-substituted ligand were found to show the higher catalytic activity. The distribution of olefin oligomers follows the Schulz-Flory rules, which are characterized by the constant K that represents the probability of chain propagation. As shown in Table 2, increasing the steric bulk at the orthoposition of the aryl group on the iron complexes led to an increase in K value (entries 1, 2 and 3 in Table 2). GC and GC-MS analysis of the oligomers indicated that the selectivity for linear a-olefms was higher than 78% for 3a-f at 10 atm of ethylene. Moreover, DSC studies determined the Tm values are in the range of 88 to 132 °C, which are well correlative with the linear characteristics of the PE samples with low molecular weight. For cobalt complexes, the ethylene pressure had little effect toward the activity. Dimers and trimers are major products (with a little amount of higher carbon number oleflns) and the linear a-olefins are the predominant products. The activity by nickel complexes increased upon increasing the ethylene pressure, and 4c and 4f generate butenes and hexenes as main oligomeric product and the distribution of oligomers did Table 2 Ethylene oligomerization and polymerization with 3a—fiMAO at 10 atmB Entry

Complex (umol)

Polym (g)

Mnc

Activity 1

10 g'mol-Mt-'-lf

PDF

3

(10 )

Oligom

Polym

6.20

56.70

4.7

32.7

m d lm

linear

(°C)

a-olefin (%)

132

88.8

0.83

K

1

3a (42.3)

24.00

2

3b (53.9)

1.15

1.44

2.10

1.3

90.3

122

82.1

0.93

3

3c (36.5)

1.13

1.90

3.20

1.0

4.2

124

92.1

0.96

4

3d (34.1)

trace

4.06

-

-

-

-

78.3

0.73

E

5

3e (42.5)

1.67

30.60

3.90

0.5

2.4

88

92.0

0.81

6

3f(36.9)

3.50

3.90

9.50

0.7

2.4

110

95.8

0.81

7

4c (32.8)

0.18

3.63

0.53

1.9

36.4

125

84.6

8

4f(49.6)

0.44

23.40

0.90

1.7

16.7

125

97.9

—

9

5c (56.0)

0.85

4.88

1.50

5.5

63.2

128

15.9

—

10

5f(43.8)

0.18

27.10

0.40

2.0

25.4

123

29.5

—

11

6d(5)

8.05

0.81

—

—

133

100

—

12

6a (5)

8.36

0.4S

-

-

131

100

—

"General conditions: Al/M molar ratio 1000; 20 °C; 1 hour, 700 mL toluene. ^Determined by GC. ^Determined by GPC. determined by DSC. ''The oligomers were determined by GC, GC-MS.

146

W. Zhang etal

not follow Schulz-Floiy rules. Note that the selectivity of the oligomer was very low. In addition, the obtained PE was confirmed to be low molecular weight oligomers possessing small amount of w-butyl branches (the branching degree about 2 w-butyls per 1000 methylenes) in the main chain. At 10 atm ethylene pressure, the palladium complexes showed moderate polymerization activity, and the addition of the PPh3 led to the rapid decrease of activity. 4. CONCLUSIONS A series of late-transition metal complexes containing 2-earboxylate-6~ iminopyridine were synthesized and tested for ethylene polymerization and oligomerization. Upon treatment with MAO, these complexes exhibited the high or moderate activities. The ligand environment affected toward the polymerization behavior for all the complexes, and the higher pressure could lead to the higher activity for these complexes except the cobalt complexes. Addition of PPI13 had little effect toward the ethylene reactivity for iron and cobalt complexes. The oligomers produced by iron complexes were linear aolefins predominantly, and polymers obtained in some cases were linear polymeric a-olefins. Addition of PPh3 as auxiliary ligand led to much higher catalytic activity than that without PPh3 for nickel complexes, but the selectivity of a-olefm of oligomers was very low. Palladium complexes showed much lower activity than the other corresponding analogues. Acknowledgements We are grateful to the National Natural Science Foundation of China for financial supports under Grant No.20473099. Referenees [1] (a) L.K. Johnson, CM. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414; (b) CM. Killian, D.J. Tempel, L.K, Johnson, M. Brookhart, J. Am. Chem. Soc. 118 (1996) 11664; (c) D.P. Gates, S.A. Svejda, E. Onate, C M. Killian, L.K. Johnson, P.S. White, M. Brookhart. Macromolecules 33 (2000)2320. [2] (a) G.PJ. Britovesk, V.C Gibson, B.S. Kimberly, P.J. Maddox, S. J. McTarvish, G.S. Solan, A. J. P. White, D. J. Williams, Chem. Commun. (1998) 849; (b) D.G. Musaev, R.D.J. Froese, K. Morokuma, New J. Chem. 119 (1997) 6177; (c) CM. Killian, L.K. Johnson, M. Brookhart, Organometallies 16 (1997) 2005. [3] (a) X. Tang, W.-H. Sun, T. Gao, J. Hou, J. Chen, W. Chen, J. Organomet. Chem. 690 (2005)1570; (b) W.-H. Sun, X. Tang, T. Gao, B. Wu, W. Zhang, and H. Ma, Organometallies 23 (2004) 5037.


147

22

Ligand Effect in Syndiospecific Styrene Polymerization and Ethylene/Styrene Copolymerization by Some Nonbridged HalfTitanocenes Containing Anionic Donor Ligandi Hao Zhang and Kotohiro Nomura* Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Ligand effects in syndiospecifie styrene polymerization and ethylene/styrene copolymerization by half-titanoeenes of the type, Cp'Ti(L)Cl2 [Cp' = Cp, Cp*, *BuCsH4; L = O-2,6-*Pr2C6H3, N=C*Bu2, Cl], have been explored in the presence of MAO. The catalytic activities in the styrene polymerization with a series of the Cp* analogues increased in the order: OAr > Cl > N=C*Bu2. The catalytic activity, styrene incorporation as well as the microstrueture were affected by both Cp' and L in the ethylene/styrene copolymerization. 1. INTRODUCTION Nonbridged half-titanocenes containing anionic donor ligand of the type, CpTi(L)X 2 (Cp' = cyclopentadienyl group; L = anionic donor ligand such as OAr, NR25 N=PR3, N=CR2 etc.; X = halogen, alkyl etc.; R = alkyl, aryl etc.), are one of the promising candidates as the efficient catalysts for precise olefin polymerization [1-18], because this type of complex catalysts recently displayed unique characteristics as olefin polymerization catalysts producing new polymers that had never been prepared by conventional catalysts. We reported that the aryloxo analogue of the type, Cp'TiCl2(OAr), exhibited high catalytic activities for both olefin polymerization [5,6] and syndiospecific styrene polymerization [19]. These catalysts exhibited unique characteristics for

148

H. Zhang andK. Nomura

copolymerization of ethylene with a-olefm [20] as well as with styrene [21], and revealed that an efficient catalyst for desired polymerization can be modified by the substituents on Cp*. We also reported recently that ethylene/styrene copolymerization took place in a living manner when Cp*TiCl2(N=C*Bu2) (1) was chosen as the catalyst [22], whereas an efficient styrene incorporation was achieved when the aryloxide analogue, Cp*TiCl2(O-2,6-iPr2C6H3) (2) was used as the catalyst [21,22]. These results clearly indicated that anionic donor ligand plays an important key role for the copolymerization behavior and styrene incorporation. Since we also presented that the catalytic activities and molecular weights for the resultant syndiotactic polystyrenes (SPSs) were highly dependent upon the anionic donor ligand employed in the styrene polymerization [19], we explored the more detaiLln this paper, we wish to introduce detailed results for effect of anionic donor ligand in both the styrene polymerization and ethylene/ styrene copolymerization with a series of aryloxide and ketimide analogues (Chart 1). 2. EXPERIMENTAL All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox unless otherwise specified. Anhydrous grade toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) under nitrogen stream in the drybox, and was used without further purification. Styrene of reagent grade (Kanto Chemical Co., Inc.) was stored in a freezer after passing through an alumina short column under N2 in the dry box. Cp'TiClzfN^Bua) [Cp' = Cp* (1), Cp = (5)] [22,23], CpTiCyO-^e-'PraCsHs) [Cp' = Cp (6), (tert-BuCsH4 (4), Cp* (2)] [5,6] were prepared according to the previous reports. Toluene and AlMe3 in ordinary MAO [PMAO-S, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C, and then heated at >100 °C for 1 h) in the drybox to give white solids. Detailed polymerization procedures and isolation procedures were according to our previous reports [19,21,22], and molecular weights and molecular weight distributions for resultant polyethylenes were measured by gel permeation ehromatography (Tosoh HLC-8121GPC/HT) with polystyrene gel column (TSK gel GMHHR-H HT X 2, 30 cm x 7.8 mni(|> ID), ranging from Cl (3) » N=C*Bu2 (1). The observed activities increased at higher temperature as observed in our previous reports [19,24]. Moreover, the Mw value for resultant SPS was also dependent upon the anionic donor ligand employed, and the value increased in the order (at 70 °C): 2 > 3 > 1. It was revealed that the *BuCp-aryloxide analogue (4) showed remarkable catalytic activities, suggesting that the effective catalyst for the desired polymerization can be tuned by modification of the cyclopentadienyl fragment [19]. Moreover, the Mw values for resultant polymers by 4 were lower than those by the Cp* analogue 2, probably due to the different dominant chain transfer step (confirmed) between the Cp*- and Cp-aryloxide analogues [19]. It also tuned out that the activity by the Cp-ketimide analogue (5) was lower than the Cp* analogue (1) whereas both the Cp-aryloxide analogue (6) and the Cpchloride analogue (7) showed exceptionally higher catalytic activities than the Cp* analogues (1-3), and the Mw values by 5 were higher than those by 1. Based on the above results, it is thus clear that the substituents on both the cyclopentadienyl and the anionic ancillary donor ligands play an important key role for the catalytic activity and molecular weight for resultant polymer in syndiospecific styrene polymerization. 3.2. Ethylene/styrene copolymerization by using Cp 'TiCljfL) - MAO catalysts. To explore the effect of anionic ancillary donor ligand toward the catalytic activity, styrene incorporation as well as copolymerization behavior, three Cp* analogues, Cp*TiCl2(L) [L = N=C'Bu2 (1), OAr (2) and Cl (3)], were chosen for the ethylene/styrene copolymerization in the presence of MAO cocatalyst. The results at 25 °C are summarized in Table 2. The copolymerization by the ketimide analogue 1 took place in a living manner poly(ethylene-co-styrene)s exclusively with narrow molecular weight distribution {MJMn = 1.18) [22],

150

if. Zhang and K. Nomura

although the homopolymerization of ethylene nor styrene did not proceed in a living manner. The highly efficient styrene incorporation was observed in the eopolymerization using the aryloxide analogue (2), and the resultant copolymers possessed uniform composition confirmed by GPC, DSC thermograms, C Table 1. Effect of anionic donor ligand in syndiospeclfic styrene polymerization by Cp'TiG 2 (L) [Cp' = Cp*, L = N=C*Bu2 (1), OAr (2, Ar = ^fi-^CsHj), Cl (3); Cp" = *BuC5H4, L = OAr (4); Cp' = Cp, L = OAr (6% Cl (7)] - MAO catalyst systems." temp.

Cp'.L

MJM*

activity" /DC

xW4

Cp*, N=C'Bu2 (1)

25

63

lg.3

2.3

Cp*, N=CBu 2 (1)

40

81

20.9

2.3

Cp*, N=C'Bu2 (1)

55

140

22.2

2.1

Cp*, N=C'Bu2 (1)

70

222

19.1

2.1

Cp*, OAr (2)

25

190

24.3

2.4

Cp*, OAr (2)d

40

285

26.8

2.6

Cp*, OAr (if Cp*, OAr (if

55

1640

53.1

2.5

70

3600

49.0

2.2

Cp*,Cl(3)

25

210

25.0

2.2

Cp*, Cl (3)d

40

320

36.2

2.3

Cp*, Cl (3)d

55

666

33.2

2.3

d

70

1970

24.8

2.5

'BUC5H4, OAr (4)

25

3140

17.8

1.5

'BuCsH,, OAr (4)

40

7920

10.2

1.6

'BuCjH,, OAr (4)

55

12280

5.3

2.9

(

BuC5H4, OAr (4)

70

7000

3.4

3.7

Cp,OAi(6f

40

1000

5.7

2.1

Cp*, Cl (3)

Cp»OAr(6) d

55

4130

5.8

2.0

Cp, OAr (6f

70

15300

4.0

2.5

Cp, Cl (7)d

40

15800

6.7

2.8

Cp, Cl (7)d

55

17500

4.8

2.7

d

70

15300

3.3

2.4

Cp,Cl(7)

"Conditions: complex 2.0 p,mol or 1.0 ixmol, MAO (prepared by removing AlMej and toluene from PMAO) 3.0 mmol, styrene + toluene total 30 mL, 100 mL scale autoclave; bActivity in kg-polymer/mol-Ti"h; CGPC data in o-dichlorobenzene vs polystyrene standards; dCited from reference 19.

NMR spectrum and GPC/FT-IR [21,22]. No resonances ascribed to (head-totail) styrene repeating unit were seen in the 13C NMR spectrum in the copolymer prepared by 1, whereas the peaks due to two, three styrene repeating

22, Homo- and Copolymerization ofStyrene with Ethylene by Half-Titanocenes

151

units were seen for the polymer prepared by 2. Note that the polymerization by 3 under the same conditions afforded a mixture of polyethylene and syndiotactic polystyrene. These results clearly indicate that the anionic donor ligand directly affects toward the catalytic activity, styrene incorporation as well as the microstructure in the copolymer. Table 2. Effect of anionie donor ligand In ethylene-styrene copolymerization by Cp'TiClaCL) [L = N=C<Bu2(l), OAr (2), Cl (3); Cp'= 'BuCp, L = OAr (4); Cp'= Cp, L = N=CBu 2 (§)] - MAO catalyst systems.* cat.

Cp'.L

(umol)

composition I:%) b

poly(ethylene-co-styrene)s or PE, SPSb

E-S

PE

SPS

activity11

st. cont

M/xlO" 4

MJMne

1 (2.0)

Cp*, N=CBu 2

>99

trace

trace

400

7.4

9.5

1.18

2(2.0)

Cp*, OAr

>99

trace

trace

500

31.9

5.73

1.62

86.8

13.2

250

>99

5.85

1.26

—

0.29

2.69

3(2.0)

Cp*, Cl

trace

4(1.0)

'BuCp, OAr

>99

trace

trace

6300

47.6

13.6

1.68

5 (10,0)

Cp, N=C*Buz

ft

Table 1. Ethylene Polymerization with Niobium and Tantalum Complexes 1—5/MMAO. complex [A1]/[M] activity ~M? UJM? ^T 1 4 (kgPE/mol-h) (/10 ) fC) 1 100 4.25 11.3 140.3 15 1 500 133.2 0.33 4.3 70 135.2 2 100 0.48 106.9 6 129.8 500 15 2 0.70 17.9 137.6 100 5 3 127.4 500 22 3 32.4 0.42 100 4 133.6 4 128.2 500 11 4 1.29 13.8 5 132.3 100 5 0.31 6.0 130.2 500 18 Conditions; catalyst = 0.02 mmol, ethylene = 1 atm, solvent = 30 mL of toluene, temp. = r.t, time = 10 min.a)Dtermined by GPC. b) Dtermined by DSC.

25. Synthesis and Catalysis ofBis(imino)pyridine Complexes of Group 5 Metals

169

3.3. ROMP qfnorbornene by the niobium and tantalum complexes The complexes 1—5 also catalyzed polymerization of norbomene in the presence of aluminum cocatalysts. In spite of ethylene polymerization activity of the complexes 1—5 activated with MMAO, no vinyl-addition polymerization of norbomene proceeded and only ROMP of norbornene occurred even in the presence of MMAO or MAO. As observed in ethylene polymerization, bulkier niobium complex showed higher activity. The polydispersity indexes MyJMn of the resulting polymers were close to 2, indicating these systems are single-site catalysts for the ROMP of norbornene. The tantalum complex S exhibited higher activity than that of the corresponding niobium complex 1, but still less active than alkylidenetantalum complexes having aryloxide or arenethiolate ligands [13]. The molecular weight of the resulting polymer decreased with polymerization time, indicating secondary metathesis reaction of the polymer main chain. When the complexes 1—5 were activated with AlEt3, no cisftmns specificity was observed . The niobium complex 1 activated with MMAO gave fr<ms-rich polynorbomene, while the use of MMAO for the tantalum complex 5 slightly increased cis-specificity. Table 2. ROMP of Norbomene Catalyzed by the Complex 1—5. cocat. complex [A1]/[M] time yield trans-cant. * MJM* (mol/mol) % 104 % (h) AlEtj 1 73 1 34 1.96 24 55 1 40 100 17 1.70 24 MMAO 75 21 3.22 24 2 17 AlEt3 45 21 28 2.56 AlEtj 24 50 3 4 34 AlEt 3 38 1.93 24 49 S 71 A1E% 16 2.23 3 52 13 2.25 52 75 AlEt 3 6 5 A1E% 86 12 11 2.84 52 5 AlEt 3 82 24 8 3.98 53 S 3.21 100 24 5.2 5 MAO 40 46 42 100 3 16.4 4.73 42 5 MMAO 100 24 99 12.4 6.92 41 S MMAO Conditions: catalyst = 0.02 mmol, [monomer]o/[catalyst] = 100 mol/mol, solvent = 1 mL of toluene, temp. = r.t. a ' Determined by GPC calibrated with standard polystyrenes. b^ Determined by'HNMR.

4. CONCLUSIONS A series of bis(imino)pyridine complexes of tantalum and niobium were synthesized by the reaction of MCl3(DME) (M = Nb, Ta) with bis(irnino)pyridines in THF. These bis(imino)pyridine complexes showed moderate activities for ethylene polymerization upon activation with MMAO to

170

Y. Nakayama et al.

yield linear polyethylene. The niobium and tantalum complexes were also moderately active for ROMP of norbornene in the presence of AlEt3, MMAO, or MAO. The bulkiest niobium complex having 2,6-diisopropyl substituents exhibited the highest activity among the studied niobium complexes in both cases. Acknowledgements The authors are grateful to Tosoh Fineehem Co. for supplying the cocatalysts. References [I] B.L. Small, M. Brookhart and A.M.A. Bennett, J. Am. Chem. Soc, 120 (1998)4049-4050. [2] G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.J. McTavish, G.A. Solan, A.J.P. White and DJ. Williams, Chem. Commun., (1998)849-850. [3] D. Reardon, F. Gonan, S. Gambarotta, G. Yap and Q. Wang, J. Am. Chem. Soc, 121(1999)9318. [4] D.P. Gates, S.A. Svejda, E, Onate, CM. Killian, L.K, Johnson, P.S. White and M. Brookhart, Macromolecules, 33 (2000) 2320-2334. [5] M.A. Esteruelas, A.M. L6pez, L. M6ndez, M. Olivan and E. Oflate, Organometallics, 29 (2003) 395-406. [6] B.L. Small, M.J. Carney, D.M. Holman, C.E. O'Rourke and J.A. Halfen, Macromolecules, 37 (2004) 4375-4386. [7] Y. Nakayama, K. Sogo, H. Yasuda and T. Shiono, J. Polym. ScL: Part A: Polym. Chem., 43 (2005) 3368-3375. [8] K. Hiya, Y. Nakayama and H. Yasuda, Macromolecules, 36 (2003) 79167922. [9] GJ.P. Britovsek, M. Bruce, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.M.S.J. McTavish, C. Redshaw, G.A. Solan, S. Stromberg, A.J.P. White and DJ. Williams, J. Am. Chem. Soc, 121 (1999) 8728-8740. [10] EJ. Roskamp and S.F. Pedersen, J. Am. Chem. Soc, 109 (1987) 65516553. [II] K. Mashima, S. Fujikawa, Y. Tanaka, H. Urata, T. Oshiki, E. Tanaka and A. Nakamura, Organometallics, 14 (1995) 2633-2640. [12] C. Redshaw, D.M. Homden, M.A. Rowan and M.R.J. Elsegood, Inorg. Chim. Ada, 358 (2005) 4067-4074. [13] K.C. Wallace, A.H. Liu, J.C. Dewan and R.R. Schrock, J. Am. Chem. Soc, 110(1988)4964-4977.


171

26 Ethylene Polymerization with an Anilinonaphthoquinone-Ligated Nickel Complex Mitsuhiro Okada, YuushouNakayama, and Takeshi Shiono* * Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Himshima, 739-8527, JAPAN.

Abstract An anilinonaphthoquinone-ligated nickel complex activated with tris(pentafluorophenylborane) system showed high activity for ethylene polymerization at 40 °C under atmospheric pressure and gave polyethylene with long chain branches and short chain branches. The activity was decreased by lowering the polymerization temperature accompanied by the increase in molecular weight. The number of the chain branches was also decreased according to the polymerization temperature. The polyethylene produced at 20 °C had only methyl branch formed by chain work, whereas polyethylene produced at 0 °C had no branches. 1. INTRODUCTION Since Brookhart and co-workers discovered a-diimine complexes of nickel and palladium, late-transition-metal complexes have received much attention for polymerization catalysts[l-6]. Polymerization temperature significantly affects the activity, molecular weight and the structure of the polymer obtained in ethylene polymerization catalyzed by nickel complexes [7-10]. We have previously reported that an anilinonaphthoquinone-ligated nickel complex 1 activated with tris(pentafluorophenylborane) showed high activity for ethylene polymerization. The polyethylene obtained by this catalytic system at 40 °C possessed short chain branches formed by chain walk via p-hydride elimination /reinsertion/ migration Kgure 1 Nickel complex 1

172

MOkadaetal.

and long chain branches. The long chain branches should have been formed by the copolymerization of ethylene with macromonomer formed via p-hydride elimination[ll]. In this study, we report the effects of polymerization temperature on polymerization activity, molecular weight and the structure of the polymers produced in the present system. 2. EXPERIMENTAL Materials, All manipulations were carried out under a nitrogen atmosphere using standard Schlenk techniques. All solvents were refluxed with sodium/benzophenone or calcium hydride and distilled before use. The complex 1 was prepared according to the method reported previously[11 ]. Polymerization Procedure, Polymerization was performed in a 100-mL glass reactor equipped with a magnetic stirrer and carried out by the following method. At first, the reactor was charged with a prescribed amount of toluene. After the toluene was saturated with an atmospheric pressure of ethylene, polymerization was started by adding the toluene solution of 1 pre-activated with 4 equiv. B(CgFs)3 at 80 °C for 30 min. Polymerization was conducted for a certain time keeping the ethylene pressure constant and terminated with methanol. The polymers obtained were adequately washed with methanol and dried under vacuum at 60 °C for 6 h. Analytical Procedures. Molecular weights and molecular weight distributions of polyethylenes obtained were determined by gel permeation chromatography (GPC) with a Waters 150CV at 140 °C using o-diehlorobenzene as a solvent. The 13C NMR spectra of the polyethylenes were measured at 120 °C on a JEOL GX 500 spectrometer operated at 125.65 MHz in the pulse Fourier-transform mode. The pulse angle was 45* and about 4000-8000 scans were accumulated in pulse repetition of 5.0 s. Sample solutions were prepared in 1,1,2,2tetrachloroethane-^ up to 10 wt-%. The central peak of the solvent (74.47 ppm) was used as an internal reference. Differential scanning calorimetry (DSC) curves of the samples were recorded on a Seiko DSC-220 under nitrogen with a heating rate of 10 °C/min from 25 "C to 170 "C. 3. RESULTS AND DISCUSSION Ethylene polymerization was conducted by 1 at 0, 20 and 40 °C, of which results are summarized in Table 1. Polymerization proceeded irrespective of the temperature. The molecular weight of the polymer obtained drastically increased at low temperature although the polymerization activity decreased. The Tm value determined by DSC rose 113 °C to 144 °C as the polymerization temperature decreased from 40 °C to 0 DC, which indicates that the structure of

173

26, Ethylene Polymerization with am Anilinonaphthoqumone-Ligated Ni Complex

polyethylene obtained was depended on the polymerization temperature. The 13 C NMR spectra of the polyethylenes are shown in Figure 2. Table 1. Polymerization of Ethylene by an Anilinonaphthoquinone-Ligated Nickel Complex I 1 Time

T

Entry No.

Temp. /°C

/min

1

40

7

1,320

18,000

3.95

113

2

20

7

957

324,000

2.88

127

3

0

28

249

1,160,000

4.11

144

Activity13

MWDC

'm

/°c d

* Polymerization conditions: toluene = 150 ml, Revolution rate = 600 RPM, Ni = 25 (J,mol, B(C6Fj)3 = 100 jitnol, Ni complex and B(C6FS)3 were premixed at 80 °C for 30 min. b Activity in kg-polyethylene / (mol-Nrh). e Mn and MWD determined by GPC using polystyrene etandard. Determined by DSC.

45

40

35

30

25

20

IS

10

13

Figure 2. C NMR spectra of polyethylenes obtained at 40 °C (a), 20 °C (b), 0 °C (o).

We have previous reported that the polyethylene produced at 40 °C had short chain branches and long chain branches (Figure 2a)[ll]. Decreasing the

174

MOkadaetal.

polymerization temperature to 20 °C gave the polyethylene with only methyl branch which is formed by chain walk via p-hydride elimination / reinsertion / migration (Figure 2b), and the polyethylene obtained at 0 °C had no branches detected by 13C NMR (Figure 2c). The effect of polymerization temperature on the polymer structure can be interpreted as follow. At low polymerization temperature, P-hydride elimination is suppressed more than propagation, which causes to decrease the short chain branches as well as vinyl-terminated polymers via P-hydride elimination. Consequently the long chain branch formed by the copolymerization of ethylene with the vinyl terminated polymers also decreases and linear polyethylene is obtained. 4. CONCLUSIONS The anilinonaphthoquinone-ligated nickel complex 1 activated by B(C6F5)3 conducted ethylene polymerization with high activity and gave branched and linear polymers depending on the polymerization temperature. Acknowledgments The authors are grateful to Tosoh-Finechem Co., Ltd., for donating Isoper-E solution of B(CfiF5)3. The NMR measurement was made at the Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University. Reference [I] L. K. Johnson, C. M. Killian, M, Brookhart, J, Am. Chem. Soc. 117 (1995) 64145415. [2] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. 38 (1999) 428447. [3] S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 100 (2000) 1169-1203. [4] L. S. Boffa, B. Novak, Chem. Rev. 100 (2000) 1479-1494. [5] S. Mecking, A. Held, F. M. Bauers, Angew. Chem. Int. Ed. 41 (2002) 544-561. [6] ¥. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [7] S. A. Svejda, L. K. Johnson, M. Brookhart, J. Am. Chem. Soc. 121 (1999) 1063410635. [8] D. P. Gates, S. A. Svejda, E. Oflate, C. M. Killian, L. K. Johnson, P. S. White, M. Brookhart, Macromolecules 33 (2000) 2320-2334. [9] F. M. Zhu, W. Xu, X. Liu. S. Cin, J. Appl. Polym. Chem. 84(2002) 1123-1132. [10] H. Zou, F. M. Zhu, Q. Wu, J. Y. Ai, S. A. Lin, J. Polym. Sei. Part A: Polym. Chem. 43 (2005) 1325-1330. [II] M. Okada, T. Ikeda, T. Shiono, Preprints of The 8th SPSJ International Conference (2005) 509.


175

27

Ring Opening Metathesis Polymerization of Norbornene Catalyzed by V(CH2SiMe3)2(N~2,6Me2C6H3)(N=C'Bu2). In situ generation of the Vanadium-Alkylidene Kotohiro Nomura* and Junji Yamada Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract (Arylimido)(ketimide)vanadium dialkyl complex, V(CH2SiMe3)2(N-2,6Me2C6H3)(N=CfBu2) (1) could be prepared by reaction of the diehloride with two equivalent of LiCH2SiMe3 in high yield, and the complex was identified by 'H, I3C, S 1 V NMR spectra. Complex 1 showed relatively high catalytic activity for ring-opening metathesis polymerization of norbornene, and the activity increased upon the addition of PMej. Remarkable increase in the activity was observed at higher temperature, and these results suggest the formation of the vanadium-alkylidene complex, V(CHSiMe3)(N-2,6-Me2C6H3)(N=C'Bu2)(PMe3), which could be isolated upon heating the C6D6 solution containing 1 and PMe3. 1. INTRODUCTION Olefin metathesis such as ring-opening metathesis polymerization (ROMP), ring-closing (RCM) and cross metathesis (CM) reaction [1-4] have attracted considerable attention due to the promising possibility for application not only to polymer synthesis but also to synthesis of valuable organic compounds [1-4], Successful examples have been demonstrated by molybdenum [5], ruthenium [6,7], however, the examples with vanadium complexes have been limited. We recently reported that ROMP of norbornene (NBE) by (ArN)V(CH2Ph)2(O-2,6-'Pr2C6H3) (Ar = 2,6-Me2C6H3) took place to afford ultra high molecular

176

K. Nomura andJ. Yamada

weight polymer with a unimodal molecular weight distribution [8]. We also communicated that vanadium(V)-alkylidene, (ArN)V(=CHSiMe3)(L)(PMe3) (2, L = N=C'Bu2), has been isolated from (ArN)V(CH2SiMe3)2(L) (1) by othydrogen elimination, and 2 initiated ROMP of NBE [9]. Since the dialkyl analogue, 1, which could be prepared in high yield from the dichloro analogue, also initiated ROMP of NBE, yielding high molecular weight polymers with unimodal molecular weight % distributions, we explored the ^-P---, 1 + PMe3 ROMP by 1 (in situ generation ^J~~^f **" system) for more detail (Scheme 1). 1: (ArN)V(CH2S!Me3)2(N=CfBu2) 2. EXPERIMENTAL Scheme 1 All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox or using standard Schlenk techniques. All chemicals used were reagent grade and were purified by the standard purification procedure. Anhydrous-grade benzene, diethyl ether and «~hexane (Kanto Kagaku Co., Ltd,) were transferred into a bottle containing molecular sieves (a mixture of 3A, 4A 1/16, and 13X) in the drybox under N2, and were then passed through an alumina short column before use. Polymerization grade toluene was distilled from sodium and benzophenone, stored over a sodium/potassium alloy in drybox, and then passed through an alumina short column before use. 3. RESULTS AND DISCUSSION The reaction of (ArN)VCl2(L) with LiCH2SiMe3 in R-hexane afforded (ArN)V(CH2SiMe3)2(L) (1) in high yield (95 %), and the complex was identified by ]H-, 13C-, 51V-NMR spectra and elemental analysis [9], The coordination of PMe3 to 1 was not observed even by addition of excess amount (7.0 equiv.) at 25 °C, and this observation might be due to the steric hindrance of rather bulky CH2SiMe3 group around the V metal center. The complex 1 initiated ROMP of NBE in toluene (Table 1), and the activity increased especially upon addition of PMe3 (runs 3-6). This might be due to the more efficient formation of the vanadium-alkylidene (2) in the reaction mixture. However, the activity decreased upon further addition (run 7), and this can be assumed that the coordination of PMe3 into the vanadium metal center retards the propagation (coordination of NBE), leading to lower activities. Note that the observed catalytic activity (in the presence of PMe3) notably increased at higher temperature, and the higher activity was observed even at 80 °C whereas the significant decrease in the activity due to the decomposition was observed if RuCla(CHPh)(PCy3)2 (Cy = cyclohexyl) was used in place of 1 (run 17). The activity was also affected by the NBE concentration, and the

27. ROMP ofNorbornene Catalyzed by r(CH2SiMe^(N-2,6-Me2CsH3)(N=C?Bui)

177

resultant polymer possessed rather broad but unimodal molecular weight distributions probably due to the rapid propagation compared to the slow initiation. This assumption can be realized from the fact that the resultant polymer by 2 possessed narrow molecular weight distribution and that the observed activity by 2 was much higher than those by 1 (run 16). Table 1. ROMP of NBE with V(CH2SiMe3)2(NAr)(N=CtBua) (1), or RuCl2(CHPhXPCy3)2 (Ru). a run

complex

NBE

NBE

P/Vc

temp.

time

TONd

rc

/h

...

25

1

1306

0.89

3

25

6

1.6

4.24

0.89

...

50

6

0.5

1 (20.0)

4.24

0.89

3

50

3

61

5

1 (10.0)

4.24

0.89

3

50

6

140

6

1 (10.0)

4.24

0.89

3

50

6

150

7

1 (10.0)

4.24

0.89

5

50

6

66

80

6

6.8

(umol)

/mmol

1

Ru(l.O)

2

b

2.12

cone. 0.22

1 (10.0)

2.12

3

1 (20.0)

4

MJMf 4

xlO" 54

1.7

26.1

5.4

48.1

4.0

g

1 (20.0)

4.24

0.89

...

9

1 (20.0)

4.24

0.89

3

80

1

61

10

1 (10.0)

4.24

0.89

3

80

3

378

60.3

5.4

f

87

3.2

11

1 (10.0)

2.12

0.44

3

80

3

212

12

1 (10.0)

1.06

0.22

3

80

3

101

97

3,0

13

1 (10.0)

2.12

0.44

5

80

3

40

47

3.0

14

1 (10.0)

4.24

0.89

5

80

3

183

69

3.7

15

1 (10.0)

4.24

0.89

5

80

6

285

16

2(1.Of

2.12

0.22

—

80

1

1583

133

1.4

17

Ru(l.O)

2.12

0.22

—

80

1

350

"Conditions: NBE 1.06-4.24 mmol, toluene. Initial NBE concentration in mmol/mL, cMolar ratio ofPMej/V. d*TON TON = NBE consu consumed (mmol)/V (mmol). BGPC data vs polystyrene standards. 'Completion of polymerization.

Resultant polymer possessed ring-opened structure containing a mixture of cis- and trans- olefmic double bonds, as shown in Figure 1, and the fact was somewhat different from those observed in the ROMP by (ArN)VCl2(O-2,6- AlMe3 catalyst system [8]. This would be assumed as due to the

178

degree of synlanti rotamer (rotational isomer or rotamer) and/or the mode of NBE coordination into the vanadium metal center proposed by the molybdenum-alky lidene catalyst [5]. Taking into account the above results, it is clear that the present catalyst system displays unique characteristic as thermally robust transition metal alkylidene which shows remarkable reactivity toward cyclic olefrns especially at higher temperature.

K. Nomura andJ. Yamada

cis

trans

5.5

5.3

5.1 5 .1

m ppm PP

Figure 1. 'H NMR spectra (CDC13) for ringopened poly(norbomene) prepared by 1 ~ PMe3 (3.0 eq) catalyst.

Acknowledgements This research is partly supported by Tokuyama Science Foundation, and authors express their thanks to Prof. Michiya Fujiki (NAIST) for helpful discussions. J.Y. expresses his thanks to the JSPS for a predoctral fellowship (No. 5042). References [1] R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol. 1-3. [2] E. Khosravi, T. Szymanska-Buzar (Eds.), Ring-Opening Metathesis Polymerisation and Related Chemistry, Kluwer, Dordrecht, 2002. [3] Y. Imamoglu, L. Bencze, (Eds.), Novel Metathesis Chemistry: Well-Defined Initiator Systems for Specialty Chemical Synthesis, Tailored Polymer and Advanced Material Applications, Kluwer, Dordrecht, 2003. [4] M. R. Buehmeiser, Chem. Rev. 100 (2000) 1565. [5] R. R. Schrock, in: R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol. 1, p 8. [6] T. M. Trnka, R. H. Grubbs, Ace. Chem. Res., 34 (2001) 18. [7] S. T. Nguyen, T. M. Trnka, R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol 1, p 61. [8] K. Nomura, A. Sagara, Y. Imanishi, Macromoleeules 35 (2002) 1583. Examples for ROMP by vanadium catalysts were cited therein. [9] J. Yamada, M, Fujiki, and K. Nomura, Organometallics 24 (2005) 2248. Detailed analysis results are shown in the Supporting Information.


179

28

Ethylene/2~Methyl-l-Pentene Copolymerization Catalyzed by Half-Titanocenes Containing Aryloxo Ligand: Effect of Cyclopentadienyl Fragment Kotohiro Nomura* and Koji TtagaM Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Efficient incorporation of 2-methyl-l-pentene (2M1P) has been observed in copolymerization of ethylene with 2-methyl-l-pentene (2M1P) using Cp*TiCl2(O-2,6-TJr2C6H3) (1) - MAO catalyst, and the resultant polymers were poly(ethylene-co-2MlP)s that possessed high molecular weights with unimodal molecular weight distributions as well as with uniform 2M1P incorporation. The tert-BuCp analogue, ('BuCsH4)TiCl2(O-2,6-'Pr2CsH3) (2), showed less efficient 2M1P incorporation than 1, whereas 2 showed better 1-hexene incorporation in ethylene/1-hexene copolymerization. The steric bulk in both 2M1P and the cyclopentadienyl fragment thus affected the comonomer incorporation in this copolymerization. 1. INTRODUCTION Evolution of new polyolefins prepared by newly designed polymerization catalysts is one of the most attractive subjects in the field of metal catalyzed coordination polymerization, because new properties that have never been observed by conventional catalysts can be highly expected [1,2] especially by the precise placement of chemical functionality and/or substituent. Only a few examples were reported for copolymerization of ethylene with isobutene (IB) using linked (amide)(cyclopentadienyl)titanium complex catalysts called constrained geometry catalyst [3-4], and the IB content was low ( N B muJTCD Contents ( n o l « . )

in

Figure 2. Refractive Index of copolymers at various copolymer compositions

The RI of E/TCD copolymer was higher than that of E/NB copolymer. The RI of E/NB copolymer less changed with NB contents, while, the RI of E/TCD copolymer increased with increasing of TCD contents. The thermo-optic coefficient (TOC) was calculated from RI of copolymers at various temperatures[5], and that was found that TOC values (~ 3.0 x 10"5/°C) of COC were lower than other amorphous polymers. References [1] G. Khanarian, Opt. Engineer., 40 (2001) 1024. [2] D.H. Lee, Y.Y. Choi, J.H. Lee, Y.S. Park, and S.S. Woo, e-Polymers, (2001) no. 019. [3] J.Y. Shin, J.Y. Park, C. Liu, J. He, S.C. Kim, Pure Appl. Chem., 77 (2005) 801. [4] I. Tritto, L. Boggioni, M.C. Sacchi, P. locatelli, D.R. Ferro, A. Provasoli, Macromol. Rapid Commun., 20 (1999) 279. [5] Y.L. Lo, C.P. Kuo, IEEE Trans. Adv. Packag., 25 (2002) 50.


189

30

Effects of Temperature in Syndiospecific Living Polymerization of Propylene with [^-BuNSiMe2(3,6*-Bu2Flu)]TiMe2-MMAO Catalyst Zhengguo Cai, Nakayama Yuushou, Takeshi SMono* Graduate School of Engineering, Hiroshima University, Kagamiyama I-4-l, HigashiHiroshima 739-8527, Japan

Abstract Propylene polymerizations were conducted by [/-BuNSiMe2(3,6~£Bu2Flu)]TiMea using trialkylaluminum-free modified niethylaluminoxane as a cocatalyst in toluene at -20, 0 and 25 °C. The raise of polymerization temperature improved the activity to produce 2400 kg of polymer per mole of Ti per hour at 25 °C, and the post-polymerization testified that the propylene polymerization proceeded in a living manner regardless of the polymerization temperature. The polymerization temperature also influenced the stereoregularity of the polypropylenes (PP). The system gave syndiotactic crystalline PP at -20 °C with a melting point of 129 °C and amorphous PP at 25 °C, respectively. 1. INTRODUCTION Single-site catalysts based on group 4 metallocene complexes have been investigated for the development of new olefin polymerization catalysis [1,2]. Intense effort has been paid to elucidate the effects of polymerization conditions (cocatalyst, monomer concentration, solvent, temperature, etc.) on the polymerization behaviour. Polymerization temperature is one of the most important factors that largely influence the activity and the stereospecificity. We have previously reported that [r-BuNSiMe2(3,6-£-Bu2Flu)]TiMe2 (1) activated by trialkylaluminum-free modified methylaluminoxane (dMMAO) conducted highly syndiospecific living polymerization of propylene in heptane at 0 °C[3].

190

Z.Caietal

In the present work, we investigated the effects of polymerization temperature on the syndiospecificity of the present catalyst in toluene. 2. EXPERIMENTAL Materials. All operations were performed under argon gas using standard Schlenk techniques and all solvents were dried by usual procedures and freshly distilled before use. The complex 1 and dMMAO were prepared according to the procedures reported previously[3,4]. Research grade propylene (Takachiho Chemicals Co.) was purified by passing it through columns of NaOH, PaOj, and molecular sieves 3 A, followed by bubbling it through a NaAlH2Et2/l,2,3,4,tetrahydronaphthalene solution. Polymerization Procedure. Polymerization was performed in a 100 mL glass reactor equipped with a magnetic stirrer and carried out by the following methods. After a certain amount of dMMAO solution in toluene had been saturated with an atmospheric pressure of propylene, polymerization was started by the addition of 1 mL solution of 1. Polymerization was conducted for a certain time and terminated with acidic methanol. The polymers obtained were adequately washed with methanol and dried under vacuum at 60 °C for 6 h. Analytical Procedures. Molecular weight and molecular weight distribution of polymer obtained were determined by gel permeation chromatography with a Waters 150 CV at 140 °C using o-dichlorobenzene as a solvent. The parameters for universal calibration were K = 7.36 x 10"s, a- 0.75 for polystyrene standard and K = 1.03 x 10"4, cr = 0.78 for PP samples. The 13C NMR spectra of PPs were measured at 130 °C on a JEOL JNM-400 spectrometer operated at 400 MHz in the pulse Fourier-Transform mode. The pulse angle was 45° and about 10 000 scans were accumulated in pulse repetition of 5.0 s. Sample solutions were prepared in I,l,2,2-tetrachloroethane-d2 and the central peak of the solvent (74.47 ppm) was used as an internal reference. Differential scanning calorimetry (DSC) analyses were performed on a Seiko DSC-220 and the DSC curves of the samples were recorded under a nitrogen atmosphere with a heating rate of 10 °C/min from 20-200 °C. 3. RESULTS AND DISCUSSION 3,1. Propylene polymerization at various temperatures Propylene polymerizations were conducted with 1-dMMAO in toluene at -20 °C, 0 and 25 °C by a semi-batch method. Polymerization was quenched before the produced polymer would interrupt effective stirring according to the

JO. Effects of Temperature on Living Polymerization ofPropylene

191

polymerization temperature. The results are summarized in Table 1. The catalytic system gave the polymers with comparatively narrow molecularweight distribution (MWD) regardless of the polymerization temperatures. The raise of polymerization temperature enhanced the activity but did not affect the number of polymer chains (N), which was about 60 - 65 % of the Ti used. These results suggest that the catalytic system should conduct living polymerization of propylene. To investigate the living nature of 1-dMMAO at these temperatures, we conducted post-polymerization by a batch method. The results of the post-polymerization indicate that the propylene polymerization proceeded in a living manner in toluene at -20, 0 and 25 °C. Table 1 Results ofPropylene Polymerization with 1-dMMAO entry

temp.

time

yield

activity h

Mnc

MJMn* 4

(xlO )

Nd

rf

T

r

fC)

(°C)

(min)

(g)

1

-20

8

0.76

285

6.5

1.35

12

0.90

129

2

0

4

2.36

1768

18.8

1.36

13

0.83

100

3

20

3

2.42

2420

17.9

1.32

13

0.60

Qimol)

a

Polymerization conditions: toluene = 30 mL, Ti = 20 junol, Al = 4.0 mmol, propylene =1,0 atm. Activity in kg-PP/(mol~Ti»h). c Number average molecular weight and molecular weight distribution determined by GPC using universal calibration. d Calculated from yield and Mn. e Determined by I3C NMR. f Melting temperature determined by DSC. BNot detected.

b

3.2. Structures of Polypropylene® obtained at various temperatures The steric pentad distributions were determined from the resonances of methyl carbons in 13C NMR spectra, and the results are shown in Table 2. The PP obtained at -20 °C showed the highest syndiotactic pentad value (rrrr) of 0,90, which decreased according to the raise of polymerization temperature to 0.83 at 0 °C and 0.60 at 25 °C. Consequently the PP obtained at -20 °C was crystalline polymer with melting point of 129 °C, whereas that obtained at 25 °C was amorphous one. In the enantiomorphic-site controlled syndiospecific polymerization with a Cs symmetric catalyst, two types of stereodefects should be formed: one is "rmrr" arising from the "chain migration" without monomer insertion and the other is "rmmr" arising from the "monomer miss-insertion" [5]. Table 2 indicates that rmrr content was increased by the raising polymerization temperature, -20 °C (0.02) < 0 °C (0.10) < 25 °C (0.23), whereas the rmmr content was almost constant and slightly increased only at 25 °C, -20 °C (0.02) = 0 °C (0.02) < 25 °C (0.04). These results imply that the decrease of the syndiospecificity caused

192

ZCaietal

by raising the temperature is mainly attributed to the frequent "chain migration". The similar phenomena were observed in the syndiospecific propylene polymerization with Cs-symmetric zirconocene catalysts[6-8]. Table 2 Stene Pentad Distributions of Polypropylenes Obtained at Various Temperatures Steric pentad content

entry (temp)

mmmfli

mmmr

rmmr

mnirr

TO

rmrr +

nnrni

rrrr

mrrr

mrrm

mmrm

1 (-20)

0.00

0.00

0.02

0.05

0.02

0.01

0.83

0,07

0.00

2(0)

0.00

0.00

0.02

0.04

0.10

0.01

0.70

0.13

0.00

3(25)

0.00

0.01

0.04

0.09

0.23

0.06

0.39

0.20

0.01

"Determined by 13C NMR.

4. CONCLUSIONS The effects of polymerization temperature were investigated in propylene polymerization by 1-dMMAO in toluene under an atmospheric pressure of propylene. The activity increased by raising the temperature from -20 °C to 25 °C with keeping living polymerization accompanied by the decrease of the syndiospecifieity. The system gave syndiotactic crystalline PP with a melting point of 129 °C at -20 °C and amorphous PP at 25 °C. Acknowledgements This work was supported by the New Energy and Development Organization (NEDO) for the Project on Nanostructured Polymeric Materials. We thank Tosoh-Finechem Co. for donating MAO. References [1] W. Kaminsky, Advances in Catalysis 46 (2001) S9-159. [2] V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [3] Z. Cai, T. Ikeda, M. Akita, T. Shiono, Macromolecules 38 (2005) 8135-8139. [4] H. Hagimoto, T. Shiono, T. Ikeda, Macromol. Rapid. Common. 23 (2002) 73-76. [5] J. A. Ewen, M. J. Elder, R. L. Jones, L. Haspeslagh, J. L. Atwood, S. G. Bott, and K. Robinson, Makromol, Chem., Macromol. Symp. 48/49 (1991) 253-295. [6] J. A. Ewen, M. J. Elder, R. L. Jones, S. Curtis, H. N. Cheng, Stud. Surf. Sci. Caial. 56 (1990) 439-412. [7] D. Veghini, L. M. Henling, T. J. Burkhardt, J. E. Bercaw, J. Am. Chem. Soc. 121 (1999) 564573. [8] M.-C. Chen, T. J. Marks, J. Am. Chem. Soc. 123 (2001) 11803-11804.


193 193

31 Copolymerteation of Styrene Derivatives and Cycloolefin with Ni Compound/MAO Catalyst Naoya Nishimura, Katsuya Maeyama, Akinori Toyota* Graduate School of Engineering, Tokyo University of Agriculture and Technology, 224-16 Naka-eho, Koganei-shi, Tokyo 184-8588, Japan, email: [email protected],ac,jp

Abstract Copolymerization of styrene derivatives, such as 4-tert-hutylstymne (4TBS), 4-methylstyrene (4MS), 4-methoxystyrene (4MOS), 4-bromostyrene (4BS), and 5-ethylidene-2-norbomene (ENB) was conducted with nickel (Ni) compound/methylaluminoxane (MAO) catalysts. Polymerization behaviors and properties of the resulting copolymers were investigated. Nickel bis(acetylacetonate) (1) / MAO showed the highest activity. Ts values of the obtained copolymers reached to ca. 300 °C. 1. INTRODUCTION Recently, papers related to copolymerization of cycloolefin and olefms have been reported[l,2], Cycloolefin copolymers have been attractive because they have the excellent properties such as high glass transition temperature, high optical transparency, low birefringence, and low moisture absorption. Copolymerization of cycloolefin with styrene has also been investigated because it is easy to obtain copolymers with higher glass transition temperature than the copolymers derived from cycloolefin/olefin. However few reports have been known on copolymerization of cycloolefin with styrene derivatives[3,4]. In this paper, we would like to report the studies on the effects of the catalyst structure and those of polymerization conditions on the activities and copolymerizability in the copolymerization with Ni compound/MAO catalysts.

194

JV. Nishimura et al.

2. EXPERIMENTAL All procedures were conducted with using Schlenk techniques under nitrogen atmosphere. Styrene derivative and ENB were placed in a 50-ml flask, and then a nickel compound (2.5 X 10"6 mol) and MAO (2.5 X 10"3 mol) were sequentially charged into the flask. The reactions were carried out at room temperature for 24 h. After completion of the reaction, excess methanol was added. The resulting polymers were purified by reprecipitation with a system of CHCls/methanol and the polymer precipitates were dried in vacuum.

CH 3

CH 3

Ni(acac)2 1

Ni stearats

bis(3,5-di-terf-butylsalicylidene}1,2-cyclohexadiamino nickel 2 3 Figure 1 Ni compounds used for copolymerization

3. RESULTS AND DISCUSSION Results of 4TBS-ENB copolymerization are shown in Table 1. 4TBSENB copolymers were obtained with all nickel compound/MAO catalysts. M(acac)2 (1) /MAO catalyst showed the highest activity among the three types of nickel compounds. ENB contents increased with increasing ENB in feed. ENB contents in copolymers were in the range from 1 4 - 5 5 mol %. This is probably due to bulkiness of 4TBS. Number average molecular weight was low, and polydispersiry was narrow. The Tg values of copolymers increased with increasing ENB content in the copolymer and reached to ca. 300 °C. Relation of between Te and ENB content in the copolymer is shown in Figure 2.

31. Copolymerization ofStyrene Derivatives and Cycloolefin with Ni compdJMAO 195 Table 1 Copolymerization of 4TBS and ENB with Ni compound/MAO catalyst* ENB in feed

ENB content0

b

entry

catalyst

1

1

10

2.38

33.8

3.9

2.8

189

2

1

30

1.94

39.0

3.6

1.6

200

3

1

50

3.54

47.6

4.1

1.8

218

4

1

70

1.47

53.4

3.8

1.8

227

5

2

10

1.00

24.8

4.7

1.4

169

6

2

30

0.870

34.6

4.4

1.6

220

7

2

50

1.09

47.1

4.4

1.5

234

8

2

70

0J36

52.4

4.2

1.6

296

9

3

10

0.976

14.6

3.3

1.3

164

10

3

30

2.39

29.8

4.3

1.7

176

11

3

50

2.61

35.5

4.5

1.8

196

12

3

70

1.86

55.8

4.1

1.8

244

Activity

(xlO3)

TO

"Polymerization conditions: total volume = 25 mL, solvent = toluene, Ni = 2.5 ^mol, Al /Ni= 1000, temperature = r.t., time = 24 h. hactivity = kg (p^) mol ^'l h"1, "determined by 'H-NMR, number average molecular weight and molecular weight distribution were determined by GPC using polystyrene standards, 'determined by DSC. 350 350 300 300 -250 250

Tg [oC]

Copolymerization of 4MS and ENB with three types of Ni/MAQ catalysts afforded copolymers. Copolymerization of 4BS and 4MOS with ENB was investigated with using Ni (1)/MAO catalyst. Correlations between Tg and ENB content are shown in Figures 3 and 4. On the other hand, 4MOS homopolymer was obtained in copolymerization of 4MOS and ENB. This polymerization probably proceeds via cationie polymerization predominantly.

8°'

D

200 150 150 100 -_ 100

O

Ni(acac)2

1 l Ni stearate Ni (salen)

50 50 0

10 10

20 20

30 30

40 40

50 50

ENB content [mol%]

Figure 2 Fg vs. ENB content for poly (4TBS-co-ENB)

60

196

N. Nishimura et al. 350 350

350

300 300

300 -

.

2000 20

o

„ 250 O

Tg [oC]

Tg [oC]

2500 25

o

f-M 200 -

150 150 100 - °CP 100

o n

A

50

00

10 10

20 20

30 30

050 150

Ni(acac)22 Ni stearate Ni (salen)

40 40

50 50

ENB content [mol %] %] Figure 3 Tg vs. ENB content for poly (4MS-CO-ENB)

< 60 60

100 inn

00

4BS-ENB

10 10

20 20 30 30 40 40 50 ENB content [mol %] %]

60

Figure 4 Tg vs. ENB content for poly (4BS-CO-ENB) obtained with Ni(acac)2 /MAO catalyst

4BS-ENB copolymers were obtained with Ni(acac)2/MAO catalyst. The Tg values of copolymers ranged from 120 to 220 °C. These copolymers have possibilities to be modified at bromo group and to be converted to functional polymers. 4. CONCLUSIONS Copolymerization of styrene derivatives and ENB was studied with using three types of nickel compounds-MAO catalysts. The catalysts showed low activity for the copolymerization, but copolymers having high Tg values in range of 90 to 300 °C were obtained. References [1] T. Hasan, T. Ikeda, and T. Shiono, Macromolecules 38 (2005) 1071-1074. [2] J. Forsyth, J. M. Perena, R. Benavente, E. Perez, 1 Tritto, L. Bogginoni, and H. H. Brintzinger, Macromol. Chem. Phys. 202 (2001) 614-620. [3] H. Suzuki, S. Matsumura, Y. Satoh, K. Sogoh, and H. Yasuda, React. Fund Polym, 58(2004)77-91. [4] C. Zhao, M.R. Ribeiro, M. F. Portela, S. Pereira, and T, Nunes, Eur, Patym. J. 37(2001)45-54.


197

32

Additive Effects of Dialkylaluminum Hydrides on Propylene~l,3-Butadiene Copolymerization Using an Isospecific Zirconocene Catalyst Takeshi Ishihara,a Hoang The Ban,a Hideaki Hagihara,b Takeshi Shionoc a

Japan Chemical Innovation Institute, AIST Tsukuba, Central 5-8, 1-1-1 Higashi, Tsukuba, Iharaki 305-8565, Japan b National Institute of Advanced Industrial Science and Technology, Tsukuba, Central 5-8, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan e Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan

Abstract Additive effects of dialkylaluminum hydrides on propylene-l,3-butadiene copolymerization were investigated with an isospecific zirconocene catalyst, rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride (4Ph), activated by modified methylaluminoxane. Dialkylaluminum hydrides improved the apparent selectivity for 1,2-insertion of 1,3-butadiene to give a pendant vinyl group. 13C NMR analysis of the eopolymers indicated that the dialkylaluminum hydride converted the 1,4-inserted butadiene unit in the copolymer to tetramethylene unit after methanolysis. 1. INTRODUCTION Polypropylene (PP) has been expanding its usage due to its mechanical balance and economical advantage. PP is, however, so hydrophobic that many attempts have been made to improve affinity of PP with other polar materials [1-2]. We have been developing copolymerization techniques to control the amount and location of polar groups in PP chain and succeeded in the selective introduction of carbon-carbon double bond as a precursor of polar group by the copolymerization of propylene and 1,3-butadiene using isospecific zirconocene

198

T. Ishihara et al,

catalysts [3-4]. The addition of hydrogen was found to hydrogenise the 1,4inserted butadiene units (1,4-BD) in the copolymer, and selectively produced PP with pendant vinyl groups. In this paper, therefore, we investigated the additive effects of dialkylaluminum hydrides on the copolymerization whether the dialkylaluminum hydrides react with 1,4-BD to produce PP having dialkylaluminum group on the main chain of the copolymer or not. 2. EXPERIMENTAL Materials. 4Ph commercially obtained from Boulder Scientific Company, and modified methylaluminoxane (MMAO) and other aluminum compounds purchased from Tosoh-Finechem. Co., were used without further purification. Other chemicals commercially obtained were purified according to the usual procedures. Polymerization procedure, Copolymerization of propylene with 1,3-butadiene was conducted in a 100-mL stainless steel autoclave by batch-wise operation at 0°C. Analytical procedures, 'H TSTMR and I3C TSTMR spectra were obtained in 1,1,2,2tetrachloroethane-d2 at 120 °C on a JEOL JNM-LA600 spectrometer. Molecular weights and molecular weight distributions of the copolymers were determined by a PL-GPC210 at 140 °C using o-dichlorobenzene as a solvent. 3. RESULTS AND DISCUSSION 3.1. Results of copolymerization The results of propylene-l,3-butadiene copolymerization using 4Ph-MMAO system are summarized in Table 1.

the

Table 1. Additive effects of aluminum compounds on propylene— 1,3-butadiene copolymerization*

additive

Yield (B)

Rsp (kgpolymer / mol-Zr»h) 13.1 15.8 35.8

(xlO3)

MJ Mnb

Mole fraction6 (%) 1,21,4H-1,4 BD BD -BD 1.43 0.76 0 0.23 1.26 0.63 0.26 0.4S 1.59

Selectivity {%) i *} nn

nan 0.08 2.4 65.3 35.7 84.6 0.1 34.2 DEAL-H 1.6 0.21 85.9 3.9 13.0 DiBAL-H "Polymerization conditions: solvent (toluene) = 40 mL, 4Ph = 2 jimol, MMAO = 4.0 mmol, 0 °C, 3 h, propylene concentration 1.8 mol / L, butadiene concentration 90 mmol / L. bNumber average molecular weight and molecular weight distribution determined by GPC using universal calibration.e Calculated from 'H and 13C NMR spectra. A Selectivities were the relative ratios of 1, 2—BD mole fractions to all double bonds.

32. Additive Effects ofDiatkylatuminum Hydrides

199

Dialkylaluminum hydrides, i.e., diethylaluminum hydride (DEAL-H) and diisobutylaluminum hydride (DiBAL—H), increased polymerization activities. The addition of DEAL-H did not affect the molecular weight (Mn) of the copolymer, whereas the introduction of DiBAL—H decreased the Ma value. An increase in polymerization activity accompanied by a decrease of molecular weight indicates that DiBAL-H caused chain transfer reaction. 3.2. Structures of copolymers The addition of the dialkylaluminum hydrides caused the decrease of 1,4—BD in the copolymer as observed in the *H NMR spectra (Fig. 1). The selectivity for 1, 2-BD in copolymers determined by 'H NMR are shown in Table 1.

I III-AI -II

Fig.l H NMR spectra of propylene- 1, 3- butadiene capolymer with and without DiBAL-H

[I'M

Fig, 2 " C NMR spectra of propylene-1, 3butadiene eopolymers synthesized with and without DiBAL-H.

The selectivity was improved from 65 to 85 % by the addition of the dialkylaluminum hydrides. To investigate the structures of copolymers in more details, we measured the 13C NMR spectra of copolymers obtained with and without DiBAL-H (Fig. 2). The signals assignable to pendant vinyl group and those to 1,4-BD structure were observed in both samples. The addition of DiBAL-H, however, caused the emergence of new signals derived from hydrogenated 1,4-BD (H-1,4-BD). The total mole fractions of 1,4-BD and H-1,4-BD were unchanged by the addition of the dialkylaluminum hydrides

200

T. Ishihara ct al.

(Table 1). The results indicate that the dialkylaluminum hydrides did not affect the mode of butadiene insertion but hydroaluminated the 1,4-BD units. A plausible copolymerization mechanism is shown in Scheme 1. Dialkylaluminum hydride and propylene competitively react with 7t-allyl Zr complex formed by 1,4-insertion of butadiene (A in Scheme 1). Insertion of propylene to A forms 1,4-BD in main chain (C), When dialkylalunium hydride reacts with A, hydroaluminated 1,4-BD is formed (B, D), which could incorporate successive propylene insertion more smoothly. The hydroaluminated 1,4-BD gives H—1,4—BD in main chain after methanolysis (E). Scheme 1 Reaction scheme &rpropylene-l,3-butadiene copolymerization with zirconocene— MMAO-dialkylaluminum hydride

4. CONCLUSIONS The 4Ph-MMAO-dialkylaluminum hydride system produced PP copolymer with pendant vinyl group. Although their selectivity of reduction from 1,4-BD to H—1,4—BD was lower than that with hydrogen [4], the copolymer possessed dialkylaluminum groups in main chain which can be utilized for functionalization of PP. Acknowledgements This work was supported by the New Energy and Development Organization (NEDO) through a grant for "Project on Nanostructured Polymeric Materials" under the Nanotechnology Program. References [1] T. C. Chung, Prog. Polym. Sci. 27 (2002) 39-85. [2] G. Moad, Prog. Polym. Sci. 24 (1999) 81-142. [3] T. Ishihara and T. Shiono, Macromolecules 36 (2003) 9675-9677. [4] T. Ishihara and T. Shiono, J. Am. Chem. Soc. 127 (2005) 5774-5775.


201

33

Pd Complex-Promoted Cyclopolymerization of Diallylmalonates Sehoon Park, Daisuke Takeuchi, Kohtaro Osakada* Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, 226-8503, Japan

Abstract Pd complexes prepared in situ from PdCl(Me)(diimine) and NaBARF (BARF = [B{CgH3(CF3)2-3,5}4]') initiate cyclopolymerization of isopropylidene diallylmalonate (I) in CH2CI2 to produce poly-I containing tmn$-\,2disubstituted cyclopentane groups. 1. INTRODUCTION The cyclopolymerization of nonconjugated dienes converts acyclic monomers into polymers with cyclic repeating units. The complexes of the early transition metals Ti, Zr, and Y catalyze the polymerization of 1,5-hexadiene and 1,6heptadiene to produce polymers with 1,3-disubstituted five- and six-membered cyclic repeating units.1 These polymers, however, consist of both trans- and eis-fused rings arranged randomly in a polymer chain. Stereoseleetive cyclopolymerization is of importance because polymers whose cyclic repeating units are arranged in a controlled manner exhibit unique properties such as a high Fm and a high Tg.2 The complexes of late transition metals such as Ru, Rh, and Pd have recently been reported to catalyze the cyclization of enynes and dienes.3'4 The Pd catalyst [PdCl(Me)(phen)]-NaBARF (BARF = [B{C6H3(CF3)2~3,5}4]~ catalyzes the cyclizative hydrosilylation and cycloisomerization of diallylmalonates to afford compounds with 1,2disubstituted trans-fused five-membered rings.5 The combination of the stereoselective ring formation and the insertion of a C=C bond of a diene, which occur alternately, produces the polymers with cyclic repeating units with a high

202

S. Park et al

regularity. In this paper, we report the Pd complex-catalyzed cyclopolymerization of diallyl malorates to produce polymers with fivemembered rings. A part of results were reported in a preliminary form.6 2. RESULTS AND DISCUSSION Pd complexes for the polymerization have been prepared in situ by addition of NaBARF (BARF = [B{C5H3(CF3)2-3,5}4]") to a CH2C12 solution of PdCl(Me)(diimme).7 Addition of isopropylidene diallylmalonate (I) to a solution of the catalyst prepared from la-NaBARF initiates cyclization polymerization of the diene to produce polymer -(CHj-CsHgfCsHgO^-CHaJn(poly-I) (eq. 1). The 'H NMR spectrum of poly-I, shown in Figure 1, indicates

1a: R1 = R2 = 'Pr, R3 = H 1b: R1 = R2 = R3 = Me

EtOOC

COOEt

+NaBARF CHaGI2 r.t.

Chart 1 poly-I

that the polymer consists of the repeating units with the five-membered ring. The ( H NMR signal at 3 1.95 (A) and the "C-^H} NMR signal at n 345.E are attributed to the CH2 d,e .0 group of the cyclopentane groups, while the CH group °^> f gives rise to 'H and 13C{'H} . 1 NMR signals at S 2.46 and S /- : 46.6-47.1, respectively. Sharp a e 4 2 os shape of the CH2 carbons of Figure 1. 1H NMR spectrum of poly-I in CDCI3 at 25 . Poly-I was prepared by polymerization of I in CHgClj under cyclopentane group and main Ar catalyzed by 1a/NaBARF ([Pd] = 10 mM, [la]/[Pd] = 70} chain indicates regulated at room temperature. The peaks with an asterisk are due stereochemistry of the produced to solvent. polymer. The JH NMR spectrum did not show signals in the region of vinyl hydrogens. CH carbon signals of the trans- and eis-cyelopentane-l,2-diyl group in the polymer obtained by the copolymenzation of 1,3-butadiene and ethylene are 8 46.5 and 43.2, respectively.8 The chemical shift of the CH carbon signal of poly-I (^46.6-47.1) is close to the trans repeating unit rather

33. Pd Complex-Promoted Cyclopofymerization of Dialfylmalonates

203

than cis repeating unit. This result indicates that the 1,2-disubstituted cyclopentane ring of the produced polymer adopts trans configuration quantitatively. The molecular weight of the polymer obtained by l a ([I]/[la] = 70) is estimated by GPC (polystyrene standard) to be Mn = 7900 (MJMn =1.51) (Table 1, run 1). Table 1 Polymerization of Diallyl Monomers by Pd Complexes" ran

monomer

Pd

solvent

time

conv.

(mL)

Mn

MJMn

(h)

(%)

1

I

la

0.5

48

80

8500

1.60

2

I

1b

0.5

12

82

9000

1.66

3

II

lb

0.25

24

22

5800

1.43

4

III

la

0.5

12

40

3600

1.28

5

1,6-heptadiene

lb

0.25

72

trace

-

-

6

diallyl ether

lb

0.25

72

trace

-

-

Reaction Conditions: Pd complex = 0.01 mmol, NaBARF = 0.012 mmol, [monomer]/[Pd] = 70, solvent = CHZC12, at r.t.

The Pd-catalyzed cyclization polymerization is applicable to other monomers listed in Chart 1 (Table 1). Diethyl diallylmalonate II, which does not have cyclic structure, also undergoes cyclization polymerization somewhat slowly to give the polymer having cyclopentane structure (run 3). Ill, which does not have carbonyl group, also polymerizes, although the polymerization get slower around 50% conversion (run 4), These results indicate that the cyclic structure and carbonyl group of the isopropylidene diallylmalonate are important for the smooth polymerization. On the other hand, 1,6-heptadiene and diallyl ether, which have no substituents between two vinyl groups of the monomers, do not give polymer (runs 5,6). These monomers with acyclic structures and without carbonyl groups do not produce high mass polymer because of chain walking of the Pd center during the reaction. Acknowledgements This work was supported by a Grant-in-Aid for Young Scientist No. 16750091 for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan.

204

S.Parketal.

References [1] (a) Y. Doi, N. Tokuhiro, K. Soga, Makromol. Chem. 190 (1989) 643. (b) L. Reseoni, R. M. Waymouth, J. Am. Chem. Soc. 112 (1990) 4953. (c) G. W. Coates, R. M. Waymouth, J. Am, Chem. Soc. 113 (1991) 6270. (d) M. R. Kesti, G. W. Coates, R. M. Waymouth, J. Am. Chem. Soc. 114 (1992) 9679. (e) C, J. Schaverien, Organometallics 13 (1994) 69. (f) M. Mitani, K. Oouchi, M. Hayakawa, T. Yamada, T. Mukaiyama, Chem. Lett. (1995) 905. (g) N. Naga, T. Shiono, T. Ikeda, Macromol. Chem. Phys. 200 (1999) 1466. (h) K. C. Jayarantne, R. J. Keaton, D. A. Henningsen, L. R. Sita, J. Am. Chem. Soc. 122 (2000) 10490. (i) P. D. Hustad, J. Tian, G. W. Coates, J. Am. Chem. Soc. 124 (2002) 3614. [2] (a) C. Janiak, P. G. Lassahn, Macromol. Rapid Commun. 22 (2001) 479. (b) I. Natori, K. Imaizumi, H. Yamaguehi, M. Kazunori, J. Polym. Sci. Part B. Polym, Phys. 36 (1998) 1657. [3] Reviews on cycloisomerization of dienes and enynes: (a) B. M. Trost, M. J. Krisehe, Synlett. (1998) 1. (b) G. C. Lloyd-Jones, Org. Bio. Chem. 1 (2003) 215. [4] Pd-catalyzed cycloisomerization of dienes: (a) R. Grigg, T. R. B. Mitchell, A. Ramasubbu, J, Chem. Soc. Chem. Commun. (1979) 669. (b) R. Grigg, J. F. Malone, T. R. B. Mitchell, A. Ramasubbu, R. M. Scott, J. Chem. Soc. Perkin Trans, 1 (1984) 1745. (c) B. Radetich, T. V, RajanBabu, J. Am. Chem. Soc. 120 (1998) 8007. (d) A. Heumann, M. Moukhliss, Sylnett (1998)1211. (e) K. L, Bray, I. J. S. Fairlamb, G, C. Lloyd-Jones, Chem. Commun. (2001) 187. (f) K. L. Bray, J. P. J. Charmant, I. J. S. Fairlamb, G. C. Lloyd-Jones, Chem. Eur. J. 7 (2001) 4205. (g) K. L. Bray, I. J. S. Fairlamb, J.-P. Kaiser, G. C. Lloyd-Jones, P. A. Slatford, Top. Cat. 19 (2002) 49. (h) A. Heumann, L. Giordano, A. Tenaglia, Tetrahedron Lett. 44 (2003) 1515. (i) A. Cortna, H. Garcia, A. Leyva, J. Organomet. Chem. 690 (2005)2249. [5] (a) R. A. Widenhoefer, M. A. DeCarli, J. Am. Chem. Soc. 120 (1998) 3805. (b) N. S. Perch, P. Kisanga, R. A. Widenhoefer, Organometallics 19 (2000) 2541. (c) N. S. Perch, R. A. Widenhoefer, J. Am. Chem. Soc. 126 (2004) 6332. (d) R. A. Widenhoefer, Ace. Chem, Res. 35 (2002) 905. [6] S. Park, D. Takeuchi, K. Osakada, J. Am. Chem. Soc. in press. [7] (a) L. K. Johnson, C. M. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414. (b) C. M. Killian, D. J. Tempel, L. K. Johnson, M. Brookhart, J. Am. Chem. Soc. 118 (1996) 11664. (c) D. J. Tempel, L. K. Johnson, R. L. Huff, P. S. White, M. Brookhart, J. Am. Chem. Soc. 122 (2000) 6686. (d) D. P. Gates, S. A. Svejda, E. Onate, C. M. Killian, L. K. Johnson, P. S. White, M. Brookhart, Macromolecules 33 (2000) 2320. [8] T. N. Choo, R. M. Waymouth, J. Am. Chem. Soc. 125 (2004) 8970.


205

34

Synthesis of Polymeric Radical Scavengers via ROMP of Norbornene Derivatives and Their Antioxidation Activities Kogen Horikawaa, Katsuya Maeyama3 and Akinori Toyota" "Graduate School of Engineering, Tokyo University of Agriculture and Technology, 224-16 Naka-cha, Kaganei, Tokyo 184-8588, JAPAN

Abstract We studied on polymerization behavior of norbomene derivatives containing 3,5~di~ferf-butyl-4-hydroxybenzoyl (DBH) groups via ring-opening metathesis polymerization (ROMP) and radical scavenging activities of the resulting polymers. New norbornene derivatives containing DBH group, i.e., 5,5BBHBN (2) and 5,6-BBHBN (1) as shown in Fig, 1 were synthesized, ROMP of these norbomene derivatives were performed by using of ruthenium trichloride hydrate and Grubbs catalyst. In order to measure radical scavenging activities (RSA) of the homopolymers and copolymers of the norbornene derivatives, cast films of the polymers were contacted with DPPH-methanol solution, RSA values of poly(5,5-BBHBN) and poly(5,6-BBHBN) were twice or more as high as those of poly(BHBN). 1. INTRODUCTION The polymeric radical scavengers are desired as easily separable antioxidant or as films having antioxidation activity. Tlenkopatchev and co-workers reported homopolymerization and copolymerization of norbomene with norbomene derivatives having 3,5~di-ferf-butyl~4-hydroxybenzoyl (DBH) group[l,2]. However, effects of structures of the norbomene derivatives upon the polymerization behavior were not reported. Radical scavenging activities of the polymers having DBH groups were not also reported.

206

K. Harikawa et al.

We would like to report studies on the ROMP behaviors of 5,5-BBHBN and 5,6-BHBN, and the radical scavenging activities of the resulting polymers from both new monomers. 2. EXPERIMENTAL Two new norbornene derivatives containing two DBH groups, 5,5BBHBN(2) and 5,6-BBHBN(l) were synthesized via esterification reaction (Fig. 1) of alcohols having norbornene rings with 3,5-di-tert-butyl-4-hydroxybenzoyl chloride(4). BHBN(3), having one DBH group, was also synthesized. These norbornene derivatives were homopolymerized and copolymerized with norbornene by using Grubbs catalyst (bis(tricyclohexylphosphine) benzylidene ruthenium dichloride) and ruthenium trichloride hydrate. The resulting homopolymers and copolymers were purified with reprecipitation. In order to measure of radical scavenging activity, cast films (1.4 mg) of the polymers were contacted to diphenylpicrylhydrazyl (DPPH)/methanol solution (0.1 mM) for 3 hr. Then absorbance of the DPPH solutions was measured at 515 nm. The radical scavenging activity (RSA) was defined as follows : RSA(%)=(A0-Af)JA0 X 100. In this equation, Ao is initial absorbance of the DPPH solution, Af is absorbance of the DPPH solutions after contact of the films with the solutions.

5,6-BBHBN AiCOCI pyridine. CHjCI; 5,5-BBHBN ArCOCI

.„

^3^

pyridine, THF BHBN

Fig. 1 Synthesis of norbornene derivatives having DBH groups.

3. RESULTS AND DISCUSSION 3.1. Copolymerization behavior of the norbornene derivatives containing DBH group and norbornene Fig. 2 shows relationships between feed composition of norbornene derivatives (5,5-BBHBN, 5,6-BBHBN, BHBN) and the norbomene derivatives content in copolymers. The left plots are the results in the case of ruthenium trichloride hydrate as a ROMP catalyst. On the other hand, the right ones show

34. Polymeric Radical Scavengers via ROMP of Norbomene Derivatives

207

the results in the case of Grubbs catalyst. In the former, conversion of 5,5BBHBN and 5,6-BBHBN were lower than that of BHBN. This is, probably, due to steric hindrance of 5,5-BBHBN and 5,6-BBHBN. Chelation of the two norbomene derivatives to the ruthenium center occurs presumably. In the latter, fed 5,6-BBHBN and BHBN were almost copolymerized with norbomene. However, copolymerizability of 5,5-BBHBN was inferior to those of 5,6-BBHBN and BHBN. When the norbomene derivatives containing an oxygen atom is polymerized by Grubbs catalyst, coordination of the oxygen atom to ruthenium center occurs and causes the decrease of polymerization rate of the oxygen-containing norbomene derivatives [3,4]. In the case of 5,5BBHBN, the coordination to the ruthenium center causes lowering of copolymerizability possibly.

5

EC -

1UU

1 D 5,5-BBHBN O 5,6-BBHBN o BHBN

0

£S :

>)

it is

1

a

'

5,5-BBHBN O 5,6-BBHBN O BHBN

o o

H

D

40 -

40 -

3

1j

n 0

O n

Q

20

40

SO

SO

2C -

100

Norbornene derivatives in feed (mol%)

(b)

)C

20

40

50

80

LOO

Norbomeiic derivatives m feed (mcl%)

Fig. 2 Norbornene derivatives content in copolymer as a function of feed monomer composition, (a): ruthenium trichloride hydrate, initial monomer cone; 0.41 M, solvent; chlorobenzene, [monomer]/[catalyst]; 33, total volume; 3.4 ml, polymn. temp.; 70 °C, polymn. time; 18 hr (b):Grabbs catalyst, initial monomer cone; 0.35 M, solvent; methylene chloride, [monomer]/[catalyst]; 503, total volume; 4.0 ml, polymn. temp.; r.t., polymn. time; 2.5 hr.

3.2. DPPH radical scavenging activities of the DBH containing polymers Fig. 3 shows RSA values of the norbomene derivatives containing DBH groups and norbomene copolymers obtained with ruthenium trichloride hydrate as a function of their norbomene derivatives contents. The RSA values of the copolymers containing DBH groups depend on their DBH group contents. Fig. 4 shows RSA values of homopolymers of 5,5-BBHBN, 5,6-BBHBN and BHBN obtained with Grubbs catalyst as a function of their number average molecular weight. RSA values of poly(5,5-BBHBN)s and poly(5,6-BBHBN)s were twice or more as high as those of poly(BHBN)s. In particular, RSA values of poly(5,5-BBHBN)s were higher than those of poly(5,6-BBHBN)s.

208

K. Horikawa et at

Configuration sequences of the polymers effect DBH density on the surface of the films possibly. 14 -

-

1

' 5,5-BBHBN O 5,6-BBHBN O BHBN

O

poly(5;0-BBHBN) O pcly(BHBN) ;

20 -

lu -

-

D D

6 -

1

o

40

-

O O

O

&&? ° 20

::

:u -

c 0

1

D poly(5,5-BEIIEN)

60

30

100

Nwbornens derivatives content (mol%)

Fig. 3 RSA values vs. norbomene derivatives content (ruthenium trichloride hydrate).

z

O

105

IT'

Jlij of polymers

Fig. 4 RSA values vs. M homopolymers (Grubbs catalyst).

Of

4. CONCLUSIONS Two new norbomene derivatives containing DBH groups, i.e., 5,5-BBHBN and 5,6-BBHBN, were synthesized. Copolymerization behaviors of these norbomene derivatives and norbomene via ROMP were investigated. RSA values of poly(5,5-BBHBN)s and poly(5,6-BBHBN)s were twice or more as high as those of poly(BHBN)s. References [1] M. A. Tlenkopatchev, E. Miranda, M. A. Canseco, R. Gavino, T. Ogawa, Polym. Bull. 34(1995)385 [2] M. A. Tlenkopatchev, E. Miranda, R. Gavino, T. Ogawa, Polym. Bull. 35 (1995)547 [3] C. Slugovc, S. Demel, S. Riegler, J. Hobisch, F. Stelezer, Macromol. Rapid Commun. 25 (2004) 475 [4] D. M. Haigh, A. M, Kenwright, E, Khosravi, Macromolecules, 38 (2005) 7571


209

35

Vinyl Polymerization of Norbornene over Supported Nickel Catalyst Junxian Hou, Wenjuan Zhang, Suyun Jie and Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China

Abstract The nickel(ll) complex was immobilized onto spherical MgCl2, and performed norbornene polymerization in the existence of MAO. Spherical polymer particle morphology was observed without reactor fouling. 1. INTRODUCTION In recent years nickel-based complexes are becoming one type of important catalysts for vinyl polymerization of norbornene due to their high catalytic activities [1]. We have synthesized various nickel complexes bearing ligands of [N,O] [2] and [P,N] [3] for norbornene polymerization, however, those homogeneous catalysis resulted in a serious fouling of the reactor. The silica, silica-alumina derivatives, MgCl2 [4] and polymeric materials [S] are commonly used as supports. Therefore the immobilization and activation of the nickel complex 1 [2b] benefits the application in norbornene polymerization. 2. EXPERIMENTAL Bis-[JV-(diphenylmethyl)-salicylideneiminato]nickel(Il) (1) [2] and spherical MgCl2"nEtOH [4a, 6] were prepared according to the literature. Morphologies of the PNB particles, the catalysts were examined on a HITACHI S-4300 scan electron microscope. Elemental analysis was performed by spectrophotometry Shimadzu UV-2401PC and titration technique. Nitrogen adsorption-desorption isotherms were measured at 77 K using an ASAP2010 volumetric adsorption

210

J.Houetal

apparatus. Molecular weights were determined by Waters Alliance GPCV 2000 system at 135 °C in 1,2,4-trichlorobenzene. Viscosity measurements were carried out in chlorobenzene at 25 °C using an LJbbelohde viscometer. Typical preparation of MgCl2 supported nickel catalyst 6: To 40 ml hexane solution containing 4.64 g spherical MgCl2-2.97C2HsOH (20.0 mmol) in a 500 ml four-necked flask, 42.9 ml toluene solution of 1.4 M MAO was added over a period of 30 min, and reacted at -30 °C for 4 h. The slurry was filtered under N2 and the solid was washed twice by »-hexane (30 ml x2), dried under N2. The resulting powder was placed in the flask containing 30 ml toluene and the slurry was stirred at 25 °C, 50 ml toluene containing nickel complex 1 (0.22 mmol) was added to the slurry and stirred for 4 h. The final product was washed with toluene, until the liquid layer above became colorless. The solid catalyst (SNC1) was dried in vacuo until free flowing conditions were reached. Polymerization of norbornene: In a 100 mL Schlenk tube, the Ni catalyst (5 umol Ni), 14.08 mL toluene and 3.78 mL solution of norbomene in toluene (6.61 M) were introduced. The polymerization was initiated by addition of a 7.14 mL toluene solution of 1.4 M MAO via syringe. After 60 min, the reaction was terminated by pouring into 200 mL acidic MeOH (MeOH:HClBOTlc= 95:5). 3. RESULTS AND DISCUSSION Effects of supporting conditions: Elemental analysis, surface areas of the supported catalysts are shown in Table 1. Treatment of spherical MgCl2*nEtOH adduct produces dealcoholization without structure collapse [6]. The results indicate that Al loading on the support greatly decreased upon decreasing of the ethanol content in the MgCl2/ethanol adducts. The Ni loading increased in the order of SNC-1 < SNC-2 < SNC-3 < SNC-4. The BET surface areas and pore volume increased upon decreasing the ethanol content in its MgCl2 adduct. There was no significant change in polymer molecular weight relying on various ratio of EtOH to MgCl2 in the range of 1.50-1.98x10* g/mol. The catalytic activities are in the range of 238-281 kg PNB/mol Nrh. SNC-2 was chosen for study in detail at different conditions for its good morphology. Effects of polymerization conditions: Lower activity was observed in hexane while higher activity was obtained in toluene. However, higher molecular weights of the resulted PNBs were obtained in hexane as solvent. Increase of monomer concentration, the M/Ni ratio (M: norbomene), causes rapid increase of the activities combined with a drastic increase of molecular weight. Morphology of the PNB particles changed gigantically with monomer concentration. At an M/Ni ratio of 10000:1, polymer particle started to agglomerate along with reactor fouling, and therefore morphological control was gradually lost.

35. Vinyl Polymerization

ofNorbornene

over Supported Ni Catalyst

211

Table 1 Element analysis and BET analysis of supported catalysts Catalyst

BET ^ ^

Pore vol. ( m L / 8)

Average pore Diameter (A)

7.65

1.5

0.018

477

16.22

5.12

5.4

0.022

162

0.24

16.87

3.60

12.3

0.047

152

0.26

21.52

3.49

18.7

0.093

198

Starting

Ni

Mg

Al

material

wt.%

wt.%

wt.%

SNC-1

MgCl2-2.97Et0H

0.18

10.32

SNC-2

MgCl2-1.72EtOH

0.23

SNC-3

MgCl2'1.30EtOH

SNC-4

MgCl2-0.38EtOH

The treating spherical MgCl^ support with MAO was carried out at -30°C. Table 2. Polymerization of norbornene with supported l a Entry

Catalyst

M/Ni

Yield

Activity11

E

SNC-1

5000

59.7

MJMn

(dL/g)

g/mol)

281

1.06

16.1

4.91

% 1

M w (xl0 s

2C

SNC-1

5000

50.6

238

1.11

18.7

3.85

3

SNC-2

5000

56.9

268

1.10

19.8

5.70

4

SNC-3

5000

53.7

253

0.94

15.2

4.97

5

SNC-4

5000

51.6

243

0.96

15.0

5.76

6

SNC-2

2500

32.2

76

0.77

9.01

4.19

7

Ni(II)

2500

58.2

136

0.65

3.54

3.17

d

8

SNC-2

7500

83.3

5S8

1.39

n.d

n.d.

9

SNC-2

10000

65.9

621

1.48

n.d.

n.d.

Condition: 5 jimol Ni; 25°C; toluene; 60 min; total volume, 25 mL; M / Ni = 5000 ; MAO, Al/Ni = 2000." kg PNB/mol Nrh. c Hexane as solvent. d Not determined.

The activity of the heterogeneous catalyst is ca. 50-70% of its homogeneous catalyst under the same conditions (entry No 6, 7) in Table 2, which is a wellknown phenomenon [7-10] in olefm polymerization. However, comparing entries 6 and 7, the molar mass of the polynorbornene obtained with SNC-2 was around two times higher than that obtained with the homogeneous catalyst 1. The broadening of the molecular weight distributions was evident with the supported catalyst systems. Often the PDI values in the literature are higher for supported catalysts compared to homogeneous system [4b, 7]. Microscopy studies: Fig. la showed that spherical MgCl2-2.97EtOH had a smooth and less porous surface. The supported catalyst (Fig. lb) appeared a rough and porous surface. Fig. lc showed its PNB particle with 15-20 times larger than that of the catalyst SNC-2 (typical 30 um).

212

J. Hou et al.

Fig. 1. SEM micrographs, (a) spherical MgClz-2.97Et0H (600x), (b) SNC-6 (600x), (c) PNB particles (entry 11, 40x).

4. CONCLUSIONS Bis-[N-(diphenylmethyl)-salicylideneiminato]nickel(IT) (1) was supported on spherical MgCl2. The supported catalysts performed well for norbornene polymerization with fine morphology and high activity. The polynorbornenes produced with supported catalyst have higher molecular weight and broader molecular weight distribution than those of its homogeneous ones. Acknowledgements The project supported by NSFC 20473099. This work was partly completed in Polymer Chemistry Laboratory, Chinese Academy of Sciences and China Petro-Chemieal Corporation. References [1]

B. Berchtold, V. Lozan, P-G. Lassahn, C. Janiak, J. Polym. Sci. Polym. Chem. 40 (2002) 3604. [2] H.Yang, W.-H. Sun, F. Chang, Y. Li. Appl. Cat. A. 252 (2003) 261. [3] H. Yang, Z. Li, W.-H. Sun. J. Mol. Catal. A: Chem. 206 (2003) 23. [4] a) R. Huang, D. Liu, S. Wang, B. Mao, Macromol. Chem. Phys. 205 (2004) 966; b) H. S. Cho, W. Y. Lee, J. Mol. Catal. A. 191 (2003) 155. [5] T. R. Boussie, V. Murphy, K. A. Hall, C. Coutard, C. Dales, M. Petro, E. Carlson, H. W. Turner, T. S. Powers, Tetrahedron 55 (1999) 11699. [6] P. Sozzani, S. Bracco, A. Comotti, R. Simonutti, I. Camurati, J. Am. Chem. Soc. 125(2003)12881. [7] F. AlObaidi, Z. Ye, S. Zhu, Macromol. Chem. Phys. 204 (2003) 1653. [8] S. Collins, W. M. Kelly, D. A. Holden, Macromolecules 25 (1992) 1780. [9] M. O. Kristen, Top. Catal. 7 (1999) 89. [10] S. I. Woo, Y. S. Ko, T. K. Han, Macromol. Chem. Phys. 16 (1995) 489.


213

36 Effect of Catalyst Loading in Olefin Polymerization Catalyzed by Supported Half-Titanocenes on Polystyrene through Phenoxy Linkage Boonyaraeh Kitiyanan and Kotohiro Nomura* Graduate School of Materials Science, Nora Institute of Science and Technology 8916-5 Takayama, Ikama, Nora 630-0101, Japan

Abstract Half-titanocenes immobilized on the poly(styrene-eo-hydroxystyrene) at various Ti loading have been prepared by the reaction with Cp*TiMe3. Effect of catalyst loading toward both the activity and the polymerization behavior was explored, and the catalysts at low Ti loading showed higher activity for ethylene polymerization. These catalysts also produced syndiotactic polystyrene with the moderate activity. However, the significant decrease in the activity was observed in the ethylene/1-hexene copolymerization, affording low molecular weight polymers. 1. INTRODUCTION Design and synthesis of efficient 'heterogeneous single-site catalysts" attract particular attention not only from scientific but also from practical viewpoints [1,2]. This is because most of newly developed transition metal complex catalysts are homogeneous [3,4], and the catalysts should be heterogenized by supporting on to a carrier such as inorganic solids or polymers in order to achieve commercial significance in the current gas or slurry polymerization processes [1,2]. Although several supports such as magnesium chloride, silica, alumina, clay, zeolite, polymers were known [1,2], we focused on polymer or dendrimer supported catalysts [5,6,7], not only because there are practical concerns in using homogeneous catalysts such as separation of the products

214

B, Kitiyanan andK. Nomura

from the catalyst and ligand [8], but also because these supported catalysts play a crucial role in combinatorial and parallel synthesis. Since (aryloxo)(cyclopentadienyl)titanium complexes exhibited high catalytic activity and unique characteristics for olefin polymerization [9] particularly for ethylene (co)polymerizations [10-15], we, therefore, have an interest to prepare the supported complex on polystyrene through phenoxy linkage and explore the possibility of using catalyst precursor for olefin polymerization. 2. EXPERIMENTAL All experiments were carried out under a nitrogen atmosphere in a vacuum atmospheres drybox unless otherwise specified. Anhydrous grade toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) in the drybox, and was used without further purification. MAO was prepared by removing toluene and AlMes in vacuo (in the drybox) from the ordinary MAO (PMAO-S, Tosoh Finechem Co.). Other chemicals, such as reagent grade acetoxy styrene, azobisisobutyronitrile (ALBN), were used as received. Polymerization, isolation procedures were according to our previous reports [11,12,16], and molecular weights and molecular weight distributions for resultant polymers were measured by GPC (Tosoh HLC-8121GPC/HT) with polystyrene gel column (TSK gel GMHHR-H HT x 2, 30 cm x 7.8 mni(|> ID), ranging from mm,tiimin

— — \ i,max

(14)

i,minJ

are maximal and minimal values of y, and

tt respectively. When y=f(t) is a strictly increasing function, Eq. 14 can be simplified as:

RSD=^-

(is)

The value of n at the minimal RSD gives the decay order.

44. Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

259

3.3. Kinetics of gas-phase Propylene Pofymerizationfl7]

J.J.I. Effects of conditions on rate It is desirable to determine the catalyst efficiency since a trace level of impurities may totally deactivate active centers in an olefin polymerization. Catalyst residues in the feed line may also result in an underestimate of the catalyst activity (as shown in Fig.5). The cocatalyst also has an effect on the catalyst activity. There is an optimal cocatalyst/catalyst ratio under which the catalyst has the highest activity (as shown in Fig.6).

30

60

90

120

150

Massofthecatalyst/mg

Figure 5. Determination of the catalyst efficiency at 70 °C.

B. Li et al.

260

2500

500

100

150

200

AI/Ti ratio/moLmor

Figure 6. Effects of Al/Ti ratio on polymer yield at 70 °C

The effect of monomer concentration was investigated under 70 °C. As shown in Fig.7, the monomer pressure is in the range of 0.50~-'1.15MPa. The rate is proportional to the monomer concentration.

0.00

0.25

0.50

0.75

1.00

1.25

Monomer conccntration/niol.L-amorp

Figure 7 Mean reaction rate at 70 °C during One-hour polymerization.

3.3.2. Determination of the decay order of the active centers A typical experimental reaction rate curve is shown in Fig.8. As we can see a fast decay in the early stage followed a steady decay. The relative standard


261

deviations (RSDs) were plotted against the decay order n for each experiment set as shown in Fig, 9, The decay order was determined to be 2.5 by the mean value of these RSDs as shown in Fig. 10. 1500 a 1200

experi merit Exponential

decay

0.6

0.9

0.3

fit

1.2

Time/h

Figure 8 Typical experimental reaction rate at 70 "C, 0.60 Mpa

0.20 Relative standard deviation

Run numbs H305A H309A H311A H313A * H315A e H319A H H321A

o e

0.16 0.12

V 4

*

H321A H308A H310A H312A H314A H316A H320A

0.08 0.04 0.00

1

2

3

4

5

Decay order n

Figure 9 Determination of the decay order of the active sites for each of the experiments.

262

B.Lietal

Mean relative standard deviation

0.15 0.12 0.09 0.06 0.03

1

2

3

4

5

Decay order n

Figure 10 Determination of the decay order of the active sites for all the experiments.

3.3.3. Estimate of the apparent activation energy and other rate constants

100000

-1

-1

Rp0 /L-amorp.gPP.gcat .hr .mol

-1

The rate constants were determined in Fig. 11-12, and the values of these constants were listed in Table 1 in detail.

10000

1000

100 10 2.85

2.90

2.95 3.00 3.05 -1 -1 1 T'/IOOO.K T /1000.K

3.10 3.10

Figure 11 Arrhenius plot of the initial reaction rate at 49—76 °C.

44, Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

263

2.85 2.90 2.95 3.00 3.05 3.10 T"1 /1000.K"1 Figure 12 Arrhenius plot of the deactivation constant k^/kp1'5 at 49~76 °C. Table 1. Constants of the Kinetic Model for Gas-Phase Propylene Polymerization Constants

Units

Values 2.5

kJ/mol

77.1

kJ/mol

51.8

gPP.L-amorp.gcat" .hr" .mol"

2.80x10 15

(goat/gpp) L 5 (mol/L-amorp) L5 hr 0 - 5

3.66x10',-15

3.3.4. Model test The model predictions and experimental data were plotted simultaneously, as shown in Fig. 13, the model describes the experiments reasonably well.

264

5. Li et al.

o.3

o.a

o.a

Time/hr

(b) at 65.2 °C, 0.595 MPa,

(a) at 76.2 °C, 0.808 MPa;

Figure 13 Comparison of experimental and simulated reaction rate

3.4. Kinetics of liquid-phase Propylene Polymerization 3.4.1. Polymerization rate The rate of liquid-phase polymerization was obtained by correlating the yield versus time data using Fig,14~15. 30

exper i rent ExpAssoc fi t

25-

J20 B5

I15" 1 1050

0.0

0.2

0.4

0.6

0.8

1.0

Time(h) Figure 14 Yield of the catalyst as a function of main polymerization time at 80 °C.


265

20000 f 18000| 16000| 14000

I 12000| 10000-

I 8000-

^ eooort

40002000 0,0

0,2

0,4

0,6 0.

1,0

Figure 15 Instantaneous polymerization rate as a function of main polymerization time at 80 °C.

3.4.2. Determination of Decay Order The decay order is determined to be 1.7 (as shown in Fig. 16)

2

3

4

Decay order

Figure 16, Determination of the decay order of catalyst decay for all the experiments

3.4.3. Estimate of the apparent activation energy and other rate constants The rate constants were determined in Fig, 17-18, and the values of these constants were listed in Table 2 in detail.

266

B. Li et at.

ft 10 t*

2.8

2.9

3.0

rViooo.iT1 Figurel?. Arrhenius plot of the initial reaction rate at 50-80 °C

2.80 2.85 2.90 2.95 3.00 3.05 3.10 3.15 T"1 /1000.K"1 Figure l i . Arrhenius plot of the deactivation constant k^/kp

at 50~i0 °C.

Table 2. Constants of the Kinetic Model for Liquid-Phase Propylene Polymerization Constants

£„

Units

Values

i

1.7

kJ/mol

72.9

kJ/mol

48.7

gPP.L-amorp.gcat" .hr" .mol"

1.45x10 15

(gcat/gpp) °- 7 (moyL-amorp)0-7hr"0-3

1.34xlO":

44, Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

267

3,4.4. Model test

The model predictions and experimental data were plotted simultaneously, as shown in Fig. 19, the model describes the experiments well. o

2020

25 experiment -model model

Yield (kgPP/gCat.)

Yield gPP/gCa»t.) t.) Yiel i (k (kgPP/gC

25

15 15O —

1010 ^—-

55 0 00.0

0.2

0.6 0.4 Time (h)

0.8

experiment model

20 15 10 5 0

1.0

0.0

(a) at 60 °C

0.2

0.4 0.6 Time (h)

0.8

1.0

(b) at 70 °C

Figure 19. Comparison of experimental and simulated reaction rate.

3.5. Comparison of Gas-phase and Liquid-phase Polymerization Systems 3.5.1. Comparison of the catalyst composition Table 3, Comparison of the catalyst composition for gas- and liquid-phase propylene polymerization system Polymerization system

DQcat

Aim

tag

/moLmol -1

Gas-phase

50-120

150

7.5

Liquid-phase

20

720

36

Si/Ti /moLmol

-1

From the table we can find that there are differences in the catalyst composition between the two catalyst systems. J. 5.2. Comparison of the reaction rate The reaction rates of gas- and liquid-phase polymerization were compared in Fig. 20~21. From these figures we can see that the gas-phase polymerization rate is much lower than that of the liquid-phase counterpart. Theoretically, they

268

B. Li et al.

should be equal at the same temperature. This may suggest that the efficiency of the catalyst in the gas-phase be much lower than that in the liquid-phase. 14000

°

liquid-phase gas-phaie at 0.559 MPa

q12000B

0.0

0.3

0.9

1.2

Time(h)

Figure 20 Comparison of reaction rate for liquid and gas phase experiments at 70.0 °C.

0.0

0.2

0.4

0.6

0.8

1.0

Time(h}

Figure 21 Ratio of reaction rate for gas and liquid phase experiments at 70.0 °C.

3.5.3. Comparison of the decay orders and activation energies It was found that the apparent activation energies in both phases were similar to each other, while the decay order in the liquid phase was found to be 1.7, lower than that in the gas phase process. This may imply that less thermal runaway was achieved in the liquid process.

44. Kinetics of Propylene Bulk Polymerization with a Ziegler-Natta Catalyst

269

Table 4. Comparison of the decay orders and activation energies for gas- and liquid-phase propylene Polymerization system Polymerization system Gas-phase

« / ' 25

£p

Ed

/kJ.moP TTA

/klmol" 1 SL8

Liquid-phase

1.7

72.9

48.7

T

T

4. CONCLUSIONS The kinetic models of bulk propylene polymerization have been developed for both gas- and liquid-phase using a spherical Ziegler-Natta catalyst. A faster decay order was found in the gas-phase system, suggesting that thermal runaway may be more severe in the gas-phase process than in the liquid-phase. The differences in the reaction rates and in the catalyst compositions between gas- and liquid-phase polymerization systems suggest that the catalyst efficiency in the gas-phase be much lower than that in the liquid-phase due to a trace amount of impurities. Both models describe the experiments moderately well. Acknowledgement! This work was financially supported by the Special Fund for Major State Basic Research Projects (No.20G5CB623804), the National Science Fund for Oversea Distinguished Young Scholars (No.20428605), and the National Science Fund (No.20476090). References [1] P. Galli, J. C. Hayloek, Die Makrom. Chem. Macromol, Symp, 63 (1992) 19. [2] J. A. Debling, J. J. Zacca, W. H. Ray, Chem. Eng. Sci. 52 (1997) 1969. [3] P. Galli, G. Collina, P. Sgarzi, G. Baruzzi, E. Marchetti, J, Appl. Polym. Sci. 66(1997)1831. [4] G. Collina, T. Dall'oeco, M. Galimberti, E. Albizzati, L. Noristi, WO9611218. [5] H. G. Yuan, T. W. Taylor, K. Y. Choi, W. H. Ray, J. Appl. Polym. Sci. 27 (1982)1691 [6] J. C. W. Chien, C. I. Kuo, T. L. Ang, J. Polym. Sci.: Polym. Chem. 23 (1985) 723 [7] J. C. W. Chien, C. I. Kuo, J. Polym. Sci.: Polym. Chem. 23 (1985) 731.

270

B.Lietal.

[8] J. C. W. Chien, C. I. Kuo, J. Polym. Sci.: Polym. Chem. 23 (1985) 761. [9] C. Dumas, C. C, Hsu, J. Appl, Polym. Sci. 37 (1989) 1625. [10] S. Cai, S. Xiao, Y. Liu, Chinese J. Catalysis, 12 (1991) 409. [11] X. Xia, B. Mao, Petrochem. Tech, 21 (1992) 440. [12] X. Xia, B. Mao, Petrochemical Technology, 21 (1992) 507. [13] 1. Kim, H. K. Choi, J. H. Kim, S. I. Woo, J. Polym. Sci.: Polym. Chem. 32 (1994)971 [14] I. Kim, H. K. Choi, J. H. Kim, S. I. Woo, J. Appl. Polym. Sci. 52 (1994) 1739. [15] J. Xu, L. Feng, S. Yang, Petrochem. Tech. 26 (1997) 581. [16] V. Mates, N. A. G. Mattes, J. C. Pinto, J. Appl. Polym. Sci. 79 (2001) 2076. [17] J. Hu, H. Fan, Z, Bu, B. Li, Journal of Chemical Industry and Engineering (China) 57 (2006) 429 [18] G. C. Han-Adebekun, J. A. Debling, W. H. Ray, J. Appl. Polym. Sci. 64 (1997) 373 [19] J. Hu, H. Fan, Z. Bu, B. Li5 Proceedings of 1st Chinese National Chemical and Biochemical Engineering Annual Meeting, Nanjing, China, (2004) 349. [20] B. Li, H. Fan, J. Hu, Z. Bu, J. Zhang, CN 1657543A. [21] M. Ferrero, M. G. Chiovetta, Polym. Eng. Sci. 27 (1987) 1436. [22] M. Ferrero, M. G. Chiovetta, Polym. Eng. Sci. 27 (1987) 1448 [23] R. A. Hutchinson, C. M. Chen, W. H. Ray, J. Appl. Polym. Sci. 44 (1992) 1389 [24] J. A. Debling, W. H. Ray, Indus, and Eng. Chem. Research, 34 (1995) 3466 [25] J. Kosek, Z. Grof, A. Novak, F. Stepanek, M. Marek, Chem. Eng. Sci. 56 (2001)3951 [26] S. A. Stern, J. T. Mulhaupt, P. J. Garies, AICHE J, 15 (1969) 64. [27] J. Samson, B. Middelkoop, G. Weickert, K. Westerterp, AICHE J, 45 (1999)1548. [28] R. A. Hutchinson, W. H. Ray, J. Appl. Polym. Sci. 14(1990) 51 [29] Y. Banat, U. P.Veera, G.Weickert, Proceedings of 2nd ECOREP, Lyon, France, July (2002)1.


271

45

Effect of a-Olefins on Copolymerization of Ethylene and a-Olefin with [*-BuNSiMe2Flu]TiMe2 Catalyst Nawaporn mtaragamjona, Takeshi Shionob*, Bunjerd Jongsomjif** Piyasan Praserthdam8* "Center of Excellence on Catalysis and Catalytic Reaction Engineering Department of Chemical Engineering, Faculty of Engineering Chulalomgkam University, Bangkok 10330 Thailand ^Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8527, JAPAN.

Abstract The effect of a-olefm was observed in ethylene/a-olefin copolymerization toward [?-BuNSiMeaFlu]TiMe2 catalyst with MMAO. Three kinds of a-olefm monomers were chosen for the present study. Activity, polymer microstrueture, thermal properties, molecular weight and molecular weight distribution of polymers were investigated. Our results revealed that the activity of polymerization was strongly dependent on the a-olefins employed. Thus, the polymerization behavior can be altered with the a-olefins used during polymerization. It indicated that the crystallinity of polyethylene was broken by the large amounts of a-olefin insertion on ethylene and a-olefin copolymer. 1. INTRODUCTION From the industrial point of view, linear low-density polyethylene (LLDPE) is produced in gas, solution and high pressure processes. The density of polyethylene is an important variable that we use to control polymer properties. Density of polyethylene can be controlled in many ways, especially, the level and distribution of branching. The catalytic polymerization of ethylene with «olefins is a typical way of introducing short-chain branching in polyethylene

272

JV. Intaragamjan et al,

backbone. Nowadays, new generation of polymerization catalysts i.e. metallocene and late transition metal catalysts, can control the amount of aolefin insertion into polyethylene with uniform and homogeneous sequence and composition distributions. With the difference of comonomer composition and its distribution, it can cause significant changes in polymer properties. These included differences in glass transition, melting temperatures, melt viscosity, the mechanical and optical properties [1-7]. As a matter of fact, we can use the ethylene/a-olefm in the wide range of applications. In the present paper, we are communicating the results of polymerization regarding to the a-olefin monomer in ethylene/oc-olefin polymerization behaviors. Polymerization proceeded with [t-BuNSiMe2Flu]TiMe2 and modified-methylaluminoxane (MMAO) system using heptane as the solvent medium. Polymer properties and polymer microstructure were also investigated to suggest the interpretation of comonomer effect on the copolymer composition and comonomer distribution. 2. EXPERIMENTAL Materials; All manipulations were carried out under an argon atmosphere using standard Schlenk techniques. All solvents were refluxed with sodium/benzophenone or calcium hydride and distilled before use. The complex was prepared according to the method reported previously [8]. Polymerization Procedure; Ethylene/a-olefm copolymerizations were carried out in a 100-ml semi-batch stainless steel autoclave reactor equipped with a magnetic stirrer. Heptane was introduced to reactor followed by the addition of the desired amount of MMAO. The catalyst was added to the reactor in a glove box. The reactor was then immersed in liquid nitrogen to freeze the solution and evacuated to remove argon. The a-olefin was added to the freezed reactor equipped with Schlenk line to keep system in argon atmosphere. After that, the reactor was heated to the desired polymerization temperature. Feeding ethylene started the reaction. The pressure in the reactor was kept at 50 psi by a continuous ethylene feed. Polymerizations were conducted on the certain time and terminated with acidic methanol. The polymer obtained was precipitated in acidic methanol, filtered, adequately washed with methanol, and finally dried in the atmospheric pressure for 3 days to ensure for solvent evaporation. Analytical Procedures; Molecular weights and molecular weight distributions of polyethylene obtained were determined by gel permeation chromatography (GPC) with a Waters 150CV at 135 °C using 1,,2,4-trichlorobenzene as a solvent. The 13C NMR spectra of the polyethylene were measured at 70 "C on a JEOL GX 500 spectrometer operated at 125.65 MHz in the pulse Fourier-transform mode. The pulse angle was 90° and about 5000 scans were accumulated in pulse

45. Effect ofa-Olefin on Copolymerization with [t-BuNSiMe3Flu]TiMe2 Catalyst

273

repetition of 4.0 s. Sample solutions were prepared in ehloroform-a?i up to 10 wt-%. Differential scanning calorimetry (DSC) curves of the samples were recorded on a Perkin-Elmer DSC P7 under nitrogen with a heating rate of 10 "C/min. 3. RESULTS AND DISCUSSION Ethylene/a-olefin copolymerization was conducted at 70 °C with various aolefin types, of which results are summarized in Table 1. The copolymerization of ethylene/a-olefin gave the highest activity when 1-octene was employed. From this evident, it should be noted that the active species of ion pair can be affected from the second monomer in polymerization. In this case the proper geometry and steric of 1-octene can generate the highest activity in ethylene/aolefin polymerization. Again, from Table 1, we found that the molecular weight of polymer was reduced when the copolymerization was conducted. This was because the chain transfer of polymer occurred after the a-olefin insertion unit during copolymerization. Moreover, with the higher a-olefin monomer, we obtained the higher molecular weight of copolymer. Table 1 Results of ethylene/a-olefin copolymerization3 Polymer

Yield (g)

Activity"

M n (10 4 ) 6

MWff

E°

0.75 3,08

1000 2460

4.2 2.6

3.9 2,2

3.52

2g20

3.6

2.0

2.31

1840

3.6

2.1

EH EO ED

7? 134

99

'Polymerization conditions: Ti = 5 (xmol, Al/Ti = 1000, 50 psi of ethylene pressure, polymerization temperature = 70 °C, bActivity = kg(polymer) mor'fTi) hr"1. cNumber of average molecular weight and molecular weight distributions were measured by GPC analysis using poly styrene as reference. d Measured by DSC (°C) "Using Ti = 3 junol.

A quantitative analysis of triad distribution for all copolymer samples was performed by 13C NMR. The assignments of the spectra their analysis were based on those of ethylene/1-hexene copolymer [9]. The triad distribution and product reactivity ratio of monomer are shown in Table 2. It should be noted that the a-olefin incorporation in the main chain of copolymer apparently decreased with the larger a-olefin monomer applied. The next focus was on the copolymer structure. The product of monomer reactivity ratios increased from 1.1 with 1-hexene to 2.4 with 1-decene according to the size of a-olefin, which indicates that the comonomer distribution in the

274

N. Intaragamjon et al.

copolymer was changed from random to blocky by the size of a-olefin comonamer. Table 2 Microstrueture and comonomer content of the copolymers Polymer

ccc

ECC

ECE

EEE

CEC

EEC

%E

%C

We

EH

0.097

0.243

0.124

0.203

0.137

0.196

54

46

1.14

EO

0.064

0.136

0.119

0.362

0.086

0.233

68

32

1.67

ED

0.025

0.106

0.096

0.558

0.064

0.150

77

23

2.36

E and C denote ethylene and comonomer (H = hexene, O = octene and D = decene), respectively.

4. CONCLUSIONS Comonomer effects were investigated in the copolymerization of ethylene and a-olefin with the [/-BuNSiMe2Flu]TiMe2MMAO catalyst. The size of the aolefin used as a comonomer was found to affect the copolymerization ability of the catalytic system, which was probably caused by the a-olefin inserted at the propagation chain end. Acknowledgments We give the grateful thanks to the Thailand Research Fund (TRF), The Thailand Japan Technology Transfer Project (TJTTP), and the Royal Golden Jubilee program scholarship. References [1] S. Bensason, J. Miniek, A. Moet, S. Chum, A. Hiltner, E. Baer, J. Polym. Sci., PartB: Polym. Phys. 34 (1996) 1301. [2] DJR, Burfield, Macromolecules 20 (1987) 3020. [3] R.G Alamo, L. Mandelkern, Thermochim. Acta 238 (1994) 155. [4] A. Alizadeh, L. Richardson, J. Xu, S. McCartney, H. Marand, Macromolecules 32 (1999) 6221. [5] D. Mader, Y. Thomann, J. Suhm, R. Mulhaupt, J. Appl polym. Sci. 74 (1999) 838. [6] A.G. Simanke, G.B. Galland, R.B. Neto, R. Quijada, R.S. Mauler, J. Appl. Polym. Sci. 74(1999)1194. [7] X.R. Xu, J.T. Xu, L.X. Feng, W. Chen, J. Appl. Polym. Sci. 77 (2000) 1709 [8] H. Hagihara, T. Shiono, T. Ikeda, Macromolecules 31 (1998) 3184. [9] James C. Randall, J. Macromol. Sci., Macromol, Chem, Phys. C29 (1989) 201.

Author Index Asuka, K. Babkina, O. N. Ban, H. T, Bravaya, N. M. Cai, Z. Chukanova, O. N. Dong, Q. Duan, Y-Q, Eisen, M. S. Faingol'd, E. E. Fan,H. Fan,Z. Fang,Y. Fu,Z, Fujita, T. Fujiwara, A. Guo, C. Hagihara, H. Hasebe, K. Horikawa, K. Horikosi, T. Hou, J. Hou, Z. Hu,J, Ikeda, T. Ishihara, T. Itagaki, K.

229,237 77 197 77 47,189 77 25 113 105 77 245,253 25 225 25 159 43 245 197 43 205 13 209 95 253 241 197 179

Jie, S. Jongsomjit, B Jung, M.-S. Kaneko, H. Kang, N. Kashiwa, N. Kawahara, N Kawamoto, N Kawamura, T. Kim, C. Kitiyanan, B. Kouzai, I. Kuwabara, J, Lee, D. W. Lee, D.-H Lee, H. Y. Lee, I.-M. Lee, Y. R. Li, B.-G. Li,N Li, X.-F. Li, Y.-S. Lisovskii, A. Liu,B. Luo, Y. Lyoo, Y. S. 275

87,209 271 53 1 31 1 1 13 229 59 213 237 135 59 53, 69,185 185 59 69 245,253 25 113 113 105 129,219,225, 229,237 95 69

276 Author Index Maeda, N. Maeyama, K. Matsugi, T. Matsumae, T. Matsuo, T. Michiue, K. Mitani, M. Miyamoto, K. Monrabal, B. Nakano, H. Nakayama, Y. Intaragamjon, N Negishi, Y. Nishii, K. Nishimura, N. Nitta, K. Noh, S. K. Nomura, K. Nomura, K. Nozaki, T. Okada, M. Onda, M. Osakada, K. Panin, A. N. Park, S. Praserthdam, P. Qin, H. Ryabenko, A. G. Sagae, T. Saito, J. Sanginov, E. A. Saratovskikh, S. L. Shiga, A.

165 193,205 1 241 1 159 159 43 35 19 47,165,171, 189 271 13 241 193 229,237 53, 69,185 13 123,147,175, 179,213 43 171 159 135,201 77 201 271 233 77 7 1 77 77 219

Shiono, T. Su,Z. Sudhakar, P. Suehiro, K. Sugano, T. Sumino, K, Sun, W.-H. Sundararajan, G Sung, J.-K. Takahashi, T. Takeuchi, D. Tayano, T. Terano, M. Tobita, E. Toyota, A. Uchino, H, Ushakov, E. N. Volkis, V. Wang, D. Wang, W. Wang, X. Watanabe, H. Wu,B. Wu,J. Xia,W. Xu,D. Xu,J. Xu,Y, Yamada, J. Yamaguchi, M. Yang, M. Yokota, H. Yoon, K.-B.

47,165,171, 189,197,241,271 35 153 7 19 229

87,141,209 153 53 19

135,201 19

7,13, 129, 219,225,229,237 7,13 193,205 19 77 105 31 123 25 43 141 31

129,225 31 25 31

123,175 229 233 13 53,185

Author Index 277 Zhang, H. Zhang, S. Zhang, W. Zhang, W. Zhang, X. Zhao,Y. Zhou, D. Zhu, S.

147 87,233 87 141,209 31 31 225 245, 253


Subject Index polyethylene 173 ethylene/norbornene copolymer 187 cobalt 141,144,145 cocatalyst effect of 28,126 comonomer effect 95,100,274 eompatibilizer 233,235 composite polyethylene/clay 234,236 polyolefin/clay 235 polypropylene/SiOi 229,238 composition distribution 9,25,27,35, 36,272 controlled radical polymerization 1,4 copolymer ethylene 31 ethylene/1-decene 273 ethylene/1-hexene 273 ethylene/1-octene 273 ethylene/norbornene derivative 53 ethylene/propylene 25,27 ethylene/vinyl acetate 31 organic/inorganic 53 thermal property 63 thermal stability 64 copolymerization ethylene 55 ethylene/1 -hexene 46,95,99,213, 216 ethylene/2-methyl-l-pentene 179 ethylene/a-olefm 271,273 ethylene/cycloolefin 186 ethylene/norbomene 185 ethylene/propylene 19,23 ethylene/styrene 147,149,151 ethylene/tetracyclododecene 185

activation energy 256,262,268 antioxidant 11,13,15,16 (arylimido)(ketimide)vanadium 125, 175 (arylimido)vanadium dichloride 133

B bimetallic Zr complex 1,3-butadiene

135,137,138 197

Cj-symmetry 108 Cj -symmetry 153 chain migration 51,191 chain transfer 45, 83,98,116,117,139, 157,183,199,241,243,273 chain walk 174,203,248,249 chemical composition distribution 35 chiral organo-siloxane ligand 225,227 chromic acid 219, 221,223 chromium trioxide 129 clay acid strength of 18,20,23 support-activator 10 modified 233,235,236 13 CNMR wax 93 ethylene/1-hexeneeopolymer 100 polynorbornene 120 poly(methylene-1,3-cyclopentane) 139 279

280 Subject Index norbornene/norbornene derivative 206 norbomene/styrene derivative 194 197,198 propylene/1,3-butadiene styrene derivative 193 crystallization analysis fraetionation 35,38 (CRYSTAF) 50,52 Cs-symmetric cyclization polymerization 202,203 cyclopolymerization 201,202 1,5-hexadiene 135,138

D decay model decay order

253 253,258,260, 261,265,

density functional theory (DFT) 130,131, 132,223 deuterated propylene deuterium-hydrogen exchange diethylaluminum chloride diethylaluminum hydride a-diimine nickel diisobutylaluminurn hydride

129, 110 111 126 199 245 199

I in-reactor alloy 25 iron 87, 88, 89,90,93, 141,142,145, 146 isopropylidene diallylmalonate 201, 202,203

K P-ketoimine kinetic curve kinetic model

E enantiomorphic site enantioselectivity epimerization

95,96, 97,100 half-sandwich 147,213,216 half-titanocene 69,71,73,74 dinuclear immobilized 213 180,183 nonbridged 214 polymer-supported 256 Henry constant 53 hybrid eopolymer 156,172,174 P-hydride elimination hydrogenation 45 P-hydrogen elimination 98,107,183 hydrogen addition of 25 30 effect of

61 226,227,228 257,269

51,191 51 110

Flory-Huggins interaction parameter 257 FTIR ethylene copolymers 31, 33,34

Lewis base promoting effect of 82 ligand effects 71,135,147,179 living polymerization 50, 52, 189,191, 192,241,243 long chain branch 171,173 low-molecular-weight wax

90, 93

G 100,159,163 205, 206,207

group 4 metal Grubbs catalyst

H hafnocene

77, 79, 83

M macroinitiator 1,2, 3 metallocene 10,11,21,23,39, 55, 73, 75, 85, 137,186 cationization 22 methylaluminoxane (MAO) 53, 65, 87,

Subject Index 281 90,108,133,135,148,153,156, 159,162,163,165,168,169,179, 181,183,192,193,194,195,196, 197,209,216,230,238,247 modified (MMAO) 47,49, 50,51, 53, 55, 58,61, 65,67, 70, 81,113, 115,120,169,170,186,189,190, 191, 197,198, 200, 241, 243, 244, 271,274 montmorillonite 19,20,235 morphology 210,212,251,256 polypropylene 10,254 clay 10 control 10 polymer particle 209 polymer 229 spherulite 238

N nanoeomposite 235,239 palypropylene/SiOz 229,231,237, 240 nickel 59, 67,113,115,116,117,119, 120,121,141,142,145,146,171, 174,193,194, 196,209, 212,245, 248,251 niobium 165,167,168,169

o 135,137,219 olefin metathesis ollgomerization ethylene 87, 90, 92, 93,141,143, 146 organic/inorganic hybrid 53

paired interacting orbitals (PIO) 129,130,131,132, 133,134, 219,220,221,222,223 palladium 59, 61, 67, 141, 143,146, 201,202 9,11,17 pelletizing process Phillips catalyst 129,134, 219, 223,

225,228 photo-oxidation 233,235 photo-stability 229 photo-stabilization 235 poly(styrene-eo-hydroxystyrene) 213, 214 polyethylene 72 crystallization analysis fractionation 38 polymerization 1-hexene 95, 97,153, 154 2-hydroxyethyl methacrylate 1 bulk 14,253 ethylene 19,45,59,61,123,125, 126, 135, 137, 141, 143,144, 145, 157, 168, 171, 172, 213,216, 225, 247 gas-phase 245,247,248,249,250, 251,254,259,267,268,269 kinetics 225 liquid-phase 254,255,264,267, 268,269 norbornene 61,113,115,119,209 olefin 219 propylene (propene) 23,47,49, 52, 77, 79, 82, 83, 105, 106, 135,138, 140,189,190,191,192,241,242, 243,244,254,259,264,267,269 styrene 74, 99,147,149,157,159, 161,163,216,217 syndiospecific 50,147,149,161, 216,217 polymer-supported catalyst 215, 216 polymorphism of ethylene copolymers 36 polynorbornene 13 CNMR 120 glass transition temperature 120 polypropylene crystallization analysis fractionation 39 elastomeric 106,107 injection molding 8 isotactic 135,138 macroinltiator 1,3 powder stability 13,14

282 Subject Index process 7 spherulite 237,238 surface 4 syndiotactic 189,191,192 polystyrene syndiotactic 69,71,73, 74,75,149, 213 post-polymerization 47, 50, 189,191 preactivation 77,79, 80, 81 prepolymerization 19,22,24 pseudo-Cj -symmetry 153

R radical scavenger 205 radical scavenging activity 205,207 rate constant 257,262,265 reactor blend 245,248,250,251 refractive index 185 ring-opening metathesis polymerization norbornene 165,169,175,176 norbornene derivatives 205, 206,

192,242 syndiotactic pentad

191

tantalum 165,167,168,169 Tebbe reagent 43,45,46 Temperature Rising Elution Fractionation (TREF) 37, 38, 39,40, 41 titanium 65, 71, 74,75,105, 106,108, 153,154,155,156,157,182,215,

216,217,241,244 titanium benzamidinate complex 105 triisobuiylaluminum 19,22,23,24,28, 77,79,80,81,82,83,84,85 tris(pentafluorophenylborane) 171

U UV-vis

19,21,22,23, 80, 81,188

vanadium 123,125,127,175,176,178 scandium bis(alkyl) complex 95, 97 Schulz-Flory 90,145,146 short chain branch 171,173,225 silsequioxane 53 Simple Plastic Manufacturing 7 SiOa nanoparticle 230, 231 spherical MgCl2 209,210,211,212 stabilizer 7,11 stereoblock 78,84 stereoerror 110,111 stereoseleetlvity 78,85 supported catalyst 25,30,210,211, 212,214,215,216, syndiospecificity 51, 52, 70,190,191,

X-ray erystallography67, 141,142, 167 X-ray diffraction analysis 87,90

Ziegler catalyst 13 Ziegler-Natta catalyst 9, 10,254,269 zirconium 21,153, 154, 157,197 zirconocene 52, 77, 80, 81, 82, 135 isospecific 197 syndiospecific 83

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