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Homo‐ and copolymerization of ethylene by cationic hafnocene catalysts based on tetrakis(pentafluorophenyl)borate
Author(s) -
Yano Akihiro,
Sone Makoto,
Yamada Satoru,
Hasegawa Saiki,
Akimoto Akira
Publication year - 1999
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19990401)200:4<924::aid-macp924>3.0.co;2-v
Subject(s) - ethylene , methylaluminoxane , copolymer , polymer chemistry , cationic polymerization , catalysis , chemistry , polyethylene , hexene , metallocene , polymerization , boron , zirconium , organic chemistry , polymer
Ethylene homopolymerization and ethylene/1‐hexene copolymerization were conducted at different temperature and ethylene pressure using several hafnocenes activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH·B(C 6 F 5 ) 4 ). rac ‐Ethylene(bisindenyl)hafnium dichloride ( rac ‐Et(Ind) 2 ‐HfCl 2 ) activated with Me 2 PhNH·B(C 6 F 5 ) 4 shows ten times higher activity than methylaluminoxane(MAO)‐activated catalyst for ethylene polymerization at 40°C, and produces high molecular weight polyethylene with high activity even at 150°C independent of ethylene pressure. The molecular weight of ethylene/1‐hexene copolymers synthesized at high temperature is influenced by the ligand structure, and a rac ‐(dimethylsilyl)bis(2,4‐dimethylcyclopentadienyl)hafnium dichloride ( rac ‐Me 2 Si(2,4‐Me 2 Cp) 2 HfCl 2 )‐based catalyst exceptionally produces only low molecular weight copolymers. These copolymers contain high amount of vinylidene end groups, indicating that β ‐H transfer from propagating chains containing primary inserted 1‐hexene as terminal unit occurs frequently. At high ethylene pressure, the rac ‐Et(Ind) 2 HfCl 2 ‐based catalyst produces high molecular weight ethylene/1‐hexene copolymers with high activity, but this activity is slightly lower than that of zirconium analogs.