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Homo‐ and copolymerization of ethylene at high temperature with cationic zirconocene catalysts
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<917::aid-macp917>3.0.co;2-n
Subject(s) - ethylene , polymer chemistry , isomerization , cationic polymerization , copolymer , polyethylene , 1 hexene , catalysis , polymerization , chemistry , chain transfer , hexene , metallocene , materials science , photochemistry , organic chemistry , polymer , radical polymerization
Homo‐ and copolymerization of ethylene with 1‐hexene were conducted at different temperature and ethylene pressure with several zirconocenes activated with dimethylanilinium tetrakis(pentafluorophenyl)borate (Me 2 PhNH·B(C 6 F 5 ) 4 )/triisobutylaluminium (i‐Bu 3 Al) to study the effect of ligand structure and polymerization conditions on catalytic activity, molecular weight and chain transfer reactions. At high temperature and low ethylene pressure, rac ‐ethylene(bisindenyl)zirconium dichloride ( rac ‐Et(Ind) 2 ZrCl 2 ) activated with Me 2 PhNH·B(C 6 F 5 ) 4 /i‐Bu 3 Al initially gives a highly active catalyst that is rapidly deactivated. trans ‐Vinylene double bonds, which were not formed at low temperature, were detected in polyethylene synthesized at high temperature and low ethylene pressure. They reasonably arise from β ‐H transfer after isomerization reaction. The molecular weight of ethylene/1‐hexene copolymers decreases with increasing 1‐hexene feed, followed by the formation of vinylidene end groups. This reveals that β ‐H transfer from propagating chains containing primary inserted 1‐hexene as a terminal unit is predominant. This reaction is influenced by the ligand structure. At high temperature and high ethylene pressure, trans ‐vinylene and vinylidene contents decrease and the vinyl content increases, indicating that the high ethylene pressure controls β ‐H transfer after isomerization reaction.