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Polyethylenes Having Well‐Defined Bimodal Molecular Weight Distributions Formed with Bis(phenoxy‐imine) Zr Complexes
Author(s) -
Tohi Yasushi,
Nakano Takashi,
Makio Haruyuki,
Matsui Shigekazu,
Fujita Terunori,
Yamaguchi Tsutomu
Publication year - 2004
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/macp.200400039
Subject(s) - imine , cationic polymerization , polymer chemistry , ligand (biochemistry) , polymerization , catalysis , chemistry , materials science , organic chemistry , polymer , receptor , biochemistry
Summary: Bis(phenoxy‐imine) Zr complexes with MAO activation can produce polyethylenes with well‐defined bimodal molecular weight distributions. Polymerization behavior indicates that minor changes in the ligand structures can have a significant effect on the modality of the resulting polyethylenes. Although there is no direct relationship between the bimodal catalytic behavior and the structure of a precatalyst complex in solution, a precatalyst complex having a methyl or methoxy group para to the phenoxy‐oxygen inclined to exhibit bimodal behavior whereas that with a pentafluorophenyl group on the imine‐nitrogen displayed unimodal behavior. Polymerization results suggest that bimodal behavior is linked to the presence of two kinds of cationic active species, which arise from different modes of ligand coordination. A qualitative correlation was found between the calculated amounts of possible cationic active species and the uni‐ and bimodal catalytic behavior. Based on the results obtained, we concluded that the bimodal polyethylenes are produced by two kinds of cationic active species having two available cis ‐located sites with cis ‐N, trans ‐O and cis ‐N, cis ‐O arrangements. The results introduced herein are rare examples of the production of well‐defined bimodal polyethylenes using a single precatalyst.Bis(phenoxy imine) Zr complexes can produce well‐defined bimodal polyethylenes.