Journal of Polymer Science Part A: Polymer Chemistry, Vol.45, No.16, 3599-3610, 2007
Polymerization of 1-olefins by zirconium/titanium precatalysts with O,N,O-ligating atoms - Can aggregation of catalyst be inferred from the reaction profile?
The 2-[benzyl-(2-hydroxy-2-phenylethyl)-amino]-1-phenylethanol ligand (1-H-2) prepared as a diastereomeric mixture or in racemic and meso forms, from known procedure, has been disodiated and complexed with ZrCl4. The precatalysts (mix-1-ZrCl2, rac-1-ZrCl2, and meso-1-ZrCl2) were used in combination with methylaluminoxane and found to be active for the polymerization of 1-hexene and 1-octene. The high molecular weight polyhexenes (PHs) and polyoctenes (POs) thus obtained were isotactic in nature and showed a negligible amount of end groups arising from the chain termination reactions. In PHs and POs, there was linear correlation in the modified Arrhenius plot (the natural logarithm of the number-average molecular weight vs. the reciprocal of the temperature), indicating the presence of a single active species. The enantiomerically pure titanium precatalyst ((R,R)-1-TiCl2), when employed for the polymerization of 1-hexene, was found to be active and the modified Arrhenius plot showed linear dependence demonstrating presence of a single active species. The analogous titanium precatalysts (mix-1-TiCl2, rac-1-TiCl2, and meso-1-TiCl2) obtained from known procedures were also found to be active for the polymerization of 1-octene. The rac-1-TiCl2 precatalyst demonstrated a sigmoidal behavior in the modified Arrhenius plot for the POs and the mix-1-TiCl2 precatalyst showed an exponential type of behavior. The obtained POs seemed to have small amounts of chain termination via beta-hydride elimination alone. (C) 2007 Wiley Periodicals, Inc.