Vinyl-type homo- and copolymerization of norbornene catalyzed by bis(phenoxyimine) titanium complex

Abstract

A ternary catalytic system consisting of a bis(phenoxyimine) titanium complex, triisobutylaluminium and an organoboron compound exhibited high activity in the vinyl-type homopolymerization of norbornene. The obtained polynorbornene showed a modest molecular weight (M n ≈ 5 × 10 4 g mol −1 ) and broad molecular weight distribution (polydispersity index ≈ 3.5). A copolymer of norbornene with 1,3-butadiene was prepared using a binary catalytic system consisting of bis(phenoxyimine) titanium complex and triisobutylaluminium. The norbornene units in the copolymer adopted a vinyl-type addition structure confirmed using distortionless enhancement by polarization transfer 135 13 C NMR microstructure analyses. Polymerization kinetics studies showed that neither monomer feed ratio nor conversion had an effect on the composition of the copolymer backbone which was composed of 55% norbornene units and 45% 1,3-butadiene units. The essentially constant polymer composition implied an alternating nature of chain propagation. The copolymer exhibited good thermal stability and moderate glass transition temperature (50.9-68.2 ∘ C) with a relatively high molecular weight (M w = 0.18 × 10-1.31 × 10 5 g mol −1 ), and excellent transparency (maximal transmittance >80%). 1618 www.soci.org J Meng et al. Scheme 1. Structure and synthesis of bis(phenoxyimine)titanium complex 1.