Substituent effects in ethene/styrene copolymerization: Dormant state destabilization?

Homogeneous metallocene and CGC catalyzed copolymerizations of ethene (E) and various substituted styrenes are examined. It is found that those with p-tert-butylstyrene (TBS) occur with dramatically higher degrees of incorporation and overall productivity than those observed under the same conditions with styrene. It is argued that that the sigma-donating effect of the tert-butyl substituent is responsible for this performance, effecting a destabilization of an otherwise dormant benzylic species following 2,1-insertion of the styrene. It was found possible to produce what is essentially TBS-alt-E (44% TBS with no sequential TBS units) using a standard constrained geometry catalyst at impressively high productivity 1.1.5 x 10(6) g/(mol(Ti).bar(E).h)] and unusually low concentration of TBS (0.7 M). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 31,11-3117, 2009