Synthesis and Application of Ketene Silylacetal-Ended Polystyrene

In order to synthesize ketene silylacetal-ended polystyrene (PSt), anionic living PSt was end-capped with 1, 1- diphenylethylene, then the resulting carbanion was transformed into enolate anions by the reactions with methyl cinnamate (MCI), methyl crotonate (MC), and t-butyl crotonate (TBC), and finally each of them was reacted with trimethylchlorosilane (TMCS). PSt-PMMA bolck copolymers were obtained by the group transfer polymerization of methyl methacrylate (MMA) using the ketene silylacetal-ended PSt as the initiator. When MCI was used for the transformation of living PSt, the PSt-PMMA block copolymers obtained were fairly monodispersed (Mw/Mn=1.2-1.4), whereas in the cases of MC and TBC, the molecular weight distributions (MWD) of the block copolymers were broad. The ratios of [M] to [I] affected the MWD of the block copolymers and the initiator efficiency (f). The PSt-PMMA block copolymers thus prepared were also compared with those obtained by the polymerization of MMA from living PSt.