Reactions to effect the transformation of anionic polymerization into cationic polymerization: 2. Synthesis and reactivities of anionically generated xylelene bromide-terminated polymers

Abstract

A method is described whereby ‘living’ anionic polymers may be transformed via a stable intermediate stage into polymeric cations. The process involves termination with excess xylylene dibromide, and the subsequent reaction of the polymeric product with an appropriate silver salt in the presence of a second monomer. Living polystyrene and polybutadiene may be transformed by this technique, and block copolymers have been prepared with tetrahydrofuran from both these starting materials. The efficiency of initiation in this system at room temperature is considerably greater than that obtained from ‘living’ polymer terminated with elemental bromine but some transfer process still occurs. ‘Living’ cationic AB block copolymers have been synthesized, which have subsequently been coupled using disodium resorcinate to yield ABA blocks with 70% efficiency.