ATRP-RCM polymer cyclization: synthesis of amphiphilic cyclic polystyrene-b-poly(ethylene oxide) copolymers

A novel amphiphilic block copolymer, i.e., cyclic polystyrene-b-poly(ethylene oxide) (cyclic PS-b-PEO 2), was synthesized through atom-transfer radical polymerization (ATRP), followed by ring-closing metathesis (RCM). Thus, a bromobenzyl-terminated PS-b-PEO-b-PS (6) was first prepared by ATRP of styrene using a PEO macroinitiator having 2-bromoisobutyryl groups (5). The subsequent end-group conversion into allyl groups was performed quantitatively with allyltrimethylsilane (ATMS) in the presence of TiCl4. The allyl-telechelic triblock copolymer PS-b-PEO-b-PS (7) thus obtained was subjected to metathesis polymer cyclization with a Grubbs' 2nd generation catalyst to produce amphiphilic cyclic PS-b-PEO (2).