Synthesis of α-bromine-terminated polystyrene macroinitiator and its initiation of MMA polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. alpha-Bromine-terminated polystyrenes (PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, alpha-methylstyrene (alpha-MeSt) as the capping group and liquid bromine (Br-2) as the bromating agent. The effects of reaction conditions such as the amounts of alpha-MeSt, THF, and Br-2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate (MMA) in the presence of copper(I) halogen and 2,2'-bipyridine (bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by H-1 NMR spectra.