Synthesis of block copolymers by transformation of free radical promoted cationic polymerization to atom transfer radical polymerization

Abstract

The transformations of free radical promoted cationic polymerization to atom transfer radical polymerization (ATRP) to form the block copolymers of cyclohexene oxide (CHO) with styrene (St) were performed. In the first step, bromine terminated poly(CHO)s (PCHO-Br) were prepared by free radical promoted cationic polymerization of CHO monomer in the presence of 2-oxo-1,2- diphenylethyl-2-bromopropanoate, shortly bromo benzoin, (B-Br) and an onium salt namely 1-ethoxy-2-methylpyridinium hexafluorophosphate (EMP+SbF 6-) as the initiating system. The bromine functionalized polymers thus prepared were used as initiators in ATRP of St, in bulk, in conjunction with CuBr/2,2′-bipyridine as catalyst gave well-defined block copolymer of CHO and St. Block copolymer formations were evidenced by 1H NMR and gel permeation chromatography (GPC) measurements.