SYNTHESIS OF TRIBLOCK AND RANDOM COPOLYMERS OF 4-ACETOXYSTYRENE AND STYRENE BY LIVING ATOM-TRANSFER RADICAL POLYMERIZATION

Triblock copolymers containing polystyrene (PSt) and poly(4-acetoxysty rene) (PAcOSt) segments have been prepared by atom transfer radical po lymerization (ATRP). In the first step one of the two monomers was pol ymerized in bulk using the initiating system alpha,alpha'-dibromo-p-xy lene/CuBr/2,2'-bipyridine (1/1/3). Subsequently the resulting telechel ic polymers with active bromo end group structures were used as macroi nitiators for the polymerization of the second monomer under ATRP cond itions. This process gave PAcOSt-PSt-PAcOSt and PSt-PAcOSt-PSt tribloc k copolymers with predetermined molecular weights and narrow molecular weight distributions. Polymerization of a mixture of equal molar amou nts of the two monomers yielded a random copolymer with narrow molecul ar weight distribution.