The synthesis of poly(styrene-b-alkyl acrylate) and poly(styrene-b-methyl methacrylate) block copolymers by atom transfer radical ppolymerization (ATRP) with CuX(X=Cl

or Br)/2

2′-bipyridine (bipy) complex as the catalyst was studied in this work. When chlorine capped polystyrene (PSt-Cl) synthesized by ATRP was used to initiate the polymeriztion of methyl acrylate

ethyl acrylate or n-butyl acrylate in the presence of CuCl/bipy

well-defined poly(styrene-b-alkyl acrylate) block copolymers were obtained. However

when PSt-Cl or PSt-Br was used as macroinitiator to initiate the polymerization of the macroinitiator PSt-X(X=Cl.or Br)

showing the blocking efficiency was low. While the ATRP of styrene with PMMA-Cl as the macroinitiator gave well-defined poly(methylmethacrylate-b-styrene) block copolymer. These results wereexplained according to the aifference of C-X bond dissociation energy between PSt-X and PMMA-X(X=Cl

or Br).