Ethyl α,α dibromoacetate was confirmed to be a difunctional initiator for the atom transfer radical polymerization of n butyl acrylate by means of gel penetration chromatography. When the polymerization of n butyl acrylate was carried out at different molar ratios of ethyl α,α dibromoacetate and ethyl α bromopropionate with CuBr/2,2′ bipyridine as the catalyst, polymers with bimodal molecular weight distributions were obtained, consisting of two narrowly distributed fractions, one of which was of a molecular weight double the other. Poly( n butyl acrylate) obtained with ethyl α,α dibromoacetate as the difunctional initiator was further used as the macroinitiator for styrene and methyl methacrylate in the presence of CuBr/2,2′ bipyridine respectively to prepare ABA triblock copolymers. It was found that high blocking efficiency was obtained for styrene. However, the polymer with bimodal molecular weight distribution was obtained for methyl methacrylate with a low molecular weight peak corresponding to that of poly( n butyl acrylate) macroinitiator. If the blocking polymerization was conducted with CuCl/ 2,2′ bipyridine as the catalyst to replace CuBr/2,2′ bipyridine, a high blocking efficiency was also obtained. [WT5HZ]
