One of the most useful methods for synthesizing the graft and well-defined copolymers is the atom transfer radical polymerization (ATRP) method. The polymerization was initiated by polystyrene (PS) carrying chloroacetyl groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy). The macroinitiator (chloroacetylated PS) was prepared by successive chloroacetylation of PS under mild conditions and these reaction conditions overcome the problem of gelation and crosslinking in polymers. Successful graft copolymerizations were performed with methyl methacrylate (MMA) in toluene at 80 degrees C and with acrylonitrile (AN) in tetrahydrofuran/ethyl-enecarbonate (62.5/37.5 v/v %) mixed solvent at 55 degrees C. The characterization of the copolymers was investigated by H-1-NMR and FT-IR spectroscopices. Gel permeation chromatography measurement indicated an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator. This measurement also indicated the monomodal molecular weight distribution. (c) 2006 Wiley Periodicals, Inc.