N,N-Dimethylaniline functional polystyrenes with well-defined structures and low polydispersities were synthesized by atom transfer radical polymerization of styrene in bulk at 110degreesC using 4-(dimethylamino)benzyl 4-(bromomethyl) benzoate as initiator in conjunction with a cuprous complex [Cu(I)Br/bipyridine]. These polymers were further used in block copolymerization with methyl methacrylate and cyclohexene oxide (CHO) by photoinduced radical and radical-promoted cationic polymerization routes, respectively. In the former case, macroradical generation was achieved with benzophenone sensitizer by photoexcitation followed by hydrogen abstraction from amino end groups. A visible light initiating system was used in the radical-promoted cationic polymerization of CHO. The system involves a xanthene dye (erythrosin B) as the sensitizer, an aromatic N,N-dimethyl amino group and diphenyl iodonium hexafluorophosphate as the radical source and radical oxidizer, respectively. Whereas pure block copolymers were obtained in the free-radical route, the free-radical-promoted cationic polymerization yielded both block and homopolymers. (C) 2004 Wiley Periodicals, Inc.