Controlled/living radical polymerization of styrene has been achieved by atom transfer radical polymerization (ATRP) catalyzed by cobaltocene (PDI = 1.27-1.41). The effects of the initiators, temperatures and solvents were studied. The end group of PS-Br was characterized by H-1 NMR. Block co-polymerization proved that the polymer end is still living and the PMMA-b-PSt block copolymer was synthesized. (c) 2008 Elsevier Ltd. All rights reserved.