A substituted E-caprolactone, alpha-bromo-epsilon-caprolactone, was synthesized from alpha-bromocyclohexanone by Baeyer-Villiger reaction using 3-chloroperoxybenzoic acid. The ring-opening copolymerization of this monomer with epsilon-caprolactone was carried out with aluminum isopropoxide as the initiator, giving poly (epsilon-caprolactone-co-alpha-bromo-epsilon-caprolactone) copolymer. This copolymer was used as the macroinitiator for the controlled atom transfer radical polymerization (ATRP) of styrene for the synthesis of poly(epsilon-caprolactone)-g-polystyrene graft copolymers. The results showed that all the initiating sites along the macroinitiator chain initiated ATRP of styrene, and that the molecular weights of the graft copolymers increased with styrene conversion and agreed well with the theoretical values. (c) 2005 Elsevier Ltd. All rights reserved.