Copolymerization of styrene and acrylonitrile was carried out via reversible addition-fragmentation chain transfer process (RAFT) in the presence of cumyl dithiobenzoate with AIBN as initiator. Copolymerization proceeded in a controlled/"living" fashion, and the copolymer composition depended on the feed ratio of monomer pairs. Block copolymers comprising styrene and acrylonitrile (SAN) segments and various functional blocks were synthesized through chain extension using the first blocks as macromolecular chain transfer agents (macroCTAs). Since the polymerization of both blocks proceeded through the RAFT process, the resulting block copolymers exhibited relatively narrow molecular weight distribution, with polydispersity indices in the range of 1.29-1.46. Gel permeation chromatography (GPC), and H-1 NMR and FTIR measurements confirmed the successful synthesis of the functionalized block copolymers. (c) 2006 Wiley Periodicals, Inc.