An asymmetric difunctional initiator 2-phenyl-2-[(2,2,6,6 tetramethylpiperidino)oxyl ethyl 2-bromo propanoate (1) was used for the synthesis of ABC-type methyl methacrylate (MMA)-tert-butylacrylate (tBA)-styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free-radical polymerization (SFRP). The ATRP-ATRP-SFRP or SFRP-ATRP-ATRP route led to ABC-type triblock copolymers with controlled molecular weight and moderate poly-dispersity (M-w/M-n < 1.35). The block copolymers were characterized by gel permeation chromatography and H-1 NMR. The retaining chain-end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. (C) 2002 Wiley Periodicals, Inc.