Novel asymmetric difunctional initiators 2-phenyl-2-[(2,2,6,6-tetramethylpiperidino)oxy]ethyl 2-bromo-2-methyl propanoate and of 2phenyl-2-[(2,2,6,6-tetramethylpiperidino)oxy]ethyl 2-bromo propanoate were synthesized in a three-step reaction sequence and used in atom transfer radical polymerization (ATRP) of methyl methacrylate or tert-butyl acrylate leading to corresponding polymer with tempo moiety as chain end. These polymers were found to be efficient initiators for stable free radical polymerization (SFRP) of styrene. H-1 NMR and g.p.c. studies of the obtained polymers show that block copolymers are readily formed as a result of combination of ATRP and SFRP mechanisms. (C) 2001 Elsevier Science Ltd. All rights reserved.