Statistic and block copolymers exhibiting activated ester side groups were synthesized by reversible addition-fragmentation chain transfer polymerization in the presence of cumyl dithiobenzoate, benzyl dithiobenzoate, and 4-cyano-4-((thiobenzoyl)sulfanyl)pentanoic acid as chain transfer agents. Pentafluorophenyl methacrylate and pentafluorophenyl 4-vinyl-benzoate were used to enable a sequential functionalization of the obtained copolymers by conversion of the activated esters with different amines. H-1 NMR spectroscopy, F-19 NMR spectroscopy, and FTIR spectroscopy showed the successful step-by-step conversion of the different activated esters by aniline followed by aliphatic amines, thereby realizing a sequential functionalization of block copolymers with just one specific reactive group. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3683-3692, 2010