A star-like amphiphilic copolymer was synthesized via RAFT polymerization by using a pentaerythritol-based compound (PTDBA) as a chain transfer agent with Styrene and DMAEMA as monomers. The polymer structure was characterized by FTIR (1)H NMR, (13)C NMR and SEC/MALLS. After the retardation period, the molecular weight of PS-CTA and PMMA-CTA increased linearly with monomer conversion. The amphiphilic copolymer self-assembled into spherical micelles when water was added into its DMF solution. The particle size and polydispersity index (PDI) of the micelles in deionized water were about 406 nm and 0.113, respectively, In a pH 10 buffer solution and low micelle concentration, the micelle size decreased with temperature increase, At higher temperatures and micelle concentrations the size increased, resulting in precipitation among agglomerating micelles. This phenomenon was not observed in deionized water. Furthermore, the copolymer effectively prolonged the release time of chlorambucil (CLB) in deionized water. (C) 2008 Elsevier Ltd. All rights reserved.