Reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloyl-L-proline methyl ester (A-ProOMe) was investigated in order to find suitable conditions to achieve controlled synthesis of amino acid-based polymers with pre-determined molecular weight, narrow polydispersity, well-defined chain end structure, and characteristic thermo-responsive property. The effect of various parameters, such as chain transfer agent (CTA)/initiator ratio, solvent, and temperature, on RAFT polymerization of A-Pro-CiNle was examined using benzyl dithiobenzoate as a CTA. Chain-end structure of the resulting poly(A-Pro-OMe) was confirmed by H-1 NMR analysis, MALDI-TOF mass spectroscopy, and chain extension experiment. Thermally induced phase separation behaviors of poly(A-Pro-OMe)s prepared by RAFT and conventional free radical polymerizations were also studied in aqueous solution. (c) 2007 Elsevier Ltd. All rights reserved.