Controlled synthesis of thermoresponsive polymer via RAFT polymerization of an acrylamide containing l-proline moiety

Reversible addition-fragmentation chain transfer (RAFT) polymerization of N-acryloyl-l-proline methyl ester (A-Pro-OMe) 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 thermoresponsive property. The effect of various parameters, such as chain transfer agent (CTA)/initiator ratio, solvent, and temperature, on RAFT polymerization of A-Pro-OMe was examined using benzyl dithiobenzoate as a CTA. Chain-end structure of the resulting poly(A-Pro-OMe) was confirmed by 1H 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.