Controlled/living polymerization of methacrylamide in aqueous media via the RAFT process

The polymerization of methacrylamide (MAM) was performed in aqueous media via reversible addition fragmentation chain transfer (RAFT) polymerization with the dithiobenzoate chain-transfer agent (CTA) 4-cyanopentanoic acid dithiobenzoate (CTP) and 4,4'-azobis(4-cyanopentanoic acid) (V-501) as initiator. The polymerization in unbuffered water at 70 degrees C with a CTP/V-501 ratio of 1.5 was controlled for the first 3 h, after which the molecular weight distribution broadened and a substantial deviation of the experimental from the theoretical molecular weight occurred, presumably because of a loss of CTA functionality at longer polymerization times. Conducting the polymerization in an acidic buffer afforded a well-defined homopolymer (M(n) = 23,800 g/mol, M(w)/M(n) = 1.08). To demonstrate the controlled/living nature of the system, a block copolymer of MAM and acrylamide was successfully prepared (M(n) = 33,800 g/mol, M(w)/M(n) = 1.25) from a polymethacrylamide macro-CTA. (c) 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3141-3152, 2005.