RAFT Cryopolymerizations of N,N-Dimethylacrylamide and N-Isopropylacrylamide in Moderately Frozen Aqueous Solution

Aqueous reversible addition-fragmentation chain transfer (RAFT) cryopolymerizations of N,N-dimethylacrylamide (DMA) and N-isopropylacrylamide (NIPAM) with potassium persulfate/sodium ascorbate as redox initiators were performed at -15 degrees C. For the homopolymerizations, water-soluble chain transfer agents (CTAs) of 2-(1-carboxy-1-methylethyl-sulfanylthiocarbonylsulfanyl)-2-methylpropionic acid and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methylpropionyl-capped methoxy poly(ehylene glycol) were used For the sequential block copolymerizations, the obtained trithiocarbonate-functionalized polymers were used as macro-CTAs Although well-defined homo and block polymers of DMA and NIPAM were synthesized and these RAFT cryopolymerizations were well controlled, their behavior depended on the monomers and CTAs The polymerization kinetic and polymer structure were studied by proton nuclear magnetic resonance analysis and gel permeation chromatography measurement. Poly(N,N-dimethylacrylamide)-based cryogels crosslinked with reductively cleavable disulfide-containing diacrylamide, N,N'-bisacryloylcystamine, were synthesized via RAFT cryopolymerization Scanning electron microscopy observation revealed that the porous Structure of cryogels depended on the CTA used. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A Polym Chem 47 6863-6872, 2009