P(N-isopropylacrylamide)(PNIPAM)prepared by reversible addition fragmentation chain transfer(RAFT) polymerization exhibited gelation retardation.The intermediate before gelation was characterized and indicated the presence of branched or hyperbranched chains.The swelling behavior was investigated,and the gel by RAFT polymerization(RAFT gel)showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional gels(CG).The study was extended to gels prepared by using 2-hydroxy-1-ethanethiol as chain transfer agent and by using low concentration solutions. The two systems also exhibited retardation effects and improved deswelling kinetics.The different swelling behaviors of these gels and CG could be attributed to the presence of dangling chains caused by gelation retardation.
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