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Keywords:

  • branched polymer;
  • nanoparticle;
  • thermogelling;
  • disulfide bonds

Abstract

Highly branched poly(N-isopropylacrylamide) (PNIPAM) has been synthesized by a reversible addition-fragmentation chain transfer (RAFT) copolymerization of NIPAM and a vinyl contained trithiocarbonate RAFT agent. 1H-NMR measurements revealed that the degrees of branch (DB) are in the range of 0.032–0.105. Laser light scattering (LLS) measurements gave the hydrodynamic radii (Rh) of the polymers to be 3.6–5.7 nm with molecular weight in the range of 1.3 × 104 g/mol–2.3 × 10−4 g/mol. Highly branched PNIPAM with terminal thiol groups were obtained by aminolysis the polymers, and the product can be oxidized by air to form disulfide bonds ([BOND]S[BOND]S[BOND]) among chains and resulting in the formation of nanoparticle in aqueous solution. Interestingly, the nanoparticle in size of Rh ˜ 80 nm showed a thermogelling behavior to form bulk hydrogel when the temperature was increased up to 25°C due to the thermo-induced association of the PNIPAM chains among the nanoparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010