Synthesis and characterization of water-soluble gold nanoparticles stabilized by comb-shaped copolymers

The water-soluble gold nanoparticles stabilized by well-defined comb-shaped copolymers have been synthesized successfully. The hybrid nanoparticles consist of gold core and poly[poly(ethylene oxide) methyl ether acrylate]-block-poly(N-isopropylacrylamide) [P(A-MPEO)-block-PNIPAM] shell. The water-soluble comb-shaped copolymers, P(A-MPEO)-block-PNIPAM with PNIPAM as a handle, were successfully synthesized via a macromonomer technique using reversible addition fragmentation chain transfer (RAFT) polymerization method. The terminal dithioester group of the comb-shaped copolymer was reduced to a thiol end group forming SH-terminated copolymers, P(A-MPEO)-block-PNIPAM-SH. Successively they were used to stabilize gold nanoparticles by the "grafting-to" approach. The hybrid nanoparticles were characterized by TEM, UV-vis, and HRTEM. Because of the thermosensitive property of PNIPAM in aqueous solution, the comblike copolymer-tethered gold nanoparticles show a sharp and reversible phase transition at 30 degrees C in aqueous solution, which was determined by microdifferential scanning calorimetry. (C) 2007 Wiley Periodicals, Inc.