Polysulfone-g-poly(N-isopropylacrylamide) (PSf-g-PNIPAAm) graft copolymers were prepared from atom transfer radical polymerization of NIPAAm using chloromethylated PSf as a macro-initiator. The chain lengths of PNIPAAm of the graft copolymers were controllable with polymerization reaction time. The chemical structures of the graft copolymers were characterized with FTIR, NMR, and elemental analysis and their amphiphilic characteristics were examined and discussed. The PSf-g-PNIPAAm graft copolymers and the nanoparticles made from the graft copolymers exhibited repeatable temperature-responsive properties in heating-cooling cycles. (C) 2008 Wiley Periodicals, Inc.