A series of thermosensitive copoly(oligoethylene oxide) acrylates with narrow polydisper- sities were prepared by the copolymerization of oligo(ethylene oxide) acrylate and di(ethylene oxide) ethyl ether acrylate using reversible addition-fragmentation chain transfer polymerization (RAFT). These copolymers exhibit tunable LCST behavior over the range of 15-90 ?C dependent on their monomer compositions. Subsequently, these copolymers were grafted onto gold nanoparticle (GNP) surfaces yielding thermosensitive gold nanoparticles. The thermoresponsive properties of these hybrid GNPs/poly(OEG-A- co-DEG-A) nanoparticles were evaluated in solution using dynamic light scattering and UV-vis spectroscopy. In addition, the susceptibility of these GNPs to protein fouling was assessed by a Bradford s assay and found to be significantly reduced by the copolymer stabilizing layer. We also demonstrate, in a unique one- pot assembly process, the synthesis of a hybrid nanoparticle that shows dual temperature responsiveness. These hybrid nanoparticles open new applications in biotechnology and medicine.