The bimetallic nanoparticles were protected by a double stimuli-sensitive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(4-vinylpyridine) (PNIPAM-b-P4VP), which was synthesized via the reversible addition-fragmentation chain transfer (RAFT) polymerization. The obtained nanocomposites were made up of bimetallic nanoparticles cross-linked P4VP core and PNIPAM shell. Energy-dispersive X-ray (EDX) spectra and UV-vis transmittance revealed the formed nanoparticles was truly bimetallic particles with incomplete core-shell structures, Au as core and Pd as shell, rather than the physical mixture of monometallic nanoparticles. Laser light scattering (LLS) demonstrated the nanocomposites exhibit both thermo and pH sensitivity. X-ray diffraction (XRD) clearly showed Au formed a high-ordered crystal while Pd fashioned amorphous aggregates. In addition, the bimetallic nanocomposites show special responsiveness for temperature and better catalytic activity than corresponding monometallic nanocomposites. (C) 2008 Elsevier Inc. All rights reserved.