Well-defined poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) brushes with high density were synthesized on the surface of polystyrene latex by atom transfer radical polymerization (ATRP) using acetone/water as the solvent and CuCl/CuCl2/bpy as the catalyst. It was found that the polydispersity of PDMAEMA brushes decreased with the increasing external CuCl2 concentration. The polymer brushes showed their lower critical solution temperature (LCST) at 31 and 33 degrees C under pH values of 10.0 and 8.0, respectively. Dynamic light scattering studies demonstrate that PDMAEMA brushes were pH- and salt-responsive. PDMAEMA domains were used as the nanoreactors to generate gold nanoparticles on the surface of colloid particles. TEM results indicate that monodispersed gold narroparticles were obtained. These gold composite narroparticles displayed effective catalytic activity in the reduction of 4-nitrophenol by NaBH4. (c) 2007 Elsevier Ltd. All rights reserved.