Synthesis of pH- and temperature-responsive chitosan-graft-poly[2-(N,N-dimethylamino) ethyl methacrylate] copolymer and gold nanoparticle stabilization by its micelles

Novel pH- and temperature-responsive chitosan-graft-poly[2-(N,N-dimethylamino)ethyl methacrylate] (chitosan-g-PDMAEMA) copolymers were successfully synthesized by homogeneous atom transfer radical polymerization (ATRP) under mild conditions. Chitosan macroinitiator was prepared by phthaloylation of amino groups of chitosan and subsequent acylation of hydroxyl groups of chitosan with 2-bromoisobutyryl bromide. The copolymers were obtained by ATRP of 2-(N,N-dimethylamino)ethyl methacrylate and they can self-assemble into stable micelles in water. Hybrid micelles with a PDMAEMA corona incorporating gold nanoparticles (Au NPs) were prepared in situ via the reduction of HAuCl4 with NaBH4. The pH and temperature responses of the copolymer micelles and hybrid micelles were characterized using UV-visible spectroscopy and dynamic laser light scattering. The morphology of the micelles was observed using transmission electron microscopy and atomic force microscopy. The PDMAEMA corona of the micelles acts as the 'nanoreactor' and the 'anchor' for the in situ formation and stabilization of Au NPs. Therefore, the spatial distribution of Au NPs within the micelles can be tuned by varying the temperature and pH value. (C) 2010 Society of Chemical Industry