Nitroxide-mediated radical polymerization from CdSe nanoparticles

We report the use of nitroxide-mediated controlled free radical polymerization directly from the surface of CdSe nanoparticles to prepare polymer-nanoparticle composite materials. While free radicals can quench the fluorescence of CdSe nanoparticles, nitroxide-mediated polymerization allows for the preparation of the desired polymer-nanoparticle composites while maintaining the inherent fluorescence of the nanoparticles. The low concentration of radicals inherent to this controlled free radical polymerization technique contributes to the success of this process. Nitroxide-containing ligand 2 was prepared for this study and used to functionalize 3-4-nm CdSe nanoparticles. By this method, polystyrene and poly(styrene-r-methyl methacrylate) copolymers were grown from the nanoparticle surface. Displacement of these polymers from the surface, and subsequent analysis by gel permeation chromatography (GPC), revealed the success of this method. The effect of the polymerization conditions on dispersion and fluorescence of the nanoparticles is described.