Atom transfer radical dispersion polymerization of styrene in ethanol

An atom transfer radical dispersion polymerization of styrene in ethanol was successfully carried out with the formation of uniform sized particles. This was accomplished by using a two-stage polymerization technique, in which the first stage involves a standard free radical polymerization and the second a controlled/living radical polymerization. The required nucleation stage was completed in a relatively short period, and therefore particles with uniform size were achieved. The particles contained polymers with molecular weight similar to 20 000 g/mol and relatively low polydispersity (M-w/M-n = 1.4-1.8, compared with M-w/M-n = 4-5 from conventional dispersion polymerization), indicating a high fraction of retained chain-end functionality which can be readily employed for further modification of the particles. Monodisperse cross-linked polystyrene particles were also synthesized using the same technique; these particles were successfully chain-extended with 2-hydroxyethyl methacrylate, thereby modifying the surface properties of the particles.