The copolymer microspheres of styrene (St) and maim anhydride (MA) were synthesized by stabilizer free dispersion polymerization and the polymerization process was explored in detail The results showed that the homopolymerization of St formed in initial polymerization period served as stabilizer and reaction solvent of closer solubility parameter would benefit the stabilizer free dispersion polymerization In addition some principal factors affecting the microspheres size such as reaction time reaction temperature monomer concentration molar feed ratio reaction media and cosolvent were investigated as well (c) 2010 Wiley Periodicals Inc J Polym Sci Part A Polym Chem 48 5652-5658 2010