The size

monodispersity and surface properties of polymer microspheres are especially important in biomedical field

information industry and microelectronics applications. The aim of the study is to obtain monodisperse microspheres carrying functional group in the micron size range by copolymerization．In this study

monodisperse St-MMA copolymer microspheres with a diameter of 5.4 μm were prepared by dispersion polymerization in absolute ethanol media using polyvinylpyrrolidone K-30(PVP) as a steric stabilizer and 2

2′-azobisizobutyronitrile (AIBN) as an initiator．The comparison of dispersion polymerization and emulsion polymerization indicated that their reaction mechanism were different．The copolymer microspheres prepared by emulsion polymerization were in the size range of 0.1～0.5 μm and the size distribution was broad．The kind of copolymer microspheres can coagulate easily and disperse hardly because of the residual emulsifer. The copolymer microspheres prepared by dispersion polymerization were spherical

monodisperse and were able to disperse easily．The statistical results showed that the size distribution of copolymer microspheres conform to normal distribution．The average size was 5.4 μm．The standard deviation(δ) was 0.16 and the dispersion parameter (ε) was 0.02．The SEM photographs showed that the copolymer microspheres had smooth surface and good sphericity．The FTIR results showed that the functional group (MMA) had been successfully incorporated onto the microspheres by copolymerization．