PEG macromonomer with one methacryloyl end group for per polymer chain was selected as reaction stabilizer. PEG grafted poly (acrylonitrile/styrene) particles with sub-micron to nano sizes were prepared by dispersion copolymerization of acrylonitrile with styrene using 2

2′-azobisisobutyrnitrile (AIBN) as a free radical initiator in the presence of PEG macromonomer in ethanol／water (Vol／Vol=7／3) mixed solvents at 60℃ for 24 h．The nanoparticles having narrow size-distribution were observed based on the studies of transmission electron microscopy (TEM) and laser light scattering (LLS). The surfaces of the nanoparticles have unusual structures which can be control by changing molecular weight of PEG macromonomer and other reaction conditions．The dynamic diameter of the nanoparticles can be controlled in range from 110 to 920 nm by changing reaction factors such as solvent composition

concentration of PEG macromonomer or styrene．X-ray photoelectron spectroscopy analysis shows PEG segments were covered into the surfaces of the nanoparticles．The structure of the freeze-dried nanoparticles was investigated by XRD．XRD pattern of any particles showed a distinct diffraction peak at 2θ=22.6。corresponding to a spacing of 0.39 nm and some small peaks in the 2θ range of 5～30。

indicating that the particles are crystallized．