Highly monodisperse crosslinked polystyrene microparticles by dispersion polymerization

Highly monodisperse polystyrene microparticles crosslinked with urethane acrylates were produced by dispersion polymerization in ethanol solution in the presence of 2,2'-azobis (isobutyronitrile) initiator, polyvinylpyrrolidone stabilizer, and Aerosol-OT costabilizer. Different from conventional crosslinkers, the urethane acrylates employed as a crosslinker showed an excellent effect on maintaining the monodispersity of polystyrene microparticles even in the moderate crosslinker concentration. This was believed that the urethane acrylate helped forming the monomer-swellable surface of primary particles, because of its structurally long tetramethylene oxide groups in its molecule. However, at high concentration of the urethane acrylate, the rough surface and the coagulum of particles were observed, which was attributed to the seriously decreased solubility of the monomer mixtures in ethanol solution. The solubility of the mixtures of styrene monomer and urethane acrylate in the media had a serious effect on the average particle size and morphology of the final particles. This could be confirmed by the measurement of cloud points and fractional conversions.