Size control of highly monodisperse polystyrene particles by modified dispersion polymerization

Highly monodisperse polystyrene (PS) particles have been synthesized by modified dispersion polymerization in which aqueous alcohols, polyvinylpyrrolidone (PVP), and ammonium persulfate (APS) are used as a medium, steric stabilizer, and initiator, respectively. An ionic initiator, APS, in typical dispersion polymerization would help stabilize the growing PS particles by electrical repulsion, resulting in a monodisperse particle size distribution. Moreover, the dual functions of APS as an initiator and electric stabilizer compete to determine the final size of the PS particles and lead the size of PS particles to be less sensitive to the APS concentration. Therefore, it was possible to control precisely the size of highly monodisperse PS particles in the diameter range, 800 to 2,000 nm. In addition, the highly monodisperse PS particles below 800 nm in size could be obtained just by quenching the reactant with time. Therefore, these PS particles can be used readily to fabricate colloidal crystals owing to their high monodispersity.