Synthesis of polystyrene microspheres by dispersion polymerization using poly(vinyl alcohol) as a steric stabilizer in aqueous alcohol media

Dispersion polymerization of styrene was investigated using PVA as a steric stabilizer in aqueous alcoholic media. In aqueous methanol and alcohol media, colloidally stable monodisperse polystyrene microspheres are synthesized using BPO and AIBN as initiators and various PVA concentrations of 0.5-10 wt.% relative to styrene. The effect of PVA on the size variation is found to be similar to that of conventional stabilizer, PVP. The yield of polymerization is significantly influenced by the amount of PVA. When initiator is changed to AIBN, the yield of polymerization is substantially lower than the BPO systems. Both chemical grafting and physical adsorption of PVA endow stability of the polystyrene particles. Such a mechanism was justified from the FT-IR spectrum of polystyrene particles in which characteristic peaks of PVA molecules are witnessed. The molecular weight increases with the PVA content due to the reduced particle size. The glass transition temperatures of the polystyrene particles lie in 98.9-104.4 °C regardless of PVA concentrations. Contrary to PMMA dispersion polymerization with a PVA stabilizer, no discernable change in the glass transition temperature is observed.