Preparation of Monodisperse and Anion-Charged Polystyrene Microspheres Stabilized with Polymerizable Sodium Styrene Sulfonate by Dispersion Polymerization

A novel dispersion polymerization system to produce clean polystyrene (PS) particles, using a polymerizable sodium styrene sulfonate (NaSS) as stabilizer, and a mixture of methanol/water (MeOH/H2O) as the reaction medium was investigated. The effects of the polymerization parameters, such as the methanol/water ratio in the medium, the concentration of the stabilizer, the initiator and the monomer on the resulting particles were studied. By observing the morphological changes of the PS particles by SEM and analyzing the surface chemical composition of these particles by XPS, it is found that this system had the following unique features: as little as 0.05 wt.-% of NaSS (based on styrene as opposed to 5 wt.-% for a routine dispersion polymerization system) was enough to prepare stable latex with monodisperse particles; as high as 20 vol.-% of monomer (as opposed to 5 wt.-% for polymerization system in the absence of surfactants) could be added into the polymerization system to produce monodisperse particles; surface-charged and monodisperse particles with average diameters of approximately 470-1600 nm could be directly obtained.