Preparing of monodisperse and cation-charged polystyrene particles stabilized with polymerizable quarternary ammonium by dispersion polymerization in a methanol-water medium.

A novel dispersion polymerization system, with a methanol/water (MeOH/H2O) mixture as reaction medium and a polymerizable dimethylaminomethacrylate methyl chloride (DMC) as stabilizer was developed. By monitoring the polymerization evolution and observing the morphological changes of the polystyrene (PS) particles by SEM, it was found that this system had the following unique features: (1) a much lower amount of DMC (0.025 mass% based on styrene as opposed to 5 mass% for a routine system) was required to prepare monodisperse and stable PS particles; (2) the rate of polymerization was fast and the conversion was very high; (3) the monodisperse particles with average diameters of approximately 200-1600 nm could be directly obtained. These features were explained by a synergistic interaction between water and the quarternary ammonium cations. Combined with XPS, ion-exchange/conductometric titration, FTIR and 1H NMR analysis, a plausible polymerization mechanism through which the particles were stabilized by the PS-PDMC copolymer formed in situ was proposed.