Formation of monodisperse PMMA particles by radiation-induced dispersion polymerization--I. Synthesis and polymerization kinetics

Highly monodisperse poly(methyl methacrylate) microparticles were directly prepared by radiation-induced dispersion polymerization at room temperature in aqueous alcohol media using poly(N-vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The gel effect was evident from the increase of the molecular weight with conversion and also from the percentage conversion vs. time curves. The influences of dose rate, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate and the molecular weight of polymer have been examined. It was found that the overall activation energy for the rate of polymerization is 18.44 kJ/mol (10-25 deg. C). Based on the experimental results, the polymerization mechanisms were discussed