Growth of polymer particles in microemulsion polymerization of methyl methacrylate

Polymerizations of methyl methacrylate in microemulsion stabilized with emulsifier BOA were initiated with gamma ray, KPS, BPO and AIBN, respectively. The microemulsion with high monomer content remained clear after polymerization, The growth of particles and their size distribution were detected at different conversions. The average hydrodynamic diameter of final polymer particles was between 50 similar to 70nm. It was found that there was some resemblance among polymerization initiated with the four initiators. However, there were also obvious differences. When the microemulsion polymerization was initiated with KPS or gamma ray, homogenous nucleation predominated at low conversion, and micellar nucleation dominated at high conversion. When it was initiated with BPO or AIBN, at low conversion, polymerization mainly took place in the big droplets, and micellar nucleation became the only nucleation route at high conversion.