Microemulsion Polymerization. 3. Molecular Weight and Particle Size Distributions

Molecular weight and particle size distributions of latexes prepared by free radical polymerization of n -butyl methacrylate, tert -butyl methacrylate, n -hexyl methacrylate, and styrene in aqueous microemulsions of dodecyltrimethylammonium bromide surfactant are measured using GPC/MALLS, QLS, and cryo-TEM. The results are compared to a molecular weight distribution model derived from the monomer partitioning and kinetic studies described in the accompanying papers. Polystyrene with weight-average molecular weights of ∼15 × 10 6 Da, which are 7 times greater than the limiting molecular weight imposed by chain transfer to monomer, are consistently obtained. Diffusion-limited exit of monomer radicals, generated by chain transfer, to the aqueous phase coupled with chain transfer to polymer are likely reasons for the enhanced polystyrene molecular weights.