Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide: Control of molecular weight distribution by adjusting particle surface area

Expts. of Me methacrylate dispersion polymn. are carried out in a reaction calorimeter using PDMS-mMA (methacrylate-terminated polydimethylsiloxane) as surfactant. Different stabilizer concns. from 0 to 10 wt% with respect to monomer have been considered in order to control particle morphol. The anal. by SEM reveals a definite decrease of the total particle surface area at decreasing stabilizer concn. At the same time, the anal. of the polymer microstructure by gel permeation chromatog. shows a trend of the av. mol. wt. towards smaller values. In particular, a second mode at low mol. wts. has been obsd. leading to bimodal mol. wt. distributions. The exptl. results are compared with simulation results obtained through a detailed kinetic model developed in previous studies. The key role of the radical exchange between continuous and dispersed phases is confirmed.