FORMATION OF COLLOIDAL PMMA PARTICLES VIA FREE-RADICAL AND GROUP-TRANSFER DISPERSION POLYMERIZATION OF METHYLMETHACRYLATE AND METHYLMETHACRYLATE ETHYLENEGLYCOLDIMETHACRYLATE

Non-aqueous dispersions of colloidal PMMA microparticles with average sizes ranging from 70 to 330 nm were prepared by living polymerization of methylmethacrylate (MMA) and methylmethacrylate/ethyleneglycoldime thacrylate (EDMA) in n-heptane diluent using 2-methyl-1-methoxy-1-trim ethylsilyloxy-prop-1-ene (MTS) as initiator in the presence of tetrabu tylammonium fluoride (TBAF) or tetrabutylammonium cyanide (TBAC) as ca talyst, and polystyrene-block-poly(ethene-alt-propene) (SEP) as disper sing agent. The influence of process parameters such as concentrations of MMA, EDMA crosslinking agent, TBAF, and SEP on conversion, molecul ar weight, particle size, and molecular weight and particle size distr ibutions has been investigated. In contrast to GTP in solution, group transfer dispersion polymerization (GTDP) was markedly slower and acco mpanied by agglomeration and drastic broadening of both molecular weig ht and particle size distributions with increasing MMA conversion. In a new GTDP process colloidal PMMA microparticles, obtained by free rad ical dispersion polymerization, were added as seeds, thus affording mu ch narrower particle size distribution and high MMA conversion.