Nonspherical dented poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) particles formed in seeded soap-free emulsion copolymerization

In this study, nonspherical poly(methyl methacrylate)/poly(styrene-co-divinylbenzene) [PMMA/P(St-co-DVB)] particles having multiple dents on the surface were prepared by seeded soap-free emulsion copolymerization of St and DVB (used as a crosslinker) on spherical linear PMMA seed particles. The effect of various polymerization parameters on particle morphology, as well as polymerization kinetics and morphological evolution, were investigated in detail. It was found that, to prepare this kind of nonspherical particles, it was necessary to conduct the polymerization at a relatively low temperature, using batch monomer addition mode and PMMA seed of relatively high molecular weight. The formation of the nonspherical particles was attributed to the phase separation between the second-stage monomers and the crosslinked P(St-co-DVB) network being formed during polymerization.