Simulation of secondary particle formation in seeded emulsion polymerization: The effect of surface charge density

Abstract

Mathematical modeling and simulation were carried out to investigate the effects of the surface charge density of seed particles on secondary particle formation and the rate of polymerization in the early stage of emulsifier-free seeded emulsion polymerization of methyl methacrylate. Limited coagulation theory was applied to simulate new particle nucleation. The main factor influencing the capture rate of oligomeric radicals in a growing seed particle was assumed to be the electrostatic repulsion of seed particles. DLVO (Deryagiun-Landau-Verwey-Overbeek) theory was also introduced to estimate the electrical repulsion between seed particles and oligomeric radicals in the aqueous phase. In the case of highly charged seed particles, the adsorption rate of oligomeric radicals in the aqueous phase showed a strong effect on the polymerization rate. The low adsorption of oligomeric radicals results in a low value of the average number of radicals per particle. The surface charge density of seed particles was found to play an important role in limiting the polymerization rate at the beginning of the reaction and even in affecting the formation of secondary particles.