Shape of the particles produced by seeded dispersion polymerization of styrene

In this work, seeded dispersion polymerization of styrene was carried out in the presence of various types of seed particles. We found that in the case of polystyrene and poly(methyl methacrylate) seeds, the shape of the resulting particles remained spherical. For styrene/poly( n butyl methacrylate) (P n BMA) and styrene/poly(lauryl methacrylate) seeding particles, raspberry like particles were produced along with those of occluded morphology. We studied the effects of various polymerization factors such as concentrations of a stabilizer, an initiator, and a monomer, a weight ratio of methanol to water, a type of initiator, weight ratio of styrene to P n -BMA seed particles, and polymerization temperature on the formation of these raspberry-like particles. The experimental results showed that the increase of concentrations of the initiator and the stabilizer as well as that of methanol favors the formation of such particles by increasing their surface roughness. An increase of the temperature of polymerization had the same effect on the morphology of resulting product. We hypothesized that the nucleation and growth of specifically fine-structured polystyrene domains on the surface of the Pn-BMA particles guides the formation of non-linear morphology during seeded polymerization in colloidal solution.