Anomalous particles formed in two-stage soap-free emulsion polymerization of styrene on poly(2-acetoxyethyl methacrylate)

In two-stage soap-free emulsion polymerization of styrene on cross-linked poly(2-acetoxyethyl methacrylate) (PAEMA), the resulting PAEMA/polystyrene latex interpenetrating polymer network particles were found to be nonspherical, assuming a wide variety of surface morphologies, such as "confetti-like", "raspberry-like", "popcornlike", "void-containing" particles, "doublets" and "triplets". The anomalous particles were characterized by transmission electron microscopy and atomic force microscopy, as a function of the degree of cross-linking of the PAEMA seed, the composition, the addition mode of the second-stage monomer, and the initiator type.