Kinetic and mechanistic aspects during a styrene-based Pickering emulsion polymerization: Importance of the co-aid adsorption

A Pickering emulsion polymerization (PEP) was performed with styrene (Sty), silica and an initiator, both anionic, and small amounts (1.1 wt % total) of 4-vinyl pyridine (4VP), vinyl benzene sulfonate (VBS) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as co-aids. We focus on the analysis of the possible phenomena occurring during the formation of these hybrid particles. Kinetic data was gathered by gravimetry and correlated with Raman spectroscopy. The particle formation along the reaction was tracked by light dispersion and transmission electron microscopy (TEM). Pickering particles were formed early in the reaction. A stable emulsion system was achieved even when continuous nucleation and a partial coagulation were present in the reaction. A peak at around 2888 cm(-1) appeared in the Raman spectra at high conversions, attributed to PEGMA regrouping around silica. Possible mechanisms for the formation of a styrene-based PEP in a batch reactor are discussed herein.