Emulsion copolymerization of styrene and methacrylic acid in the presence of a polyethylene oxide based-polymerizable stabilizer with a shorter chain length

The emulsion copolymerization of styrene and methacrylic acid (MAA) was performed in the presence of a relatively new macromonomer, poly(ethylene glycol) ethyl ether methacrylate (PEG-EEM) as a stabilizer. In contrast to similar studies, a macromonomer having relatively shorter polyethylene oxide chain length (i.e., M_n:246, n ≈ 3.0) was selected for this study. Highly uniform and carboxyl functionalized latex particles in the size range of 0.16–0.50 μm were obtained by changing MAA, PEG-EEM, total monomer, and initiator concentrations. The use of PEG-EEM as a stabilizer resulted in larger monodisperse particles relative to those obtained by the emulsifier-free emulsion copolymerization of styrene and MAA. The particle size decreased and the polymerization rate increased with the increasing MAA feed concentration. The application of power law model indicated that MAA concentration was more effective in the presence of PEG-EEM for control of particle size relative to similar systems. The latex particles with higher numbers of surface-carboxyl groups were obtained with the higher MAA feed concentrations. Although the particle size decreased and the polymerization rate increased with the increasing PEG-EEM concentration in the emulsion polymerization of styrene, both of them remained roughly constant with the increasing PEG-EEM concentration in the presence of MAA. Received: 21 December 2000 Accepted: 13 July 2000