Emulsion copolymerization of styrene and poly(ethylene glycol) ethyl ether methacrylate

In this study, a relatively novel macromonomer having a relatively shorter chain length, poly(ethylene glycol) ethyl ether methacrylate (PEG-EEM) was used to increase the stability of styrene-water emulsion. The uniform latex particles in the range of 0.4-1.2 mu m were prepared by the emulsion copolymerization of styrene (S) and PEG-EEM. The copolymerizations were achieved by using potassium persulphate (KPS) as the initiator in an aqueous emulsion medium including NaCl. To achieve uniform copolymer particles with different size and surface properties, PEG-EEM/S volume ratio, KPS concentration, monomer/water ratio and NaCl concentration were changed. The results indicated that the average particle size decreased with the increasing PEG-EEM/S ratio. Higher PEG-EEM/S ratios provided copolymer latex particles with higher yield and higher monodispersity. The copolymer latex particles with lower mass and surface charge densities were obtained with the higher PEG-EEM/S ratios. The power law dependency of particle number density on the PEG-EEM concentration was also determined. The average particle size increased with the increasing KPS and NaCl concentrations. Excess KPS or NaCl concentrations led to copolymer latex particles with a bimodal size distribution. (C) 1999 Elsevier Science Ltd. All rights reserved.