The kinetics of dispersion copolymerization of methacryloyl-terminated poly( oxyethylene)( PEG-MA) and p-vinylbenzyl-terminated (PEG-St) polyoxyethylene macromonomers and styrene (St), initiated by a water- and/or oil-soluble initiator, was investigated using conventional gravimetric and NMR methods at 60 degrees C. The batch copolymerizations in the water/ethanol continuous phase were conducted to high conversion. The rate of polymerization was described by the curve with a maximum at very low conversion. The initial rate of polymerization and the number-average molecular weight were found to decrease with increasing [PEG-MA], and the decrease was more pronounced in the range of a high macromonomer concentration. The rate per particle(at ca. 20% conversion) was found to be proportional to the -1.55th, the particle size to the -0.92nd, and the number of particles (at final conversion) to the 3.2nd power of [PEG-MA], respectively. At the beginning of polymerization the continuous phase is the main reaction locus. As the polymerization advances, the reaction locus is shifted from the continuous phase to the polymer particles. The transform of the reaction loci from the continuous phase to the polymer particles increases the rate of polymerization and the polymer molecular weights. The increase of the weight ratio PEG-MA/St favors the formation of monodisperse polymer particles, the colloidal stability of dispersion, and the formation of a larger number of polymer particles.