DISPERSION COPOLYMERIZATION OF POLY(OXYETHYLENE) MACROMONOMERS AND STYRENE

The kinetics of dispersion copolymerization of methacryloyl-terminated poly( oxyethylene)( PEG-MA) and p-vinylbenzyl-terminated (PEG-St) pol yoxyethylene macromonomers and styrene (St), initiated by a water- and /or oil-soluble initiator, was investigated using conventional gravime tric and NMR methods at 60 degrees C. The batch copolymerizations in t he water/ethanol continuous phase were conducted to high conversion. T he rate of polymerization was described by the curve with a maximum at very low conversion. The initial rate of polymerization and the numbe r-average molecular weight were found to decrease with increasing [PEG -MA], and the decrease was more pronounced in the range of a high macr omonomer concentration. The rate per particle(at ca. 20% conversion) w as 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 t he continuous phase is the main reaction locus. As the polymerization advances, the reaction locus is shifted from the continuous phase to t he polymer particles. The transform of the reaction loci from the cont inuous phase to the polymer particles increases the rate of polymeriza tion and the polymer molecular weights. The increase of the weight rat io PEG-MA/St favors the formation of monodisperse polymer particles, t he colloidal stability of dispersion, and the formation of a larger nu mber of polymer particles. (C) 1997 John Wiley & Sons, Inc.