Syntheses of super-fine monodispersed particles of poly (Styrene-co-methyl methacrylate) by dispersion polymerization

Abstract

Microsphere particle sizes of poly (styrene-co-methacrylate) were prepared by dispersion polymerization in ethanol/water media. Poly (N-vinyl pyrrolidone) (PVP K-30) and azobisisobutyronitrile were utilized as matrix polymer and initiator, respectivelyl The effects of matrix polymer concentrations. Ethanol/water ratio, reaction temperature, reaction time, agitation rate and feed ratio of styrene/methyl methacrylate monomers on the particle sizes, particle size distribution, average molecular weights and molecular weight distribution of the copolymer wete investigated. The effect of the matrix polymer on particle sizes of the copolymer were studied. Monomer conversion and the copolymer particles growth 10 h were also investigated. The particle sizes and particle size distribution were characterized by SEM; the average molecular weights and molecular weight distribution by GPC; the thermal analysis by DSC; the copolymer compositions by NMR; and EA; and the functional group by FTIR. Poly (styrene-co-methyl methacrylate) with spherical shape, smooth surface, the size range of 0.3-1.5 µm and narrow size distribution (CV<10%) were obtained by dispersion polymerization in the presence of the matrix polymer. The copolymers by solution polymerization (without the matrix polymer) were formed in sheets and lumps It was found that the biggest and smallest particles were obtained in the homopolymers of poly (methyl methacrylate) and polystyrene. Respectively. The average particle size decreased with increasing the matrix polrix polymer concentration, polarity of the dispersion medium, and agitation rate. The increase in the polymerization temperature and reaction time resulted in an increase in the average particle size. When water and ethanol were used as solvent, the copolymer particles have a broad size distribution. When the solvent mixture containing 10-30 parts of water. The appropriate temperature for dispersion polymerization was 70℃ . The molecular weight distribution range of the copolymer was 2-3. This research has elucidated has elucidated the mechanisms of super-fine, monodispersed copolymer formation by the theories of solubility parameter and matrix polymer anchoring.