SYNTHESIS AND CHARACTERIZATION OF POLY(DIVINYLBENZENE) MICROSPHERES

Highly cross-linked and narrow dispersed poly(divinylbenzene)(PDVB) microspheres were prepared by the dispersion polymerization of commerical divinylbenzene using acetonitrile as solvent in the presence of 2,2′-azobis(2-methylpropionitrile) (AIBN) initiator and polyvinylpyrrolidone (PVP) stablizer. The particle average diameter and the particle size distribution were determined by SEM. Narrow dispersed microspheres with diameters between 3 and 5 μm depending on the conditions were produced.The effects of concentrations of initiator and stabilizer, solvent variety, ratio of monomer and solvent on particle average diameters and particle size distributions were investigated. Based on an optimal codition, larger particle size and narrower dispersed microspheres can be synthesized, the particle average diameter is 3^95 μm and the coefficient of particle size distributions (PSD) is 0^106. The time dependence of stabilizer (PVP) content, residual double-bonds and the relative ratio of para-and meta-divinylbenzene in the microspheres were studied by IR psectra. The ratios of characteristic absorbance of components changing with time showed the change of each component in the polymerization product. Monomer conversion was determined gravimetrically after washing residual monomers from the raw particle slurries and drying under vacuum. It is revealed from the conversion-time curve that the polymerization reaction is almost complete in 12 h. The content of residual double-bonds in the microspheres was determined by the reaction with Br-2/H-2O, then titrated by 0^1mol/L criterion NaOH solution. The microspheres produced by dispersion polymerization as mentioned above contain(1^7±0^5)mol/g residual double-bonds. The thermostability of microspheres were determined by TG.The starting temperature of decomposition is above 400℃, the fastest decomposing temperature is 461^6℃, showing that PDVB microspheres have high thermo-stability.