Highly crosslinked polymer particles by dispersion polymerization

Monodisperse poly(divinylbenzene) and poly(styrene‐co‐divinylbenzene) particles were prepared in the 0.4−3 μm size range by dispersion polymerization in methanol and methanol/co‐solvent mixtures. The effects of polymerization parameters, such as the crosslinking monomer concentration, the co‐solvent, and the presence of oxygen were studied. For good colloidal stability, it was necessary to use a relatively large fraction of crosslinking monomer. The initial presence of oxygen was also found to play an important role in determining the colloidal stability during the polymerization. Although the exact mechanism is not certain, it is considered likely that the oxygen promotes the grafting of poly(divinylbenzene) to the polyvinylpyrrolidone (PVP) stabilizer molecules. The growing particles were investigated by electron microscopy. Precipitation of small particles onto the nucleated particles was determined to be the primary mechanism of particle growth.