Effect of reaction parameters on the dispersion polymerization of 1-vinyl-2-pyrrolidone

Nonporous hydrogel microspheres 0.1–1.3 μm in diameter were prepared by the dispersion copolymerization of 1-vinyl-2-pyrrolidone and ethylene dimethacrylate as a crosslinking agent. The crosslinking was evidenced by solid state 13C NMR and elemental analysis. The effect of various parameters including selection of solvent (cyclohexane, butyl acetate), initiator (4,4′-azobis(4-cyanopentanoic acid), 2,2′-azobisisobutyronitrile, dibenzoyl peroxide) and stabilizer on the properties of resulting microspheres has been studied. Dynamic light scattering and photographic examination were used for determination of the diameter and polydispersity of microspheres. Increasing concentration of steric stabilizer in the initial polymerization mixture decreased the particle size. The particle size depended on the molecular weight of polystyrene-block-hydrogenated polyisoprene stabilizer, but not on the number of PS and polybutadiene blocks in the styrene–butadiene block copolymer stabilizers. Dibenzoyl peroxide used as an initiator resulted in agglomeration of particles.