Preparation of poly(acrylamide)/nanoclay organic-inorganic hybrid nanoparticles with average size of ∼250 nm via inverse Pickering emulsion polymerization

Abstract

In this study, the preparation of poly(acrylamide)/nanoclay organic-inorganic hybrid nanoparticles via surfactant-free inverse emulsion polymerization by using organically modified clay platelets as stabilizers was discussed. Colloidally stable inverse Pickering emulsions of aqueous acrylamide solution in cyclohexane (solvent) stabilized by hydrophobic Cloisite 20A (MMT20) were prepared. Polymerization was carried out via 2,2′-azobis(isobutyronitrile) and composite particles with an average size of ∼250 nm were obtained. The effect of initiator and solvent type on the stability, size, size distribution, and morphology of the produced composite particles was examined. It was observed that in the presence of xylene as solvent, particles with bigger sizes and broader size distribution were obtained. Furthermore, using an ionic initiator resulted in a slight coagulation during polymerization and smaller particles. Moreover, the effect of various polymerization conditions such as temperature, initiator, and crosslinking agent concentration and clay content on the polymerization rate was evaluated. The experimental results showed that polymerization rate increases with an increase in polymerization temperature, crosslinking agent concentration, and initiator content. However, increasing in clay content results in a lower polymerization rate.