Polymer-clay nanocomposite latex particles by inverse pickering emulsion polymerization stabilized with hydrophobic montmorillonite plates

We present the first surfactant-free inverse emulsion polymerization by using organically modified clay platelets as stabilizers. Colloidally stable inverse Pickering emulsions of aqueous acrylamide (AAm) or 2-hydroxyethyl methacrylate (HEMA) in cyclohexane stabilized by hydrophobic Cloisite 20A (MMT20) were prepared. With both oil-soluble 2,2'-azobis(isobutyronitrile) (AIBN) and water-soluble 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) as initiators, inverse latexes in the size range of 700-980 nm were successfully obtained. It has been revealed by SEM and cryo-TEM that the latexes were stabilized by hydrophobic clays, as exemplified by the rugged surface of the particles. It was shown from thermogravimetric analysis (TGA) that all the clay platelets were incorporated into the composite particles, and in partially exfoliated state as indicated by X-ray diffraction study.