Polymer modification of colloidal particles by spontaneous polymerization of surface active monomers

Adsorption and spontaneous polymerization of head- or tail-type surface active monomers having long methylene chains on colloidal silica and ii-alumina were investigated. Both head-type and tail-type ammonium monomers on silica in chloroform or tetrahydrofuran had the maximum adsorption on the respective adsorption isotherm. Above the monomer concentration giving the maximum adsorption, it was observed that the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from the silica surface. At the monomer concentration giving the maximum adsorption, heating the silica suspension containing the monomer at 40 degrees C or 60 degrees C in tetrahydrofuran or chloroform solution resulted in spontaneous polymerization. The composite particles formed by polymerization were observed to have many spots consisting of polymer on the surface. Therefore, it is suggested that the monomers are concentrated by micelle-like aggregation on the silica surface and consecutively spontaneous polymerization takes place. Adsorption of an anion-type monomer having a carboxyl group on delta-alumina, which exhibited a positive zeta potential in neutral aqueous solution, was higher than that on colloidal silica, but did not spontaneously polymerize on alumina.