ZETA-POTENTIAL MEASUREMENTS ON CONDUCTING POLYMER-INORGANIC OXIDE NANOCOMPOSITE PARTICLES

We describe some of our recent results on the characterization of aqueous colloidal dispersions of conducting polymer-inorganic oxide nanocomposite particles. Such colloids are easily prepared by synthesizing the conducting polymer in the presence of commercially available ultrafine silica (or tin(IV) oxide) particles in aqueous media. In the present study we present electrokinetic data as a function of pH for the following systems: polypyrrole-silica, carboxylic acid-functionalized polypyrrole-silica, amine-functionalized polypyrrole-silica, polyaniline-silica, and polypyrrole-tin(IV) oxide colloids. These data show that both the isoelectric points and zeta potentials of these nanocomposite dispersions are governed primarily by the nature of the charged groups at the inorganic oxide surface rather than by the conducting polymer component. This suggests that the inorganic oxide is the major component at the particle surface, which is consistent with the excellent long-term colloid stability of these dispersions. The aqueous electrophoresis measurements also indicate that our surface functionalization experiments were successful: Carboxylic acid groups can be incorporated via copolymerization using an appropriate functional pyrrole comonomer, while amine groups can be introduced via derivatization of the silica component using 3-aminopropyl triethoxysilane. (C) 1995 Academic Press, Inc.