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

We describe some of our recent results on the characterization of aque ous colloidal dispersions of conducting polymer-inorganic oxide nanoco mposite particles. Such colloids are easily prepared by synthesizing t he conducting polymer in the presence of commercially available ultraf ine silica (or tin(IV) oxide) particles in aqueous media. In the prese nt study we present electrokinetic data as a function of pH for the fo llowing systems: polypyrrole-silica, carboxylic acid-functionalized po lypyrrole-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 group s at the inorganic oxide surface rather than by the conducting polymer component. This suggests that the inorganic oxide is the major compon ent at the particle surface, which is consistent with the excellent lo ng-term colloid stability of these dispersions. The aqueous electropho resis measurements also indicate that our surface functionalization ex periments 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 silic a component using 3-aminopropyl triethoxysilane. (C) 1995 Academic Pre ss, Inc.