SYNTHESIS OF COLLOIDAL DISPERSIONS OF POLYPYRROLE-SILICA NANOCOMPOSITES USING STRINGY SILICA PARTICLES

We have investigated the oxidative polymerization of pyrrole using FeCl3 in the presence of commercially available colloidal silica particles which possess a nonspherical ''stringy'' morphology, The resulting polypyrrole-''stringy'' silica nanocomposite particles are colloidally stable in aqueous media and have been characterized in terms of their particle size and morphology, conducting polymer composition and solid-state electrical conductivity, Both the polypyrrole content and particle size decreases with increasing initial concentration of stringy silica. Use of the (NH4)(2)S2O8 oxidant for the pyrrole polymerization generally produces macroscopic precipitates rather than stable colloids even at relatively high stringy silica concentrations. However, simply reducing the (NH4)(2)S2O8 concentration to a sub-stoichiometric amount with respect to pyrrole can yield stable colloids. This latter oxidant can also be utilized to prepare the analogous polyaniline-stringy silica dispersions in 1.2 M HCl. (C) 1995 Academic Press, Inc