Synthesis of Colloidal Dispersions of Polypyrrole-Silica Nanocomposites Using "Stringy" Silica Particles

Abstract

We have investigated the oxidative polymerization of pyrrole using FeCl 3 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 (NH 4) 2S 2O 8 oxidant for the pyrrole polymerization generally produces macroscopic precipitates rather than stable colloids even at relatively high stringy silica concentrations. However, simply reducing the (NH 4) 2S 2O 8 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.