Polyaniline Dispersions. 6. Stabilization by Colloidal Silica Particles

Abstract

Aniline was polymerized in the presence of ultrafine colloidal silica particles (hydrodynamic diameter 35 nm) in aqueous media and, given a sufficient silica concentration, colloidally stable polyaniline−silica particles were obtained. The particle size of the resulting dispersions was determined by both dynamic light scattering and disk centrifuge photosedimentometry. The typical size of these polyaniline−silica particles is in the range 300−600 nm and is insensitive to the concentration of components in the reaction mixture, temperature, or acidity of the reaction mixture. Particles produced at 0 °C are spherical and their shape becomes less defined when polymerization proceeds at 25 °C. As the silica size is increased, the composite particles become larger and their raspberry morphology more distinct. The electrical conductivity of a typical polyaniline (37.8 wt%)−silica composite is 6.1 × 10-2 S cm-1 at 25 °C. It grows with increasing temperature and does not depend on the frequency in the investigated range from 20 Hz to 1 MHz.