Dielectric and rheological properties of polyaniline organic dispersions

Abstract

This paper reports the examination of the evolution of polyaniline-organic solvent interactions in the temperature range of 294–353 K. For this purpose, rheological and dielectric investigations have been undertaken for dispersions of plast-doped polyaniline in two different solvents (dichloroacetic acid and formic acid/dichloroacetic acid mixture). Dielectric permittivity has been investigated using the open ended coaxial line method in the frequency range of [100 MHz, 10 GHz]. Dielectric loss spectra of both dispersions showed a relaxation peak which was well fitted by Havriliak-Negami function. The relaxation was attributed to a Maxwell Wagner Sillars relaxation within polyaniline clusters. The difference found between relaxation parameters of the pure solvent and polyaniline dispersions was attributed to the solvent/polyaniline interactions. The relaxation time relative to the PANI/DCAA dispersion followed an Arrhenius law. While a Vogel-Fulcher-Tammann law was found for the relaxation time of PANI/DCAA-FA dispersion. Above a certain temperature, 318 K for PANI/DCAA and 313 K for PANI/DCAA-FA, the rheological parameters of the dispersions changed, thus indicating a morphological change of polyaniline in the dispersion. In the same range of temperature, α and β relaxation parameters undergo significant changes. Those changes in dielectric and rheological parameters seem to be related to a structural change occurring in the polyaniline organic dispersion systems while increasing temperature. An interesting correlation between permittivity and viscosity was obtained.