EFFECTS OF THERMAL AGING ON ELECTRIC-CONDUCTIVITY OF POLYANILINE

Results of electrical conductivity and optical absorption spectra measurements of polyaniline are reported. Samples prepared by casting were heated at 90 approximately 270-degrees-C and then dipped into aqueous solutions of H2SO4. The conductivity increases with the decrease of the aging temperature. In the case of lower heating temperatures up to 190-degrees-C, the doping may result in a oxidation of the amine units to imine units, which would enhance the formation of the polaron band and the density of free carriers. On higher temperature treatment, thermally induced changes in morphology, crosslinking, and/or other chemical reactions should lower the level of the oxidation of amines, prevent formation of the polaron band, and suppress the conductivity.