Alternating electrical conductivity of polyaniline

The ac complex conductivity sigma*( f) of polyaniline (PAN) films at differ ent doping levels and different temperatures, in the 1-100 KHz frequency ra nge, are reported. The results are typical of a disordered medium where the real component of ac conductivity is frequency independent at low frequenc ies, rising for higher values of frequencies. In order to interpret both th e real and the imaginary components of sigma*( f), we developed a model whi ch considers the doped PAN as a disordered insulating matrix, sprinkled wit h conductive islands generated by doping, as indicated by energy dispersed x-ray microanalysis. The conduction through the insulating matrix obeys the random free energy barrier model, while in the conductive islands a metall ic frequency-independent conductivity is considered. From the fittings we o btained the activation energy value of the maximum energy barrier of the do ping mechanism and estimated the concentration of hopping sites. (C) 1999 A merican Institute of Physics. [S0021-9606(99)70806-8].