Dielectric properties of conducting polyaniline films by THz time-domain spectroscopy

The dielectric function of composite polyaniline (PANI)/polyurethane (PU) is studied in the terahertz range. Different free-standing films of composite PANI-CSA/PU with different PANI concentrations are measured by terahertz time-domain spectroscopy (THz-TDS). The Fourier transmission spectrum, the permittivity and conductivity are then precisely obtained between 0.1 and 4 THz. The behaviour of the dielectric function does not follow Drude theory and the extracted data are well fitted by Jonscher's universal dielectric response. Furthermore, the percolation threshold is also deduced from the insulating to conducting transition extracted for several doping level at very high frequency. (c) 2007 Elsevier Ltd. All rights reserved.