Determination of physical parameters of conducting polymers by photothermal spectroscopies

Photothermal spectroscopies, photopyroelectric and photoacoustic, were used to obtain physical parameters of polyaniline-emeraldine base (PANI-EB) and poly(o-methoxyaniline)-emeraldine base (POMA-EB), such as thermic parameters like thermal diffusivity, thermal conductivity, and specific heat. These studies were done for PANI-EB and POMA-EB films in the 400<lambda<900 nm wavelength range. The photopyroelectric intensity V-n(f ) and the phase F-n(f ) (f being the chopping frequency) for a given lambda of the saturation part of the PPES spectrum signal were independently measured, as well as the intensity V-n(lambda) and its phase F-n(lambda). Equations of both the intensity and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the PANI and POMA films and the pyroelectric detector, were used to fit the experimental results. It was observed that, in contrast with the strong doping dependence of the electrical conductivity, the thermal parameters of PANI films remained practically unchanged under doping. This apparent discrepancy is explained by the granular metal model of doped PANI. (C) 2003 American Institute of Physics.