Photopyroelectric spectroscopy of polyaniline films

Photopyroelectric spectroscopy (PPES), in the 400 < lambda < 900 nm wavelen gth range, was used to study thermal properties of differently doped polyan iline (PAN) films. The photopyroelectric intensity signal V-n(lambda) and i ts phase F-n(lambda) were independently measured, as well as the intensity V-n(f) and the phase F-n(f) (f being the chopping frequency) for a given A of the saturation part of the PPES spectrum. Equations of both the intensit y and the phase of the PPES signal, taking into account the thermal and the optical characteristics of the PAN films and the pyroelectric detector, we re used to fit the experimental results. From the fittings we obtained, wit h great accuracy, the values of thermal conductivity k and thermal diffusiv ity coefficient a of PAN films of different doping degrees. It was observed that, in contrast with the strong doping-dependence of the electrical cond uctivity, the thermal parameters of PAN films remained practically unchange d under doping. This apparent discrepancy is explained by the granular meta l model of doped PAN. (C) 2000 John Wiley & Sons, Inc.