Application of a distributed impedance model in the analysis of conducting polymer films

The problem analysed is whether the electrochemical transfer in the doping of conducting polymer electrodes must be described as a macroscopic resistance localised at the outer boundaries of the polymer layer, or by a distributed process inside the film region. Impedance measurements of poly(thiophene-3-acetic acid) film in its oxidised state are reported for various values of pH in solution. The analysis shows that the observed response consists on the coupling, throughout the polymer film, of the transfer resistance with other conduction and polarisation processes. This is interpreted as evidence of a distributed charge-transfer resistance in the internal polymer/solution interface.