Electrochemical transport phenomena in conducting polymer films

Summary form only given. Conjugated-polymer films synthesized on a metal electrode surface are able to change drastically their electronic charge, conductivity and other properties in a quasi-equilibrium manner at simple sweeping the electrode polarization. This complex charging-discharging process includes intensive transport of ions and solvent across the film/solution boundary and inside the film. This presentation contains the theory of this phenomena based on general approach of irreversible thermodynamics for a coupled transport of electrons, ions and solvent species through the polymer phase, with taking into account their short-range interactions and the upper limitations for their concentrations. Both interfacial charge-transfer and double-layer charging contributions into the current are considered at both interfacial boundaries. Analytical solutions of this set of bulk film and interfacial equations at the low-amplitude alternative current passage have been obtained both for the polymer-film coated electrode and the film between two metal or two solutions. Effect of slow ionic and solvent transport is especially pronounced within intermediate and low frequency range and may strongly modify the complex-impedance plots of these systems. In particular, this analysis has shown that slow film swelling may be responsible for an usually observed shape of these plots, a gradual increase of their slope from unity to infinity, instead of a sharp transition from the Warburg behavior to a vertical line (pure capacitive charging of the film) predicted by the previous theories.