Electroactive Polymers as Mixed Conductors

Quasl-Equillbrium Charging of Electroactive Polymer Films 

In this section we present a more detailed treatment of the oxidation/reduction (charging) reaction of an electroactive polymer coating. In particular the effects of a changing Donnan potential and site-site interactions are considered. The polymer is assumed to be in quasi-equilibrium with the electrode, as in Section 3. The redox sites react similarly to a redox species in an electrolyte that is confined to a thin layer cell. The concentrations (activities) of the electroactive sites are described by the Nemst equation, cf. Eqn. 29. The current peaks associated with linear sweeps of the electrode potential are well described in the literature see for instance Ref. 62. We can also characterize such systems by charging curves 

As shown in Eqn. 26, the degree of oxidation or reduction of the electroactive coating is determined by the potential drop across the metal/polymer interface. Thus to describe the degree of charging of the system as a function of the electrode polarization E (relative to a reference electrode in the electrolyte), we must take into account the Donnan potential Disregarding short-range interactions of ionic 

Therefore, includes the density of charged redox sites. At a sufficiently 

The same equation (though with a different expression for E ) is obtained if the oxidation level of the polymer has a maximum value caused by geometrical restrictions for the concentration of counterions in the polymer phase dx - 

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