The Coupling among Electron and Proton binding in Electroactive Polymers: the case of polyaniline

W. MARMISOLLÉ; M. I. FLORIT; D. POSADAS

Niza, Francia

Congreso; 61st Annual Meeting of the International Society of Electrochemistry (ISE); 2010

International Society of Electrochemistry (ISE)

In this work, we presente a equilibrium statistical thermodynamic model that has into account for the coupling between the electron and proton binding in electroactive macromolecules.  According to this model, both the apparent formal redox potential and  the formal  potential distibution depend on the state of proton binding. Correspondingly, the apparent pKa values also depends on the oxidation degree of the macromolecule. Spectroelectrochemical data for polyaniline films in sulphuric acid solutions are presented in order to support the proposed model. The spectroelectrochemical measurements allows obtaining the oxidation degree of the polyaniline films in different conditions.Polyaniline films were electrosynthetized upon ITO electrodes from aniline 0.5M in H2SO4 3.7M aqueous solution by cyclic voltammetry. The film coated electrode (working electrode) was  placed in a commercial quartz spectrophotometric cubette (1x1cm) togeher with a platinum mesh (counter electrode) and the Luggin capilar of a Saturated Calomel Electrode (reference). UV-vis spectra were taken in the transmitance way at different applied potentials. The changes in the absorption band at 320nm was used to calculate the degree of oxidation. Mathematical treatment of the oxidation degree as a function of potential allows succesfully fitting the parameters of the model.