Tbe determination of tbe anion content in polyaniline as a function of the PH and tee electrode potential: an in situ ATR FTIR spectroscopic study

Abstract

Summary form only given. Polyaniline is outstanding amongst the conducting polymers for its exhibiting potential induced as well as pH induced insulator to metal transitions. As an adherent film on the surface of an electrode, it can exist in different forms depending on the pH value of the electrolyte (salt forms and base forms) and on the potential of the electrode (leucoemeraldine form, emeraldine form, pernigraniline form). The mechanisms of the salt-base transitions and the transitions between the different oxidation states are still subject of discussion. Especially the determination of the amount of anions incorporated in the polymer film at a distinct pH value and a distinct electrode potential is of basic interest for the determination of the reaction mechanisms. Due to changes of the chemical environment using ex situ techniques, these values can be measured only with subtle in situ techniques. In this paper, we describe the determination of the anion content of polyaniline films on the Surface of IR transparent electrodes using in situ ATR FTIR spectroscopy. Since the pH value of the elec trolyte and the potential of the electrode can be varied during the spectroscopic characterization of the anion content, we can derive three dimensional plots of the amount of incorporated anions vs. the pH and the oxidation degree of the polymer. Using these results, the meachnisms of the various transitions of polyaniline can be described with better accuracy.