The effect of incorporated negative fixed charges on the membrane properties of polypyrrole films

Polypyrrole (PPy) and poly-N-methylpyrrole (PMPy) films have been prepared on electrodes in NaCl, polystyrenesulphonate (PSS), and dodecylsulphate (ROSO3–) electrolytes. The redox-switching of these coatings has been studied, mainly in NaCl electrolytes. At various electrode potentials the coated electrodes were withdrawn from the solutions to determine the composition of the films. Volta potential measurements, were conducted to obtain information on the Donnan potential. Based on these measurements, the effect of the negative fixed charge groups incorporated into the PPy or PMPy matrix on the membrane properties of the films was analysed. The anion exchange, cation exchange, and neutral states of the various coatings are defined over a range of electrode potentials. In one situation (PPy/PMPy/ROSO3–), the reversible and complete electrochemical redox transition between anion- and cation-exchange character is demonstrated.