Measuring the Proton Conductivity of Ion-Exchange Membranes Using Electrochemical Impedance Spectroscopy and Through-Plane Cell

The role of the incorporation of conducting polymer (CP), doped with different sulfonic acid organic molecules, in polystyrene (PS) and high-impact polystyrene (HIPS) with poly(styrene-ethylene-butylene) (SEBS) triblock copolymer has been investigated. Two factors associated with this model membrane system are addressed: (i) the influence of the presence of a low concentration of doped conducting polymer and (ii) the influence of the membrane preparation method. Membrane characterization and bulk conductivity measurements allowed the conclusion that proton conductivity has been promoted by the addition of CP; the best results were achieved for PAni-CSA, in either PS/SEBS or HIPS/SEBS blends. Additionally, the water uptake only decreased with the addition of PAni-doped molecules compared to the pure copolymer, without loss of ion-exchange capacity (IEC). Electrodialysis efficiency for HIPS/SEBS (before annealing) is higher than that for HIPS/SEBS (after annealing), indicating that membrane preparation method is crucial. Finally, through-plane cell arrangement proved to be an effective, quick, and time-saving tool for studying the main resistance parameters of isolating polymers, which is useful for application in industry and research laboratories working with membranes for electrodialysis or fuel cells.