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

New Sulfonated Polystyrene and Styrene–Ethylene/Butylene–Styrene Block Copolymers for Applications in Electrodialysis

In this study we prepared blends of polystyrene (PS) and high-impact polystyrene (HIPS) with poly­(styrene–ethylene–butylene) (SEBS) triblock copolymer. After sulfonation, blends were used to fabricate ion-exchange membranes by solvent-casting and subsequent thermal treatment to obtain homogeneous packing densities. The morphology and structure of the blends were investigated by scanning electron microscopy, atomic force microscopy, and FTIR spectroscopy. Furthermore, the thermal transitions and stability of all the blends were characterized using calorimetric techniques and compared with those of the individual polymers. Analyses of the physical properties (i.e., ionic conductivity, ion-exchange capacity, water uptake, dimensional stability, mechanical properties, etc.) showed that the performance of the PS-containing membranes is, in general, higher than that of the HIPS containing one. Furthermore, the highest sulfonation degree was also found for the PS/SEBS membranes. The capabilities of the membranes were tested by investigating the extraction of Na⁺ by electrodyalisis. Comparison of the percentage of extracted ions indicates that the incorporation of SEBS results in a significant improvement with respect to membranes made of individual polymers