Electrochemical characterization of sulfonated poly(arylene ether sulfone) (S-PES) cation-exchange membranes

Sulfonated poly(arylene ether sulfone) (S-PES) cation-exchange membranes with various degrees of the sulfonation were prepared via direct polymerization and characterized in terms of the electrochemical properties, including the surface heterogeneity and the current–voltage (I–V) relation. The S-PES membranes exhibited moderate swelling properties and ion-exchange capacities (IECs) for electro-membrane applications. Moreover, the membranes with the mole ratio of sulfonated monomers of over 40% showed excellent electrochemical properties. The electrical resistances were below 1.0 Ω cm2 in a 0.5 mol dm−3 NaCl and the ionic permselectivities were comparable to those of commercial membranes. The fraction of conducting regions, ε, on the membrane surface was evaluated through a chronopotentiometry. The ε values of the S-PES membranes were higher than those of the sulfonated poly(arylene ether sulfone) membranes prepared via conventional post-sulfonation route, leading to a low electrical resistance and a high ionic permselectivity. Considering the mechanical properties, the S-PES membrane with the mole ratio of sulfonated monomers of 40% was found to be very suitable for electro-membrane applications.