The Effect of Imidazolium Ionic Liquids on the Properties of Sulfonated Poly (styrene-isobutylene-styrene) Membranes

Ionic liquids (ILs) with different anions and cations were incorporated in sulfonated poly(styrene-isobutylene-styrene) (SIBS) as an attempt to modify it’s chemical, thermal, morphological, and transport properties. Different amounts of ILs and different solvents were also studied in order to have a better understanding of the incorporation process and the ability of the solvent to enhance the interaction between the IL and the sulfonated polymer. Membranes’ morphological characterization was performed with small and wide angle X-ray scattering (SAXS and WAXS). Significant variations were observed when different concentrations of ILs were used. The effect of the different chemical variations and compositions of ILs were analyzed with FT-IR to evaluate chemical interactions and with AFM characterizations to evaluate surface effects and morphology changes. The most significant changes were obtained when studying the effect of concentration of the same IL. Phase images showed changing domain sizes as the IL concentration changed. Thermal and transport properties were studied and the results from the morphological and chemical characterizations were used to explain changes in these properties.