Imidazolium ionic liquid incorporation on sulfonated poly(styrene‐isobutylene‐styrene) proton exchange membranes

ABSTRACT Ionic liquids (ILs) with different anions and cations were incorporated in sulfonated poly(styrene‐isobutylene‐styrene) (SIBS) to modify its chemical, morphological, and transport properties for direct methanol fuel cell (DMFC) applications. Different loadings of IL and different solvents were studied to have a better understanding of the incorporation process and the ability of the solvent to affect the interaction of the IL with the sulfonated polymer. Morphological characterization with SAXS and AFM suggested changes caused by the incorporation of the IL and by the solvent used. FT‐IR spectra showed small variations in energy related to interactions of the IL with the sulfonic groups which caused thermogravimetric stabilization of the ionic domains. Other results suggest that water has a very significant effect on the morphology, interaction with the IL, and transport properties of the membranes. Optimal concentration of IL (∼10 mol %) provides enough water to produce efficient proton conductivity (0.15 S/cm) and minimal methanol permeability (0.8 × 10−6 cm2/s). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44900.