Ternary proton exchange membranes with low‐cost raw materials: Solvent type influence on microstructure development, high ionic conductivity, and ionic liquid lixiviation protection

ABSTRACT A critical stage of solvent evaporation during membrane casting was identified as responsible for significant differences in performance of ternary membranes composed of PEEK with 73% of sulfonation degree. DemaTfO and MmtdemaDMF showed to be the best solvent for casting of membranes prepared through the present study, which is against the observations made through other different studies. Fractal structures are formed regardless of solvent polarity, and interlamellar spacing is found to be higher when DMF is used, which led to higher conductivity and IL leaching protection. Proton relaxometry showed that only the membranes made with DMF and DMAc possess one single mobility domain. Transmission electron microscopy micrographs showed a higher damage in membranes with two different mobility domains and consequent phase separation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46012.