Interplay between structure and mechanical relaxations based on PFSA proton conducting membranes

Abstract

The mechanical, structural and ionic conductivity properties of the polymeric composite membranes are elucidated here according to the weight% amount of inorganic additives. 3 M PFSA (perfluorosulfonic acid) polymer, borosilicate glass particles coated with nanoparticles and sulfuric acid (H2SO4) as functionalized solid inorganic additives (FSIA) are used to improve the overall properties. Wide–angle X-ray diffraction (WAXS) results elucidated the presence of both non-crystalline and crystalline ordered-disordered hydrophobic regions. In the presence of water, the size of the crystalline domains increased which help to increase the crystallinity. The dynamic mechanical analysis (DMA) results indicate the improved mechanical stability of the polymeric composite membranes and the results are consistent with the suggestions that dynamic cross-links [R-SO3H…. (SiO2)] density is higher in the composite membranes and supports to enhance the properties without compromising ionic conductivity unless the amount of FSIA exceeds 3 weights (wt.) %. The coating of nanoparticles made an excellent interface between FSIA and polymer matrix as observed in SEM analysis and block the movement of other ions such as SiO2, Na+, K+ which could also participate in overall ionic conductivity. Moreover, as a result, the mobility of polymer side chains increased in conjunction with water-FSIA-H2SO4 because of strong hydrogen bonding, which help to improve the ionic conductivity of final polymer composite.