Relationship between structural and proton conductive properties of crosslinked-fluoropolymer-based electrolyte membranes; Consideration based on nanometer-to-micrometer hierarchical structures

Yamaki, Tetsuya; Motokawa, Ryuhei   ; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari

The nanometer-to-micrometer hierarchical structure of cPTFE-based electrolyte membranes was investigated by SANS or SAXS analysis, DPD simulation and transmission electron microscopy observation. The grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The ionic clusters basically appeared smaller than that of Nafion, and the phase-separated domain including them grew large by connecting with each other towards high ion exchange capacities. This morphological change was accompanied by an increase in the self-diffusion coefficient of protons representing proton conductivity.