Hierarchical structure analysis of poly(ethylene-co-tetraflouroethylene)-based graft-type polymer electrolyte membranes by small angle X-ray scattering

Tran, D. T.; Sawada, Shinichi; Hasegawa, Shin; Yoshimura, Kimio; Oba, Yojiro*; Onuma, Masato*; Katsumura, Yosuke*; Maekawa, Yasunari

Fundamental understanding of the structure-property relationship of PEM is prerequisite for a material design satisfying PEM performance requirement. Therefore, the hierarchical structures of ETFE-PEMs were characterized using wide q observation in small angle X-ray scattering (SAXS) by comparing those of precursor original ETFE and polystyrene-grafted film (grafted ETFE). ETFE-PEM possesses three distinct structures: (1) Graft polymer domains with d-spacing of 390 nm, which should act as ion conducting layer; (2) Lamellar structures with d-spacing of 29 nm; (3) An inner structure of graft domains with d-spacing of 1.5 nm correspond to correlation distances of sulfonic acid group. The ion-conducting layers and lamellar structures with d-spacing of 390 nm and 29 nm in ETFE-PEM can be confirmed by atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM), respectively.