Small angle neutron scattering study on morphology and water distribution in block-copolymer electrolyte membranes

Zhao, Y.; Koizumi, Satoshi; Rikukawa, Masahiro*; Yoshida, Miru*

In this study, we employed Small-angle neutron scattering method to investigate the morphology and water distribution in a polymer electrolyte membrane, made by comb-shaped poly(sulphonate phenylene)-bpoly(arylene ether ketone) (PSP-PAEK) block copolymer. Two scattering maximums were found in both low q and high q regions, where q is the scattering vector. The low q maximum is attributed to the interaction among the self-assembly hydrophilic and hydrophobic micodomains, whereas the high q maximum is due to the water channels, namely, ion clusters. To understand the structure, a random sphere model is applied to fit the scattering data. This model reproduces experimental data well. From this model, we are able to estimate the size and volume fraction of water in hydrophilic microdomains. The analysis of front factor gives us the information of volume fraction of water in the interconnected regions. Thus the possible morphology of the membranes can be deduced.