where As and Ad correspond to the areas of the wet and dry membranes.
Both water content and the change in area of the membranes were measured in 10% methanol aq. at 60 °C and compared to dry conditions.
The micro-structures of the membranes were examined by STEM (Hitachi High-Technologies Corporation, HD-2000) and SAXS (Rigaku Corporation, ATX-G) same as our previous report [13]. The specimens were dipped in a 1 mol/l CsCl aqueous solution to substitute the protons in the hydrophilic segments with cesium cations prior to the STEM and SAXS measurements. The average sizes of the micro-phase-separated structures were calculated using software JADE 7 (Materials Data, Inc.) from the SAXS profiles. The background was subtracted from the profile and the periodic sizes were calculated using the angle of peak top and Bragg law.