Analysis of water sorption in sulfonated polyimide membranes- Effect of the membrane nanostructure

Water sorption in sulfonic polyimides with or without ionic block structure was analysed with Feng´s new dual mode model. The model parameters Cp and A´ correspond to the sorbed water molecules on the first layer close to the ionic groups and on the subsequent layers, respectively. From these fitted physical parameters, the water sorption on membranes with different counter ions was studied and the hydration energy and size of counter ions were proved to have much influence on the Cp values. The impact of the nano / microstructure of the copolymers on the Cp / A´ values and on the water sorption isotherms was discussed and compared with that for the well-known Nafion® membranes.