Low water uptake content and low water/methanol transport in CP/Nafion hybrid membrane with high non-hydrogen bonding

We investigated the relation between water uptake content and water/methanol transport and non-hydrogen bonding ratio for the cast Nafion and calcium phosphate (CP)/Nafion composite membranes. The water/methanol uptake content was evaluated with FT-IR, vacuum-drying method and thermogravimetry (TG). It was found that composite membranes have lower water/methanol uptake content with increasing CP compared to cast Nafion. We evaluated the non-hydrogen (NH) bonding ratio (RA), representing the ratio of the non-hydrogen bonding to the sum of NH-bonding and H-bonding. As a result, RA increased in the CP/Nafion composite membrane compared to the cast Nafion. It is due to the formation of new non-hydrogen bonding interaction between CF main backbone and OH− in the incorporated CP. On the other hand, water/methanol permeability, measured by water sorption/desorption and methanol permeation tests, decreased in the CP/Nafion composite membranes. Finally, we can conclude that lower water/methanol uptake and water/methanol transport in the composite membranes result from the formation in new non-hydrogen bonding due to the incorporation of CP.