The effect of temperature and humidity on the oxygen sorption in Diels–Alder polyphenylenes

The gas transport properties of post-sulfonated Diels–Alder polyphenylene (SDAPP) membranes were measured and compared to poly(perfluoro sulfonic acid) (Nafion 112). The SDAPP materials had ion exchange capacities of 1.6 and 2.2 mequiv/g. The O2 gas permeability in the SDAPP 2.2 was about half that observed in Nafion@ 112. The O2 sorption in each membrane was measured in both the non-humidified and humidified state. In the non-humidified state, the O2 sorption followed Henryʹs Law behavior. The enthalpy of sorption for the SDAPP materials in the dry state was about double that measured for Nafion@ 112. In the presence of moisture, the O2 sorption followed Type IV behavior typically exhibited by hydrophilic polymers. The SDAPP samples had a higher percent wet-O2 mass uptake compared to Nafion@ 112, because of a higher ion exchange capacity.