Sulfonated poly(arylene ether)s with high content of phosphine oxide moieties for proton exchange membranes

Sulfonated poly(arylene ether)s with high content of phosphine oxide moieties were achieved by polycondensation of bis(4-hydroxyphenyl)phenyl phosphine oxide with sulfonated bis(4-fluorodiphenyl)phenyl phosphine oxide and bis(4-fluorophenyl)phenyl phosphine oxide (or decafluorobiphenyl) for the first time. The high content phosphine-oxide moieties are expected to improve the oxidative stability of membranes, while the decafluorobiphenyl units were used to depress the swelling. The studies illustrated that all these membranes exhibited outstanding oxidative stability because of high content phosphine oxide moieties. On the other hand, the membranes with decafluorobiphenyl moieties (sPEPOF) displayed low swelling. This originates from these hydrophobic groups because they facilitated the membranes to form narrow ionic clusters. In summary, the sPEPOF membranes exhibited excellent overall properties. For instance, the sPEPOF membrane with 80% sulfonation degree displayed a proton conductivity of 0.077 S/cm as well as a swelling of 12% at 80 °C. It also exhibited outstanding oxidative stability and high thermal stability.