1,2,4-Triazole functionalized poly(arylene ether ketone) for high temperature proton exchange membrane with enhanced oxidative stability

A series of novel 1,2,4-triazole grafted poly(arylene ether ketone) membranes were prepared to absorb phosphoric acid and used as high temperature proton exchange membranes. Poly(arylene ether ketone) is firstly bromomethylated, followed by nucleophilic substitution of bromomethylated poly(arylene ether ketone) with 3-mercapto-1,2,4-triazole. The structure and the degree of substitution were confirmed by their 1H NMR spectra. 1,2,4-Triazole functionalized poly(arylene ether ketone) membranes exhibited high thermal decomposition temperature (Td(5%) higher than 271 °C) and tensile strengths (higher than 78 MPa). After doping with phosphoric acid, these membranes showed enhanced abilities to phosphoric acid absorption with increasing the amount of triazole groups on the side chains. Phosphoric acid doped MTZPAEK(2.15) showed the highest Wdoping value of 142% and the proton conductivity of 51 mS cm−1 at 190 °C. Remarkably, all the membranes exhibited great oxidative stabilities and could retain their shapes for more than 50 h in Fenton's reagent (3 wt% H2O2, 4 ppm Fe2+) at 80 °C. This advantage could be ascribed to the unique sulfide groups, which were introduced by nucleophilic substitution reaction and acted as free radical scavengers. The supposed mechanism of enhancing oxidative stability by sulfide groups was confirmed via FT-IR.