Novel poly(arylene ether ketone)s containing sulfonic/carboxylic groups: Synthesis and properties

Novel poly(arylene ether ketone)s containing phenyl- and 4-cyanophenyl substituents were synthesized and subsequently used as starting material to prepare polymer electrolyte membranes for fuel cells application. FTIR and 1H NMR spectra indicated that both a sulfonation reaction on the pendant phenyl and a hydrolysis reaction on the cyano groups occurred simultaneously. After sulfonation/hydrolysis, flexible and transparent membranes with sulfonic and carboxylic groups as the proton conducting sites were prepared. And they all exhibited reasonable and tensile moduli in the range of 0.62–1.50 GPa. The proton conductivities of the membranes cast from the resulting polymers were all higher than 10−2 S cm−1 at room temperature. At 100 °C, the high proton conductivities of 0.149 and 0.199 S cm−1 were obtained from SPAEK-Ph80 and SPAEK-Ph90, respectively, which were both higher than that of Nafion 117 (0.145 S cm−1). Several other properties relative to their applications as proton exchange membranes, such as water absorption, thermal-oxidative and dimensional stability and methanol crossover were also evaluated. Atomic force microscopy (AFM) was used to observe the membrane microstructure for evidence of microphase separation between ionic and hydrophobic domains.