Synthesis of poly(arylene ether ketone) containing phenylsulfonic acid pendant for proton exchange membrane

Abstract

A series of phenylsulfonic acid–containing poly(arylene ether ketone) (psa-PAEK) were synthesized via polycondensation from 2-(4-methoxy)phenylhydroquinone and other commercial monomers, followed by postsulfonation approach under mild reaction conditions. Controlled substituted sites and the degree of sulfonation were realized using quantities of 2-(4-methoxy)phenylhydroquinone. Giving the psa-PAEK can be soluble in common organic solvents such as Dimethylsulfoxide, purity ≥99.5% (DMSO, Sinopharm Chemical Reagent Co., Ltd, Shanghai, China), NMP, 1-Methyl-2-pyrrolidinone purity ≥99.0% (NMP, Sinopharm Chemical Reagent Co., Lted, Shanghai, China), and N,N-dimethylacetamide, purity ≥99.0% (DMAc, Sinopharm Chemical Reagent Co., Lted, Shanghai, China). The tough and transparent polymer membrane was prepared by the solution casting method, which exhibited excellent mechanical properties and high proton conductivities. The tensile stress at maximum load and elongation at break of these membranes are 28.3–34.1 MPa and 101–126% in dry state, respectively. The proton conductivities of these membranes were higher than 10−2 S cm−1 at room temperature in water. Especially, the psa-PAEK-90 with ion exchange capacity of 1.62 mequiv. g−1 exhibited the proton conductivity of 176 mS cm−1 at 80°C in water. The clear microphase separation morphology was observed by small-angle X-ray scattering, which is a powerful evidence to explain their high conductive behaviors. These results suggest that the psa-PAEK membranes have great potential as a candidate membrane for proton exchange membrane fuel cell applications.