Synthesis and characterization of cross-linked poly(arylene ether ketone) containing pendant quaternary ammonium groups for anion-exchange membranes

We report an effective and simplified procedure for the synthesis of cross-linked alkaline anion-exchange membranes (AEMs). A new monomer containing two tertiary amine groups on 4,4′-dihydroxydiphenyl ether (DABPE) is used in nucleophilic aromatic substitution step-growth copolymerization with 4,4′-difluorobenzophenone, 2,2′,6,6′-tetramethyl-4,4′-biphenol to obtain the corresponding poly(arylene ether ketone) copolymers containing tertiary amine groups. After partial quaternization, the residual tertiary amine groups of the polymer react with p-xylylene dichloride to produce a cross-linked membrane, which is followed by anion exchange with hydroxide ions. The resulting cross-linked membranes exhibit high hydroxide ion conductivity (above 10−2 S cm−1 at room temperature), good mechanical properties, and reduced water uptake relative to the linear uncross-linked membrane. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells