Crosslinked norbornene copolymer anion exchange membrane for fuel cells

Abstract A series of crosslinked anion exchange membranes (AEMs) were prepared through ring-opening metathesis polymerization (ROMP) of tetraalkylammonium-functionalized norbornene derivatives. Dimensional stability and mechanical properties were enhanced by the crosslinker of 2, 2′-(hexane-1,6-diyl) bis(2-methyl-2, 3, 3a, 4, 7, 7a-hexahydro-1H-4, 7-methanoisoindol-2-ium) iodide (b3). The thermal stability, ion exchange capacity (IEC), water uptake, swelling ratio, ion conductivity and mechanic property of the membranes were investigated. The molar ratios of monomer (3aR, 4 S, 7 R, 7aS)− 2-methyl-2-(3-(trimethylammonio)propyl)−2, 3, 3a, 4, 7, 7a-hexahydro-1H-4,7-methanoisoindol-2-ium iodide (a3): norbornene: monomer b3 was 1:6:3, 2:6:2, 3:6:1 in AEM-1, AEM-2, AEM-3. The resultant AEM-3 membrane had an IEC of 2.89 mmol g −1 , an ion conductivity of 64.79 mS·cm −1 , a water absorption of 12.5% and a tensile strength of 15.18 MPa at 25 °C. The swelling ratio of AEM-1 (the molar ratio of monomer a3: norbornene: monomer b3 was 1:6:3) was 9.28% at 20 °C and 9.92% at 60 °C. The tensile strength of membranes was improved by the crosslinker. A single cell was built with this AEM-3 membrane and the performance was evaluated. A maximum power density of 152 mW cm −2 at 50 °C was demonstrated. The membranes show great promise to serve as membranes for fuel cells due to excellent performances of higher ion conductivity and better dimensional stability.