Expanding metal cation options in polymeric anion exchange membranes

Abstract

Here we present the synthesis of new metal-containing ROMP-based anion exchange membranes (AEMs) incorporating either ruthenium, nickel, or cobalt. To accomplish this, homoleptic norbornene monomers were synthesized, cross-linked, and compared to systems previously synthesized, which featured heteroleptic ruthenium-containing monomers. This produced AEMs with varying metal cations, in an effort to elucidate the effect different metals have on AEM properties. The metal had minimal effect on water uptake and mechanical properties, while also maintaining excellent chemical stability. Conductivity, however, appeared to change as the metal changed, with the nickel-cation-containing AEM performing the best among all equivalent metal cations studied. These results indicate that metal-cation-based AEMs need not be limited to ruthenium.