This paper discusses a new class of high performance polyethylene-based anion exchange membranes (PE-AEMs) that contain a wide concentration range of pendant (flexible) ammonium chloride (NR3+Cl-) groups and with or without a cross-linked PE matrix structure. The chemistry involves a metallocene-mediated polymerization of ethylene, silane-protected α,ω-amino-olefin [CxN(SiMe3)2], with or without styrenic diene (cross-linker), to form ethylene/C xN(SiMe3)2 copolymers and ethylene/C xN(SiMe3)2/diene terpolymers, respectively. The resulting co- and ter-polymers were completely soluble in common organic solvents and were solution-casted into uniform films (thickness, 50-70 μm; without backing material) and then thermal cross-linked in ethylene/C xN(SiMe3)2/diene case, further interconverting the silane-protected amino groups into the desired -NR3 +Cl- groups (R: H, CH3, and C3H 7) under solid state conditions. The resulting PE-NR3 +Cl- and cross-linked x-PE-N(CH3) 3+Cl- membranes were systematically studied to understand how the PE structure (-NR3+Cl- concentration, R group, cross-linking density, etc.) affects ionic conductivity, water uptake, film stability, and ion selectivity. For comparison, several commercially available AEMs were also examined. Evidently, an x-PE-N(CH 3)3+Cl- membrane, with 28.1 mol % -N(CH3)3+Cl- groups and 0.2 mol % cross-linkers, shows moderate water swelling and outperforms all commercial membranes with exceptionally high ionic conductivities of 119.6 mS/cm in 2 N HCl solution and 78.8 mS/cm in 2 N HCl-0.2N CuCl solution at room temperature.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry