Optimization of anionic conductivity through the coexistence of ionomer cluster and backbone-backbone morphologies in anion exchange membranes |
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| Authors: | Chinomso Nwosu Tara P. Pandey Andrew M. Herring Soenke Seifert E. Bryan Coughlin |
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| Affiliation: | 1. Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, USA;2. Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado, USA;3. X-ray Science Division, Argonne National Laboratory, Argonne, Illinois, USA |
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| Abstract: | Random copolymers of poly(4-vinylpyridine) and polyisoprene were synthesized, and subsequently quaternized with 1-alkylbromides. The number of carbons on the pendant side-chain of the resultant comb-shaped polymer, n, ranged from 2–8. The comb-shaped polymers were crosslinked employing thiol-ene chemistry to give mechanically robust ion conducting membranes. Analysis by wide and medium-angle X-ray scattering show three morphology regimes that are dependent on the number of carbons on the pendant side-chains. When n = 2, ionomer cluster morphology was dominant, when n = 8 backbone-backbone morphology was dominant, and when n = 3–6, the membrane showed a coexistence of both ionomer cluster and backbone-backbone morphologies. Evaluation of the water uptake of the membranes showed a maximum water uptake per cation of 9.5 when n = 5 at 95% relative humidity (RH) and 60°C. Conductivity of the samples characterized by electrochemical impedance spectroscopy showed bromide conductivity as high as 110 mS/cm when n = 3 at 95% RH and 90°C. |
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| Keywords: | anion exchange membranes backbone-backbone morphology dipole–dipole interactions ionomer cluster morphology optimization of ionic conductivity water uptake per cation |
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