Size dependent ion-exchange of large mixed-metal complexes into Nafion® membranes

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dc.contributor.authorNaughton, Elise M.en
dc.contributor.authorZhang, Mingqiangen
dc.contributor.authorTroya, Diegoen
dc.contributor.authorBrewer, Karen J.en
dc.contributor.authorMoore, Robert Bowenen
dc.contributor.departmentChemistryen
dc.contributor.departmentMacromolecules Innovation Instituteen
dc.contributor.departmentInstitute for Critical Technology and Applied Scienceen
dc.date.accessed2016-03-17en
dc.date.accessioned2016-03-18T22:24:54Zen
dc.date.available2016-03-18T22:24:54Zen
dc.date.issued2015-08-18en
dc.description.abstractPerfluorosulfonate ionomers have been shown to demonstrate a profound affinity for large cationic complexes, and the exchange of these ions may be used to provide insight regarding Nafion® morphology by contrasting molecular size with existing morphological models. The trimetallic complex, [{(bpy)2Ru(dpp)}2RhBr2]5+, is readily absorbed by ion-exchange into Na+-form Nafion® membranes under ambient conditions. The dimensions of three different isomers of the trimetallic complex were found to be: 23.6 Å × 13.3 Å × 10.8 Å, 18.9 Å × 18.0 Å × 13.7 Å, and 23.1 Å × 12.0 Å × 11.4 Å, yielding an average molecular volume of 1.2 × 103 Å3. At equilibrium, the partition coefficient for the ion-exchange of the trimetallic complex into Nafion® from a DMF solution was found to be 5.7 × 103. Furthermore, the total cationic charge of the exchanged trimetallic complexes was found to counterbalance 86 ± 2% of the anionic SO3− sites in Nafion®. The characteristic dimensions of morphological models for the ionic domains in Nafion® were found to be comparable to the molecular dimensions of the large mixed-metal complexes. Surprisingly, SAXS analysis indicated that the complexes absorbed into the ionic domains of Nafion® without significantly changing the ionomer morphology. Given the profound affinity for absorption of these large cationic molecules, a more open-channel model for the morphology of perfluorosulfonate ionomers is more reasonable, in agreement with recent experimental findings. In contrast to smaller monometallic complexes, the time dependent uptake of the large trimetallic cations was found to be biexponential. This behavior is attributed to a fast initial ion-exchange process on the surface of the membrane, accompanied by a slower transport-limited ion-exchange for exchange sites that are buried further in the ionomer matrix.en
dc.description.notes2015 Royal Society of Chemistry Open Access Gold Articleen
dc.description.sponsorshipVirginia Tech. Department of Chemistryen
dc.description.sponsorshipVirginia Tech. Institute for Critical Technology and Applied Scienceen
dc.description.sponsorshipUnited States. Department of Energyen
dc.description.sponsorshipNational Science Foundation (U.S.)en
dc.format.extent10 p.en
dc.format.mimetypeapplication/pdfen
dc.identifier.citationNaughton, E. M., Zhang, M., Troya, D., Brewer, K. J., & Moore, R. B. (2015). Size dependent ion-exchange of large mixed-metal complexes into Nafion® membranes. Polymer Chemistry, 6(38), 6870-6879. doi:10.1039/C5PY00714Cen
dc.identifier.doihttps://doi.org/10.1039/C5PY00714Cen
dc.identifier.issn1759-9954en
dc.identifier.issue38en
dc.identifier.other2015_Naughton_Size_dependent_ion_exchange.pdfen
dc.identifier.otherDE FG02-05-ER15751en
dc.identifier.otherDMR-0923107en
dc.identifier.urihttp://hdl.handle.net/10919/64960en
dc.identifier.volume6en
dc.language.isoen_USen
dc.publisherThe Royal Society of Chemistryen
dc.rightsCreative Commons Attribution-NonCommercial 3.0 Unporteden
dc.rights.urihttp://creativecommons.org/licenses/by-nc/3.0/en
dc.titleSize dependent ion-exchange of large mixed-metal complexes into Nafion® membranesen
dc.title.serialPolymer Chemistryen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten

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