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Title
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Evidence of temperature-induced subdiffusion of water on the micrometer scale in a nafion membrane
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Author
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Abstract
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| To investigate the topological features of proton transport in perfluorosulfonic membranes, we performed time-dependent 1H NMR pulsed gradient spin−echo experiments on four samples of Nafion-115 with λ = 0.5, 3.2, 5.8, and 12.4 water molecules per sulfonic group at different temperatures ranging from 278 to 348 K. A subdiffusive behavior of water, = 2Dαtα with 0.75 < α < 1, was observed above 320 K for each of the four samples. The onset of water subdiffusion with increasing temperature, basically independent of membrane hydration, supports the hypothesis of a drop in dimensionality for the diffusion space. Diffusion−diffraction effects on the NMR echo-signal attenuation confirm that proton displacement is restricted because of an interconnected pore structure with a coherence length of ∼1 μm, which depends on temperature and water content. |
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Language
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English
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Source (journal)
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Macromolecules / American Chemical Society. - Washington, D.C.
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Publication
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Washington, D.C.
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2010
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ISSN
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0024-9297
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DOI
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10.1021/MA902323T
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Volume/pages
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43
:2
(2010)
, p. 638-642
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ISI
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000273618100010
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Full text (Publisher's DOI)
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