Nafion
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| Identifiers | |
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66796-30-3 
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| Properties | |
| C7HF13O5S . C2F4 | |
| Molar mass | See Article |
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Related compounds
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Aciplex Flemion Dowew fumapem F |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Nafion is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer discovered in the late 1960s by Walther Grot of DuPont. It is the first of a class of synthetic polymers with ionic properties which are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (Teflon) backbone. Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent thermal and mechanical stability.
The chemical basis of Nafion's superior conductive properties remain a focus of research. Protons on the SO3H (sulfonic acid) groups "hop" from one acid site to another. Pores allow movement of cations but the membranes do not conduct anions or electrons. Nafion can be manufactured with various cationic conductivities.
Nafion can be produced as both a powder resin and a copolymer. It has various chemical configurations and thus several chemical names in the IUPAC system. Nafion-H, for example, includes the following systematic names:
The molecular weight of Nafion is uncertain due to differences in processing and solution morphology. The structure of a Nafion unit, shown at the top of the page, illustrates the variability of the material; for example, the most basic monomer contains chain variation between the ether groups (the z subscript). Conventional methods of determining molecular weight such as light scattering and gel permeation chromatography are not applicable because Nafion is insoluble, although the molecular weight has been estimated at 105–106 Da. Instead, the equivalent weight (EW) and material thickness are used to describe most commercially available membranes. The EW is defined as the weight of Nafion (in terms of molecular mass) per sulfonic acid group. For example, Nafion 117 indicates a material with 1100 g EW and 0.007 inches in thickness. In contrast to equivalent weight, conventional ion-exchange resins are usually described in terms of their ion exchange capacity (IEC), which is the multiplicative inverse or reciprocal of the equivalent weight, i.e., IEC = 1/EW.
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