The Ion-exchange Resin Nafion

The ionic groups (-SO3H) form clusters in the chemically stable Teflon-like matrix (-CF2CF2-) [6]. These hydrophilic domains form micelles, surrounded by the hydrophobic fluorocarbon backbone and connected by small channels. The Nafion resin is prepared as a copolymer of tetrafluoroethylene and perfluoro-2-(fluorosul-fonylethoxy)propyl vinyl ether [1,7]. Unlike other resinsulfonic acids, e. g. sulfo-nated polystyrenes (Dowex-50, Amberlyst-15, Amberlite IR-112, etc.), Nafion and related perfluoroalkanesulfonic acids are stable in corrosive environments and the maximum operating temperature is up to 473K [8]. 

Nafion is commercially available as Nafion NR50 (DuPont) in the form of relatively large (2-3 mm) beads. A disadvantage of these beads is the low surface area (typically 0.02 m g ) [8]. Water-selective Perma Pure membranes also consist of the polymer Nafion and were especially developed for removal of water from gas-phase streams [9]. Nafion is also available as a 5 % solution in a mixture of lower aliphatie alcohols and water [10]. 

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