Influence of Anions on Proton-Conducting Membranes Based on Neutralized Nafion 117, Triethylammoniunn Methanesulfonate, and Triethylammonium Perfluorobutanesulfonate. 2. Electrical Properties

The electrical properties of a Nafion proton exchange membrane change dramatically when neutralized and then doped with a proton-conducting ionic liquid (PCIL). Broadband electric spectroscopy elucidates the molecular relaxation and polarization. phenomena of neutralized Nafion (nN117) doped with triethylammonium methanesulfonate (TMS) and triethylammonium perfluorobutanesulfonate (TPFBu) ionic liquids. These data, coupled with those of part 1 suggest proton conduction mechanisms for both the pure 5 PCILs and in PCIL-doped nN117. At 130 degrees C, the PCILs have conductivities of sigma(TMS) = 1.4 x 10(-2) S/cm and sigma(TPFBu) = 9 x 10(-3) S/cm, while correspondingly doped nN117 have conductivities of sigma(NTMS) = 6.1 x 10(-3) S/cm and sigma(NTPFBu) = 1.8 x 10(-3) S/cm. The pure PCILs show three interfacial polarizations associated with proton transfer mechanisms above the melting point. PCIL-doped nN117 also has three interfacial polarizations that depend on the nanostructure characteristics of the PCIL sorbed within the nN117 polar domains. Below the PCIL melting point, doped nN117 has two dielectric relaxations, alpha and beta, associated with dipolar relaxations involving both the sorbed PCILs and the ionomer matrix The data indicate a long-range charge transfer process that occurs through proton exchange between cationic dusters. Segmental motion of the polymer chains and the molecular dimensions of the ionic liquid nanoaggregates mediate this charge transfer.