Cation/polymer interactions region

The spectroscopic techniques, on the other hand, probe individual species which make up the various regions. Infrared (chapter 8) and nuclear magnetic resonance (chapter 7) address themselves to water and the interactions of water with the various species with which it is in contact. Mossbauer spectroscopy (chapter 9), in addition, provides valuable information on the proximity of the cations and their environment. Mechanical (chapter 6) and transport (chapter 4) properties provide more indirect insight into the structural aspects, which is supplemented by thermodynamic studies (chapters 2 and 5) of the interaction between the polymer and water or other liquids. All these techniques are discussed in the present volume, and from these studies several structural models have emerged (chapter 13). 

Quaternary Ammonium Ions. In a recent study (17), 1200 EW Nafion has been used to construct a membrane ion selective electrode. The electrode was placed in both the tetrabutylammonium ion and cesium ion forms, and the response characteristics of each form were measured. These electrodes show Nernstian responses, and the tetrabutylammonium ion electrode has no interference from inorganic cations such as Na" ", K" ", and Ca2" ". However, this electrode shows a marked interference with decyltri-methylammonium ion. In addition the cesium ion electrode response is sensitive to the presence of tetrabutylammonium ion and especially dodecyltrimethylammonium ion. Although membrane electrode sensitivities are not in general proportional to thermodynamic selectivity coefficients, the results do indicate that these large, hydrophobic cations are preferred over smaller inorganic cations by the polymer. The authors suggest that the surfactant character of the two asymmetric tetraalkylammonium ions may lead to non-electrostatic interactions with the fluorocarbon regions of the polymer, which would enhance their affinities (17). 

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