Cation-conducting ionomers made by ion exchange of sulfonated poly-ether-ether-ketone: Hydration, mechanical and thermal properties and ionic conductivity

The hydration in liquid water of various thermally treated SPOOK membranes was determined and confronted with data in saturated water vapor. Significant differences, which Correspond to the so-called Schroder paradox, are observed only in un-crosslinked ionomers with IEC > 2 eq/kg. After cation exchange in electrolyte solutions (2 and 0.1 mol/L), the hydration and density of the ionomers was determined and confronted with a physical model. There is 110 clear Correlation with cation properties, such as ionic radius or Robinson-Stokes hydration numbers. The ionic conductivity ranges from 3 mS/cm for K, NH4 and Mg-exchanged membranes to 0.6 mSicm for Ca and Zn. Although the latter might be related to ionic cross-linking by the divalent cations, the relatively high conductivity of Mg ions might be useful for electrochemical applications. (C) 2014 Elsevier By. All rights reserved.