Conductivities and thermal studies of polymeric electrolytes based on poly(epichlorohydrin)/sodium salts

Abstract

The halogenated polyether named Hydrin-T® is a terpolymer constituted of epichlorohydrin-ethylene oxide-allyl glycidyl ether. It was studied as a polymeric electrolyte in polymer/NaX systems (X = Br - , I-, SCN - , ClO 4 - and B(C 6 H 5 ) 4 - ). In this work we present an investigation of the ionic conductivity (measured by impedance spectroscopy) and thermal properties (measured by differential scanning calorimetry-DSC, modulated DSC and thermogravimetry) of the polymeric electrolyte as a function of the composition in the range of 5 to 40 m/m (%) of the sodium salt. The solubility of sodium salts in the elastomer terpolymer matrix is comparable to the solubility in the best known matrix of linear semicrystalline PEO. The conductivities of the terpolymer/Nal electrolytes are higher than those of membranes prepared with other salts studied (10 -5 S/cm for the former versus 10 -7 to 10 -6 S/cm for the latter). This system also is the most homogeneous up to 40 m/m (%) and showed the smallest increase of T g values as a function of salt concentration [between -53°C for the pure polymer and -35°C for the 40 m/m (%) of NaI]. Modulated DSC confirmed the homogeneity of the terpolymer/NaI system showing T g transition in a range of only 5°C. A decrease of variation of heat capacity during glass transition with the increase of salt concentration was observed.