Comb shaped polymer-salt systems: A.C. conductivity and differential scanning calorimetry studies

Abstract

It is anticipated that a polymer electrolyte which exbibits properties superior to those exhibited by polyethylene oxide (PEO) -salt complexes, particularly at low temperatures, would be suitable for use in the development of a solid state cell. Comb-shaped polymers were used as the host materials in the polymer electrolytes examined in this study. Conductivities were measured as a function of temperature and the levels of conductivity measured for the various amorphous polymer-salt complexes prepared were dependent on the character of the polymeric host, the nature and concentration of the salt dopant and the temperature of examination. Dissociation of a salt in a polymer resulted in the glass transition temperature (Tg) of the polymeric host increasing. The increase in Tg with salt concentration was measured using differential scanning calorimetry. It was therefore possible to identify malts which generated a great many charge carriers when dissolved in a polymer. Such salts were particularly effective dopants. Certain polymer-salt complexes examined in this study exhibited higher conductivities at low temperatures than those reported for PEO-salt complexes. These materials were found to have relatively low Tg values when large number of charge carriers had been generated in the system. Conductivity-temperature data were linearised using the Vogel-Tammann-Fulcher equation and the configurational entropy model of Adam and Gibbs was used to interpret the conductivity-temperature behaviour in a meaningful manner.