Effect of donor number of solvent on the conductivity behaviour of nonaqueous proton-conducting polymer gel electrolytes

The effect of donor number of solvent on the conductivity behaviour of gel electrolytes has been studied. Liquid electrolytes were prepared by dissolving salicylic acid in solvents based on ethylene carbonate (EC), propylene carbonate (PC) and dimethylformamide (DMF) with different donor number and dielectric constant values. Three different polymers, polymethylmethacrylate (PMMA), polyacrylonitrile (PAN) and polyethylene oxide (PEO), were used as the gelling polymer. The conductivity of polymer gel electrolytes has been found to be higher than the corresponding liquid electrolytes, i.e. σ (gel)>σ (liquid). This has been explained to be due to an increase in carrier concentration by the dissociation of undissociated salicylic acid/ion aggregates present in the electrolytes with the addition of polymer. However, the relative increase in conductivity observed with the addition of different gelling polymers has been found to depend upon the donor number of the solvent used.