Viscoelastic and high ion conducting gum tragacanth-based gel polymer electrolytes

Gum tragacanth (GT) based gel polymer electrolytes (GPEs)/hydrogels have been synthesized using deionized water (DW) and NaOH salt, and characterized through ionic conductivity, Fourier transform infrared (FTIR), pH, thermal and mechanical studies. Ionic conductivity decrement of liquid and GPEs was observed with the increase of temperature that contradicts pre-existing theoretical equation, i.e., σ = σ_o exp. (-E_a/kT) and maximum ionic conductivity of 8.75 x 10^-2 S cm^-1 observed for GPE containing 0.625 M NaOH salt at 30°C. Effect of temperature on pH has been investigated for different GPEs and the results were also supported by FTIR studies by formation of new and disappearance of old peaks. Thermogravimetric analysis studies involved the measurements of T_g for GPEs with the incorporation of different concentrations of NaOH salt, supported by DTG thermograms. Viscoelastic behaviour of GPEs with and without salt have been described by rheological studies at 30°C. In spite of that, time-dependent high structure recovery ratio pointed out the sol to gel transition in GPEs after the removal of applied shear rate. Due to high ion conducting, thermally and mechanically strengthened GPEs-based materials may make them applicable for their use in different device applications. (author)