Exerted influence of deep eutectic solvent concentration in the room temperature ionic conductivity and thermal behavior of corn starch based polymer electrolytes

Abstract

A series of biodegradable polymer electrolytes were fabricated by utilizing corn starch (CS), lithium bis(trifluoromethanesulfonyl)imide (LITFSI) and deep eutectic solvent (DES) (synthesized from the mixture of choline chloride and urea with 1:2 ratio) by solution casting technique. The incorporation of DES in plasticizing the CS:LiTFSI matrix was valued primarily due to its capability in increasing the amorphous elastomeric phase that is crucial in enhancing the ionic transport mechanism. The conductivity–temperature plot reveals the nature of the cation transport which commensurates with Arrhenius rule. The highest conducting sample was identified for the composition CS:LiTFSI:DES (14 wt.%:6 wt.%:80 wt.%) exhibiting the ionic conductivity value of 4.56 × 10 − 3 S cm − 1 at 50 °C with activation energy of 8.22 kJ mol − 1 . The relaxation frequency of sample DES-80 is log ω m = 6.03 Hz, being the lowest relaxation time as revealed by the dielectric loss tangent plot. The decreasing trends in the melting temperature of polymer electrolytes with increase in DES content correlate to the occurrence of complexation that induces structural disorderliness. The heat-resistivity of polymer electrolyte diminishes with the addition of DES and enhancement in the thermal stability was observed at the minimum DES content as revealed in TGA analysis.