Thermal Properties and Conductivity of Thermally Treated Epoxidized Natural Rubber‐Based Solid Polymer Electrolytes

Thermal properties and ionic conductivity of epoxidized natural rubber (ENR)‐based solid polymer electrolytes (SPEs) are influenced by their sample preparatory pathways. In literature, there are inconsistencies reported on conductivity values in the range of 10−8–10−9 S cm−1 due to different sample preparatory pathways for same systems at constant salt concentration. In this study, simple thermal treatment was adopted on SPE films for regulating the thermal properties of the materials which in turn to govern the conductivity of the materials. ENR (with 25 and 50 mol% epoxidation) and lithium perchlorate salt (0–20 wt.%) were used. The ENR‐based SPE films were thermally treated with three different annealing times (i.e. t = 0, ½, 24 h) at 80 °C under nitrogen atmosphere. Differential scanning calorimetry and impedance spectroscopy were utilized to analyze the thermal properties and ionic conductivity at room temperature, respectively. The glass transition parameters such as glass transition temperature, change in heat capacity, width of glass transition and change in enthalpy of endothermic overshoot were elucidated. Higher glass transition temperature values are noted for ENR‐based SPEs films with longer annealing time, which may imply higher extent of intermolecular interaction between ENR and salt, thus leading to an increase in ionic conductivity of ∼10−10–10−8 S cm−1 for t = 0 and 24 h, respectively at mass fraction of salt, WS = 0.107. Consequently, it is deemed important to have precise control in the thermal treatment of ENR‐based SPEs during their preparatory stage.