Fig. 4 shows the variation of conductivity with temperature for Starch/PVA-LiBr polymer electrolytes with different contents of nano fumed silica.
All the samples show an increasing trend with temperature.The increase in the conductivity of polymer electrolyte systems with temperature reflect the ease of ion movement due to increased segmental motion of the polymer chains which can be explained by the free volume theory.
Moreover with the addition of nano fillers the augmentation in conductivity of the system results from the synergized contribution of increased segmental motion and the buildup of conductive pathways. Starch and PVA both are semicrystalline polymers. In general for Starch or Starch based blends some crystallite phases are present in the system. When the temperature is raised these remnant crystallite phases melt at some particular temperatures. The melting of these crystallite phases facilitate the ionic motion in the system and there is an increase in ionic conductivity. Thus the fluctuations or irregularities observed in the temperature dependent conductivity profile are attributed to the melting of the remnant crystallite phases [31–37].