Characterization of PMMA based nanocomposite plasticized polymer electrolytes: Effect of plasticizer and fumed silica

Polymethylmethacrylate (PMMA) based polymer electrolytes containing ammonium trifluoromethane sulphonate (NH4CF3SO3), have been synthesized by solution casting method. Ionic conductivity of polymer electrolytes has been measured and maximum conductivity of 2.05 x10(-4) S/cm at room temperature has been observed at 10wt% NH4CF3SO3. The conductivity of polymer electrolytes has been found to increase with the addition of plasticizers. The effect of dielectric constant of plasticizer has also been studied and found that the increase in ionic conductivity containing high dielectric constant plasticizer DMA (37.8) is more than that of electrolyte containing low dielectric constant plasticizer DEC (3.2). The conductivity of plasticized polymer electrolytes further increases by a factor with the addition of fumed silica (SiO2) along with an increase in mechanical strength. The increase in ionic conductivity of polymer electrolytes with the addition of nano-filler has been explained by double threshold percolation model. Thermal stability of nano-composite plasticized polymer electrolytes has been checked by simultaneous measurement of DSC/TGA curves. The small change in ionic conductivity of nano-composite plasticized polymer electrolytes with temperature and time suggests that these electrolytes are thermally stable in 30-130 degrees C temperature range, which is useful for their use in electrochemical device applications like fuel cells, supercapacitors, proton batteries etc.