Structural, thermal and electrical transport behaviour of polymer electrolytes based on PVA and imidazolium based ionic liquid

A series of polymer electrolyte films based on Poly(vinyl alcohol) (PVA) and ionic liquid, 1-Butyl-2, 3-dimethylimidazolium tetraflouroborate [BDMITFB], PVA-BDMITFB-1 to PVA-BDMITFB-5, has been prepared by varying the concentration of BDMITFB viz. 5, 10, 15, 20, 25 wt%, respectively using solution cast technique. These samples were characterized using Attenuated Total Reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermo gravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC) and AC impedance spectroscopic techniques. The ATR-FTIR analysis shows the interaction of cationic ionic liquid, BDMITFB with hydroxyl group of PVA. TGA results show that thermal stability of PVA-BDMITFB films decreases with increasing content of BDMITFB. DSC results reveal that glass transition temperature (Tg), melting temperature (Tm) and percentage degree of crystallinity (%Xc) decreased with increasing BDMITFB content in PVA films except in PVA-BDMITFB-3. Similar results were also observed from XRD analysis. The changes in film morphology were examined by SEM which reveals the aggregation of PVA/BDMITFB. The fractional area% for decomposition peak, Td2, peak of PVA-BDMITFB complex estimated from 1st derivative of TGA (DTGA) curves exhibit the aggregation of polymer. Ionic conductivity, log σ vs. 1/T plots for PVA-BDMITFB films show Arrhenius type behaviour. Loss tangent, tan δ shifts to the higher frequency region with increasing temperature.