Effect of ionic liquid on structural, thermal and electrical transport properties of PVA-PVP based polymer blend electrolyte membrane

Abstract

The present paper deals with the loading effect of ionic liquid (IL), 1-ethyl-3-methylimidazolium methylsulfate [EMIM][MS] on structural and electrical transport properties of polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG)- salt, sodium methyl sulfate (MeSO4Na) based polymer blend electrolyte (PBE) films. The samples were prepared using conventional solution cast method. The x-ray Diffraction (XRD) result shows that PBE films has characteristic peak with broad halo appeared in the range 2θ = 19.95° to 22.72° reveals the amorphous nature (semi-crystalline).The % degree of crystalinity (X c ) of prepared IL based PBE films were found to decreases with increasing IL content. Fourier transform infrared (FTIR) in total attenuated reflectance (ATR) mode analysis reveals the interaction between the functional groups (C=O and O–H) of polymer electrolyte with the cation, EMIM+/anion of IL/salt. Thermogravimetric analysis (TGA) shows that IL based PBE samples decomposes in multistep and Td,onset/peak value decreases with IL loading. Sample containing 30 wt%IL shows optimum dc conductivity value ∼1.5 × 10−4 S cm−1 at 30 °C with minimum activation energy ∼0.21 eV. Logσ versus 1000/T plot for all PBE sample follow the Arrhenius type thermally activated process and activation energy decreased with increasing IL content in PBE films. Frequency dependent conductivity behavior for IL based PBE film follow the Jonscher’s power law with power law exponent, n value<1 (amorphous polymeric system). AC conductivity spectra and loss tangent spectra (tanδ) with respect to IL/temperature content scalled successfully. Dielectric relaxation behavior and conductivity relaxation were analyses with respect to IL content and temperature. Mobility, total number of charge/ion density, ion diffusivity was estimated. Ionic transference number (ITN) measurement (tion ∼0.98, tele ∼0.02) reveals that ions are principal charge carriers in present system. Linear sweep voltametry (LSV) and cyclic voltamerty (CV) measurements show that 30 wt%IL containing sample has electrochemical stability window (ESW) ∼±2.7volt and Faradic oxidation reduction peaks were observed, respectively.