Electrical and structural studies of ionic liquid-based poly(vinyl alcohol) proton conductors

Ionic liquid-based proton conducting polymer electrolytes containing poly(vinyl alcohol) (PVA), ammonium acetate (CH3COONH4) and 1-butyl-3-methylimidazolium bromide (BmImBr) are prepared and investigated in this present work. The ionic conductivity of polymer electrolytes increases with temperature as shown in temperature dependent-ionic conductivity study. All the polymer electrolytes follow Vogel-Tamman-Fulcher (VTF) relationship. This principle infers the coupling effect of ionic hopping mechanism and free volume theory. The pseudo-activation energy of all the polymer electrolytes is also determined by fitting the plots with VTF empirical equation. The complexation between PVA, CH3COONH4 and BmImBr is verified in Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) study. Addition of ionic liquid reduces the crystallinity of polymer electrolytes as proven in x-ray diffraction (XRD) by calculating the degree of crystallinity of polymer electrolytes. The crystallite sizes of polymer electrolytes are also determined using XRD. Proton nuclear magnetic resonance (H-NMR) spectrum reveals the rapid conduction mechanism in the polymer electrolyte by determining the ion diffusion coefficient.