Conductivity and dielectric relaxation of cross-linked PVA/montmorillonite electrolyte films

Abstract

The objective of this work is to prepare and characterize polyvinyl alcohol/montmorillonite clay (PVA/MMT) composite films at various clay amounts. The PVA is cross-linked with oxalic acid at the cross-linking degree of 20%. The composite films are characterized by X-ray diffraction, water uptake and swelling measurements, Ac electrical conductivity and dielectric measurements, surface morphology study by scanning electron microscopy, thermal gravimetric analyses and dynamic mechanical analyses. X-ray diffraction study shows the presence of characteristic peaks of PVA with a decrease of the crystalline degree by addition of clay. The morphological study shows the presence of the montmorillonite phase in good dispersion in the PVA matrix. The water uptake and swelling behavior show a dependence on the clay percentage. The presence of clay enhances the thermal stability of the composite and increases the Young modulus and ductility of the films. The Ac conductivity between 100 Hz and 1 MHz shows response well fitted by the universal Jonsher law compatibly with charge transport in disordered materials. The DC conductivity shows an Arrhenius response with activation energy values compatible with ionic transport. The use of the dielectric permittivity and the modulus formalisms show the presence of two relaxation processes.