Effects of PEG plasticizer concentrations and film preparation methods on the structural, dielectric and electrical properties of PEO–PMMA blend based plasticized solid polymer electrolyte films

Abstract

Low molecular weight poly(ethylene glycol) (PEG) has been used as plasticizer in the preparation of plasticized solid polymer electrolyte (PSPE) films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend based matrix with lithium tetrafluoroborate (LiBF₄) as dopant ionic salt. Solution cast (SC) melt–pressed and the ultrasonic-microwave (US–MW) irradiated solution cast melt–pressed methods have been used for the preparation of these PSPE films. The dielectric dispersion, ac ionic conductivity and structural dynamics of these electrolytes have been studied by employing the dielectric relaxation spectroscopy (DRS) over the frequency range from 20 Hz to 1 MHz, at room temperature. The structural properties of these materials have been characterized by their X–ray diffraction (XRD) measurements. The influence of varying PEG concentrations (5, 10 and 15 wt%) and also the sample preparation methods on the complex dielectric function, ac electrical conductivity, electric modulus and the impedance spectra of these electrolytes have been explored. The ionic conductivity of US–MW prepared PSPE films enhances non-linearly, whereas for the SC prepared films it vary anomalously with the increase of PEG concentrations. The variations in conductivity of these PSPEs are governed by the change in strength of polymer-ion, plasticizer-ion and the polymer-plasticizer interactions and also the polymer chain segmental motion in the solid ion-dipolar complexes. Room temperature ionic conductivity values of the PEG concentrations and sample preparation methods dependent these PSPE electrolytes at low concentration of dopant salt are found in the range from 1.79 to 4.22 mS cm^–1, which confirm their suitability in preparation of the all-solid-state ion conducting devices.