Ion specificity towards structure-property correlation of poly (ethylene oxide) [PEO]-NH ₄ I and PEO-KBr composite solid polymer electrolyte

Ion conduction mechanism in polymer-salt composite is highly dependent on the optimization of the process parameters. In this investigation, studies on poly (ethylene oxide) [PEO] with different salt viz. ammonium Iodide (NH ₄ I) and potassium bromide (KBr) [represented as N-series and K-series respectively] are carried out. Highest ionic conductivity of ~ 10 ⁻⁴  S cm ⁻¹ is observed for PEO-NH ₄ I (20%) composite which is found to be the most amorphous. FTIR spectra of N-series are deconvoluted within 3187–3442 cm ⁻¹ in order to estimate the percentage of free and contact ions. Number density of free ions is found to increase proportionately with the salt content. Detailed characterization is carried out in view of salt-induced microstructural inhomogeneity. Flexibility of the polymer blend is reflected in several ion-transport parameters like carrier concentration, mobility, etc. Two relaxation times [τ ₁ (~ 10 ⁻⁴  s) and τ ₂ (~ 10 ⁻⁷  s)] as being exhibited in the complex electric modulus clearly illustrate the existence of both amorphous and crystalline regimes within PEO-salt composite.