AC/DC conductivity and dielectric relaxation behavior of ionic solutions of 1-butyl-3-methylimidazolium chloride in methanol

Abstract

The complex relative dielectric function, ε*(f) of solutions of 1-butyl-3-methylimidazolium chloride ([BMiM][Cl]) in methanol (MeOH) of varying concentration and temperature have been measured in lower (20 Hz–2 MHz) and microwave (200 MHz–20 GHz) frequency regimes using precision LCR meter and Vector Network Analyzer (VNA) respectively. Complex ac conductivity, σ*(f) of the liquid samples were determined from the measured low frequency ε*(f). DC conductivity, σdc of the samples were also determined. The influence of concentration and temperature variation on the complex permittivity and electrical conductivity of the solutions is discussed. σdc of pure [BMiM][Cl] and pure MeOH is significantly enhanced in diluted to moderately concentrated solution of [BMiM][Cl] in MeOH. Experimental values of σdc at different concentrations were fitted to the empirical Casteel-Amis (CA) equation. Static dielectric constant of ionic solutions was determined from complex permittivity measurements in the microwave frequency range, using which, information about the molecular interaction between [BMiM][Cl] and MeOH was revealed. Viscosity (η), molar conductivities (Λm), infinite dilution conductance (Λ0) and Walden product (W) of the solutions were also determined. Orientational relaxation behavior of the mixture solutions in microwave frequency region is not influenced by variation in concentration of [BMiM][Cl] in MeOH. Different contribution arising in the dielectric spectra are discriminated.