Viscosity and electrical conductivity of ether-functionalized ionic liquids-[C1OC2mim][OAc], [C1OC2mim][Pro] and [C2OC2mim][Pro]

Abstract 1-(2-Methoxyethyl)-3-methylimidazolium acetic acid ([C1OC2mim][OAc]), 1-(2-methoxyethyl)-3-methylimidazolium propionic acid ([C1OC2mim][Pro]) and 1-(2-ethoxyethyl)-3-methylimidazolium propionic acid ([C2OC2mim][Pro]) were successfully prepared by two-step synthesis method. Based on the standard addition method, the physicochemical parameters of the density, viscosity and electrical conductivity for ether-functionalized ionic liquids (ILs) were measured. The volume properties of three ether-functionalized ILs and their homologues were estimated by semi-empirical methods. According to the Eying viscosity equation, the relationship between viscosity and activation Gibbs energy for viscous flow (ΔG≠) was studied. The activation energy values for three ether-functionalized ILs were calculated by Arrhenius empirical equation. The activation energies of these ether-functionalized ILs are arranged in the following order: [C1OC2mim][Pro] (Eη = 39.17 kJ·mol-1) > [C2OC2mim][Pro] (Eη = 37.26 kJ·mol-1) > [C1OC2mim][OAc] (Eη = 37.23 kJ·mol-1). Futhermore, the Vogel-Fulcher-Tamman (VFT) equation is used to describe the relationship between viscosity (or electrical conductivity or molar electrical conductivity) and temperature, and the experimental results show that VFT equation has good general applicability.