Transport properties and ionicity in allyl-/alkylether-based ILs and their binary systems with acetonitrile as the potential electrolytes: Correlation with interactions and structures

Abstract

In this paper, three functionalized ionic liquids (ILs), N-(2-methoxyethyl)-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C1OC2pyrr][NTf2]), N-(2-methoxyethyl)-N-methylpyrrolidinium dicyanamide ([C1OC2pyrr][DCA]) and 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([AMIM][NTf2]) were designed, synthesized and structurally characterized by 1H NMR and 13C NMR, and their thermal stability was determined. The viscosity and conductivity of the pure ILs and their binary mixtures with acetonitrile were measured at standard pressure, 288.15–318.15 K. The temperature dependencies of viscosity and conductivity were described by Arrhenius equation, and the composition of the system with maximum conductivity was obtained according to Castel-Amis four-parameter equation. In addition, the interactions and structures are illustrated by the viscosity deviations (Δη), and the excess Gibbs energy of activation for viscous flow of the relative viscosity (ΔG≠E), mainly include the influences of the hydrogen bonding between cations and acetonitrile, close packing and the size of anion. The ionicity of systems were investigated qualitatively based on the Walden rule, and it can be judged that three ILs are not completely ionized and may form network structures, which dissociate into CIPs with further dilution. Moreover, it is found that ionicity is related to the kinds of ions, stability of network and viscosity.