Viscosity Measurements for Binary Mixtures of 1-Ethyl-3-Methylimidazolium Tetrafluoroborate with Acetonitrile, Ethylene Glycol, and Methanol

The viscosities of binary mixtures of the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate with acetonitrile, ethylene glycol, and methanol were measured. The dynamic viscosities of IL binary mixtures of a range of compositions under atmospheric pressure and at temperatures from 303.15 to 333.15 K were studied. Marked reductions in the viscosity values of the mixtures were noted when organic solvents were added to the IL. Furthermore, the viscosities decrease with increasing temperature. The viscosity deviations of the IL binary mixtures were then calculated and were found to be negative. The negative viscosity deviation indicates that the anion–cation interaction in pure ILs is weakened by the addition of organic solvents and that the viscosity decrease is considerable. The calculated viscosity deviations were correlated using a four parameter Redlich–Kister equation. Satisfactory correlation results were obtained; the optimally fitted parameters are described. Furthermore, to analyze the intermolecular interactions in these three binary mixtures, the experimental reduced Redlich–Kister viscosity deviations, excess molar volumes, excess Gibbs energy of activation for viscous flow, and Arrhenius activation energy for viscous flow were calculated.