Viscosities and Conductivities of Binary Mixtures of 4-(Diethoxyphosphoryl)butyl Triphenylphosphonium Hexafluorophosphate with Organic Solvents

In this work, a phosphonate-functionalized ionic liquid, 4-(diethoxyphosphoryl)butyl triphenylphosphonium hexafluorophosphate (PFIL) has been synthesized and characterized by FTIR, NMR and HRMS spectra. The viscosities (eta) and conductivities (kappa) of three binary mixtures of PFIL with acetonitrile (ACN), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), respectively, were investigated in the temperature range from 293.15 to 343.15 K at atmospheric pressure. Solid PFIL dissolves in all these polar solvents within the concentrations studied (mole fraction of PFIL from 0.01 to 0.14). The experimental studies indicate that the viscosities of the three binary mixtures decrease in the following order: [PFIL(1) + DMSO(2)] > [PFIL(1) + DMF(2)] > [PFIL(1) + ACN(2)], while as expected, the conductivities increase in the following order: [PFIL(1) + ACN(2)]>[PFIL(1) + DMF(2)]>[PFIL(1) + DMSO(2)]. The conductivities as a function of temperature have been well correlated by Vogel-Fulcher-Tammann (VFT) and Arrhenius equations, while viscosities can be better fitted by using VFT equation. The dependence of conductivity on concentration for the studied systems is well represented by Casteel-Amis equation.