Properties of Four Deep Eutectic Solvents: Density, Electrical Conductivity, Dynamic Viscosity and Refractive Index

Four deep eutectic solvents (DESs) were prepared from tetrabutylammonium chloride: tetrabutylammonium chloride:propionic acid [TBAC:2PA], tetrabutylammonium chloride:ethylene glycol [TBAC:2EG], tetrabutylammonium chloride:polyethylene glycol [TBAC:2PEG], and tetrabutylammonium chloride:phenylacetic acid [TBAC:2PAA]. The density, electrical conductivity, dynamic viscosity, and refractive index of the samples were measured at 288.15-338.15 K under atmospheric pressure. The influence of the temperature on the density, electrical conductivity, dynamic viscosity, and refractive index are discussed. The thermal expansion coefficient, molecular volume, standard molar entropy, and lattice energy were determined from the measured values using empirical equations. The temperature dependences on the electrical conductivity and dynamic viscosity of the DESs were fitted by the Vogel-Fulcher-Tamman (VFT) equation. The Arrhenius equation is also discussed for the electrical conductivity and dynamic viscosity. The above study will be of great significance for the industrial and engineering applications of DESs.