Thermophysical properties of diethylammonium (acetate + water) mixtures at different temperatures

Abstract

Density (ρ), speed of sound (w), dynamic viscosity (η), and the electrical conductivity (κ) of the protic ionic liquid (PIL) diethylammonium acetate ([DEA][Ac]), in binary mixtures with water, were measured in order to evaluate how these thermophysical properties are affected by the variation of temperature along a wide composition range. The studied temperature range used for ρ and w was (293.15–323.15) K, for η was (283.15–343.15) K, and for κ was (298.15–363.15) K. The pressure was 100.90 kPa. The values obtained for ρ and w were used to calculate the apparent molar volume (vϕ), excess volume (vE), the thermal expansion coefficient (α), and the isentropic compressibility (ks). It was found that temperature affects the properties of the binary mixtures differently and at different degrees, depending on the mole fraction of the PIL. It can also be noted that the electrical conductivity of the system does not depend on its dynamic viscosity only, which would be expected if the electrical conductivity was dominated by diffusion. The other known electrical conductivity mechanisms for PILs are dependent on the formation of hydrogen bonds. Therefore, based on the combined evaluation of the measured properties, [DEA][Ac] seems capable of forming hydrogen bonds with water, leading to high conductivities and making it promising for electrochemical applications.