Thermophysical properties of ionic liquid {1-butyl-3-methylimidazolium bromide [bmim][Br] in alkoxyalkanols + water} mixtures at different temperatures

The interactions of alkoxyalkanols with the ionic liquid 1-butyl-3-methylimidazolium bromide [bmim][Br] as a function of temperature were investigated by combination of volumetric and acoustic methods. The density, ρ, and speed of sound, u, of ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and triethylene glycol monomethyl ether (0.00–1.01 mol·kg−1) in aqueous 1-butyl-3-methylimidazolium bromide solutions ranging from pure water to 0.29 mass% of ionic liquid have been measured at T = (288.15, 298.15 and 308.15) K and atmospheric pressure. The apparent molar volume (Vϕ) and adiabatic compressibility (Kϕ,S  ) of alkoxyalkanols in aqueous ionic liquid solution were determined at the measured temperatures. The partial molar volume (Vϕ0) and partial molar adiabatic compressibility (Kφ0) of alkoxyalkanols at infinite dilution were evaluated. Transfer volumes (ΔVϕ0) and transfer adiabatic compressibility (ΔKϕ0) at infinite dilution from water to aqueous ionic liquid solution were also calculated. The temperature dependence of the apparent molar volume was used to calculate apparent molar expansivity (ϕE0) and the Hepler’s constant values, (∂2Vϕ0/∂T2). The results were explained on the basis of competing patterns of interactions of co-solvent and the solute.

► Densities and speeds of sound of alkoxyalkanols in [bmim][Br].
► Synthesis of room temperature ionic liquid [bmim][Br].
► Partial molar volumes and compressibility of transfer.
► Apparent molar expansivities and the Hepler’s constant were calculated.
► Solute–solute and solute–solvent interactions and the structural changes of the solutes.