Thermophysical properties of aqueous solution of ammonium-based ionic liquids

Experimental densities (I), ultrasonic sound velocities (u), viscosities (I), and refractive indices (n_D) of binary mixtures of ammonium-based ionic liquids (ILs) such as diethylammonium acetate (DEAA) [(CH ₃CH₂)₂NH][CH₃COO], triethylammonium acetate (TEAA) [(CH₃CH₂)₃NH][CH ₃COO], diethylammonium hydrogen sulfate (DEAS) [(CH ₃CH₂)₂NH][HSO₄], triethylammonium hydrogen sulfate (TEAS) [(CH₃CH₂)₃NH][HSO ₄], trimethylammonium acetate (TMAA) [(CH₃) ₃NH][CH₃COO], and trimethylammonium hydrogen sulfate (TMAS) [(CH₃)₃NH][HSO₄] with water are reported over the wide composition range at 25 °C under atmospheric pressure. The excess molar volumes (V^E), deviation in isentropic compressibilities (Δκ_s), deviation in viscosities (Δη) and deviation in refractive indices (Δn_D) are calculated from experimental values and are correlated by Redlich-Kister polynomial equations. The V^E and Δκ_s values for the aforesaid systems are negative over the entire composition range while the Δη and Δn_D values are positive under the same experimental conditions. The intermolecular interactions and structural effects were analyzed on the basis of measured and derived properties. A qualitative analysis of the results is discussed in terms of the ion-dipole, ion-pair interactions and hydrogen bonding between ILs and water. Furthermore, the hydrogen bonding features between ILs with water were analyzed by using a molecular modeling program with the help of HyperChem7.