Lyu Xingmei

The density and viscosity of aqueous solutions of quaternary ammonium-amino acid ionic liquids

Three quaternary ammonium-amino acid ionic liquids ([N2222][AA]) tetraethylammonium L-a-aminopro- pionic acid salt ([N2222][Ala]), tetraethylammonium L-amino-3-hydroxypropionic acid salt ([N2222][Ser]), and tetraethylammonium L-aminosuccinic acid salt ([N2222][Asp]) were prepared by the neutralization method and characterized by 1H NMR, 13C NMR, IR and elemental analysis. The density and viscosity of binary mixtures ([N2222][AA] + water) with different compositions were determined at T = 293.15-343.15 K by using an Anton Paar DMA 5000 densimeter and an Anton Paar AMVn measuring assembly systematically. The temperature dependence of density and viscosity for [N2222][AA] and water mixtures can be described by an empirical linear equation and by the Vogel-Tammann-Fucher (VTF) equation, respectively. The excess volume ( V E) and viscosity deviation (Δ η ) were calculated and correlated by Redlich-Kister polynomial equation, respectively. Based on the measured and derived properties, the influence of the interaction between ILs and water and hydrogen bonds formed between amino acid ionic liquids (AAILs) and water on density and viscosity were analyzed.