Density, Viscosity, and Refractive Index of Ionic Liquid Mixtures Containing Cyano and Amino Acid-Based Anions

In this work, mixtures of five ionic liquids (ILs) based on a common cation, 1-ethyl-3-methylimidazolium ([C₂mim]⁺), and amino acid anions, namely glycinate ([Gly]^a), l-alaninate ([l-Ala]^a), taurinate ([Tau]^a), l-serinate ([l-Ser]^a), and l-prolinate ([l-Pro]^a) with 1-ethyl-3-methylimidazolium tricyanomethane, [C₂mim][C(CN)₃], were prepared. The thermophysical properties, namely density, viscosity, and refractive index, of the neat ILs and their mixtures were measured in the temperature range of T = (293.15 up to 353.15) K. The thermal expansion coefficients were calculated for the neat ILs and were considered to be independent of temperature in the working temperature range. Overall, experimental density, viscosity, and refractive index data of the neat AAILs were in a good agreement with those reported in literature. A dramatic decrease in the viscosity was observed for the IL mixtures as the [C₂mim][C(CN)₃] content increased. The obtained results indicate that mixing [C₂mim][C(CN)₃] with amino acid-based ILs is a potential mean to further increase flexibility and the fine-tune capacity of the physical and chemical properties of amino acid-based ILs.