Synthesis, Characteristics, and Thermodynamic Properties of the Ionic Liquid [Na][TOTO] and Its Binary Mixtures with Different Solvents

The ionic liquid (IL) of [Na][2,5,8,11-tetraoxatridecan-13-oate] ([Na][TOTO]) was synthesized and characterized, and its physicochemical properties, including density, viscosity, and conductivity, were experimentally determined. The structural characteristics of [Na][TOTO] via NMR, IR, and TGA techniques confirmed the successful synthesis of the target IL with high purity, demonstrating the validity of the proposed synthetic route. The binary mixtures of [Na][TOTO] with common solvents (water, methanol, and ethanol) were then investigated over the temperature range of 298.15-333.15 K and atmospheric pressure. The excess molar volume and viscosity and the conductivity of these mixtures were calculated, and empirical models were successfully used to correlate the experimental data. The analysis from the molecular level was made, suggesting that the hydrogen bonds played a key role in the changes of thermophysical properties. Generally, the results provided a deeper understanding of the relationships among different solvents for the thermophysical properties, which may promote further applications of [Na][TOTO].