Tools for extending the dilution range of the “solvent-in-DES” regime

• Published in: Journal of molecular liquids Vol. 329; p. 115573
• Main Authors: Zhang, Huan, Ferrer, M. Luisa, Jiménez-Riobóo, Rafael J., del Monte, Francisco, Gutiérrez, María C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2021
• Subjects: Calorimetry; Deep eutectic solvents; DES dilutions; Excess properties; NMR and Brillouin spectroscopy; Solvent-in-DES regime; NMR and Brillouin spectroscopy; Calorimetry; Solvent-in-DES regime; Deep eutectic solvents; DES dilutions; Excess properties
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.115573

Deep eutectic solvents (DESs) and dilutions thereof are currently gaining increased interest in sustainable processes. DES dilutions are particularly interesting in the so-called “solvent-in-DES” regime where the intriguing features of DESs remain (coming from hydrogen bonding among the components) and some typical drawbacks (e.g., high viscosity, low electrical conductivity, etc.) are mitigated. Actually, DES dilutions may exhibit excellent performances (more so than the original neat DESs) in certain applications. Knowing about the tools that allow predicting (and eventually extending) the dilution range of the “solvent-in-DES” regime is obviously of interest. With this aim, we herein studied two sets of DES dilutions. In the first set, we used the DES composed of choline chloride (ChCl) and urea (U) and its dilutions in H2O, methanol (MeOH) and ethanol (EtOH). In the second set, we studied two DESs composed of ethylene glycol (EG) and either tetraethylammonium bromide (TEABr) or tetrabutylammonium bromide (TBABr), and their dilutions in H2O. Data coming from DSC, 1H NMR spectroscopy, and Brillouin spectroscopy revealed how the dilution range of the “solvent-in-DES” regime in ChClU dilutions in H2O, MeOH and EtOH increased in the order H2O < MeOH < EtOH while in aqueous dilutions of TEABrEG and TBABrEG increased in the order TEABrEG < TBABrEG. Our results suggest that the extension of the dilution range of the “water-in-DES” regime could be tuned by both the DES components solubility in the different solvents, and the strength and/or number of the hydrogen bonds established between DES components and solvent molecules. [Display omitted] •Revealing some common features of dilutions of different DESs in different solvents.•Extending the dilution range of the solvent-in-DES regime.•Correlating results from Brillouin spectroscopy, NMR spectroscopy, excess properties and melting point.