Looking at the “Water-in-Deep-Eutectic-Solvent” System: A Dilution Range for High Performance Eutectics

Abstract

Deep eutectic solvents (DESs) are lately expanding their use to more demanding applications upon aqueous dilution thanks to the preservation of the most appealing properties of the original DESs while overcoming some of their most important drawbacks limiting their performance, like viscosity. Both experimental and theoretical works have studied this dilution regime, the so-called “water-in-DES” system, at near-to stoichiometric amounts to the original DES. Herein, we rather studied the high-dilution range of the “water-in-DES” system looking for enhanced performance because of the interesting properties (a further drop of viscosity) and cost (water is cheap) that it offers. In particular, we found that, in the “water-in-DES” system of a ternary DES composed of resorcinol, urea and choline chloride (e.g., RUChClnW, where n represents mol of water per mole of ternary DES), the tetrahedral structure of water was distorted as a consequence of its incorporation, as an additional hydrogen bond donor or hydrogen bond acceptor, into the hydrogen bond complexes formed among the original DES components . DSC confirmed the formation of a new eutectic, with a melting point below that of its respective components, the original ternary DES and water. This depression in the melting point was also observed in the same regime of reline and malicine aqueous dilutions, thus suggesting the universality of this simple procedure (i.e., water addition to reach the high-dilution range of the “water-in-DES” system) to obtain deeper eutectics eventually providing enhanced performances and lower cost.

High‐Molecular‐Weight Polyampholytes Synthesized via Daylight‐Induced, Initiator‐Free Radical Polymerization of Renewable Itaconic Acid

“…Due to the lack of strict definition, the mixtures are commonly called deep eutectic solvents (DESs), hydrophobic eutectic solvents, natural deep eutectic solvents (NADESs) or low‐transition temperature mixtures (LTTMs). Although they can contain relatively simple compounds such as choline chloride (CC), amides, carboxylic acids, sugars, and even water, their thermodynamic properties and molecular structure are subjects for intense debate and investigations . In every case, the importance of the mixtures for many fields of chemistry, including polymers chemistry is indisputable …”

Carbon and carbon composites obtained using deep eutectic solvents and aqueous dilutions thereof

“…7). 78 Interestingly, all the DES/H 2 O binary mixtures with melting points at the lowest temperature were those with water contents where the plot of v H versus DES content obtained by Brillouin spectroscopy deviated from linearity (Fig. 5b).…”

“…This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. In the particular case of DES/H 2 O binary mixtures, e.g., DESs composed of resorcinol, phosphoric acid, glycerol, and ChCl (RPGC), 50 DESs composed of resorcinol, urea and ChCl (RUChCl), 78 and DES composed of resorcinol, 4-hexylresorcinol, and tetraethylammonium bromide, (RHRTEA), 72 the representation of v H versus DES content in wt% provided an even more illustrative display of the deviation with two well-distinguishable regions when transitioning from the v H of neat H 2 O -e.g., ca. 1460 m s À1 -to that of neat DES (Fig.…”

“…Interestingly, in a recent work dealing with pseudo-concentrated aqueous solutions of DES composed of resorcinol, urea, and ChCl, we demonstrated that water played the role of an additional HBD or HBA and, hence, was interstitially accommodated within the DES-based 3D H-bonded network, thus forming the ''water-in-DES'' system. 78 Moreover, the phase behaviour of aqueous solutions of ethaline has been recently described. 79 The achievement of new eutectic mixtures with significant water contents is indeed of relevance in practical applications as we may preserve and even improve some of the most interesting features of DESs such as low melting points ( Fig.…”

Aqueous Co‐Solvent in Zwitterionic‐based Protic Ionic Liquids as Electrolytes in 2.0 V Supercapacitors

“…The temperature was fixed at 100 °C to avoid the freezing of the systems during the simulation due to the viscous nature of the studied ZPILs. The complete set of settings of the MD simulations was reported in our previous studies [67,68] …”