Glycerol Hydrogen-Bonding Network Dominates Structure and Collective Dynamics in a Deep Eutectic Solvent

Abstract

The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.

Electron Transfer Kinetics in a Deep Eutectic Solvent

“…7 The relaxation times  L are derived from dielectric loss measured by dielectric spectroscopy techniques. 38,39 Several studies were dedicated to ionic liquids (see for example 40 for investigation of imidazolium-based ionic salts and reference used for Table S1 in SI) but Ethaline was only recently investigated by dielectric spectroscopy in a wide range of frequencies and temperatures. 38 Authors have observed that a single relaxation time describes the reorientational dipolar motions for Ethaline with times close to those of the molecular component.…”

Deep Eutectic Solvents for Pretreatment, Extraction, and Catalysis of Biomass and Food Waste

“…Moreover, for materials of an ionic nature, dielectric spectroscopy is an effective method by which to understand the mechanisms related to charge transport [152]. Despite many studies on ILs, only a few studies on the dielectric properties of DESs have been performed [152,153,154,155,156,157,158,159]. For example, Griffin et al [159] utilized broadband dielectric spectroscopy in combination with depolarized dynamic light scattering to explore the charge transport and structural dynamics of a deep eutectic mixture, {Lidocaine:2Decanoic acid}.…”

Strong Microheterogeneity in Novel Deep Eutectic Solvents

“…Because hydrogen bonds were subject to many extensive discussions in literature, we show in Figure only for selected examples the corresponding combined distribution function for the hydrogen bonds between chloride and the cation as well as the EG. It is clear from these examples and from literature that the hydrogen bonds in the different DES are all very strong, because they exhibit an extremely directional behavior, i. e., angles a (Cl−H−O) are close to 180 degrees and the peaks extend only to 165 degrees. This is different for aprotic ionic liquids, see for example [51, 55, 56], where usually such a directionaly cannot be achieved, because the donor atom often is a carbon atom.…”

“…Because hydrogen bonds were subject to many extensive discussions in literature, [18,21,[52][53][54] we show in Figure 5 only for selected examples the corresponding combined distribution function for the hydrogen bonds between chloride and the cation as well as the EG. It is clear from these examples and from literature [18,21,[52][53][54] that the hydrogen bonds in the different DES . Spatial distribution function [43,51] in order to illustrate the side chain conformers.…”