Dynamics of type V menthol-thymol deep eutectic solvents: Do they reveal non-ideality?

Ionic Conductivity of a Lithium-Doped Deep Eutectic Solvent: Glass Formation and Rotation–Translation Coupling

“…The sample with a 5 mol % salt content exhibited qualitatively similar results. The main features in these spectra are the same as those previously found for other ionically conducting DESs. ,− , At high temperatures and low frequencies, ε′(ν) (Figure a) approaches “colossal” values, exceeding 10 5 in the present case. This is due to electrode polarization, which is a common finding for ionic conductors. , This arises from a space-charge region close to the sample surface that forms when the ions reach the electrodes at low frequencies, where their motion essentially becomes blocked.…”

“…As often found for eutectic mixtures, many DESs exhibit a glass transition at low temperatures and the concomitant characteristic properties of supercooled liquids. ,,,− As pointed out in several earlier works by our group, this can also affect their room-temperature properties, including the technically relevant direct current (dc) conductivity. ,,− Moreover, most DESs contain dipolar entities (e.g., glycerol molecules in glyceline), which can reveal reorientational dynamics that are intimately connected with the glassy freezing detected in the viscosity . Such dipole rotations in ionic conductors are also of interest because they can play an important role in the enhancement of ionic mobility, as explicitly shown for ionic liquids and various crystalline systems. − Interestingly, varying degrees of correlations of reorientational dipolar and translational ionic motions were recently found for a number of DESs, too. ,− ,, However, overall, the glassy freezing and dipolar dynamics of DESs were only rarely investigated until now. To our knowledge, only in ref the glass transition in lithium-doped DESs was briefly discussed, based on temperature-dependent conductivity and differential scanning calorimetry (DSC) measurements.…”

“…At frequencies beyond the Maxwell–Wagner-dominated regime, another step-like decrease in ε′(ν) appears (see the inset of Figure for an enlarged view). In analogy to other DESs, ,− ,, we ascribe it to an intrinsic dipolar relaxation process due to the reorientational motions of the dipolar entities in this DES, termed α relaxation. With decreasing temperature, these relaxation steps strongly shift to lower frequencies, indicating the continuous slowing down of the molecular dynamics typical for dipolar glass-formers. , This is confirmed by the occurrence of a typical glass-transition anomaly in the DSC results obtained for this DES (Figure S1).…”

Solute dynamics of a hydrophobic molecule in a menthol–thymol based type-V deep eutectic solvent: effect of composition of the components

“…Recent studies on menthol/ thymol-based type V DES reported the presence of clusters with hydroxyl cores and exteriors of alkyl rich moieties, and preferential H-bond interactions between unlike molecules, which create non-ideality in the DES. 15,35 This further supports our assumption of the existence of different dipolar regions in the investigated type V DESs.…”

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

“…% of maline consists of dipolar molecules, the presence of a dipolar relaxation feature is expected, as reported in various other DESs containing dipolar constituents. [53][54][55][56][57][68][69][70] Upon cooling, the rotational dynamics of the dipoles gradually slow down, leading to the observed shift of the α relaxation step toward lower frequencies [Fig. 1(a)].…”