Translational and reorientational dynamics in deep eutectic solvents

Abstract

Note: This paper is part of the JCP Special Topic on Chemical Physics of Deep Eutectic Solvents.

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

“…The increase of the apparent activation energy on approaching the glass transition is a salient feature of supercooled liquids, and it has been also observed for hydrophilic DESs based on choline chloride and their aqueous mixtures. [14,28,29] The classical Vogel-Fulcher-Tammann (VFT) law (Eq. 4) was fitted to the dipolar relaxation time,…”

“…To reach this goal, dielectric spectroscopy (DS) is a perfectly wellsuited method as it allows covering a broad range of frequencies (MHz-Hz) corresponding to the DES molecular dynamics, as already demonstrated in recent studied of ionic DESs based on choline chloride derivatives. [14,28,29] We combined DS to differential scanning calorimetry (DSC) in order to bridge the gap from short (∼10 −6 s) to ultra-long (∼10 2 s) timescales, that are typical for glassforming liquids.…”

Lithium-salt-based deep eutectic solvents: Importance of glass formation and rotation-translation coupling for the ionic charge transport

“…In the following, we adhere to the approach in our earlier works on DESs 23,25,34 and ionic liquids, 22 analyzing the complex dielectric permittivity, ε * = ε ′ − iε ′′ , which is the natural representation for materials with reorientational degrees of freedom and also allows for a direct comparison with our previous results on glyceline, ethaline, and reline. 23,34 In addition, we provide the real part of the conductivity σ ′ , which is proportional to ε ′′ ν and enables the direct identification of the dc conductivity. At the end of this section, we will also discuss an evaluation of the present experimental results in terms of the dielectric modulus.…”

Structural properties of supercooled deep eutectic solvents: choline chloride–thiourea compared to reline

“…Upon freezing, many DESs can be supercooled and even turned into an amorphous state. 19–21 Moreover, liquid DESs are known to possess dynamical properties typical for glassy liquids – such as stretched exponential relaxation of H-bonds, 22 heterogeneous orientational relaxations and translation–rotation decoupling. 10 So one may assume that the structural organization of DESs in their fluid and supercooled states may possess some common features, and peculiarities of the molecular packing found at reduced temperatures in the glassy state are related to those at the temperatures of their technological application.…”