Temperature-Dependent Dielectric Relaxation in Ionic Acetamide Deep Eutectics: Partial Viscosity Decoupling and Explanations from the Simulated Single-Particle Reorientation Dynamics and Hydrogen-Bond Fluctuations

Abstract

We report here temperature-dependent (293 ≤ T (K) ≤ 336) dielectric relaxation (DR) measurements of (acetamide + LiBr/NO 3 −

Difference in “Supercooling” Affinity between (Acetamide + Na/KSCN) Deep Eutectics: Reflections in the Simulated Anomalous Motions of the Constituents and Solution Microheterogeneity Features

“…15 Such a power law dependence is typical for relaxations in glassy systems, 17−22 and this finding immediately provided the much needed fillip to explore the spatio-temporal heterogeneity of these apparently simple systems at temperatures much above T g . Subsequent DR studies, 14 dynamic Stokes shift measurements employing a fluorescence upconversion technique, and fluorescence correlation spectroscopic measurements 23 indeed reflected heterogeneous relaxation dynamics in (acetamide + LiBr/NO 3 / ClO 4 ) DESs via fractional viscosity dependence of average relaxation times.…”

“…Subsequent temperaturedependent DR measurements with (acetamide + LiBr/NO 3 / ClO 4 ) DESs showed a significant anion dependence of the DR parameters and DR activation energies along with a strong anion impact on the heterogeneous dynamics of these ionic media. 14 Interestingly, simulation studies of the nature of the angular moves of different particles in these systems performed earlier 15,16 had predicted not only jump rotations for acetamide molecules but also found a significant dependence of these non-Brownian orientational moves on the identity of the ionic species. In addition, the simulated waiting time distributions showed a power law dependence, P(t jump ) ∝ (t jump /τ) −γ , with τ and γ exhibiting a considerable dependence on the ion identity.…”

“…Dielectric relaxation (DR) measurements (0.2 ≤ν/GHz≤ 50) of several ionic acetamide DESs revealed that the presence of a uni-univalent electrolyte had substantially decreased the static dielectric constant of neat molten acetamide, and the maximum reduction was recorded for the Na + ion-containing DES. Subsequent temperature-dependent DR measurements with (acetamide + LiBr/NO 3 /ClO 4 ) DESs showed a significant anion dependence of the DR parameters and DR activation energies along with a strong anion impact on the heterogeneous dynamics of these ionic media . Interestingly, simulation studies of the nature of the angular moves of different particles in these systems performed earlier , had predicted not only jump rotations for acetamide molecules but also found a significant dependence of these non-Brownian orientational moves on the identity of the ionic species.…”

Dielectric relaxation and dielectric decrement in ionic acetamide deep eutectic solvents: Spectral decomposition and comparison with experiments

“…5 Often, the term DESs is used somewhat loosely to encompass the molten phase of the multicomponent mixtures at temperatures and compositions that are away from those corresponding to the eutectic points. [6][7][8][9][10][11][12] Several outstanding solvent features, such as, viscosity and polarity turnabilities, relatively lesser environmental footprints, easy to prepare and handle, low vapor pressure, wider thermal and electrochemical windows, etc. have made DESs as popular solvents as reaction media not only for targeted chemical synthesis but also for engineering materials related to technological applications.…”

“…[19][20][21][22] The entropy gains for being in the liquid phase then completes the driving force behind the stable liquidous regime in DESs, although theoretical/computational investigation for the composition and temperature dependent entropy gain (both rotational and translational) are still unavailable. Different experiments, such as, time-resolved fluorescence experiments, 6,8,9,[23][24][25] dielectric relaxation and conductivity measurements, 11,12,26 and femtosecond Raman induced Kerr effect spectroscopic (fs-RIKES) measurements 27 have been carried out in the last several years and each of these measurements indicated micro heterogeneous relaxation dynamics for the studied ionic DESs.…”