Dielectric relaxation spectroscopy of an acetamide–sodium thiocyanate eutectic mixture

Abstract

The permittivity and dielectric loss of an acetamide-sodium thiocyanate mixture have been measured over a wide frequency interval, from lo-' to 10' Hz. The observed dielectric dispersions have been interpreted on the basis of a polymeric model previously proposed. The dipole moment of the acetamide molecule as a function of temperature and the displacement and mobility of solvated Na+ ion have been estimated.

Dielectric Relaxations of (Acetamide + Electrolyte) Deep Eutectic Solvents in the Frequency Window, 0.2 ≤ ν/GHz ≤ 50: Anion and Cation Dependence

“…Prediction for wildly varying rotational volumes for acetamide may suggest involvement of cooperative small-amplitude motions and/or reorientational jumps. 58,72,73 The cooperativity may arise, as discussed in earlier works, 18,19 from the formation of H-bonded complexes between ions and acetamide molecules extended over a few-toseveral molecular diameters, promoting small amplitude collective rotation at the expense of molecular rotation. In such a scenario, breaking and re-formation of H-bonds for acetamide molecules of ion−acetamide complexes can be a source for the observed slowing down.…”

“…19,20 These relatively low frequency measurements have suggested inhomogeneous relaxation kinetics and a colossal static dielectric constant (ε 0 ). Temperature-dependent relaxation times detected in these measurements have been found to spread over half-of-a-second to a couple of nanoseconds, suggesting extremely slow relaxation originating from movements of nanosized domains formed via the interaction between amide molecules and electrolytes.…”

Medium decoupling of dynamics at temperatures ∼100 K above glass-transition temperature: A case study with (acetamide + lithium bromide/nitrate) melts

“…A model solution structure consisting of salt domains, amorphous amide, and amide interacting with ions was proposed 13 in order to uniformly explain the relaxation characteristics revealed by the above experiments. Most striking of these experimental studies had been the suggestion of colossal (∼10 6 ) static dielectric constant (ε 0 ) for these melts by the DR measurements 3, 12,13,26 performed in the frequency range, 0.1 ≤ ν/H z ≤ 10 6 , which also reported Cole-Cole 28 relaxation processes with a strong stretching exponent (or shape parameter), particularly at the high frequency region, for (CH 3 CONH 2 + NaSCN) melt. In addition, depending upon temperature (265 ≤ T /K ≤ 311), extremely slow relaxation times -one varying between ∼10 ms and ∼0.5 s at the low frequency regime and the other between ∼25 ns and ∼250 ns at the high frequency regime -characterized the acetamide-thiocyanate melt data.…”

“…In addition, depending upon temperature (265 ≤ T /K ≤ 311), extremely slow relaxation times -one varying between ∼10 ms and ∼0.5 s at the low frequency regime and the other between ∼25 ns and ∼250 ns at the high frequency regime -characterized the acetamide-thiocyanate melt data. 12 In contrast, similar measurements with (CH 3 CONH 2 + CF 3 COONa) and (CH 3 CONH 2 + Ca(NO 3 ) 2 ) melts 3 reported that even though the DR data were equally describable by either Cole-Cole or Davidson-Cole 29 processes, spectral characteristics did not deviate much from the conventional Debye description. 30 Interestingly, the diameter of the charged domain, thought to be responsible for the mega-value of ε 0 and formed via ion aggregation, was estimated to be ∼10 nm and in equilibrium with two types of amide environments.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Acetamide has been one of the most frequently used amides because of its unique solvating power [14][15][16][17][18][19] which arises due to the presence of several functional groups, high molecular dipole moment (3.7 D), and fairly large static dielectric constant (ε 0 ≈ 60) 17 in molten state (melting point ∼353 K, boiling point ∼495 K). These interesting solvent properties coupled with a wide thermal window have made molten mixtures of (acetamide + electrolyte) to be used not only as reaction media in chemical industry but also as materials for electrochemical applications at elevated temperatures.…”