High dielectric constant supercooled liquids, tools in energetic problems

Berchiesi, G.; Farhat, Farhat; Angelis, Marco de; Barocci, S.

doi:10.1016/0167-7322(92)80073-q

Cited by 18 publications

(17 citation statements)

References 18 publications

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“…Furthermore, a recent ab initio molecular dynamics simulation study did not find any evidence of charge delocalization in three different choline chloride-based DESs . While many previous experimental studies have centered on the structure and dynamics of components in different acetamide type I DESs, − a few have concentrated on the type III DES, − , which is the motivation of this study. Importantly, the effects of the chemical structure of the hydrogen bond acceptor (HBA) cation on the resulting structure of the DESs remains unexplored.…”

Section: Introductionmentioning

confidence: 84%

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Cui

Kuroda

2018

J. Phys. Chem. A

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The liquid structure of five different amide-based deep eutectic solvents (DESs) as a function of the chemical structure of the hydrogen bond acceptor (HBA) was investigated by linear Fourier transform infrared (FTIR) and two-dimensional infrared (2DIR) spectroscopies. Linear FTIR spectroscopy shows that the amide band of the DESs is not significantly affected by the chemical structure and symmetry of the HBA cation. However, its excitonic nature does not allow us to draw further conclusions. Analysis of the C amide line shapes derived from the 2DIR spectra reveals that the different DESs do not show appreciable differences in the level of disorganization. The vibrational dynamics, derived from the photon echo experiments on theC amide, shows that there is a fast component with a time scale of ∼1 ps irrespective of the HBA. The ultrafast dynamics is assigned to hydrogen bond making and breaking between amides. In addition, a slow dynamical component is observed in the time evolution of the photon echo signal. This contribution appears to be correlated with the asymmetry and polarity of the moieties of the HBA. The overall dynamics is rationalized in terms of a microscopic heterogeneous structure of the DESs, where the heterogeneities create domains that slow the hydrogen bond making and breaking. Molecular dynamics simulations provide additional support for our modeling of the data. In addition, the presence of nanoscopic heterogeneities is consistent with the observation of an endortherm at 23 °C in the differential scanning calorimetry thermogram, which evidenced a phase transition at 23 °C, even though the tested DESs have a melting temperature below -40 °C.

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Section: Introductionmentioning

confidence: 84%

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Cui

Kuroda

2018

J. Phys. Chem. A

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“…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.…”

Section: Introductionmentioning

confidence: 93%

“…20,21 These molten mixtures (or simply, melts) are characterized by estimated glass transition temperatures (T g ) ∼190 < T g /K < 250 range, [22][23][24][25] and are termed as supercooled mixtures as they remain in the liquid phase at temperatures much below the respective melting temperatures of the constituents. This "supercooling" phenomenon and the associated importance for chemical industry have motivated much of the research on the basic scientific aspects, because developing these melts into useful dielectric materials 13,26 requires deeper understanding of medium structural and transport properties. a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

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

Guchhait

Daschakraborty

Biswas

2012

The Journal of Chemical Physics

126

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Time-resolved fluorescence Stokes shift and anisotropy measurements using a solvation probe in [0.78CH(3)CONH(2) + 0.22{f LiBr + (1-f) LiNO(3)}] melts reveal a strong decoupling of medium dynamics from viscosity. Interestingly, this decoupling has been found to occur at temperatures ∼50-100 K above the glass transition temperatures of the above melt at various anion concentrations (f(LiBr)). The decoupling is reflected via the following fractional viscosity dependence (η) of the measured average solvation and rotation times (<τ(s)> and <τ(r)>, respectively): <τ(x)> ∝ (η∕T)(p) (x being solvation or rotation), with p covering the range, 0.20 < p < 0.70. Although this is very similar to what is known for deeply supercooled liquids, it is very surprising because of the temperature range at which the above decoupling occurs for these molten mixtures. The kinship to the supercooled liquids is further exhibited via p which is always larger for <τ(r)> than for <τ(s)>, indicating a sort of translation-rotation decoupling. Multiple probes have been used in steady state fluorescence measurements to explore the extent of static heterogeneity. Estimated experimental dynamic Stokes shift for coumarin 153 in these mixtures lies in the range, 1000 < Δν(t)/cm(-1) < 1700, and is in semi-quantitative agreement with predictions from our semi-molecular theory. The participation of the fluctuating density modes at various length-scales to the observed solvation times has also been investigated.

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“…[39][40][41][42] In addition, the dielectric relaxation, density, and viscosity of CH 3 CONH 2 -NaSCN eutectic mixtures have also been reported. 26,43,44 In this communication, we present a systematic analysis of the dielectric relaxation behavior of DESs: 0.78CH 3 CONH 2 + 0.22LiNO 3 and 0.75CH 3 CONH 2 + 0.25NaSCN, over a wide temperature and frequency range with the aim to understand the conductivity relaxation and secondary processes. To describe the ion dynamics of the DESs, we have adopted the complex electrical modulus M * (υ) and complex conductivity σ * (υ) functions.…”

Section: Introductionmentioning

confidence: 99%

Glass transition dynamics and conductivity scaling in ionic deep eutectic solvents: The case of (acetamide + lithium nitrate/sodium thiocyanate) melts

Tripathy

Wojnarowska

Knapik

et al. 2015

The Journal of Chemical Physics

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A detailed investigation on the molecular dynamics of ionic deep eutectic solvents (acetamide + lithium nitrate/sodium thiocyanate) is reported. The study was carried out employing dielectric relaxation spectroscopy covering seven decades in frequency (10(-1)-10(6) Hz) and in a wide temperature range from 373 K down to 173 K, accessing the dynamic observables both in liquid and glassy state. The dielectric response of the ionic system has been presented in the dynamic window of modulus formalism to understand the conductivity relaxation and its possible connection to the origin of localized motion. Two secondary relaxation processes appear below glass transition temperature. Our findings provide suitable interpretation on the nature of secondary Johari-Goldstein process describing the ion translation and orientation of dipoles in a combined approach using Ngai's coupling model. A nearly constant loss feature is witnessed at shorter times/lower temperatures. We also discuss the ac conductivity scaling behavior using Summerfield approach and random free energy barrier model which establish the time-temperature superposition principle. These experimental observations have fundamental importance on theoretical elucidation of the conductivity relaxation and glass transition phenomena in molten ionic conductors.

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High dielectric constant supercooled liquids, tools in energetic problems

Cited by 18 publications

References 18 publications

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

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

Glass transition dynamics and conductivity scaling in ionic deep eutectic solvents: The case of (acetamide + lithium nitrate/sodium thiocyanate) melts

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