Viscoelastic and ultrasonic relaxation in molten mixture of acetamide and calcium nitrate

Berchiesi, G.; Vitali, G.; Płowiec, R.; Barocci, S.

doi:10.1039/f29898500635

Cited by 19 publications

(15 citation statements)

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“…Presence of microheterogeneity in solution structure was suggested earlier by viscoelastic, 11,27 ultrasonic, 3, 26 nuclear magnetic resonance, 10 and dielectric relaxation (DR) 3, 12 experiments with (amide + salt) 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.…”

Section: Introductionmentioning

confidence: 74%

“…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. 3 Further viscoelastic and ultrasonic relaxation measurements 27 revealed the proposed aggregation phenomenon was less pronounced for melts containing ions other than Na + . This variation notwithstanding, microheterogeneity had been a recurrent theme in the early literature while analyzing the experimental results for these melts.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 74%

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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“…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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“…The negative deviation in conductivity (--27%) in the Na+ -ion-rich region below =323.15 K may be governed by two factors: firstly, due to the greater polarization of SCN-on the Na+ ion causing a decrease in the ionic mobility, and secondly, interaction of Na+ ion with acetamide resulting in a polymeric type of solvated ion (15) with further decrease in ionic mobility. As a result a rigid structure with very high relaxation time prevails in the Na+-ion-rich region in the present system (15,19). Therefore, the high relaxation time, which is also one of the criteria (4) for the onset of MAE, together with the polarization effect causes maximum negative x l mot fraction deviation in the electrical conductivity in the Na+-ion-rich region.…”

Section: I Mol T R a C T I O Nmentioning

confidence: 96%

Mixed alkali effect in sodium thiocyanate–potassium thiocyanate – acetamide melt systems

Mahiuddin¹

1996

Can. J. Chem.

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Electrical conductivity and molar volume of the 0.25[xNaSCN + (1 -x)KSCN] + 0.75CH3CONH, systems were measured as functions of temperature (~293.15-358.15 K) and composition (x = 0.0 -1 . O mol fraction). Temperature dependence of the electrical conductivity was non-Arrhenius in nature and has been analysed by using the Vogel-TammannFulcher (VTF) equation. Molar volume data were fitted to an equation similar to the VTF equation based on the free volume model. Molar volumes and intrinsic volumes were found to be additive in nature. Electrical conductivity isotherms deviate from linearity in different fashion for different temperature regions. The onset of the mixed alkali effect is governed by the anion polarization effect, by a contribution of the auto-dissociated molten acetamide, and by polymeric-type solvated ions.

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Viscoelastic and ultrasonic relaxation in molten mixture of acetamide and calcium nitrate

Cited by 19 publications

References 0 publications

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

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

Evidence of Molecular Heterogeneities in Amide-Based Deep Eutectic Solvents

Mixed alkali effect in sodium thiocyanate–potassium thiocyanate – acetamide melt systems

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