Dynamically asymmetric binary glass formers studied by dielectric and NMR spectroscopy

Körber, T.; Minikejew, Rafael; Pötzschner, B.; Bock, D.; Rössler, E. A.

doi:10.1140/epje/i2019-11909-5

Cited by 13 publications

(4 citation statements)

References 77 publications

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“… 34 , 68 – 73 are critical in restoring the verity of the dynamics obtained by using dielectric permittivity spectroscopy of polar glass-formers. On the other hand, the presence of the JG β-relaxation and its relations to the α-relaxation was not recognized in the papers of Körber et al 19 , 74 , Gabriel et al 21 , 62 , and Pabst et al 22 , and the consequence is that they were not able to reach the same conclusion.…”

Section: Discussionmentioning

confidence: 96%

Comparative analysis of dielectric, shear mechanical and light scattering response functions in polar supercooled liquids

Ngai

Wojnarowska

Paluch

2021

Sci Rep

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The studies of molecular dynamics in the vicinity of liquid–glass transition are an essential part of condensed matter physics. Various experimental techniques are usually applied to understand different aspects of molecular motions, i.e., nuclear magnetic resonance (NMR), photon correlation spectroscopy (PCS), mechanical shear relaxation (MR), and dielectric spectroscopy (DS). Universal behavior of molecular dynamics, reflected in the invariant distribution of relaxation times for different polar and weekly polar glass-formers, has been recently found when probed by NMR, PCS, and MR techniques. On the other hand, the narrow dielectric permittivity function ε*(f) of polar materials has been rationalized by postulating that it is a superposition of a Debye-like peak and a broader structural relaxation found in NMR, PCS, and MR. Herein, we show that dielectric permittivity representation ε*(f) reveals details of molecular motions being undetectable in the other experimental methods. Herein we propose a way to resolve this problem. First, we point out an unresolved Johari–Goldstein (JG) β-relaxation is present nearby the α-relaxation in these polar glass-formers. The dielectric relaxation strength of the JG β-relaxation is sufficiently weak compared to the α-relaxation so that the narrow dielectric frequency dispersion faithfully represents the dynamic heterogeneity and cooperativity of the α-relaxation. However, when the other techniques are used to probe the same polar glass-former, there is reduction of relaxation strength of α-relaxation relative to that of the JG β relaxation as well as their separation. Consequently the α relaxation appears broader in frequency dispersion when observed by PCS, NMR and MR instead of DS. The explanation is supported by showing that the quasi-universal broadened α relaxation in PCS, NMR and MR is captured by the electric modulus M*(f) = 1/ε*(f) representation of the dielectric measurements of polar and weakly polar glass-formers, and also M*(f) compares favorably with the mechanical shear modulus data G*(f).

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Section: Discussionmentioning

confidence: 96%

Comparative analysis of dielectric, shear mechanical and light scattering response functions in polar supercooled liquids

Ngai

Wojnarowska

Paluch

2021

Sci Rep

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“…Recently, it was suggested in the literature that the dynamics of protein-water [60] or polymer-water [61] mixtures have similar characteristics to those of highly asymmetric mixtures of two glass-formers or polymers. These systems, called HAM (highly asymmetric mixtures), were intensely studied in the literature [62][63][64][65]. HAM refers to the mixture of two polymer or glassformers (A and B) with glass transition temperatures T g,A ) T g,B .…”

Section: Comparison Between Highly Asymmetric Mixtures Of Liquids And...mentioning

confidence: 99%

Influence of ice formation on the dynamic and thermodynamic properties of aqueous solutions

2022

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“…Testing the NMR time scale reflected by R 2 ( T ): plot of R 2 /(5 K Q τ ref ) vs the reciprocal temperature. Reference time scales are given by those from DLS or viscosity η: data of (a) o -terphenyl- d 14 ( R 2 , DLS, η), (b) glycerol- d 5 ( R 2 , DLS, η), (c) butanol- d 1 ( R 2 , η) and 2-ethyl-1-hexanol- d 1 ( R 2 , η see Figure S2 in the SI), and (d) toluene- d 3 and toluene- d 5 . The solid lines represent the temperature dependence of R 2 /(5 K Q τ DLS,η ) calculated from eq .…”

Section: Spin–spin Relaxation As a Probe For The Nmr Time Scalementioning

confidence: 99%

Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes

et al. 2021

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Spin-lattice relaxation rates R 1 (ω,T), probed via highfield and field-cycling nuclear magnetic resonance (NMR), are used to test the validity of frequency−temperature superposition (FTS) for the reorientation dynamics in viscous liquids. For several liquids, FTS is found to apply so that master curves can be generated. The susceptibility spectra are highly similar to those obtained from depolarized light scattering (DLS) and reveal an excess wing. Where FTS works, two approaches are suggested to access the susceptibility: (i) a plot of deuteron R 1 (T) vs the spin−spin relaxation rate R 2 (T) and (ii) a plot of R 1 (T) vs an independently measured reference time τ ref (T). Using single-frequency scans, (i) allows one to extract the relaxation stretching as well as the NMR coupling constant. Surveying 26 data sets, we find Kohlrausch functions with exponents 0.39 < β K ≤ 0.67. Plots of the spin−spin relaxation rate R 2 rescaled by the NMR coupling constantas a function of temperature allow one to test how well site-specific NMR relaxations couple to a given reference process. Upon cooling of flexible molecule liquids, the sitespecific dynamics is found to merge, suggesting that near T g the molecules reorient essentially as a rigid entity. This presents a possible resolution for the much lower stretching parameters reported here at high temperatures that contrast with the ones that were reported to be universal in a recent DLS study close to T g . Our analysis underlines that deuteron relaxation is a uniquely powerful tool to probe single-particle reorientation.

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Dynamically asymmetric binary glass formers studied by dielectric and NMR spectroscopy

Cited by 13 publications

References 77 publications

Comparative analysis of dielectric, shear mechanical and light scattering response functions in polar supercooled liquids

Comparative analysis of dielectric, shear mechanical and light scattering response functions in polar supercooled liquids

Influence of ice formation on the dynamic and thermodynamic properties of aqueous solutions

Nuclear Spin Relaxation in Viscous Liquids: Relaxation Stretching of Single-Particle Probes

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