Local Dielectric Relaxation by Solvation Dynamics

Richert, Ranko

doi:10.1007/978-3-642-56120-7_15

Cited by 3 publications

(3 citation statements)

References 38 publications

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“…To understand the heterogeneous character of nonequilibrated polymers, experiments (e.g., nonlinear dielectric spectroscopy) and simulations could focus on higher-order nonlinear susceptibilities. These quantities, as already verified in the case of small molecules, , provide signatures of the nature and the length scale of dynamic heterogeneities.…”

Section: Perspectives and Outlookmentioning

confidence: 99%

Processing Pathways Decide Polymer Properties at the Molecular Level

et al. 2019

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Conditions of rapid processing often drive polymers to adopt nonequilibrium molecular conformations, which, in turn, can give rise to structural, dynamical, and mechanical properties that are significantly different from those in thermodynamic equilibrium. However, despite the possibility to control the desired nonequilibrium properties of polymers, a rigorous microscopic understanding of the processing–property relations is currently lacking. In an attempt to stimulate progress along this topical direction, we focus here on three prototypical and apparently different cases: spin-coated polymer films, rapidly drawn polymer fibers, and sheared polymer melts. Inspired by the presence of common observations in the chosen cases, we search for order parameters as, for example, topological correlations and heterogeneities, which may allow characterizing the processing-induced behavior of polymers. We highlight that such approaches, necessitating concerted efforts from theory, simulations, and experiments, can provide a profound understanding leading to predictable and tunable properties of polymers.

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Section: Perspectives and Outlookmentioning

confidence: 99%

Processing Pathways Decide Polymer Properties at the Molecular Level

et al. 2019

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“…The dipolar probe used in the present work is sensitive to the electric modulus response of the solvent at the microscopic level. 33 The results can thus be compared with shear modulus data or with the measured electric impedance represented in modulus form. 34 It is not clear which process dominates the physical aging of monohydroxy alcohols, because so far only somewhat incomplete or inconclusive dielectric measurements exist: [35][36][37] The available data do not allow one to decide whether aging takes place on the α time scale or on a somewhat longer scale.…”

Section: Introductionmentioning

confidence: 99%

Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide

Preuss

Gainaru

Hecksher

et al. 2012

The Journal of Chemical Physics

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Binary solutions of 2-ethyl-1-hexanol (2E1H) with 2-ethyl-1-hexyl bromide (2E1Br) are investigated by means of dielectric, shear mechanical, near-infrared, and solvation spectroscopy as well as dielectrically monitored physical aging. For moderately diluted 2E1H the slow Debye-like process, which dominates the dielectric spectra of the neat monohydroxy alcohol, separates significantly from the α-relaxation. For example, the separation in equimolar mixtures amounts to four decades in frequency. This situation of highly resolved processes allows one to demonstrate unambiguously that physical aging is governed by the α-process, but even under these ideal conditions the Debye process remains undetectable in shear mechanical experiments. Furthermore, the solvation experiments show that under constant charge conditions the microscopic polarization fluctuations take place on the time scale of the structural process. The hydrogen-bond populations monitored via near-infrared spectroscopy indicate the presence of a critical alcohol concentration, x(c) ≈ 0.5-0.6, thereby confirming the dielectric data. In the pure bromide a slow dielectric process of reduced intensity is present in addition to the main relaxation. This is taken as a sign of intermolecular cooperativity probably mediated via halogen bonds.

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“…About 10 –4 mol of QX was added to an (NEA) 0.4 (NMF) 0.6 mixture. Subsequent to laser excitation, triplet-to-singlet (T 1 → S 0 ) emission spectra of QX were recorded for several temperatures in the time range 1 ms < t < 1 s. The long time limit is set by the phosphorescence lifetime of QX of about 0.3 s. More details regarding equipment and data analysis can be found elsewhere. , …”

Section: Methodsmentioning

confidence: 99%

Dynamics in Supercooled Secondary Amide Mixtures: Dielectric and Hydrogen Bond Specific Spectroscopies

et al. 2015

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Alkylacetamide-based model peptides display an intense Debye-type dielectric relaxation. In order to explore the extent to which this feature has to be regarded analogous to that in other supramolecular liquids, notably the monohydroxy alcohols, we applied broadband dielectric, time-dependent solvation, and near-infrared spectroscopies as well as shear rheology and various nuclear magnetic resonance techniques to mixtures of N-methylacetamide (NMA) or N-ethylacetamide (NEA) with N-methylformamide. Compared in the modulus format, dielectric relaxation, solvation dynamics, and mechanical response indicate a common global and local dynamics. The present spin-relaxation measurements reflect motional processes which are significantly faster than the dominant Debye dielectric response, and a similar conclusion is drawn from measurements of the shear viscosity. The NH overtone stretching vibrations reveal a temperature-dependent hydrogen-bond equilibrium that changes its characteristics near temperatures of 325 K. Finally, dielectric low-temperature data recorded for (NEA)0.4(NMF)0.6 mixed with 2-picoline indicate the existence of a critical concentration akin to the situation in various monohydroxy alcohol mixtures.

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Local Dielectric Relaxation by Solvation Dynamics

Cited by 3 publications

References 38 publications

Processing Pathways Decide Polymer Properties at the Molecular Level

Processing Pathways Decide Polymer Properties at the Molecular Level

Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide

Dynamics in Supercooled Secondary Amide Mixtures: Dielectric and Hydrogen Bond Specific Spectroscopies

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