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Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions

Böhmer, Till ; Horstmann, Robin ; Gabriel, Jan Philipp ; Pabst, Florian ; Vogel, Michael ; Blochowicz, Thomas (2021):
Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions.
In: Macromolecules, ACS Publications, ISSN 0024-9297,
DOI: 10.1021/acs.macromol.1c01414,
[Article]

Abstract

Due to their size disparity, the dynamics of solvent molecules in concentrated polymer solutions can be faster by several orders of magnitude compared to the polymer matrix. Despite these observations, past research suggests that a fraction of the solvent contributes to the slow dynamics on the timescale of the macromolecules. By combining depolarized dynamic light scattering and molecular dynamics simulations, we show that long-lived solvent–solvent cross-correlations cause these slow solvent contributions. They originate from the energy landscape that the solute imprints onto the neighboring solvent, leading to enhanced correlations between the positions and orientations of different solvent molecules until the solute relaxes. This mechanism explains the discrepancies found between the results of techniques probing collective and single-particle dynamics, such as dielectric and nuclear magnetic resonance spectroscopy. Our findings shed new light on how solvents behave in the vicinity of macromolecules and are of relevance for materials ranging from polymer-plasticizer systems to hydrated proteins.

Item Type: Article
Erschienen: 2021
Creators: Böhmer, Till ; Horstmann, Robin ; Gabriel, Jan Philipp ; Pabst, Florian ; Vogel, Michael ; Blochowicz, Thomas
Title: Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions
Language: English
Abstract:

Due to their size disparity, the dynamics of solvent molecules in concentrated polymer solutions can be faster by several orders of magnitude compared to the polymer matrix. Despite these observations, past research suggests that a fraction of the solvent contributes to the slow dynamics on the timescale of the macromolecules. By combining depolarized dynamic light scattering and molecular dynamics simulations, we show that long-lived solvent–solvent cross-correlations cause these slow solvent contributions. They originate from the energy landscape that the solute imprints onto the neighboring solvent, leading to enhanced correlations between the positions and orientations of different solvent molecules until the solute relaxes. This mechanism explains the discrepancies found between the results of techniques probing collective and single-particle dynamics, such as dielectric and nuclear magnetic resonance spectroscopy. Our findings shed new light on how solvents behave in the vicinity of macromolecules and are of relevance for materials ranging from polymer-plasticizer systems to hydrated proteins.

Journal or Publication Title: Macromolecules
Publisher: ACS Publications
Divisions: 05 Department of Physics
05 Department of Physics > Institute for Condensed Matter Physics
05 Department of Physics > Institute for Condensed Matter Physics > Molecular dynamics of condensed matter
05 Department of Physics > Institute for Condensed Matter Physics > Struktur und Dynamik amorpher Systeme
Date Deposited: 11 Nov 2021 07:08
DOI: 10.1021/acs.macromol.1c01414
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