Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions,Macromolecules

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Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions
Macromolecules ( IF 5.1 ) Pub Date : 2021-11-02 , DOI: 10.1021/acs.macromol.1c01414
Till Böhmer ₁ , Robin Horstmann ₁ , Jan Philipp Gabriel ₂ , Florian Pabst ₁ , Michael Vogel ₁ , Thomas Blochowicz ₁

Affiliation

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.

中文翻译：

浓缩聚合物溶液中表观慢溶剂动力学的起源

由于它们的尺寸差异，与聚合物基质相比，浓缩聚合物溶液中溶剂分子的动力学可以快几个数量级。尽管有这些观察，过去的研究表明，一小部分溶剂导致了大分子时间尺度上的缓慢动力学。通过结合去偏振动态光散射和分子动力学模拟，我们表明长期存在的溶剂 - 溶剂互相关导致这些缓慢的溶剂贡献。它们源自溶质压印到相邻溶剂上的能量景观，导致不同溶剂分子的位置和方向之间的相关性增强，直到溶质松弛。这种机制解释了在探测集体动力学和单粒子动力学的技术结果之间发现的差异，例如介电和核磁共振波谱。我们的研究结果揭示了溶剂在大分子附近的行为方式，并且与从聚合物-增塑剂系统到水合蛋白质的材料相关。

更新日期：2021-11-23

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