Comparative molecular dynamics simulation studies of simple and polymerized ionic liquids†

IF 2.8 3区 化学 Q3 CHEMISTRY, PHYSICAL
Soft Matter Pub Date : 2025-06-09 DOI:10.1039/D5SM00307E
Arshid Ahmad, Robin Köster, Sebastian Kloth and Michael Vogel
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引用次数: 0

Abstract

We perform molecular dynamics simulations to compare the structures and dynamics of a simple and a polymerized ionic liquid. The latter comprises [BF4] anions and [(CH2)6–C3H3N2]25 cations and, hence, the charged imidazolium rings are, unlike in most previous studies, embedded in the polymer backbone rather than in side chains. It is found that cation polymerization weakly affects the local structure but leads to a strong slowdown and an enhanced heterogeneity of the dynamics. Despite strongly different diffusion coefficients of the anions and polymerized cations, reflecting single ion conductor behavior, the structural relaxation of the anions remains coupled to the segmental polymer motion. A comparison with literature results indicates that polymerized cations with embedded and pendant imidazolium rings exhibit different anion association and cause different anion transport mechanisms, with prevailing diffusive and hopping motions, respectively. In addition, we observe that the Rouse model reasonably well describes the polymer dynamics in our case of charged chains strongly interacting with counterions. Specifically, it captures the static amplitudes and time constants of the lower Rouse modes, while there are strong deviations from the model predictions for the higher Rouse modes, which are associated with smaller length scales and sensitive to structural and dynamical heterogeneity related to polycation–anion association.

Abstract Image

简单和聚合离子液体的分子动力学模拟比较研究。
我们进行分子动力学模拟来比较简单离子液体和聚合离子液体的结构和动力学。后者由[BF4]阴离子和[(CH2)6-C3H3N2]25阳离子组成,因此,与大多数先前的研究不同,带电的咪唑环嵌入在聚合物主链而不是侧链中。发现阳离子聚合对局部结构的影响较弱,但导致了强烈的减速和动力学的非均质性增强。尽管阴离子和聚合阳离子的扩散系数有很大的不同,反映了单离子导体的行为,阴离子的结构弛豫仍然耦合于聚合物的节段运动。与文献结果的比较表明,嵌入咪唑环和悬垂咪唑环的聚合阳离子表现出不同的阴离子缔合机制,引起不同的阴离子传输机制,分别以扩散运动和跳跃运动为主。此外,我们观察到,Rouse模型相当好地描述了我们的带电链与反离子强烈相互作用的聚合物动力学。具体来说,它捕获了低劳斯模式的静态振幅和时间常数,而高劳斯模式的模型预测存在很大偏差,因为高劳斯模式具有较小的长度尺度,并且对与阳离子-阴离子结合相关的结构和动力学异质性敏感。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Soft Matter
Soft Matter 工程技术-材料科学:综合
CiteScore
6.00
自引率
5.90%
发文量
891
审稿时长
1.9 months
期刊介绍: Soft Matter is an international journal published by the Royal Society of Chemistry using Engineering-Materials Science: A Synthesis as its research focus. It publishes original research articles, review articles, and synthesis articles related to this field, reporting the latest discoveries in the relevant theoretical, practical, and applied disciplines in a timely manner, and aims to promote the rapid exchange of scientific information in this subject area. The journal is an open access journal. The journal is an open access journal and has not been placed on the alert list in the last three years.
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