Arshid Ahmad, Robin Köster, Sebastian Kloth and Michael Vogel
{"title":"Comparative molecular dynamics simulation studies of simple and polymerized ionic liquids†","authors":"Arshid Ahmad, Robin Köster, Sebastian Kloth and Michael Vogel","doi":"10.1039/D5SM00307E","DOIUrl":null,"url":null,"abstract":"<p >We perform molecular dynamics simulations to compare the structures and dynamics of a simple and a polymerized ionic liquid. The latter comprises [BF<small><sub>4</sub></small>] anions and [(CH<small><sub>2</sub></small>)<small><sub>6</sub></small>–C<small><sub>3</sub></small>H<small><sub>3</sub></small>N<small><sub>2</sub></small>]<small><sub>25</sub></small> 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.</p>","PeriodicalId":103,"journal":{"name":"Soft Matter","volume":" 26","pages":" 5231-5241"},"PeriodicalIF":2.8000,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soft Matter","FirstCategoryId":"92","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2025/sm/d5sm00307e","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
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.
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.