Structure and dynamics of short-chain polymerized ionic liquids.
Structure and dynamics of short-chain polymerized ionic liquids.
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DOI：
10.1063/1.5109228
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
F. Wieland;V. Bocharova;P. Münzner;W. Hiller;R. Sakrowski;C. Sternemann;R. Böhmer;A. Sokolov
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文献类型：
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作者：
F. Wieland;V. Bocharova;P. Münzner;W. Hiller;R. Sakrowski;C. Sternemann;R. Böhmer;A. Sokolov
结合x射线散射和场梯度核磁共振（NMR）获得的实验结果，以及对新的和以前的介电和流变学数据的评估，我们的研究重点是同源系列共价键离子液体的局部结构和动力学的分子量（Mw）演变。本研究对一系列具有定制程度离子解耦的电解质进行了研究，揭示了单体和低聚体熔体在结构组织、质量和电荷传输以及分子扩散方面的差异。我们的研究表明，对于单体化合物，宽带电导率和力学光谱反映了相同的潜在激活势垒分布，并且随机势垒模型相当好地描述了这些材料中的离子和结构弛豫过程。此外，含有10段链的低聚物仅表现出真正聚合物的结构和动力学指纹。利用核磁共振探测的自扩散系数和直接用介电光谱探测的系数估计的电导率水平的比较揭示了离子相关性的出现，这种相关性以链长依赖的方式影响这些材料中的宏观电荷输运。
Combining experimental results obtained with X-ray scattering and field-gradient nuclear magnetic resonance (NMR) and an assessment of new and previous dielectric and rheology data, our study focuses on the molecular weight (Mw) evolution of local structure and dynamics in a homologous series of covalently bonded ionic liquids. Performed on a family of electrolytes with a tailored degree of ionic decoupling, this study reveals the differences between monomeric and oligomeric melts with respect to their structural organization, mass and charge transport, and molecular diffusion. Our study demonstrates that for the monomeric compound, the broadband conductivity and mechanical spectra reflect the same underlying distribution of activation barriers and that the Random Barrier Model describes fairly well both the ionic and structural relaxation processes in these materials. Moreover, the oligomers with chains comprising ten segments only exhibit both structural and dynamical fingerprints of a genuine polymer. A comparison of conductivity levels estimated using the self-diffusion coefficients probed via NMR and those probed directly with dielectric spectroscopy reveals the emerging of ion correlations which are affecting the macroscopic charge transport in these materials in a chain-length dependent manner.