Ion dynamics in pendant and backbone polymerized ionic liquids: A view from high-pressure dielectric experiments and free-volume model
Ion dynamics in pendant and backbone polymerized ionic liquids: A view from high-pressure dielectric experiments and free-volume model
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DOI：
10.1103/physreve.105.054502
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发表时间：
2022-05-09
影响因子：
2.4
通讯作者：
Paluch, Marian
中科院分区：
文献类型：
--
作者：
Cheng, Shinian;Wojnarowska, Zaneta;Paluch, Marian
聚合离子液体（PILs）是典型的单离子导体，其中一种离子要么作为链的垂基团（pendant PILs），要么直接并入聚合主链（backbone PILs）。本文比较了悬垂型和主干型聚合物的热力学、离子动力学和力学性能。结果表明，在玻璃化转变附近，悬浮型PIL的离子跃迁能垒要低得多，而主干型PIL对压力的敏感性要高得多。同时，本文提出了一个基于自由体积的模型来理解所研究的两种pil在高压条件下的离子动力学。与主干PIL相比，确定的临界体积（定量离子跳跃所需的最小体积）显着减少，这很可能是悬浮PIL在玻璃化转变附近离子电导率增强的原因。我们发现，所提出的模型等效于常用的压力对应的Vogel-Fulcher-Tammann方程。
Polymerized ionic liquids (PILs) are typically single-ion conductors, where one kind of ionic species is either placed as the pendant group to the chain (pendant PILs) or directly incorporated into the polymeric backbone (backbone PILs). This paper compares the thermodynamics, ionic dynamics, and mechanical properties of pendant and backbone PILs. The results indicate that near the glass transition, the energy barrier for ion hopping is much lower for pendant PIL while the backbone PIL shows a much stronger sensitivity to pressure. At the same time, a free-volume based model was proposed here to understand the ion dynamics of both studied PILs at high-pressure conditions. The determined critical volume, quantifying the minimal volume required for ion hopping, of the pendant PIL is significantly reduced compared to the backbone PIL, which is most likely the reason for the enhanced ionic conductivity of the pendant PIL near the glass transition. We found that the proposed model is equivalent to the commonly used pressure counterpart of the Vogel-Fulcher-Tammann equation.