Faculty of Science and Technology, Institute of Physics, University of Silesia in Katowice, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland.
Faculty of Science and Technology, Institute of Materials Science, the University of Silesia in Katowice, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland.
J Phys Chem Lett. 2023 Mar 30;14(12):2958-2964. doi: 10.1021/acs.jpclett.3c00099. Epub 2023 Mar 20.
The existence of more than one liquid state in a single-component system remains the most intriguing physical phenomenon. Herein, we explore the effect of cation self-assembly on ion dynamics in the vicinity of liquid-liquid and liquid-glass transition of tetraalkyl phosphonium ([P], = 4, 6; = 2-14) ionic liquids. We found that nonpolar local domains formed by 14-carbon alkyl chains are crucial in obtaining two supercooled states of different dynamics within a single ionic liquid. Although the nano-ordering, confirmed by Raman spectroscopy, still occurs for shorter alkyl chains ( = 6, < 14), it does not bring calorimetric evidence of LLT. Instead, it results in peculiar behavior of ion dynamics near the liquid-glass transition and 20-times smaller size of the dynamic heterogeneity compared to imidazolium ionic liquids. These results represent a crucial step toward understanding the nature of the LLT phenomenon and offer insight into the design of efficient electrolytes based on ionic liquids revealing self-assembly behavior.
在单一组分系统中存在多种液态仍然是最引人入胜的物理现象。在此，我们探讨了阳离子自组装对靠近四烷基鏻([P]， = 4, 6； = 2-14)离子液体液-液和液-玻璃转变的离子动力学的影响。我们发现，由 14 个碳烷基链形成的非极性局部域对于在单个离子液体中获得两种不同动力学的过冷状态至关重要。尽管 Raman 光谱证实了较短的烷基链（ = 6, < 14）仍存在纳米级有序，但它没有带来 LLT 的量热证据。相反，它导致离子动力学在液-玻璃转变附近以及与离子液体相比动态不均匀性小 20 倍的特殊行为。这些结果是理解 LLT 现象本质的关键一步，并为基于离子液体揭示自组装行为的高效电解质的设计提供了深入的见解。
