Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
J Phys Chem B. 2020 Mar 19;124(11):2230-2237. doi: 10.1021/acs.jpcb.9b11753. Epub 2020 Mar 11.
Recently, it has been observed that choline chloride ([Ch][Cl]) based deep eutectic solvents (DESs) may possess nanostructures in which chloride ions play a major role by providing a backbone for the bridged hydrogen bond network. In this article, we present a fundamental study on the role of hydration on the nanostructure of a [Ch][Cl] based DES, ethaline. In this molecular dynamics investigation, we observe a nonlinear change in the structural morphology of ethaline on gradual addition of water. The initiation of disruption of the native structure of the DES at 40 mol % of water is clearly observed, after which the increasing dilution rapidly destructs the long-range as well as short-range intermolecular interactions existing between the constituent species of pure ethaline. Herein, we find that, at very high hydration level, chloride ion no longer acts as a bridge between the choline cation and ethylene glycol, as it forms strong hydrogen bond with water. Intriguingly, the strengthening of hydrogen bonding interactions among the ethylene glycol molecules is observed on increasing hydration level. Hence, it is predicted that segregation of ethylene glycol can occur in the pool of aqueous mixtures of [Ch][Cl] at very high hydration level.
最近，人们观察到氯化胆碱([Ch][Cl])基深共熔溶剂(DES)可能具有纳米结构，其中氯离子通过提供桥接氢键网络的骨架来发挥主要作用。在本文中，我们对基于[Ch][Cl]的 DES 乙撑亚胺的水合作用对其纳米结构的作用进行了基础研究。在这项分子动力学研究中，我们观察到乙撑亚胺在逐渐加入水时结构形态的非线性变化。在 40mol%的水时，明显观察到 DES 原生结构的破坏开始，之后不断稀释迅速破坏了纯乙撑亚胺中各组成物质之间的长程和短程分子间相互作用。在此，我们发现，在非常高的水合水平下，氯离子不再充当胆碱阳离子和乙二醇之间的桥梁，因为它与水形成了强氢键。有趣的是，随着水合水平的增加，观察到乙二醇分子之间氢键相互作用的增强。因此，可以预测在非常高的水合水平下，[Ch][Cl]的水溶液混合物中可能会发生乙二醇的分离。
