氯化胆碱类低共熔溶剂结构与性质的分子动力学研究

Molecular dynamics simulation of the structures and properties of deep eutectic solvents

摘要:

低共熔溶剂是一种类离子液体的绿色溶剂，具有低饱和蒸汽压、低熔点、无毒、可降解以及价格廉价等优势，被广泛应用于科学研究和工程应用，其理化性质，如密度、黏度以及晶格结构等是开发具有特定功能溶剂及其应用的基础. 本文采用分子动力学模拟的方法，利用GAFF力场计算了氯化胆碱类低共熔溶剂在293.15~353.15 K下的密度和黏度，与文献实验值的平均绝对偏差分别为0.30%和6.19%，显示出较好的一致性. 同时在分子水平上，本文利用径向分布函数分析了不同体系内的结构分布以及氢键网络的形成，发现了低共熔溶剂中存在的大量氢键网络主要由Cl原子和羟基上的H原子相互作用形成的，且他们间的相互作用随着温度的升高而减弱，随着氢键供体烷基链长度的增加而增强. 这些微观上的认识，有助于进一步研究低共熔溶剂的组成、结构与其物理性质间的作用机制.

Abstract:

As a new kind of green ionic liquid, deep eutectic solvents have many advantages such as low saturated vapor pressure, low melting point, low price, non-toxicity and degradability, and are widely used in scientific research and engineering applications. Their physical and chemical properties, such as density, viscosity and lattice structure, are the basis for developing solvents with specific functions and their applications. In this work, the density and viscosity of choline-based deep eutectic solvents at 293.15~353.15 K were calculated by molecular dynamics simulation within the framework of GAFF force field, and their average absolute deviations with experimental values in literature were 0.30% and 6.19%, respectively. At the molecular level, the radial distribution function is used to describe the structure distributions in different systems and the formation of hydrogen bonds network. It was found that the extensive hydrogen bonds network of the deep eutectic solvent system was mainly formed by the interaction of Cl atoms and H atoms on hydroxyl, and the interaction decreases with the increase of temperature, and increases with the increase of the length of the hydrogen bond donor alkyl chain. The present study will help us to further study the interaction mechanism between the composition, structure and physical properties of deep eutectic solvents.