Stefanovic Ryan, Ludwig Michael, Webber Grant B, Atkin Rob, Page Alister J
Priority Research Centre for Advanced Fluids and Interfaces, The University of Newcastle, Callaghan, NSW 2308, Australia.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3297-3306. doi: 10.1039/c6cp07932f.
Deep eutectic solvents (DESs) are a mixture of a salt and a molecular hydrogen bond donor, which form a eutectic liquid with a depressed melting point. Quantum mechanical molecular dynamics (QM/MD) simulations have been used to probe the 1 : 2 choline chloride-urea (ChCl : U), choline chloride-ethylene glycol (ChCl : EG) and choline chloride-glycerol (ChCl : Gly) DESs. DES nanostructure and interactions between the ions is used to rationalise differences in DES eutectic point temperatures and viscosity. Simulations show that the structure of the bulk hydrogen bond donor is largely preserved for hydroxyl based hydrogen bond donors (ChCl:Gly and ChCl:EG), resulting in a smaller melting point depression. By contrast, ChCl:U exhibits a well-established hydrogen bond network between the salt and hydrogen bond donor, leading to a larger melting point depression. This extensive hydrogen bond network in ChCl:U also leads to substantially higher viscosity, compared to ChCl:EG and ChCl:Gly. Of the two hydroxyl based DESs, ChCl:Gly also exhibits a higher viscosity than ChCl:EG. This is attributed to the over-saturation of hydrogen bond donor groups in the ChCl:Gly bulk, which leads to more extensive hydrogen bond donor self-interaction and hence higher cohesive forces within the bulk liquid.
深共熔溶剂（DESs）是一种盐与分子氢键供体的混合物，它们形成熔点降低的共熔液体。量子力学分子动力学（QM/MD）模拟已被用于探究1:2的氯化胆碱-尿素（ChCl:U）、氯化胆碱-乙二醇（ChCl:EG）和氯化胆碱-甘油（ChCl:Gly）深共熔溶剂。利用深共熔溶剂的纳米结构和离子间相互作用来解释深共熔溶剂共熔点温度和粘度的差异。模拟结果表明，对于基于羟基的氢键供体（ChCl:Gly和ChCl:EG），本体氢键供体的结构在很大程度上得以保留，导致熔点降低幅度较小。相比之下，ChCl:U在盐和氢键供体之间展现出完善的氢键网络，导致熔点降低幅度更大。与ChCl:EG和ChCl:Gly相比，ChCl:U中这种广泛的氢键网络还导致其粘度显著更高。在两种基于羟基的深共熔溶剂中，ChCl:Gly的粘度也高于ChCl:EG。这归因于ChCl:Gly本体中氢键供体基团的过饱和，这导致氢键供体之间更广泛的自相互作用，从而使本体液体内部具有更高的内聚力。
