Hydrophobic deep eutectic solvents (DESs) emerge as candidates to extract organic substrates from aqueous solutions. The DES-aqueous liquid–liquid interface plays a vital role in the extraction ability of DESs because the nonbulk structure of interfacial molecules could cause thermodynamic and kinetic barriers. One question is how the DES compositions affect the structural features of the interface. We investigate the density profile, dipole moment, and hydrogen bonds of eight hydrophobic DES-aqueous interfaces using molecular dynamics simulations. The eight DESs are composed of four organic compounds: decanoic acid, menthol, thymol, and lidocaine. The results show the variations of dipole moment and hydrogen bond structure and dynamics at the interfaces. These variations could influence the extraction ability of DES through adjusting the partition and kinetics of organic substrates in the DES-aqueous biphasic systems. We also analyze the relationship between the variation of these interfacial features and the size and hydrophobicity of DES components.

中文翻译：

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疏水性低共熔溶剂-水-液-液界面的结构和氢键

疏水性低共熔溶剂 (DES) 成为从水溶液中提取有机底物的候选物。DES-水性液-液界面对DESs的提取能力起着至关重要的作用，因为界面分子的非本体结构会引起热力学和动力学障碍。一个问题是 DES 成分如何影响界面的结构特征。我们使用分子动力学模拟研究了八个疏水性 DES-水界面的密度分布、偶极矩和氢键。八种 DES 由四种有机化合物组成：癸酸、薄荷醇、百里酚和利多卡因。结果显示了界面处偶极矩和氢键结构和动力学的变化。这些变化可以通过调节 DES-水性双相系统中有机底物的分配和动力学来影响 DES 的提取能力。我们还分析了这些界面特征的变化与 DES 组件的大小和疏水性之间的关系。