Hayler Hannah J, Hallett James E, Perkin Susan
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford OX1 3QZ, U.K.
Department of Chemistry, School of Chemistry, Food and Pharmacy, University of Reading, Whiteknights Campus, Reading RG6 6AD, U.K.
Langmuir. 2024 Mar 19;40(11):5695-5700. doi: 10.1021/acs.langmuir.3c03303. Epub 2024 Mar 5.
Deep eutectic solvents (DESs) show promise as boundary lubricants between sliding surfaces, taking advantage of their physical stability, chemical stability, and tunability. Here, we study friction forces across nanofilms of two archetypal DES mixtures: choline chloride + ethylene glycol and choline chloride + glycerol. Using a surface force balance, we control the film thickness (to subnanometer precision) and determine the friction force simultaneously. Measurements are made at different mole fractions of the choline chloride salt and the molecular solvent, allowing us to determine the role of each species in the observed behavior. We find that the nature of the molecular solvent is dominant in determining the lubrication behavior, while the fraction of ChCl is relatively less important. By analyzing the steps in friction and the gradient of friction with load as the layers squeeze away from between the surfaces, we learn various mechanistic aspects of lubrication across the DES nanofilms of relevance to design and optimization of these promising fluids.
深共熔溶剂（DESs）因其物理稳定性、化学稳定性和可调性，有望成为滑动表面之间的边界润滑剂。在此，我们研究了两种典型DES混合物纳米薄膜上的摩擦力：氯化胆碱+乙二醇和氯化胆碱+甘油。使用表面力天平，我们控制薄膜厚度（达到亚纳米精度）并同时测定摩擦力。在氯化胆碱盐和分子溶剂的不同摩尔分数下进行测量，从而使我们能够确定每种物质在观察到的行为中的作用。我们发现，分子溶剂的性质在决定润滑行为方面占主导地位，而氯化胆碱的比例相对不太重要。通过分析摩擦力的变化步骤以及随着层从表面之间挤出时摩擦力随负载的梯度，我们了解了与这些有前景的流体的设计和优化相关的DES纳米薄膜润滑的各种机理方面。
