Hydrogen bond donors dictate the frictional response in deep eutectic solvents

Hayler, H. J. ORCID: https://orcid.org/0000-0002-0626-1522, Hallett, J. E. ORCID: https://orcid.org/0000-0002-9747-9980 and Perkin, S. ORCID: https://orcid.org/0000-0002-5875-5217 (2024) Hydrogen bond donors dictate the frictional response in deep eutectic solvents. Langmuir, 40 (11). pp. 5695-5700. ISSN 1520-5827 doi: 10.1021/acs.langmuir.3c03303

Abstract/Summary

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.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/115760
Identification Number/DOI	10.1021/acs.langmuir.3c03303
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
Uncontrolled Keywords	Electrochemistry, Spectroscopy, Surfaces and Interfaces, Condensed Matter Physics, General Materials Science
Publisher	American Chemical Society (ACS)
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