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Solidification and superlubricity with molecular alkane films

Smith, A. M., Hallett, J. E. ORCID: and Perkin, S. (2019) Solidification and superlubricity with molecular alkane films. Proceedings of the National Academy of Sciences of the United States of America, 116 (51). pp. 25418-25423. ISSN 1091-6490

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To link to this item DOI: 10.1073/pnas.1910599116


Hydrocarbon films confined between smooth mica surfaces have long provided an experimental playground for model studies of structure and dynamics of confined liquids. However, fundamental questions regarding the phase behavior and shear properties in this simple system remain unsolved. With ultrasensitive resolution in film thickness and shear stress, and control over the crystallographic alignment of the confining surfaces, we here investigate the shear forces transmitted across nanoscale films of dodecane down to a single molecular layer. We resolve the conditions under which liquid–solid phase transitions occur and explain friction coefficients spanning several orders of magnitude. We find that commensurate surface alignment and presence of water at the interfaces each lead to moderate or high friction, whereas friction coefficients down to μ≈0.001 are observed for a single molecular layer of dodecane trapped between crystallographically misaligned dry surfaces. This ultralow friction is attributed to sliding at the incommensurate interface between one of the mica surfaces and the laterally ordered solid molecular film, reconciling previous interpretations.

Item Type:Article
Divisions:No Reading authors. Back catalogue items
ID Code:101369
Publisher:National Academy of Sciences

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