Kraack, H.Ocko, B. M.Pershan, PeterSloutskin, E.Tamam, L.Deutsch, M.2013-02-282004Kraack, H., B. M. Ocko, Peter S. Pershan, E. Sloutskin, L. Tamam, and M. Deutsch. 2004. Fatty acid Langmuir films on liquid mercury: X-ray and surface tension studies. Langmuir 20(13): 5375-5385.0743-7463http://nrs.harvard.edu/urn-3:HUL.InstRepos:10354248The structure and phase behavior of liquid-mercury-supported molecular films of fatty acids (\(CH_{3}(CH_{2})_{n-2}COOH\),denoted CnOOH) were studied for molecular lengths 7 \(\leq\) n \(\leq\) 24, by surface tensiometry and X-ray methods. Two qualitatively different film structures were found, depending on coverage. For high coverage, the film consists of a monolayer of roughly surface-normal molecules, showing a pressure-dependent sequence of structures similar, though not identical, to that of the corresponding water-supported Langmuir films. At low coverage, phases consisting of surface-parallel molecules are found, not observed on the aqueous subphases employed to date. In this range, a two-dimensional (2D) gas followed by a single and, for 14 \(\leq\) n \(\leq\) 24, also by a double layer of surface-parallel molecules is found as coverage is increased. Depending on chain length, the flat-lying phases have a crystalline 2D ordered, a smectic-like 1D-ordered, or a disordered in-plane structure consisting of molecular dimers. The structure and thermodynamics of the films are discussed.en-USJournal Article10.1021/la049977y