Modification of deeply buried hydrophobic interfaces by ionic surfactants

Lilach Tamam, Diego Pontoni, Zvi Sapir, Shai Yefet, Eli Sloutskin, Benjamin M. Ocko, Harald Reichert, Moshe Deutsch

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Hydrophobicity, the spontaneous segregation of oil and water, can be modified by surfactants. The way this modification occurs is studied at the oil-water interface for a range of alkanes and two ionic surfactants. A liquid interfacial monolayer, consisting of a mixture of alkane molecules and surfactant tails, is found. Upon cooling, it freezes at Ts, well above the alkane's bulk freezing temperature, Tb. The monolayer's phase diagram, derived by surface tensiometry, is accounted for by a mixtures-based theory. The monolayer's structure is measured by high-energy X-ray reflectivity above and below Ts. A solid-solid transition in the frozen monolayer, occurring approximately 3 °C below Ts, is discovered and tentatively suggested to be a rotator-to-crystal transition.

Original languageEnglish
Pages (from-to)5522-5525
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number14
DOIs
StatePublished - 5 Apr 2011

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