title: Modification of deeply buried hydrophobic interfaces by ionic surfactants.
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 T(s), well above the alkane's bulk freezing temperature, T(b). 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 T(s). A solid-solid transition in the frozen monolayer, occurring approximately 3 °C below T(s), is discovered and tentatively suggested to be a rotator-to-crystal transition.
authors.affiliation: Physics Department and Institute of Nanotechnology and Advanced Materials, Bar-llan University, Ramat-Gan 52900, Israel.
authors.forename: Lilach
authors.initials: L
authors.lastname: Tamam
authors.forename: Diego
authors.initials: D
authors.lastname: Pontoni
authors.forename: Zvi
authors.initials: Z
authors.lastname: Sapir
authors.forename: Shai
authors.initials: S
authors.lastname: Yefet
authors.forename: Eli
authors.initials: E
authors.lastname: Sloutskin
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Ocko
authors.forename: Harald
authors.initials: H
authors.lastname: Reichert
authors.forename: Moshe
authors.initials: M
authors.lastname: Deutsch
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D008956:Models, Chemical; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000473:Alkanes; D052578:Ionic Liquids; D013501:Surface-Active Agents