title: Line tension of alkane lenses on aqueous surfactant solutions at phase transitions of coexisting interfaces.
abstract: Alkane droplets on aqueous solutions of surfactants exhibit a first-order wetting transition as the concentration of surfactant is increased. The low-concentration or "partial wetting" state corresponds to an oil lens in equilibrium with a two-dimensional dilute gas of oil and surfactant molecules. The high-concentration or "pseudo-partial wetting" state consists of an oil lens in equilibrium with a mixed monolayer of surfactant and oil. Depending on the combination of surfactant and oil, these mixed monolayers undergo a thermal phase transition upon cooling, either to a frozen mixed monolayer or to an unusual bilayer structure in which the upper leaflet is a solid layer of pure alkane with hexagonal packing and upright chains while the lower leaflet remains a disordered liquid-like mixed monolayer. Additionally, certain long-chain alkanes exhibit a surface freezing transition at the air-oil interface where the top monolayer of oil freezes above its melting point. In this review, we summarize our previous studies and discuss how these wetting and surface freezing transitions influence the line tension of oil lenses from both an experimental and theoretical perspective.
authors.affiliation: Department of Chemistry, Faculty of Sciences, Kyushu University, Higashi-ku, Hakozaki 6-10-1, Fukuoka 812-8581, Japan. Electronic address: h.matsubarascc@chem.kyushu-univ.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsubara
authors.affiliation: Department of Chemistry, Faculty of Sciences, Kyushu University, Higashi-ku, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
authors.forename: Baku
authors.initials: B
authors.lastname: Ushijima
authors.affiliation: Condensed Matter Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506-2601, USA.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Law
authors.affiliation: Department of Chemistry, Faculty of Sciences, Kyushu University, Higashi-ku, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Takiue
authors.affiliation: Department of Chemistry, Faculty of Sciences, Kyushu University, Higashi-ku, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Aratono
keywords: Alkane; Line tension; Surface phase transition; Surfactant; Wetting transition