title: Wetting, mixing, and phase transitions in Langmuir-Gibbs films.
abstract: Millimolar bulk concentrations of the surfactant cetyltrimethylammonium bromide (CTAB) induce spreading of alkanes, H(CH(2))(n)H (denoted C(n)) 12< or =n< or =21, on the water surface, which is not otherwise wet by these alkanes. The novel Langmuir-Gibbs film (LGF) formed is a liquidlike monolayer comprising both alkanes and CTAB tails. Upon cooling, an ordering transition occurs, yielding a hexagonally packed, quasi-2D crystal. For 11< or =n< or =17 this surface-frozen LGF is a crystalline monolayer. For 18< or =n< or =21 the LGF is a bilayer with a crystalline, pure-alkane, upper monolayer, and a liquidlike lower monolayer. The phase diagram and film structure were determined by x-ray, ellipsometry, and surface tension measurements. A thermodynamic theory accounts quantitatively for the observations.
authors.affiliation: Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel.
authors.forename: E
authors.initials: E
authors.lastname: Sloutskin
authors.forename: Z
authors.initials: Z
authors.lastname: Sapir
authors.forename: C D
authors.initials: CD
authors.lastname: Bain
authors.forename: Q
authors.initials: Q
authors.lastname: Lei
authors.forename: K M
authors.initials: KM
authors.lastname: Wilkinson
authors.forename: L
authors.initials: L
authors.lastname: Tamam
authors.forename: M
authors.initials: M
authors.lastname: Deutsch
authors.forename: B M
authors.initials: BM
authors.lastname: Ocko