title: Langmuir monolayers of a hydrogenated/fluorinated catanionic surfactant: from the macroscopic to the nanoscopic size scale.
abstract: Langmuir monolayers of the hydrogenated/fluorinated catanionic surfactant cetyltrimethylammonium perfluorooctanoate at the air/water interface are studied at room temperature. Excess Gibbs energies of mixing, DeltaG(E), as well as transition areas and pressures, were obtained from the surface pressure-area isotherm. The DeltaG(E) curve indicates that tail-tail interactions are more important than head-head interactions at low pressures and vice versa. Atomic force microscopy and molecular dynamics simulations allowed a fine characterization of the monolayer structure as a function of the area per molecule at mesoscopic and nanoscopic size scales, respectively. A combined analysis of the techniques allow us to conclude that electrostatic interactions between the ionic head groups are dominant in the monolayer while hydrophobic parts are of secondary importance. Overall, results obtained from the different techniques complement to each other, giving a comprehensive characterization of the monolayer.
authors.affiliation: Department of Applied Physics, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Blanco
authors.forename: Angel
authors.initials: A
authors.lastname: Piñeiro
authors.forename: Reinhard
authors.initials: R
authors.lastname: Miller
authors.forename: Juan M
authors.initials: JM
authors.lastname: Ruso
authors.forename: Gerardo
authors.initials: G
authors.lastname: Prieto
authors.forename: Félix
authors.initials: F
authors.lastname: Sarmiento
mesh_terms: D018625:Microscopy, Atomic Force; D015394:Molecular Structure; D055672:Static Electricity; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D013501:Surface-Active Agents