title: Sodium dodecyl sulfate at water-hydrophobic interfaces: a simulation study.
abstract: Using molecular dynamics simulations, we have studied the water-vapor and water-oil (decane) interfaces of aqueous solutions of sodium dodecyl sulfate (SDS). The water-vapor interface is often used as a model for water-oil (hydrophobic) interfaces, yet we observe that the behavior of amphiphilic DS(-) ions at these two interfaces is very different. Specifically, on a water-vapor interface, SDS forms aggregates at low coverages, while it is homogeneously distributed on the water-oil interface. Two decane parametrizations resulted in dramatically different conformations: decane parametrized based on a GROMOS force field "froze", while decane parametrized with a TraPPE force field remained liquid at 300 K. The calculated effective second-order susceptibilities and nonlinear sum frequency scattering intensities of DS(-) ions at the "frozen" decane-water agree well with experimental data of DS(-) ions at the hexadecane droplet-water interface. This suggests that the orientation of longer alkane molecules is predominantly parallel to the interface and that, at low coverages, DS(-) ions follow the orientation of oil molecules.
authors.affiliation: National Centre for Biomolecular Research, Faculty of Science and CEITEC-Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno-Bohunice, Czech Republic. robertvacha@gmail.com
authors.forename: Robert
authors.initials: R
authors.lastname: Vácha
authors.forename: Sylvie
authors.initials: S
authors.lastname: Roke
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D012967:Sodium Dodecyl Sulfate