SIMULATION OF SODIUM DODECYL-SULFATE AT THE WATER-VAPOR AND WATER-CARBON TETRACHLORIDE INTERFACES AT LOW SURFACE COVERAGE

To study the effect of the interface on the properties of an anionic s urfactant molecule, sodium dodecyl sulfate (SDS), we performed two mol ecular dynamics computer simulations. In one simulation, the behavior of SDS at the water-vapor interface was examined. In parallel, we perf ormed a simulation with the molecule embedded at the water-CCl4 interf ace. A substantial difference in the configurational properties of the amphiphile was observed. At the water-vapor interface, the solute in its most probable configuration was bent, giving rise to two domains w ithin the molecule: the first, containing the head group and several m ethyl groups, was solvated in water; the second, containing the rest o f the molecule, lay down on the water surface. In contrast to these re sults, the molecule at the water-CCl4 interface was straight on averag e, with a inclination of approximately 40 degrees from the surface nor mal.