Vaporization and Layering of Alkanols at the Oil/Water Interface

Abstract

This study of adsorption of normal alkanols at the oil/water interface with x-ray reflectivity and tensiometry demonstrates that the liquid to gas monolayer phase transition at the hexane/water interface is thermodynamically favorable only for long-chain alkanols. As the alkanol chain length is decreased, the change in excess interfacial entropy per area decreases to zero. Systems with small values of excess interfacial entropy form multi-molecular layers at the interface instead of the monolayer formed by systems with much larger excess interfacial entropy. Substitution of n-hexane by n-hexadecane significantly alters the interfacial structure for a given alkanol surfactant, but this substitution does not change fundamentally the phase transition behavior of the monolayers. These data show that the critical alkanol carbon number, at which the change in excess interfacial entropy per area decreases to zero, is approximately six carbons larger than the number of carbons in the alkane solvent molecules.

arXiv comment27 pages, 10 figures, to be published in J. Phys. Cond. Mat

References in corpus (1)

• X-ray study of the electric double layer at the n-hexane/nanocolloidal silica interface

Cited by in corpus (4)

• Kinetics of the Phospholipid Multilayer Formation at the Surface of the Silica Sol
• Study of DMPS Monolayers on a Water Substrate with Laboratory X-ray Reflectometer
• Diffuse X-Ray Scattering near a Two-Dimensional Solid - Liquid Phase Transition at the n-Hexane - Water Interface
• The Critical Crossover at the n-Hexane - Water Interface