Neutron reflection measurement of near-surface structural change in an oil-water-surfactant system

The interfacial characteristics of an oil-water-surfactant sample were studied using the thermal neutron reflectometer at the Rhode Island Nuclear Science Center (RINSC). The sample was a mixture of deuterated octane with H2O and non-ionic surfactant (C10E4), spread onto an H2O substrate. A mixture of low surfactant concentration was used so that it could demix into a lamellar oil-water structure, stabilized by a monolayer of surfactant intervening at each oil-water interface. The reflectivity data showed a clearly visible difference between 25.2 C and 30.2 C, indicating that the significant increase of interfacial tension between these two temperatures induced a structural transition