NEUTRON REFLECTIVITY AT LIQUID INTERFACES

Examples of the potential of neutron reflectivity techniques are prese nted with studies of thin layers at the air-water and oil-water interf aces. In the case of air-water interfaces, we have studied mixed polym er (polydimethyl-siloxane)-surfactant layers. Selective deuteration al lowed us to show that the mixed film is a superposition of two layers, and to determine their degree of interpenetration. In the case of oil -water interfaces, we have used a surfactant system of low interfacial tension. The neutron reflectivity is then sensitive to both the surfa ce roughness and the surfactant layer thickness. In each case, correla tions with independent measurements using ellipsometry (light reflecti vity) are discussed.