The molecular order in thin films of surfactant solutions on solid surfaces will differ from that in bulk solutions. The unique features of the ordering may include the self-assembly of monolayers on the bounding interfaces, the induction of new liquid crystalline order in the film, and the ordering of macromolecular assemblies such as micelles within the film. Such structures will affect the stability and dynamics of these films and will control the wetting and spreading of bulk fluid bodies attached to them. Although the subject of a number of earlier investigations, questions remain open concerning the arrangement of surfactant molecules in thin films on solid surfaces. Direct measurement of this molecular ordering will clarify some of these outstanding issues, providing new understanding of the influence of interfaces on self-assembly and impacting on a number of technologies which involves interfacial properties and spreading of surfactant solutions. X-ray and neutron reflectometry are rapidly evolving techniques which can probe the molecular arrangements in such films. Using these techniques, the nature of the molecular monolayers on the bounding interfaces of thin films on solid surfaces and the ordering of the surfactant molecules within the films is explored.
