POLYMER SURFACTANT FILMS AT THE AIR-WATER-INTERFACE .2. A NEUTRON REFLECTIVITY STUDY

Mixed polymer-surfactant films at the air-water interface have been studied using neutron reflectivity. When poly(dimethylsiloxane) is spread on the surface of a surfactant layer, the resultant mixed film is a superposition of two layers: one surfactant-rich and one polymer-rich. The composition and the degree of mixing of the layers depend on the nature of the surfactant. We find significant penetration of the polymer into a monolayer of single-chain nonionic surfactant, C10E6. For a double-chain anionic surfactant, AOT, no interpenetration of the two layers is detected. This difference is most probably due to the greater flexibility of the C10E5 Monolayer compared to that of AOT. The higher degree of hydration of the nonionic surfactant layer could also play a role in the mixing behavior of the polymer and surfactant layers. The molecular thickness of the polymer layer indicates a flat two-dimensional conformation of the spread polymer. The results from this study together with those in part 1 our paper suggest that the wetting behavior of the polymer is related to the degree of interpenetration of the polymer and surfactant layers.