MIXED POLYMER SURFACTANT LAYERS AT THE AIR-WATER-INTERFACE

We have studied mixed molecular layers of polydimethylsiloxane (PDMS) and surfactants, using different techniques: surface tension, ellipsom etry, neutron reflectivity and Brewster angle microscopy. On pure wate r, the polymer layer is generally inhomogeneous, showing surface domai ns of different discrete thicknesses. The penetration of the polymer i nto the surfactant monolayer found on the surface of aqueous surfactan t solutions depends on the surfactant. On a surfactant layer with litt le penetration by the polymer, the polymer layer remained inhomogeneou s. With other surfactants, the polymer penetrated appreciably into the surfactant layer, and the polymer layer was homogeneous. These differ ences between surfactants correlate with the wetting behavior of PDMS on the aqueous surfactant solutions.