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, ellipsometry, neutron reflectivity and Brewster angle microscopy. On pure water, the polymer layer is generally inhomogeneous, showing surface domains of different discrete thicknesses. The penetration of the polymer into the surfactant monolayer found on the surface of aqueous surfactant solutions depends on the surfactant. On a surfactant layer with little penetration by the polymer, the polymer layer remained inhomogeneous. With other surfactants, the polymer penetrated appreciably into the surfactant layer, and the polymer layer was homogeneous. These differences between surfactants correlate with the wetting behavior of PDMS on the aqueous surfactant solutions.