Polymer-surfactant films at the air-water interface. 1. Surface pressure, ellipsometry, and microscopic studies

Mixed films formed by an insoluble polymer, poly(dimethylsiloxane) (PDMS), placed on the surface of aqueous solutions of two different soluble surfactants are studied by surface tension isotherms, ellipsometry complemented by the neutron reflectivity experiments and direct observations of the surface via the Brewster angle microscope. A vertical separation into superimposing surfactant and polymer layers is exhibited, with mixing between the layers depending on the surfactant. On one but not the other of the surfactant solutions studied, a lateral separation of the polymer monolayer is also observed, into domains similar to those previously observed on pure water