Properties of mixed monomolecular films of poly(benzyl-methacrylate) and arachidic acid

Binary mixed monomolecular films of poly(benzyl-methacrylate) and arachidic acid at the water/air interface have been studied with respect to compatibility and stability. The surface pressure — area isotherms indicate compatibility of the two components. However, the miscible state is unstable at high surface pressures. This is demonstrated by the constant pressure relaxation of the mixtures. There is a mechanism of separation and nucleation of the arachidic acid from the film for mixtures with high polymer content at a surface pressure of 30 mN/m. For lower concentrations of polymer in the mixtures and at a surface pressure of 20 mN/m the fatty acid is stabilized by the polymer.