Wetting films of aqueous solutions of Silwet L-77 on a hydrophobic surface

Abstract

The formation of wetting films of aqueous solutions of Silwet L-77 on hydrophobic substrates takes place only at concentrations above the critical aggregation concentration (CAC). At concentrations above the critical wetting concentration (CWC) a new phenomenon was found: the formation of multilayered spots of thicker films in the wetting film of aqueous solutions of Silwet L-77 on hydrophobic surfaces. An expansion of the thicker spots within the film and the formation of “channels” between the spots and the edge of the film led to a continuous shrinkage of the wetting film and its disappearance in the end. We suggested that the multiple thicker films originate from the multilayer structuring of trisiloxane bilayers within the wetting film.