Surfactantco-assembly and ion exchange to modulate polyelectrolyte multilayer wettability

Abstract

Coatings with controllable wettability are of interest in a number of applications. Modulation of surface wettability is often necessary for these applications. It has been demonstrated many times that surface topography is key to the ability to make superhydrophobic surfaces, but at the same time surface chemistry is key. The layer-by-layer technique of fabricating coatings based on the complexation of oppositely charged polyelectrolytes can be a versatile method for producing precisely controlled thin films with a wide range of properties. In order to control wettability, hierarchical textures are generally needed, but the underlying surface energy of the material is also important. Generally, these films are made out of commercially available polymers, thereby limiting the range of available surface energies. Ion exchange of the counterions on the surface of the film is one way to modify materials properties, but we show that co-assembly with a surfactant is another way to achieve an even greater range of surface wettabilities. Our films have contact angles of as high as 110° with ion exchange and even up to 140° with surfactant co-assembly without any added texture to the surfaces. Co-assembly with a surfactant has not been widely studied with respect to polyelectrolyte multilayers and may prove to be a more general method to modify film properties.