A surface layer that contains both hydrophobic and hydrophilic domains can function as a semi-permeable barrier, as a depot for material to be released from the different domains, or as an absorbent of substances in a surrounding fluid phase. For all these functions, it is of importance to control the size of the domains, their geometry, and their orientation (for non-spherical pores) relative to the surface. As one part of the larger SSF program "Porous surface layers through polymer-assisted deposition", this project investigates the making of hydrated liquid-crystalline polymer-surfactant layers from associating oppositely charged polymer-surfactant pairs. Direct application of ethanol solutions of polyion-surfactant ion "complex salts" on a surface, followed by evaporation of the ethanol, has proven to be an easy method to coat hydrophobic as well as hydrophilic surfaces with complex salt assemblies. The surface layers swell, but do not dissolve, in water, and the structures of the layers can be controlled by choice of polyion, surfactant ion and added co-surfactant, and they also respond to the humidity of surrounding air, and to solutes such as salts, acids, surfactants and polymers in a surrounding aqueous solution. Detailed SAXS studies of the liquid crystalline structures give both kinetic and equilibrium information, and confirm that the structures largely correspond to those found in studies of bulk systems of the same compositions. Detailed kinetic and equilibrium studies of the sorption/desorption of water from/to surrounding "air" give additional insights and suggest a general strategy to study the kinetics of water vapor exchange processes for thin hydrated films.

People: Charlotte Gustavsson, Lennart Piculell, Joaquim Li, Marc Obiols-Rabasa, Karen Edler. 

Contact person: Lennart Piculell