Polyelectrolyte complexes at interfaces

Multilayers were built up by polyelectrolyte complexation at interfaces, using a number of new charged species, some of them with rather unusual features. Coloured species such as azo dyes were incorporated into the polycations, facilitating the analysis and serving as a probe of the local electronic environment. Copper/polyethylene-imine complexes were used as polycations, the charges being provided by the complexed inorganic ions. Also, polymers carrying simultaneously positive and negative charges were employed as polycations for the multilayer assembly. Further, a low molar mass azo dye bearing four negative charges was used instead of the polyanion poly(vinylsulfate). The resulting multilayers were studied by optical methods, UV/VIS-spectrometry and X-ray reflectometry. The deposition process is reproducible and provides uniform coatings. The thicknesses of the internal layers and their evolutions with distance from the substrate are strongly dependent on the details of the adsorption process and on the chemical structure of the polyions. The results demonstrate the tolerance of this method of multilayer build-up to a variety of strongly different molecular structures.