Preparation of polyelectrolyte-layered assemblies containing cyclodextrin and their binding properties

Polyelectrolyte-layered films containing alpha- and beta-cyclodextrin were prepared by a layer-by-layer deposition of sulfonated alpha- or beta-cyclodextrin (s-alpha-CyD or s-beta-CyD) and cationic poly(allylamine hydrochloride) (PAH) on a solid surface. The deposition of the films from water solutions (no salt added) afforded thin films in which s-alpha-CyD and s-beta-CyD formed roughly a monomolecular layer upon each deposition, while the films were thicker when a high-ionic-strength buffer was employed as a bathing solution. The PAH-s-alpha-CyD film bound methyl orange (MO) by forming an inclusion complex in the film, whereas MO did not form the complex with s-beta-CyD in the PAH-s-beta-CyD film but formed aggregates on the surface of the film. MO was not desorbed from the films upon rinsing in pure water or even in a HCl solution (pH 2), whereas MO was extracted from the film into a NaOH solution (pH 12). MO complexed with s-alpha-CyD in the film was protected from protonation in HCl solution (pH 2). The PAH-s-alpha-CyD film showed a binding selectivity to azoaromatic dyes depending on the size and shape of the dyes.