Characteristics of monolayers of calix[4]resorcinarenes derivatives having azobenzene chromophores

The adsorption behavior of calix[4]resorcinarenes (CRAs) and their O-carboxylmethylated and O-hydroxyethylated derivatives (CRA-CMs and CRA-HEs) from solutions was studied, aiming at the fabrication of self-assembled monolayers on polar surfaces of amorphous solid such as silica. These macrocyclic amphiphiles displayed considerably enhanced adsorption constants, due to the contribution of their multi-site adsorptivity, to form densely packed monolayers simply by immersing a silica plate in dilute solutions of the amphiphiles. CRA and CRA-CM bearing four azobenzene moieties at the lower rim of the cylindrical skeleton were prepared to modify a silica surface with photo-reactive monolayers by the surface adsorption technique. Adsorbed monolayers exhibited efficient E-to-Z photoisomerizability and applied to the photocontrol of alignment of liquid crystals and of dispersibility of colloidal silica.