Supramolecular systems based on calix[4]resorcine with mono-, di-, and tetracationic surfactants: Synergetic structural and solubilization behavior

Formation of nanosized aggregates in aqueous solutions of amphiphilic calix[4]resorcine with sulfonate groups at upper rim (CR), cationic surfactants (CS) with bicyclic head group (mono-, di-, and tetracationic alkylated derivatives of 1,4-diazabicyclo[2.2.2]octane), and their mixtures has been shown by a variety of physicochemical methods (tensiometry, conductometry, dynamic light scattering, and dye solubilization). Critical association concentration of CR is shown to be of 6.2 mM (tensiometry). Beyond this concentration, CR forms aggregates of ca. 7–10 nm, which are capable of solubilizing hydrophobic dye Sudan. The formation of mixed structures of CR with cationic surfactants has been found to proceed at the lower concentrations as compared to single CR solutions. The characteristics of mixed aggregates (size, morphology, surface potential, and solubilizing properties) depend on the concentration of the surfactants. Aggregation in mixed solutions is favored by increase in the number of charged head groups of the surfactants.