Physicochemical properties of resorcinol-type calix[4]arenes phosphoric esters having four alkyl side chains in aqueous solution

The physicochemical properties of phosphate esters of resorcinol-type of calix[4]arenes([4]Ar5P-Rn; side chain length n=6, 8, and 12) in aqueous solutions have been characterized by several techniques including surface tension and NMR. It is found that the critical micelle concentrations (cmcs) of [4]Ar5P-Rn are insensitive against the alkyl side chain length, whereas the polarity of aggregates remarkably depends on the alkyl side chain length. From static light scattering and NMR measurements it is suggested that the shapes of aggregates of [4]Ar5P-Rn are not globular and the alkyl side chains of [4]Ar5P-Rn gather loosely in the aggregates. The mixed properties of [4[Ar5P-R12 and hexaethyleneglycol dodecylether have also been investigated. The mixed cmcs are considerably greater than those of the respective surfactant cmcs and the interaction parameter calculated using a modified regular solution theory is +2.7. These results indicate that the repulsive interactions occur in the mixed micelles.