Calix[4]resorcinarene-surfactant complexes: Formulation, structure and potential sensor applications

A series of complexes formed from anionic calix[4]resorcinarenes and cationic surfactants have been formulated and their structures and binding capacity for selected guests have been studied. Calix[4]resorcinarenes were sulfonated at the 2 position by a Mannich-type reaction. Combination of aqueous solutions of these systems with cationic quaternary ammonium surfactants led to soft precipitates, which, when isolated, were shown to be composites consisting of four surfactant molecules to each (tetraanionic) calix[4]resorcinarene. X-Ray scattering experiments demonstrated the presence of a regular lamellar liquid-crystal-like layer structure within cast films of these composites. Experiments on cast films of the composites showed that they proved capable of reversibly binding a range of compounds both from the vapour phase and aqueous solutions with some selectivity, indicating the potential of using these materials within a sensor.