Supramolecular exfoliation of layer silicate clay by novel cationic pillar[5]arene intercalants

Clays are multi-layered inorganic materials that can be used to prepare nanocomposite fillers. Because the multi-layered structure is thermodynamically stable, it is difficult to change a multi-layered material into single layers to improve its dispersity. Previously, clays were modified with dodecylammonium cations to promote complexation with nylon 6, nylon 66, polypropylene, polyethylene, polystyrene, and polycaprolactone to increase the mechanical strength (and/or thermal stability) of the composite material; however, complete exfoliation could not be achieved in these composites. In this study, pillar[5]arenes are synthesized and functionalized with ten cationic substituents as novel intercalants for modifying bentonite clay, which is a multi-layered metal-cation-containing silicate. The pillar[5]arenes exfoliate the clay by forming polyrotaxanes with poly(ethylene glycol) through host-guest interactions.