Fullerene Derivatives That Bear Aliphatic Chains as Unusual Surfactants: Hierarchical Self-Organization, Diverse Morphologies, and Functions

Conventionally, amphiphiles are composed of hydrophobic and hydrophilic units. They are able to exhibit a wide variety of structures depending on the environment. Such features have been applied in supramolecular chemistry, by which apolar and polar groups are implemented in the molecular design. Here we present an attractive approach to introduce unique amphiphilicity. Relatively simple fullerene (C-60) derivatives that bear long aliphatic chains behave as uncommon surfactants in organic media. Although two hydrophobic units are used to assemble the derivatives, slight differences in their polarity and chemical nature may make them incompatible and thus arrange them in microphase-separated mesostructures as lamellar ones. These assemblies are maintained by relatively weak forces, pi-pi interactions among C-60 moieties and van der Waals forces between alkyl chains. Therefore, the derivatives can undergo "supramolecular polymorphism" by which different supramolecular assemblies arise by changing the conditions of assembly. A simple modification in their substituent motif of derivatives influences the intermolecular interactions and provides a wide variety of supramolecular materials.