Supramolecular Shape Shifter: Polymorphs of Self-Organized Fullerene Assemblies

Studies of hierarchical supramolecular assemblies of a fullerene derivative bearing three hexadecyloxy chains (1) have been carried out in various conditions, such as different organic solvents, temperatures, and with ultrasonication. The dimensional control of the hierarchical supramolecular architectures from the fullerene derivative (1), such as spherical vesicles, fibers, nano-disks, and uncommon conical and flower-shaped assemblies, was previously achieved. Here, further morphologies such as microspheres, windmill-like sheets, baton-, maracas-, and jellyfish-like assemblies were discovered. Shape shifting of supramolecular assemblies was seen only in the case of the fullerene derivative (1). Reference derivatives bearing three eicosyloxy (2) and three dodecyloxy chains (3) never showed such polymorphs, however, these derivatives self-organized into microparticles with nano-flake outer surfaces and ultra-thin disks, respectively. The fullerene derivatives studied here formed interdigitated bilayer structures with different interspacing length. There are two essential intermolecular forces present due to fullerene or aliphatic chains. Fullerene moieties exhibit strong pi-pi interactions, while van der Waals interactions between aliphatic chains can be altered by variation of their length. Three hexadecyloxy chains at the fullerene moiety (1) were the most effective substitution pattern for stimulating supramolecular shape shifting.