Hierarchically ordered self-assembly of amphiphilic bifullerenes

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Fullerenes are versatile carbon allotropes with unique electronic properties.
• Functionalized fullerenes can self-assemble into ordered structures.
• Dumbbell-shaped bifullerenes offer a platform for complex molecular architectures.

Purpose of the Study:

• To synthesize novel dumbbell-shaped bifullerenes with varying hydrophilic and hydrophobic groups.
• To investigate the self-assembly behavior of these bifullerenes in aqueous solutions.
• To elucidate the hierarchical aggregation mechanisms driving supramolecular structure formation.

Main Methods:

• Synthesis of functionalized bifullerenes via covalent linkage of C60 pentakis-adducts with cyclic bismalonates.
• Cryogenic transmission electron microscopy (cryo-TEM) for visualizing supramolecular architectures.
• Analysis of self-assembly behavior based on the hydrophilic/hydrophobic balance of substituents.

Main Results:

• Successfully synthesized novel bifullerenes with diverse functional groups.
• Observed distinct self-assembly pathways for hydrophilic and amphiphilic bifullerenes.
• Identified hierarchical aggregation, forming elementary micelles (3-4 molecules) for hydrophilic types and larger structures for amphiphilic types.
• Demonstrated that hydrophobic interactions drive the assembly of amphiphilic bifullerenes via tetrameric intermediates.

Conclusions:

• Dumbbell-shaped bifullerenes exhibit tunable self-assembly properties based on functionalization.
• Hierarchical aggregation in aqueous solution leads to complex supramolecular architectures.
• Hydrophobic interactions play a crucial role in the stepwise assembly of amphiphilic bifullerenes.