Solubilization and Encapsulation of Fullerenes by Amphiphilic Block Copolymers

Solubilization and encapsulation of fullerenes C60 and C70 by ultralarge hollow micelles formed by rod-coil diblock copolymers and characterization of the resulting self-organized fullerene-block copolymer assemblies are reported. The solubilization capacity of each fullerene in poly(phenylquinoline)-blockpolystyrene (PPQ-PS) micelles in binary solvents, trifluoroacetic acid/dichloromethane, and trifluoroacetic acid/toluene, was determined to be 200 mg of fullerene/g of PPQ-PS and found to be independent of block copolymer composition and concentration. This represents fullerene solubility enhancement by factors of 1040 and 63 compared to the solubilities in pure dichloromethane and toluene, respectively. Fullerenes C60 and C70 were found to change the micellization and self-assembly of PPQ-PS block copolymers in solution from polymorphic aggregates to only hollow spheres with encapsulated fullerenes. The solubilization and encapsulation of up to 1-10 billion fullerene molecules in PPQ-PS block copolymer micelles increased the aggregation number to over 109 while the aggregate diameter increased from 1 to 5 μm to over 30 μm. Photoluminescence emission and excitation spectra of the fullerene-PPQ-PS block copolymer assemblies evidenced fullerene-induced J-like aggregation of the conjugated PPQ blocks. In addition to providing knowledge of the effects of solubilizates on the molecular packing of block copolymer micelles, the selforganized fullerene-block copolymer assemblies constitute novel mesoscopic supramolecular materials for electronic, optoelectronic, photonic, and other applications. The present results also provide evidence of micellization and micellar solubilization phenomena at the 1-30 μm size scale.