Programmed exfoliation of hierarchical graphene nanosheets mediated by dynamic self-assembly of supramolecular polymers

Programmed formation of hierarchical graphene nanosheets, based on a combination of first and second exfoliations using the halogenated solvent ortho-dichlorobenzene (ODCB) and an adenine-functionalized supramolecular polymer (A-PPG), respectively, can be used to directly exfoliate graphite into high-quality graphene nanosheets with wide-range tunable layer thickness. In this study, we discover that natural graphite in ODCB can be directly exfoliated into well-dispersed, dozen-layer exfoliated graphite (EG) nanosheets with relatively weak interlayer interactions; this process is called first exfoliation. On subsequent addition of A-PPG into the EG solution (i.e., second exfoliation), the hydrogen-bonded adenine moieties act as indispensable key units that manipulate the self-assembly behavior of the A-PPG polymers to effectively form long-range ordered lamellar nanostructures on the surface of the graphene nanosheets. This process substantially enhances the long-term dispersion stability of EG in ODCB and achieves the production of exfoliated graphene nanosheets with the desired structural characteristics through simply adjusting the content of A-PPG in the composites. These desirable characteristics of non-covalently functionalized graphene with a supramolecular polymer are extremely rare, but highly attractive for the development of physically custom-tailored graphene based on combined first and second exfoliation processes. Thus, this development provides a facile, highly efficient graphene fabrication process for potential applications in various fields.