Preparation of uncurled and planar multilayered graphene using polythiophene derivatives via liquid-phase exfoliation of graphite

We have investigated the effects of the preparation conditions of polythiophene/graphene complexes on their dispersion in organic solvents, and on the in-solution morphology of the multilayered graphene. Among four different regioregular polythiophene derivatives synthesized, poly(3-hexylthiophene) (P3HT) with a low molecular weight (Mn 6000) was the most effective derivative for exfoliating graphite and for dispersing the multilayered graphene in toluene. Spectroscopic analysis revealed that P3HT interacted strongly with graphene to form a P3HT/graphene complex. We investigated the in situ morphology of multilayered graphene in organic solvents, using a flow particle image analyzer (FPIA) and revealed that the presence of polythiophenes produced larger P3HT/graphene complexes than that prepared in N-methylpyrrolidone (NMP). Microscopy analysis demonstrated that graphite flakes and multilayered graphene shrunk in the absence of P3HT when drying in organic solvents. The presence of P3HT immobilized the extended morphology of the multilayered graphene by forming the complex. This prevented shrinkage of the multilayered graphene when drying in toluene. Transmission electron, atomic force and field-emission scanning electron microscopy observations revealed that the P3HT/graphene complex consisted of relatively flat and ultrathin multilayered graphene of approximately <10 nm in thickness. The polythiophene/graphene complexes had high electrical conductivity, which depended on the kinds of polythiophenes. These findings further our understanding of the morphology of multilayered graphene, and will promote the development of uncurled multilayered graphene.