High-concentration organic solutions of poly(styrene-co-butadiene-co-styrene)-modified graphene sheets exfoliated from graphite

A simple method is developed to produce high-concentration organic solutions of graphene sheets noncovalently modified with poly(styrene-co-butadiene-co-styrene) (SBS). Once exfoliated from natural graphite under sonication, the graphene sheets can be stabilized by SBS through the π–π stacking with the PS chains. The PS–graphene interaction is confirmed by DSC, since the glass transition temperature of the PS blocks increases by ∼8 °C, while that of the PB block remains unchanged. The content of SBS adsorbed on the graphene sheets is determined by TGA as ∼63 wt.%. Direct morphological observation is achieved by HRTEM, which reveals an amorphous polymer layer on the graphene sheets with individual polymer chains climbing on the edges. A freestanding, highly flexible film of SBS-modified graphene is prepared. The improved solubility of graphene in the organic solvents opens up a new opportunity for the solution-phase incorporation of graphene in the polymer matrices. The graphene/SBS composite has an excellent electrical conductivity with a percolation threshold of ∼0.25 vol.%. Besides, it is proven that SBS can also be adsorbed on chemically modified graphene and carbon nanotubes, demonstrating the versatility of the π–π stacking between the PS chains and the graphitic planes.