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 pi-pi stacking with the PS chains. The PS-graphene interaction is confirmed by DSC, since the glass transition temperature of the PS blocks increases by similar to 8 degrees C, while that of the PB block remains unchanged. The content of SBS adsorbed on the graphene sheets is determined by TGA as similar to 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 similar to 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 pi-pi stacking between the PS chains and the graphitic planes. (C) 2011 Elsevier Ltd. All rights reserved.