Effect of hydrocarbon polymer, feed ratio, and interfacial interaction on the liquid exfoliation of graphite

Polymer-assisted liquid exfoliation of graphite is a promising technique for the scale production of defect-free graphene. In this paper, graphene nanosheets (less than 5 layers, with lateral size about 500–1500 nm) were successfully produced by directly exfoliating graphite in low boiling point chloroform, in the presence of hydrocarbon polymers such as linear paraffin wax and hyperbranched polyethylene. The effect of polymer topological structure, molecular weight, initial graphite concentration, the ratio of polymer and graphite on the exfoliation has been investigated in detail. CH-π interaction between the hydrocarbon polymers and aromatic structure in graphite, together with the steric repulsion and solubility of absorbed polymer, facilitating the exfoliation and stabilization of graphene sheets. C–H bond involved in CH-π interaction was mainly originated from methylene (-CH₂-) group, which has been revealed by nuclear magnetic resonance technique. This work is of practical importance for the understanding of mechanism in polymer-assisted liquid exfoliation of graphite.