Production of high-concentration graphene dispersions in low-boiling-point organic solvents by liquid-phase noncovalent exfoliation of graphite with a hyperbranched polyethylene and formation of graphene/ethylene copolymer composites
作者：L. Xu, J.-W. McGraw, F. Gao, M. Grundy, Z. Ye*, Z. Gu, J. L. Shepherd
關(guān)鍵字：無
論文來源：期刊
具體來源：Journal of Physical Chemistry C
發(fā)表時(shí)間：2019年
We report in this paper the successful production of stable high-concentration graphene dispersions in low-boiling-point, low-polarity conventional organic solvents (chloroform and THF) by liquid-phase noncovalent exfoliation of graphite assisted with a hyperbranched polyethylene (HBPE) as the stabilizer. In the exfoliation process, HBPE adsorbs onto the surface of exfoliated graphene flakes, providing steric stabilization against their restacking. A systematic investigation on the effects of exfoliation conditions, including the solvent and the amounts of graphite and HBPE, has been conducted. Graphene dispersions with the concentration up to 0.18 mg/mL in chloroform and 0.045 mg/mL in THF have been obtained. It is also demonstrated that the dispersions can be further concentrated by solvent evaporation to give highly concentrated stable dispersions at 3.4 mg/mL. Through their characterizations with transmission electron microscopy, atomic force microscopy, and Raman spectroscopy, the majority of the graphene products is found to be high-quality, defect-free, few-layer graphene flakes with the layer number between 2 and 4 and the lateral dimension in the range of 0.2–0.5 μm. The dispersions can be fabricated into flexible conductive free-standing graphene films and be used to prepare graphene/ethylene copolymer composites through solution blending, which show significant enhancements in both thermal and mechanical properties.