Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 117, Issue 20, Pages 10730-10742Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp4008009
Keywords
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Funding
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- Canadian Foundation for Innovation (CFI)
- Canada Research Chair (CRC)
- Ontario Ministry of Economic Development and Innovation
- National Natural Science Foundation of China [21074117]
- NSERC
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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 mu m. 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.
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