The fabrication and properties of a graphite nanosheet/polystyrene composite based on graphite nanosheets treated with supercritical water

In the present study, supercritical water was applied to graphite nanosheets to improve the surface activity and the dispersion of graphite nanosheets in water. The increase in the concentration of HCO and HOCO functional groups on the surface of treated graphite nanosheets was favorable to the stable dispersion of the graphite nanosheets in water, and the graphite nanosheet/polystyrene composites were subsequently fabricated by suspension polymerization. An XRD analysis obtained from the graphite nanosheets before and after the supercritical water treatment indicated that the supercritical water treatment did not change the crystal structure of graphite nanosheets. Furthermore, the graphite nanosheet/polystyrene composite was dissolved in styrene and then was extracted, and the analysis by Fourier-transform infrared spectroscopy indicated good chemical bonding between the graphite nanosheets and polystyrene. The mechanical properties of the graphite nanosheet/polystyrene composites are at least two times stronger, and the electrical conductivity is at least three orders of magnitude greater, than potassium-intercalated graphite/polystyrene composites. The significant improvement of properties was due to three aspects, specifically the intact crystal structure of the graphite nanosheets, the chemical bonding between the graphite nanosheets and polystyrene, and the good dispersion of the graphite nanosheets in polystyrene.