Stable Dispersions of Graphitic Nanoplatelets via Reduction (25052)
Northwestern researchers have developed processes to produce stable dispersions of graphite nanoplatelets in aqueous or organic media. The treated nanoplatelets can be distributed in various matrices affording unique composite materials with useful mechanical, electrical and chemical properties.
ADVANTAGES: Processes that readily exfoliate graphtic material into aqueous or organic nanoplatelet dispersions and enable utilization of carbon in a wide range of potential mechanical, electrical, chemical and biological applications. The technology is scaleable and promises cost effective manufacture of unique materials.
SUMMARY: Graphite nanoplatelets are considered an inexpensive alternative for carbon nanotubes in nanocomposites due to predicted excellent in-plane mechanical, thermal and electrical properties of graphite. Full utilization of graphite nanoplates however requires their complete separation and dispersion before incorporation into another matrix such as polymers. Two techniques have been devised to accomplish graphite exfoliation in aqueous or organic media.
One process chemically reduces exfoliated graphite oxide (GO) nanoplatelets to graphite nanoplatelets in the presence of the anionic polymer PSS, poly(sodium 4-styrenesulfonate), forming polymer coated graphitic nanoplatelets that are readily dispersible in water, which remain in solution for weeks (Figure 1A). These solutions may be utilized for a variety of composite and device applications.
A second process converts exfoliated graphite oxide nanoplatelets in organic media with organic isocyanates to carbamate and amide functionalized nanoplatelets that remain soluble in polar organic solvents (Figure 1B). Employing functionalized isocyanates affords graphitic nanoplatelets possessing chemical functions useful for further modification and applications. The solutions can be utilized for a variety of composite and device applications requiring organic media.
Utility of these materials is demonstrated in Figure 2, where polystyrene composites prepared with increasing fractions of phenyl isocyanate treated GO sheets, exhibit a rapid rise in direct current electrical conductivity in the non-conducting polymer matrix. Other exfoliated graphite properties may similarly benefit materials of interest. Thus two complementary technologies that enable the separation and utilization of graphite nanoplatelets properties are now available.
STATUS: A patent application has been filed and Northwestern University seeks to develop the invention. (J. Mater. Chem. (2006), 16,155-158; Nature (2006), 442, 282-286; Carbon (2006), 44, 3342-3347)
Rodney Ruoff, SonBinh Nguyen, Sasha Stankovich
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