Exfoliated Graphite Oxide

The relatively low cost of graphite in comparison to CNTs makes exfoliated graphite an attractive material (20). The use of graphite nanoplatelets is advantageous because of the chemistry of the graphene and graphene-Uke sheets compared to clay nanoplates. 

The initial step of the process is the intercalation and oxidation of natural graphite to form an oxidized graphite. The resulting functional groups on the oxidized graphite, such as hydroxyl, epoxy, and carboxylic groups, facilitate the retention of water molecules in 

The rate of heating can be higher than 2,000°C min. These reactions generate a pressure that exfoliates the graphite oxide sheets. The heating procedure yields disordered graphite oxide sheets which appear as a fluffy, extremely low density material with a high surface area (20). 

The thermally exfoliated graphite oxide can be dispersed in a wide variety of polymers, e.g., polyolefins, polyesters, nylons, polystyrenes, and polycarbonates, and also in elastomers. It is also possible to compoimd the thermally exfoliated graphite oxide into the monomeric precursors of these pol5miers and to effect the polymerization in the presence of the thermally exfoliated graphite oxide nanofiller. To formulate a conductive ink, solvents are added, such as N-methyl-2-pyrrolidone, dimethylformamide, tetrahydrofuran, and others (20). 

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S. Stankovich, D.A. Dikin, R.D. Piner, K. a. Kohlhaas, A. Kleinhammes, Y. Jia, et al., Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide, Carbon,... 

S. Stankovich, R.D. Piner, X. Chen, N. Wu, S.T. Nguyen, R.S. Ruoff, Stable aqueous dispersions of graphitic nanoplatelets via the reduction of exfoliated graphite oxide in the presence of poly(sodium 4-styrenesulfonate), Journal of Materials Chemistry, 16 (2006) 155. 

R.K. Prud Homme and LA. Aksay, Conductive ink containing thermally exfoliated graphite oxide and method a conductive circuit using the same, US Patent 8 048 214, assigned to The Trustees of Princeton University (Princeton, NJ), November 1, 2011. 

Zhang S, Shao Y, Liao H, Engelhard MH, Yin G, Lin Y (2011) Polyelectrolyte-induced reduction of exfoliated graphite oxide a facile route to synthesis of soluble graphene nanosheets. ACS Nano 5(3) 1785-1791... 

Figure 7.38 TEM images of exfoliated graphite oxide nanoplatelets in DMF. Reproduced from Ref [50] with permission.

Stankovich S, Kikin DA, Piner RD, Kohlhaas KA, Kleinhammes A, Jia Y, Wu Y, Nguyen ST, Ruoff RS (2007) Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide. Carbon 45 1558-1565 Star A, Steuerman DW, Heath JR, Stoddart JF (2002) Starched carbon nanotubes. Angew Chem Int Ed 41 2508-2512 Star A, Joshi V, Skarupo S, Thomas D, Gabriel JCP (2006) Gas sensor array based on metal-decorated carbon nanotubes. J Phys Chem B 110 21014-21020... 

Ghaffari M, Kinsman W, Zhou Y, Murali S, Burlingame Q, Lin M, Ruoff R, Zhang Q (2013) Aligned nano-porous microwave exfoliated graphite oxide ionic actuators with high strain and elastic energy density. Adv Mater 25(43) 6277-6283... 

The majority of the research work recently published in the area of carbon nanofillers focuses on the characterization of polymer composites with functionalized-graphene sheets, as indicated in a bibliometric survey conducted by Peng et al. (Lv et al., 2011). However, some studies are available in which the characterization of mechanical and functional properties of polymer—intercalated/exfoliated graphite oxide or GO is reported, as summarized in the following sections. 

Yang, Y., Wang, J., Zhang, J., Liu, J., Yang, X., Zhao, H., 2009. Exfoliated graphite oxide decorated by PDMAEMA chains and polymer particles. Langmuir 25, 11808—11814. 

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