Simultaneous surface functionalization and reduction of graphene oxide with octadecylamine for electrically conductive polystyrene composites

Simultaneous surface functionalization and reduction of graphene oxide (GO) was realized by simple refluxing of GO with octadecylamine (ODA) without the use of any reducing agents. The presence of the long octadecyl chain made the hydrophilic GO hydrophobic, evidenced by the selective dispersion of the ODA-functionalized GO (GO–ODA) in chloroform solvent rather than in water. Interestingly, different from the insulating GO, GO–ODA became electrically conductive due to the reduction in the presence of ODA. The electrical conductivity of GO–ODA was further increased by incidental thermal reduction during the compression-molding of its polystyrene (PS) composites at 210 °C, which exhibited a sharp transition from electrically insulating to conducting with a low percolation threshold. The high conductivity of the PS/GO–ODA composites is attributed to the improved dispersion and the reduction of GO–ODA in comparison with GO.