Direct exfoliation of graphene in methanesulfonic acid and facile synthesis of graphene/polybenzimidazole nanocomposites

The emerging field of graphene(GP)-based polymer nanocomposites has continued to be the focus of considerable interest in recent years because of the unparalleled improvement shown in mechanical, thermal, and electrical properties compared to the neat polymer. However, these improvements largely depend on the synthesis of well-exfoliated and high-quality GP. In this paper, we report a facile method for the production of GP sheets through the liquid-phase exfoliation of graphite in methanesulfonic acid (MSA). Raman, X-ray photoelectron and infrared spectroscopies reveal that the obtained GP has a low-defect density with a low degree of oxidation. Transmission electron microscopy and atomic force microscopy further confirm that the resulting GP is in the well-exfoliated state. Using this GP/MSA solution as a reaction solvent medium, polymer nanocomposites are prepared by in situ polymerization of poly [2,2'-(p-oxydiphenylene)-5,5'-bibenzimidazole] (OPBI). Compared to pure OPBI, the resulting OPBI/GP nanocomposites show simultaneously improved Young's modulus, tensile stress, toughness, storage modulus and thermal stability with the addition of extremely small amounts of GP. The high levels of reinforcement are attributed to the good dispersion and effective stress transfer between polymer and GP as evidenced by SEM images of the fracture surfaces, and the excellent intrinsic properties of the high-quality GP. All these features make this simple procedure a potential route for the fabrication of low-cost and high-performance polymer nanocomposites.