Solvothermal synthesis of graphene oxide and its composites with poly(ε-caprolactone)

Graphene oxide (GO) was prepared by a solvothermal synthesis method using sodium and ethanol. A sequence of pyrolysis, washing and purification steps was developed for the total removal of all by-products. The first pyrolysis step is essential to obtain graphitic forms of carbon while a washing and a second pyrolysis step further improved the graphenic structures obtained via the reduction of OH/COOH and C-O groups and the attendant increase in C=C bonding (sp2 hybridization). Two purification processes were employed to remove sodium carbonate (by-product), i.e. vacuum filtration and centrifugation, but the latter produced a more stable GO product, typically with a few-layer (ca 3nm) stack and relatively long platelets (up to ca 1.3 µm). The functionality of this GO was demonstrated by preparing composites of it with poly(ε-caprolactone) (PCL). The GO was arranged in flower-like domains dispersed in the PCL matrix. The crystalline content of PCL decreased on addition of GO, though the dynamic modulus of PCL increased and an electrical percolation at 0.5vol% GO was obtained, manifest by a ~104 increase in electrical conductivity (in an overall increase of ~105 achieved at > 1vol%), more than sufficient for anti-static applications