Covalent Functionalization of Graphene Flakes with Well-Defined Azido-Terminated Poly(ԑ-caprolactone) and Poly(2-oxazoline)

We report on grafting-on method to covalently functionalize exfoliated graphene flakes (GFs) synthesized via ultrasonication of graphite nanoplatelets (GNPs) in N-methylpyrrolidone (NMP). A well-defined poly(e-caprolactone) (PCL) and poly(2-isopropyl-2-oxazoline) (PIPOZ) with terminal azido group were prepared. The reactions between the azido-terminated PCL or PIPOZ and ultrasonication-assisted exfoliated GFs were carried out through nitrene chemistry to obtain PCL-grafted-GFs (PCL-g-GFs) and PIPOZ-grafted-GFs (PIPOZ-g-GFs). Infrared (IR), thermogravimetry analysis (TGA) and transmission electron microscope (TEM) measurements confirmed the structure of polymer grafted GFs. The results suggested that functionalization might be an effective approach to overcome the restacking issue of graphene. Further, the presence of polymer chains onto GFs provides solubility in a wide variety of organic solvents. This type of material may open up a new opportunity for the synthesis of graphene-based materials and fabrications.