Sustainable and versatile functionalization of graphene layers

Facile, sustainable and versatile functionalization of graphene layers was performed. Functional groups were essentially at the layer edges and the structure of the graphitic substrate remained substantially unaltered. Functionalization was done with pyrrole compounds (PyC) prepared through the Paal-Knorr reaction of a primary amine with 2,5-hexanedione. A good number of primary amines were used and a large variety of functional groups were added to the graphene layers: hydroxy, silanes, aldehydes, carboxylic acid. The functionalization reactions were carried out by simply mixing the reagents and heating, e.g at 150°C for 3 hours. The reactions had good yield, up to 96%, and atom efficiency up to 80% and scale up was done to kg level. A domino process has been hypothesized as the mechanism of the functionalization reaction, made by successive Paal Knorr reaction, carbocatalyzed oxidation and cycloaddition. A good number of applications have been successfully explored: inks and varnishes, advanced lightweight nanocomposites materials, e.g.: rubbers for low dissipation of energy, flame retardant polyurethanes, biobased carbon papers and aerogels. The intellectual property of this functionalization technology is characterized by many families of Patents.