Grafting of adipic anhydride to carbon nanotubes through a Diels-Alder cycloaddition/oxidation cascade reaction

• Published in: Carbon (New York) Vol. 98; pp. 421 - 431
• Main Authors: Araújo, Rui Filipe, Proença, Maria Fernanda, Silva, Carlos Jorge, Castro, Tarsila G., Melle-Franco, Manuel, Paiva, Maria Conceição, Villar-Rodil, Silvia, Tascón, Juan Manuel D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-03-2016
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2015.11.004

Different reactions have been reported for the successful functionalization of carbon nanotubes (CNT). The Diels-Alder cycloaddition is recognized as a plausible chemical approach, but few reports are known where this strategy has been used. In this study, the functionalization was performed by 1,3-butadiene generated from 3-sulfolene under heating conditions in diglyme. This simple and easily scalable method resulted in functionalized CNT with mass losses of 10–23% by thermogravimetric analysis (nitrogen atmosphere). The functionalization was also supported by acid-base titration, elemental analysis, temperature programmed desorption and X-ray photoelectron spectroscopy. The high content in oxygen detected on the CNT surface was assigned to anhydride formation due to a cascade oxidation of the alkene groups generated in the cycloaddition reaction. The complete evolution of the alkene leads to a grafting density of 4.2 mmol g−1 for the anhydride moiety. Ab-initio calculations in CNT model systems indicate that the Diels-Alder addition of butadiene is a feasible process and that subsequent oxidation reactions may result in the formation of the anhydride moiety. The presence of the anhydride group is a valuable asset for grafting a multitude of complex molecules, namely through the nucleophilic addition of amines.