Sustainable functionalization of carbon nanotubes via disulfide-based eutectic mixtures

The remarkable properties of carbon nanotubes (CNTs) make them highly valuable materials across a wide range of application fields. For this reason, there is considerable interest in developing innovative and sustainable functionalization strategies that can improve CNTs dispersion by introducing chemical functionalities, which can impart them specific features. Herein, we report a sustainable and efficient approach for the covalent modification of single- (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using disulfide derivatives as components of newly developed eutectic mixtures (EMs). Differential scanning calorimetry (DSC) confirmed the formation of EMs through a marked melting point depression relative to the pure components. By combining selected disulfides with appropriate hydrogen bond donor (HBD) and acceptor (HBA) species, six EMs were prepared and employed as reactive dispersion media of CNTs enabling the in situ generation of thiyl radicals. This methodology drastically reduces reaction volumes, shortens processing times, and limits the use of volatile organic solvents. The resulting hybrid materials, bearing hydroxyl, carboxyl, or amine groups, were characterized by thermogravimetric analysis (TGA), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). This EM-assisted strategy provides a greener and more convenient route for CNTs functionalization and offers a versatile alternative for producing advanced carbon-based materials with potential applications.