Tunable hydrophylicity/hydrophobicity of fluorinated carbon nanotubes via graft polymerization of gaseous monomers

Abstract

In order to further change the surface chemistry of fluorinated single-walled carbon nanotubes (SWCNTs), gas-phase grafting of monomers onto their surface was performed thanks to the presence of long-lived radicals resulted from the fluorination. Such a two-step process, i.e. fluorination followed by monomer vapor exposure, used here for the first time, resulted in a fast graft polymerization without any solvent using. The total treatment duration does not exceed 4–5 h, contrary to the other reported routes in solvent, and the grafted SWCNTs are ready for use without any purification step. The grafting of monomers from a gaseous phase allows to avoid the homopolymer formation on the tube surface. Grafting drastically changes the SWCNTs surface chemistry. The hydrophilicity/hydrophobicity character may be adjusted according to the monomer nature. Poly(acrylic acid) grafting is resulted in enhanced hydrophilicity, and consequently a better dispersion in water and ethanol. On the contrary, grafted polystyrene improves the dispersion in low-polarity organic solvents because of more hydrophobic nature. Once dispersed in an adequate solvent (commonly used in “wet” chemistry, low hazard and low toxic), the grafted fluorinated nanotubes can be then used for further uses, e.g. incorporation into nanocomposites.