Functionalization of multi-walled carbon nanotubes with perfluoropolyether peroxide to produce superhydrophobic properties

Multi-walled carbon nanotubes (MWCNTs) have been functionalized through perfluoropolyether (PFPE) radicals obtained by thermal decomposition of linear PFPE peroxide. The reactivity of MWCNTs with PFPE peroxide has been compared with the direct fluorination of MWCNTs using elemental fluorine in mild conditions. The experimental results indicated that the functionalization with PFPE peroxide and the direct fluorination with elemental fluorine were suitable techniques to modify and control the physical-chemical properties of MWCNTs. After the introduction of PFPE chains on the MWCNT surface, the wettability of MWCNTs changed from hydrophilic to superhydrophobic, because the low surface energy properties of PFPE were transferred to the MWCNT surface. However, the linkage of PFPE chains weakly influenced the electrical properties of conductive MWCNTs. The amount of PFPE chains linked to the carbon nanotubes, the PFPE fluids obtained by homocoupling side-reactions and the decomposed portion of PFPE have been evaluated by mass balance. The modified MWCNTs have been characterized by X-ray photoelectron spectroscopy, thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, contact angle and surface area measurements. The effects of the chemical treatment on the conductive properties of MWCNTs have been studied by resistivity measurements at different applied pressures.