Comparison of Branched and Linear Perfluoropolyether Chains Functionalization on Hydrophobic, Morphological and Conductive Properties of Multi-Walled Carbon Nanotubes

Abstract

The functionalization of multi-walled carbon nanotubes (MW-CNTs) was obtained by generating reactive perfluoropolyether (PFPE) radicals that can covalently bond to MW-CNTs’ surface. Branched and linear PFPE peroxides with equivalent molecular weights of 1275 and 1200 amu, respectively, have been thermally decomposed for the production of PFPE radicals. The functionalization with PFPE chains has changed the wettability of MW-CNTs, which switched their behavior from hydrophilic to super-hydrophobic. The low surface energy properties of PFPEs have been transferred to MW-CNTs surface and branched units with trifluoromethyl groups, CF3, have conferred higher hydrophobicity than linear units. Porosimetry discriminated the effects of PFPE functionalization on meso-porosity and macro-porosity. It has been observed that reactive sites located in MW-CNTs mesopores have been intensively functionalized by branched PFPE peroxide due to its low average molecular weight. Conductivity measurements at different applied pressures have showed that the covalent linkage of PFPE chains, branched as well as linear, weakly modified the electrical conductivity of MW-CNTs. The decomposed portions of PFPE residues, the PFPE chains bonded on carbon nanotubes, and the PFPE fluids obtained by homo-coupling side-reactions were evaluated by mass balances. PFPE-modified MW-CNTs have been characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), static contact angle (SCA), surface area, and porosity measurements.

Comparison of Properties of the Hybrid and Bilayer MWCNTs—Hydroxyapatite Coatings on Ti Alloy

“…This could be the result of the higher roughness of the etched surface ( Table 3). The CNTs coating was found hydrophilic [48] with the angle value 56.50°, which means that the surface is proper for its application in implantology. Türka et al achieved similar results for the contact angle of the CNTs after functionalization, 53.29° [49].…”

Growth, Properties, and Applications of Branched Carbon Nanostructures

“…Other technological applications for branched CNSs take advantage of aspects of their tunable properties, such as rheology [119] and hydrophobicity [5], as well as their electrical and electronic properties [8,16,18,29,120,121]. Hirtz and Hölscher et al used an open flame process to fabricate site-specific catalyst supports and also proposed an empirical model for the growth process, as shown in Figure 10, in agreement with SEM micrographs (Figure 11) [122].…”

“…Alternatively, sidewall functionalization of MWCNTs with branched and linear perfluoropolyether (PFPE) was achieved through the generation of reactive radical species from the thermal decomposition of PFPE peroxide precursors. The wettability of the functionalized MWCNTs was significantly reduced, as they acquired super-hydrophobicity [120].…”

Preparation and Application of Hybrid Nanomaterials

“…The reaction occurrence was made possible just by the surface energy and composition of the MWNT activated surfaces, which act as nucleation sites for the growth of the crystals. By the same principles, in the feature paper by Sansotera et al [ 16 ], the successful functionalization of MWNT by perfluoropolyether chains was controlled by the surface features of the carbon nanotubes. The resulting covalent bond produced relevant modifications of the MWNT surface energy imparting superhydrophobic behavior; branched chains, bearing CF 3 groups, produced a higher functionalization degree with respect to linear ones.…”