Publication Details (including relevant citation information):
“Understanding the silylation reaction of multi-walled carbon nanotubes”, H. Gaspar, C. Pereira, S. L. H. Rebelo, M. F. R. Pereira, J. L. Figueiredo, C. Freire, Carbon 2011, 49, 3441–3453. DOI: 10.1016/j.carbon.2011.04.041
Functional organosilanes were appended, in aprotic and anhydrous conditions, onto multi-walled carbon nanotubes (MWCNTs) previously submitted to three different oxidative treatments: acid, acid with subsequent thermal treatment at 400 °C and 5% O2/N2 treatment at 500 °C. The materials were characterised by X-ray photoelectron spectroscopy, elemental analysis, temperature programmed desorption, Fourier transform infrared spectroscopy, thermogravimetry, nitrogen adsorption isotherms at −196 °C and scanning electron microscopy. The techniques provided a correlation between the type and oxygen contents present in the oxidised MWCNTs and the silylation reaction efficiency, leading to a comprehensive overview of the reaction mechanism and materials structure/composition. The highest silylation reaction efficiencies were achieved with the aminosilane in all the oxidised materials and with mercaptosilane in the acid oxidised MWCNTs with nearly 4% Si insertion, whereas for the other organosilanes values lower than 2% were observed. The silylation mechanism was found to proceed through reaction of the alkoxy moieties from the organosilane with phenol surface groups from the MWCNTs; in the case of aminosilane for all MWCNTs and mercaptosilane in acid oxidised MWCNTs, it also occurred by reaction with the carbonyl surface groups. Furthermore, for these latter materials a polymerisation side-reaction was proposed as a parallel functionalisation pathway.
Address (URL): dx.doi.org/10.1016/j.carbon.2011.04.041