Clara Pereira - Understanding the silylation reaction of multi-walled carbon nanotubes

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        “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.

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