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Covalent modification of MWCNT with quaternary ammonium groups

Since their discovery, carbon nanotubes (CNT) have been found to be a promising material for various applications because of their unique properties like electric conductivity, mechanical strength and chemical stability. Some of the most explored fields of applications are electronics, drug delivery, composite material production, catalysis [1] and chemical sensing applications [2]. For most of the applications some kind of modification of CNT is required. Non‐covalent modification can be performed without disrupting the structure of both single wall (SWCNT) and multi walled CNT (MWCNT). Covalent modification of SWCNT can lead to a loss of advanced properties like electric conductivity because of the structural changes [3], while properties of MWCNT are not affected by this modification. Here we present a new covalent modification of pristine MWCNT by quaternary ammonium groups and their characterization. The quaternary ammonium groups have been introduced in a multi‐step reaction. The first step was nitrification which was performed by treatment of MWCNT with the mixture of concentrated HNO3 and H2SO4 in the 9:10 volume ratio at 60 °C and for 3 hours. The nitro groups were reduced to amine groups by Bechamp reduction, by applying Fe powder and hydrochloric acid, in ethanol reflux for 2 hours. After purification of amine‐modified MWCNT, direct quaternization of amine groups was performed with the application of CH3I, in dimethylformamide at room temperature. The modification steps were followed with FTIR and 13C and H NMR characterization.

multi walled carbon nanotubes ; covalent modification ; quaternary ammonium groups

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