Sidewall carboxylic acid functionalization of single-walled carbon nanotubes

The reactions of single-walled carbon nanotubes (SWNTs) with succinic or glutaric acid acyl peroxides in o-dichlorobenzene at 80-90 degreesC resulted in the addition of 2-carboxyethyl or 3-carboxypropyl groups, respectively, to the sidewalls of the SWNT. These acid-functionalized SWNTs were converted to acid chlorides by derivatization with SOCl2 and then to amides with terminal diamines such as ethylenediamine, 4,4'-methylenebis(cyclohexylamine), and diethyltoluenediamine. The acid-functionalized SWNTs and the amide derivatives were characterized by a set of materials characterization methods including attenuated total reflectance (ATR) FTIR, Raman and solid state C-13 NMR spectroscopy, transmission electron microscopy (TEM), and thermal gravimetry-mass spectrometry (TG-MS). The degree of SWNT sidewall functionalization with the acid-terminated groups was estimated as 1 in 24 carbons on the basis of TG-MS data. In comparison with the pristine SWNTs, the acid-functionalized SWNTs show an improved solubility in polar solvents, for example, alcohols and water, which enables their processing for incorporation into polymer composite structures as well as for a variety of biomedical applications.