Characterizations on the amidized multiwalled carbon nanotubes grafted with polyaniline via in situ polymerization

Abstract

A multiwalled carbon nanotubes (MWCNTs) were carboxylated after refluxing with sulfuric and nitric acids. These attached carboxylic acid groups were further condensated with o-phenylene diamine into amide catalyzed by dicyclohexyl carbodiimide (DCC). The obtained amidized MWCNTs were in situ-polymerized with aniline monomers to graft a conducting polyaniline (PANI) onto MWCNT (ES-g-MWCNTs) through the polymerization occurring in the ortho-and meta-positions. The reduced conductivity of the MWCNT after carboxylation can be recovered after grafting with PANI, which owns a strong k max at the near infrared region due to the extended conjugation from MWCNTs to PANI. Transmission electronic microscopic pictures show a gradual broadening of the MWCNT diameter after carboxylation, amidization, and polymerization. The weight loss from the thermogravimetric thermograms due to the carboxylations of MWCNTs, amidized MWCNTs, and the PANI grafted MWCNTs into CO 2 can be used to estimate the degree of carboxylation, amidization, and grafting of PANI. The degree of carboxylation of MWCNT calculated from ESCA spectrum is around 23% close to that estimated from TGA thermogram. The doping level of redoped PANI-grafted MWCNT is found to be 27.78% much less than the maximum 50% of neat PANI.

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“…The surface concentration of carboxyl groups on cCNTs and aCNTs was estimated to be 0.60 ± 0.03 and 0.36 ± 0.02 mmol g –1 , respectively, while the surface concentration of amide groups was 0.24 ± 0.02 mmol g –1 . This observation suggests that the conversion degree from carboxylic to carboxyimide groups is approximately 40%, which is 2.3-fold higher than that for the reported amidation in solution . The increased surface concentration of the charged groups could enhance the surface hydrophilicity of functionalized CNTs to the high level.…”

“…This observation suggests that the conversion degree from carboxylic to carboxyimide groups is approximately 40%, which is 2.3-fold higher than that for the reported amidation in solution. 19 The increased surface concentration of the charged groups could enhance the surface hydrophilicity of functionalized CNTs to the high level. This is supported by contact angle measurements of the cCNTs and aCNTs yielding values of 22.9 ± 2.9 and 19.8 ± 1.5, respectively.…”