Doping effect of carboxylic acid group functionalized multi-walled carbon nanotube on polyaniline

The polyaniline-carboxylic acid functionalized multi-walled carbon nanotube (PANI-fMWCNT) nanocomposites have been successfully synthesized by in situ chemical oxidative polymerization of aniline using ammonium persulfate in the absence of any added acids. The surface functionalization of multiwalled carbon nanotube (fMWCNT) was performed in concentrated sulfuric and nitric acid mixture at 90 degrees C for 24 h. FTIR spectra indicate that the carboxylic acid groups were generated on the surface of the MWCNTs through oxidation in acid mixtures. The structure and morphology of the PANI-fMWCNT nanocomposites were characterized by UV-VIS, FTIR, XRD, SEM and TEM. The results of UV-VIS and FTIR confirmed that, the synthesized PANI-fMWCNT nanocomposites were in the doped state. The images of SEM and TEM showed a uniform dispersion of the carbon nanotubes in the PANI matrix. It was observed that the PANI-fMWCNT nanocomposites showed a higher conductivity in comparison to pure PANI and it was increased on increasing the concentration of fMWCNT in the nanocomposite with <= 2 wt.% fMWCNT content. The highest average conductivity of 1.4 x 10(-1) S/cm was recorded for the nanocomposite with 2 wt.% fMWCNT content, indicating best doping effect at lower concentration of fMWCNT. However, the conductivity decreased as fMWCNT content increased from 2 to 3 wt.%. (C) 2011 Elsevier Ltd. All rights reserved.