Recently, covalent functionalization carbon nanotubes have been received special attention because of the expansive application prospect in the areas of nanoscience and nanotechnology. Moreover, covalent functionalization of carbon nanotubes can improve the solubilization of carbon nanotubes. In particular, polyaniline, due to its high electronic conductivity, good environmental stability, easy preparation and reversible acid-base doping-dedoping chemistry, has been one of the most studied conducting polymers. Recently, CNTs-PANI composites were investigated widely, such as supercapacitor, optoelectronic devices, sensing and catalysis as well. In this work, we perform in situ polymerization method at low temperatures obtaining uniform structures PANI grafted on CNTs (which has been covalently functionalized with NH₂ groups on its surface) composites. Concerning CNTs-NH-PANI composites, PANI could be covalently grafted onto CNTs through NH₂ groups. Due to the fact that CNTs-NH-PANI composites have abundant -NH₂ groups on their surface, serving as anchor centers for polymerization of aniline monomer. Introduction of NH₂ groups can not only increase the dispersion of carbon nanotubes itself, but also can be as growth sites to form PANI uniform grafted to the "core-shell" structure of carbon nanotubes in the growth process of PANI. More importantly, PANI uniformly grafted on CNTs is prone to disperse the bundle of CNTs into separated lines and improve water dispersibility of obtained CNTs-NH-PANI composites. Potential application of the composite material as high performance supercapacitor has been explored. Composite material samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical methods and so on. TEM results showed that the hierarchical CNTs-PANI composites with uniform morphology have been successfully prepared due to hydrophilic groups OH and NH₂ are successfully covalently functionalized on the surface of CNTs. Moreover, the electrochemical measurement show that CNTs-NH-PANI composites have high specific capacitance as supercapacitor material. At the current density of 0.1 A/g, the specific capacity can reach 251.2 F/g. For PANI, the capacitance contribution is higher in covalently grafted CNTs-g-PANI composites than PANI-c-CNTs. At the charge-discharge test, the composite material capacity retention stability rate at 64% after 5000 charge discharge test, higher than that of PANI-c-CNTs 48% significantly at the current density of 1 A/g.

Key words: carbon nanotube, polyaniline, covalently, supercapacitor