Highly conducting and flexible few-walled carbon nanotube thin film.

We report an effective route to prepare highly conducting and flexible few-walled carbon nanotube (FWNT) thin films. The free-standing thin films were fabricated by functionalizing FWNTs with 4-ethoxybenzoic acid (EBA) via a direct Friedel-Crafts acylation reaction in a nondestructive polyphosphoric acid/phosphorus pentoxide medium. The resulting ethoxybenzoyl-functionalized FWNT (EBA-f-FWNT) was readily dispersible in water. EBA-f-FWNT thin films were formed by a simple suction filtration of the dispersed solution. Electron microscopic studies were employed to characterize the morphologies of the resulting thin films. The obtained results indicate that the structure of FWNTs was not perturbed by the incorporation of EBA moieties, which were uniformly grafted onto FWNTs forming the FWNT networks. Room temperature electrical conductivity of the thin films was obtained using standard four-probe measurements, which revealed a value as high as 29 400 S m(-1), while the tensile strength and modulus of the film were found to be about 80 MPa and 15 GPa, respectively. Cyclic voltammograms revealed a rectangular shape, with superior capacitive behaviors nearing 133 F/g for the thin films, which is very attractive for capacitor applications.