Semiconductor to metallic behavior transition in multi-wall carbon nanotubes/polyaniline composites with improved thermoelectric properties

• Molecular conformation of PANI/MWCNTs was tuned via preparation temperature.
• High doping level, more polaron delocalization and orderly arrangement of PANI were achieved.
• Greatly increased conductivity results in a 66.7% enhancement in power factor.

Multi-wall carbon nanotubes/polyaniline (MWCNT/PANI) composites were prepared by the in situ polymerization at room temperature and in ice-water bath, respectively. Raman spectra and X-ray diffraction patterns showed that the molecular conformation and the degree of order of PANI were greatly affected by the synthesis temperature. In low temperature condition, quinoid units converted into benzenoid in PANI and meanwhile, the chain segments of MWCNT/PANI arranged in a more orderly arrangement, which resulted in a change of the conducting behavior from semiconductor to metallic and almost twice increase in conductivity. Power factor (PF) of both composites increased with the increase of MWCNTs content, and 66.7% higher PF value was obtained in metallic-like composite with 80 wt% MWCNTs loading.