The enhanced power factor of multi-walled carbon nanotube/stabilized polyacrylonitrile composites due to the partially conjugated structure

The studies of organic thermoelectric (TE) materials mainly focus on conductive polymers due to their conjugated molecular structures and high intrinsic electrical conductivity. When the conductive polymer is mixed with certain insulating polymers, the power factor was found enhanced. It is doubtful that the partially conjugated molecular structure is beneficial to the TE performance. Polyacrylonitrile (PAN) is an insulating polymer with a non-conjugated structure in its backbone, however, it has a partially conjugated structure after thermal treatment. In this work, a composite of PAN and multi-walled carbon nanotubes (MWCNT) was made and thermally treated in order to study the partially conjugated structure on the improvement of the power factor. By controlling the PAN content and the temperature of thermal treatments, a maximum power factor of 22 μW/mK2 was obtained from the MWCNT/PAN composite with 45% PAN content after thermally treated at 300 °C in air, which is 300% and 80% higher than that without PAN and before thermal treatment, respectively. It is demonstrated that the partially conjugated polymers play an important role in TE performance and they are promising candidates for high-efficient organic TE materials.