Charge Transport in Conducting Polymers: Polyacetylene Nanofibres

The preparation of individual polyacetylene nanofibres has allowed a more probing investigation of the properties of polyacetylene. A significant discovery is that at low temperatures, polyacetylene nanofibres show temperature-independent Zener-type tunnelling, that we suggest is tunnelling of the conjugated-bond pattern along single polyacetylene chains. At higher temperatures, the current shows a strong increase with temperature and the nonlinearity of the current-voltage characteristics decreases. We make a comparison with similar behaviour found in single-wall carbon nanotube networks, and show that the decrease in nonlinearity is consistent with our generic calculations for fluctuation-assisted tunnelling and thermal excitation. There is no evidence for superconductivity in resistance measurements on polyacetylene. The thermoelectric power of polyacetylene and other bulk organic conducting polymers indicates the absence of significant superconductivity arising from the conventional electron-phonon mechanism.