Electrical properties of single-wall carbon nanotube-polymer composite films

The electrical properties of single-walled carbon nanotubes (SWNTs) embedded in a poly(3-octylthiophene) matrix have been investigated as a function of SWNT concentration. The electrical conductivity and its temperature dependence were measured as a function of the SWNT concentration. As the nanotube concentration increased from 0 to 20 wt %, the conductivity of the resulting films is dramatically increased by six orders of magnitude. The enhancement in conductivity can be explained by means of a three dimension simple percolation path theory, resulting in an estimated threshold of 4 wt %. The temperature dependence of the SWNT conductivity mat obeys a three-dimensional variable range hopping. In contrast, the polymer-nanotube composite conductivity follows a fluctuation induced tunneling model. The main divergence is that in the polymer-nanotube composite, the nanotubes are coated with polymer, which acts a barrier in bundle to bundle hopping. (C) 2006 American Institute of Physics.