Frequency dependent electrical transport between conjugated polymer and single-walled carbon nanotubes

This work focuses on the combination of the complementary properties of single-walled carbon nanotube (SWNTs) and poly-3-octylthiophene (P3OT), following a dielectric route to the characterization of a novel composite material. The structural and electrical characterization of a SWNT/P3OT hybrid system performed by differential scanning calorimetry and a.c. impedance spectroscopy show interesting effects, including the tendency of the nanotube structure to nucleate crystal growth and substantial changes in the dielectric behavior of the polymer, due to the effect of the polymer on the nanotubes conformation. In particular, the curve peak of the imaginary part of the impedance spectra shows a shift to a higher frequency demonstrating that the crystallization of the polymer onto the nanotubes results into a different relaxation of the composite's electronic structure, as would be expected from a strong polymer-tube interaction. Raman spectroscopy is finally applied to suggest that in the composite film the changes in the dielectric properties can be explained in terms of a reduced vibrational freedom of the polymer chains as a consequence of the intercalation of the polymer matrix into the nanotubes' lattice. (C) 2003 Elsevier Science B.V. All rights reserved.