The effect of nanotube surface oxidation in the electrical response of MWCNT/PVDF nanocomposites

Carbon nanotubes / poly(vinylidene fluoride) composites were prepared using CNT with different oxidation and thermal treatments. The oxidation procedure leads to CNT with the most acidic characteristics that lower the degree of crystallinity of the polymer and contribute to a large increase of the dielectric constant. The surface treatments, in general, increase percolation threshold and decrease conductivity, but, on the other hand, are able to promote the nucleation of the electroactive phase of the polymer, which is suitable for the use of PVDF in sensors, actuators and other smart materials applications. Finally, the surface treatments do not seem to affect CNT interaction among them, reaching similar degrees of dispersion in all cases, as shown by the SEM results. The maximum value of the dielectric constant is ~630. It is demonstrated that the composite conductivity can be attributed to a hopping mechanism that is strongly affected by the surface treatment of the CNT.The authors thank the Fundacao para a Ciencia e a Tecnologia (FCT), Portugal, for financial support through the projects PTDC/CTM/69316/2006 and NANO/NMed-SD/0156/2007), and CIENCIA 2007 program for S.A.C.; V. S., J.S. and J.N.P. also thank FCT for the SFRH/BPD/63148/2009, SFRH/BD/60623/2009 and SFRH/BD/66930/2009 grants