Effect of the carbon nanotube surface characteristics on the conductivity and dielectric constant of carbon nanotube/poly(vinylidene fluoride) composites

Commercial multi-walled carbon nanotubes (CNT) were functionalized by oxidation with HNO3, in order to introduce oxygen-containing surface groups, and by thermal treatments at different temperatures for their selective removal. The obtained samples were characterized by adsorption of N2 at -196 ºC, temperature programmed desorption and determination of pH at the point of zero charge. CNT/poly(vinylidene fluoride) composites were prepared using the above CNT samples, with different filler fractions up to 1 %wt. It was found that oxidation reduces composite conductivity for a given concentration, shifts the percolation threshold to higher concentrations and has no significant effect in the dielectric response.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 SAC. V. S. and J.N.P. also thank FCT for the SFRH/BPD/63148/2009 and SFRH/BD/66930/2009 grants