Nematic liquid crystals of carbon nanotubes and graphene

nanotubes or graphene particles. On the other hand, the organization of nanocarbons as liquid crystals providesnew methodologies for the still challenging structural characterization of such materials.In this talk, we will present a review of our recent results in the preparation and characterization of lyotropicLC made from concentrated aqueous suspensions, stabilized by surfactants, of single-walled carbon nanotubes(SWNT) or reduced graphene oxide (RGO) [1-5]. Homogeneously oriented SWNT LC can be prepared by shearinga drop between two glass plates [1]. The order parameter of SWNT LC was found to be very sensitive to wavinessand entanglement of the nanotubes and the best orientational order was achieved after disentangling, shorteningand sorting the nanotubes using ultrasonication and ultracentrifugation [2]. Anisotropic conductive films ofnanotubes can be prepared by drying the LC. The anisotropy of conductivity of the anisotropic layers can be relatedto the order parameter through a simple analytical model assuming that the electrical resistance in a percolationpath is proportional to the number of contacts [3].Homogeneous orientation of RGO LC was achieved by centrifugating capillaries. Structural and thermodynamiccharacterizations provide statistical information on the dimensions of the graphene flakes, which are found to becomparable with those of neat graphene oxide flakes [4,5].[1] C. Zamora-Ledezma et al., Nano Lett. 8 (2008) 4103-4107 [2] N. Puech et al., J. Phys. Chem. C. 115 (2011) 3272-3278 [3] C. Zamora-Ledezma et al., Phys. Rev. E 85 (2012) 062701(5) [4] C. Zamora-Ledezma et al., J. Phys. Chem.Lett., 3 (2012) 2425-2430 [5] C. Zakri et al., Phil. Trans. R. Soc. A. 371 (2013) 201204995(15