Nematic liquid crystals of carbon nanotubes and graphene
Résumé
nanotubes or graphene particles. On the other hand, the organization of nanocarbons as liquid crystals provides
new 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 lyotropic
LC 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 shearing
a drop between two glass plates [1]. The order parameter of SWNT LC was found to be very sensitive to waviness
and entanglement of the nanotubes and the best orientational order was achieved after disentangling, shortening
and sorting the nanotubes using ultrasonication and ultracentrifugation [2]. Anisotropic conductive films of
nanotubes can be prepared by drying the LC. The anisotropy of conductivity of the anisotropic layers can be related
to the order parameter through a simple analytical model assuming that the electrical resistance in a percolation
path is proportional to the number of contacts [3].
Homogeneous orientation of RGO LC was achieved by centrifugating capillaries. Structural and thermodynamic
characterizations provide statistical information on the dimensions of the graphene flakes, which are found to be
comparable 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)