Résumé
Most of the potential applications in carbon nanotubes and graphene-based composites require suitable methods for making aligned assemblies on a large scale. Liquid crystal ordering is an opportunity to develop such materials and applications [1]. In this talk, we will present a review of our recent results in the preparation and characterization of lyotropic liquid crystals based on concentrated aqueous suspensions, stabilized by surfactants, of single-walled carbon nanotubes (SWNT) or reduced graphene oxide (RGO). In the first part we will focus on anisotropic conductive films, which are prepared by shearing and drying the LC. In particular, we will show how the electrical conductivity anisotropy increases with the orientational order parameter of the nematic liquid crystal. The order parameter can be tuned by controlling the length and entanglement of the nanotubes [1-2]. In the second part we present recent results on the morphology and anisotropy of thin conductive lines of SWCNT, inkjet-printed. Its Their morphology can be tuned from rail track to quasi-continuous lines by increasing nanotube concentration and drop density. The average order parameter is in the range 0.2–0.4 for all samples. The electrical resistivity is larger for rail tracks with respect to continuous layers, due to large amounts of electrical dead-ends in and between the inner edges of rail tracks [4]. Finally we will present how to prepare water-based Graphene Oxide (GO), and Reduced Graphene Oxide (RGO) liquid crystals stabilized by surfactant molecules. We will discuss their structural and thermodynamic characterizations, which provide indirect but statistical information on the organizations and dimensions of the graphene flakes [1-3].
1. C. Zakri et al, Phil. Trans. R. Soc. A. 371 (2013) 201204995(15)
2. Zamora-Ledezma, C. et al. J. Phys. Chem. Lett., 3 (17), pp 2425–2430 (2012)
3. Yuan J. et al. Nat. Commun. 6:8700 doi: 10.1038/ncomms9700 (2015).
4. F. Torres-Canas et al, Mater. Res. Express. DOI: 10.1088/2053-1591/aa5687 (2017)