Ordering nanocarbons using Liquid Crystalline phases
Résumé
A very active branch of materials research based on allotropic carbon nanostructures has recently
flourished, mainly due to their large potential of applications. Among the most outstanding structures are
graphene and carbon nanotubes which both possess interesting properties at the nanoscale, such as:
electronic, mechanical, optical etc... When combined with various nanoparticles (NPs), their potential is
even larger. Exploiting these properties, which are mostly anisotropic, requires to transfer them to the
macroscopic world through the preparation of ordered nanostructured composites materials. During their
processing, liquid crystal phases present an opportunity to arrange them into macroscopic assemblies of
NPs and nanocarbons with long-range ordering [1]. Nevertheless, achieving high orientational order
parameter and large monodomains remains a challenge. In this work we present some of our approaches to
achieve large and well-ordered domains of
lyotropic liquid crystals. For example the order
parameter of carbon-nanotubes based materials
can be finely tuned by controlling the length and
entanglement of the nanotubes [2] and processes
based on shear are sufficient to easily achieve a
macroscopic ordering. For graphene, it is known
that graphene oxide (GO) flakes easily disperse in
water and spontaneously form liquid crystals at
high concentrations. However, most of their electronic functionalities are lost during the oxidation
treatments. Reduced graphene oxide (RGO) is of greater interest but chemical reduction of GO in water
generally results in the aggregation of the flakes. We recently showed how to obtain water-based RGO
liquid crystals stabilized by surfactant molecules [3]. Structural and thermodynamic characterizations
provide indirect but statistical information on the dimensions of the graphene flakes. Combined with NPs,
these graphene based liquid crystals are also useful to design novel coatings and functional materials.
[1] Yuan J. et al. Nat. Commun. 6:8700 doi: 10.1038/ncomms9700 (2015).
[2] Zakri, C. et al. Phil. Trans. R. Soc. A., 371, 20120499, pp 1-15 (2013)
[3] Zamora-Ledezma, C. et al. J. Phys. Chem. Lett., 3 (17), pp 2425–2430 (2012)