Nematic liquid crystals of graphene flakes

Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneouslyaligned anisotropic particles [1,2]. In this way, the organization of graphene flakes in liquid crystals provides new methodologies for the still challenging structural characterization of such materials. In this work, we will present a review of our recent results in the preparation and characterization of lyotropic LC made from concentrated aqueous suspensions based graphene oxide (GO) and/or reduced graphene oxide (RGO), and we will show some of ours preliminary approaches to achieve large and well-ordered domains of lyotropic liquid crystals. According with literature, for graphene, it is known that 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. RGO is of greater interest since a large part of functionalities are recovered 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 statistical information on the dimensions of the graphene flakes, which are found to be comparable with those of neat graphene oxide flakes. We have started to combined these new liquid crystals with nanoparticles, these graphene-based LC/Nanoparticles composites being useful to design coatings and functional materials.References[1] Yuan J.; Luna A.; Neri W.; Zakri C.; Schilling T.; Colin A.; Poulin, P. Graphene liquid crystal retardedpercolation for new high-k materials. Nat. Commun. 6:8700 (2015) doi: 10.1038/ncomms9700[2] Zakri, C.; Blanc, C.; Grelet, E.; Zamora-Ledezma, C.; Puech, N.; Anglaret, E.; and Poulin, P. Liquid crystals ofcarbon nanotubes and graphene. Phil. Trans. R. Soc. A., 371, 20120499, pp 1-15 (2013)[3] Zamora-Ledezma, C.; Puech, N.; Zakri, C.; Grelet, E.; Moulton, S. E.; Wallace, G. G.; Gambhir, S.; Blanc, C.;Anglaret, E.; and Poulin, P. Liquid Crystallinity and Dimensions of Surfactant-Stabilized Sheets of ReducedGraphene Oxide. J. Phys. Chem. Lett., 3 (17), pp 2425–2430 (2012