Article

Liquid crystals of carbon nanotubes and graphene.

CNRS, Université de Bordeaux, , Centre de Recherche Paul Pascal (CRPP), UPR 8641, 33600 Pessac, France.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences (Impact Factor: 2.89). 04/2013; 371(1988):20120499. DOI: 10.1098/rsta.2012.0499
Source: PubMed

ABSTRACT Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneously aligned nanotubes or graphene particles. Nevertheless, achieving high orientational order parameter and large monodomains remains a challenge. In addition, our restricted knowledge of the structure of the currently available materials is a limitation for fundamental studies and future applications. This paper presents recent methodologies that have been developed to achieve large monodomains of nematic liquid crystals. These allow quantification and increase of their order parameters. Nematic ordering provides an efficient way to prepare conductive films that exhibit anisotropic properties. In particular, it is shown how the electrical conductivity anisotropy increases with the order parameter of the nematic liquid crystal. The order parameter can be tuned by controlling the length and entanglement of the nanotubes. In the second part of the paper, recent results on graphene liquid crystals are reported. The possibility to obtain water-based liquid crystals stabilized by surfactant molecules is demonstrated. Structural and thermodynamic characterizations provide indirect but statistical information on the dimensions of the graphene flakes. From a general point of view, this work presents experimental approaches to optimize the use of nanocarbons as liquid crystals and provides new methodologies for the still challenging characterization of such materials.

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    Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences 04/2013; 371(1988):20120510. · 2.89 Impact Factor
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    ABSTRACT: Besides nanostructured materials, individual particles are key elements for nanosciences. The structuring properties of liquid crystals (LCs) are appealing to assemble them, to organize them on substrates or to design functional composites. We present here an overview on particles/LC systems, the size of the dispersed particles being larger than the typical LC length. We first summarize the large number of advances made these last 10 years concerning microparticles assemblies. We then discuss the evolution of the relevant interactions between nanoparticles (NPs) dispersed in LCs when their size decreases from micrometers to nanometers. Various NPs assemblies obtained, either in LC bulk, at interfaces or within LC distorted areas or topological defects are then reported and discussed. Finally, we consider the recent possibilities to use NPs as building elements of complex fluids. We discuss accordingly the LC phases, which can be obtained with pure inorganic NPs in concentrated solution, as well as the self-assemblies which can be obtained when NPs are covered by organic mesogenic ligands.
    Liquid Crystals Reviews. 01/2013;

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May 27, 2014