Highly Ordered Carbon Nanotube Nematic Liquid Crystals
Résumé
Liquid crystal ordering is an opportunity to develop novel materials and applications with carbon nanotubes spontaneously aligned on macroscopic scales. Nevertheless, achievement of large orientational order parameter and extended monodomains remains challenging. In this work, we show that shortening nanotubes allows the formation of liquid crystals that can easily be oriented under the form of large macroscopic monodomains. The orientational order parameter of single-wall nanotube liquid crystals measured by polarized Raman spectroscopy at the isotropic-nematic transition exceeds by far the value reported in previous experiments. The presently measured order parameter approaches the value theoretically expected for liquid crystals made of rigid rods in solution. This finding suggests that the production of highly ordered nanotubebased liquid crystals was presumably limited in earlier contributions by the length and waviness of long nanotubes. Both factors increase the material viscosity, can yield some elasticity, and stabilize topological defects.