Morphology of Carbon Nanotube Liquid Crystal Solution

Carbon nanotubes (CNTs) have a remarkable combination of electrical, thermal and mechanical properties. In order to realize these properties in applications, CNTs need to be processed into scalable materials such as fibers, coatings, transparent films, and foams. Fluid-phase self-assembly is one of the most promising ways to process CNTs. Chlorosulfonic acid (CSA) has shown to be a true solvent for CNTs. CNTs, similar to other rigid rod molecules, form nematic liquid crystal phase at high concentrations. Low concentration solutions are used for making transparent films, while high concentration solutions can be spun into multifunctional fibers. Successful assembly of CNTs needs a better understanding of the phase behavior and the flow process. Here, we present our recent results on studying the morphology of CNT liquid crystal solutions and how it is affected by the CNT properties, concentration and flow process. We used techniques including polarized optical microscopy and neutron scattering to have a better understanding of the ordering inside the liquid crystal phase. Our polarized optical microscopy results show that for short CNTs at intermediate concentrations, spindle-shaped nematic droplets emerge out of the isotropic phase, while long CNTs show bi-continuous phases. Additionally, high concentrations of long CNTs show higher ordered phases while short CNTs present characteristics of the nematic phase.