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Matteo Pasquali

Assistant Professor

Department of Chemical Engineering,

Center for Nanoscale Science and Technology, and

Center for Biological and Environmental Nanotechnology

Rice University - Houston, TX 77005, USA

"Continuous, Macroscopic Fibers from Liquid Crystalline Mesophases of Single-Walled Carbon Nanotubes in Superacids".

abstract

Single Wall Carbon Nanotubes (SWNTs) are a form of carbon consisting of a single graphene sheet rolled onto itself. Their diameter ranges from approximately half to few nanometers, and their length from tens of nanometers to over a micrometer; the wall is one atom thick. Because of their structure, SWNTs have unparalleled electrical, thermal, and mechanical properties.

Until recently, progress in the field has been impaired by the lack of effective methods for dispersing high concentrations of SWNTs in liquids.

We have discovered that SWNTs can be dispersed at high concentration in superacids and that neat SWNT fibers can be spun from acid dispersions. At low concentration, SWNTs for an isotropic dispersion. As the concentration is increased, first the system turns biphasic, then it forms a polydomain liquid crystal. Optical and rheological measurements determine approximately the transitions. Reaction and purification conditions influence the rheological properties of the dispersions as well as fiber quality. Fibers spun from good-quality dispersions are highly aligned (~20 to 1 ratio of parallel to perpendicular Raman signal) and dense (~80%) even in the absence of drawing.