Dissolution of Long Carbon Nanotubes in Superacids

Controlling the phase behavior of single-walled carbon nanotubes (SWNTs) in fluids is critical for the production of SWNT-based macroscopic materials. Yet, dissolution has been a major hurdle for researchers over the past decade. Here we show that SWNTs form true thermodynamic molecular solutions in superacids. In particular, SWNTs dissolve spontaneously in chlorosulfonic acid as isotropic solutions concentrations a thousand fold higher than those previously found in other solvents; at higher concentrations, they form a liquid crystal. We also show that such superacids can even be used to dissolve long (hundreds of microns) SWNTs and multi-walled carbon nanotubes; these solutions can also form liquid crystals. Dissolution of such large nanotubes had previously been thought impossible. The liquid crystalline phase is readily processed into fibers and sheets, whose morphology is controlled by the starting fluid phase.