Significantly Increased Solubility of Carbon Nanotubes in Superacid by Oxidation and Their Assembly into High‐Performance Fibers

This study demonstrates that small amount of oxygen incorporated into carbon nanotubes (CNTs) during the purification process greatly increases their solubility in chlorosulfonic acid (CSA). Using as‐purchased and unpurified CNT powders, the optimal purification process is established to significantly increase the solubility of CNTs in CSA, and spin CNT fibers with high mechanical strength (0.84 N tex−1) and electrical conductivity (1.4 MS m−1) from the CNT liquid crystal dope with high concentration of CNTs in CSA. The knowledge obtained here may guide development of a way to dissolve extremely long CNTs at high concentration and thereby to enable production of CNT fibers with ultimate properties. The incorporation of a small amount of oxygen in carbon nanotubes (CNTs) greatly increases their solubility in chlorosulfonic acid (CSA) by providing specific centers for protonation. Based on this new understanding, macroscopic fibers are successfully fabricated by wet spinning using a liquid crystalline oxygen‐incorporated CNT/CSA solution with the remarkable electrical (≈1.4 MS m−1) and mechanical (≈0.84 N tex−1) properties.