(Invited) Dispersant Design for Organic Solvent Dispersion of Carbon Nanotubes

Highly efficient solvent dispersion of single-walled carbon nanotubes (SWCNTs) has been limited to solvents with extreme polarity, such as water or toluene. In aqueous systems, their stable colloidal dispersion is achieved by complete hydrophilization of the nanocarbon interface due to the robust water/oil interface formed by amphiphilic compounds. Dispersion by conductive polymers is one of the few successful examples, but it is limited to non-polar and low-polar solvents such as toluene. In addition, with the exception of a few magic solvents such as N-cyclohexylpyrrolidone, which is difficult to volatilize, organic solvents have not dispersed CNTs in high yields. On the other hand, from a practical point of view, the development of CNT dispersion technology in a wide range of polar solvents such as ketones, ethers, esters and alcohols is highly demanded. Although CNT dispersion in such organic solvent groups has been reported by individual groups, albeit to a limited extent, there is no unified understanding of the CNT dispersion mechanism. In this talk, I will present the high-yield dispersion of SWCNTs in a wide range of organic solvents such as alcohols, ketones, esters, and ethers using different dispersants. The presentation will also include a discussion of the parameters estimated to be necessary for stable colloidal dispersion based on feature extraction by machine learning [1], the discovery of many new dispersants based on this knowledge [2], and research on structural separation of SWCNTs. We will also present the extraction technique for semiconducting CNTs found in organic solvent-cellulose dispersants [3]. [1] Y. Nonoguchi, T. Miyao, C. Goto, T. Kawai, K. Funatsu, Adv. Mater. Interfaces 9, 2101723 (2022). [2] A. Horibe, T. Murayama, T. Kawai, Y. Nonoguchi, RSC Appl. Interfaces 1, 80–85 (2024). [3] T. Yagi, K. Yoshida, S. Sakurai, T. Kawai, Y. Nonoguchi, J. Am. Chem. Soc. 146, 20913–20918 (2024).