Influence of the chemical structure of aromatic dispersants on the dispersion of carbon nanotubes

The effect of the chemical structure of cationic dispersants on the dispersion of single-walled carbon nanotubes (SWCNTs) was investigated. Various aromatic compounds with quaternary ammonium cations were synthesized as dispersants for SWCNTs. The aqueous SWCNT dispersions were prepared using three types of SWCNTs and nine synthesized dispersants. UV–vis–NIR absorbance of the SWCNT dispersions was used to test the dispersing ability of the synthesized dispersants. This analysis showed that the dispersing ability of the synthesized dispersants was strongly dependent on their chemical structure. The dispersants possessing amide bonds showed higher dispersing ability than those with ester bonds. The increase in the number and size of the aromatic moieties also enhanced the dispersing ability. The dispersants that had a twisted-aromatic moiety and ether bonds interacted preferentially with small-diameter SWCNTs. However, dispersants with planar aromatic moieties dispersed SWCNTs of various diameters. The dispersions of the SWCNT/cationic complex had long-term stability (over 10 months at 20–30 °C), good thermal stability (1 h at 70 °C), and a wide pH range from 3 to 11.