An explanation of dispersion states of single-walled carbon nanotubes in solvents and aqueous surfactant solutions using solubility parameters

Dispersions of single-walled carbon nanotubes in various solvents and aqueous surfactant emulsions were investigated to correlate the degree of dispersion state with Hansen solubility parameters ( δ t 2 = δ d 2 + δ p 2 + δ h 2 ). It was found that the nanotubes were dispersed or suspended very well in the solvents with certain dispersive component ( δ d ) values. They were precipitated in the solvents with high polar component ( δ p ) values or hydrogen-bonding component ( δ h ) values. The solvents in the dispersed group occupied a certain region in a 3-dimensional space of three components. The surfactants with a lipophilic group equal to and longer than decyl, containing 9 methylene groups and 1 methyl group, contributed to the dispersion of nanotubes in water. The surfactants in the dispersed group had a lower limit in the dispersive component ( δ d ) of the Hansen parameter.