Dispersion of single-walled carbon nanotubes in water with polyphosphazene polyelectrolyte

Abstract

A polyphosphazene polyelectrolyte was prepared as a dispersing agent of SWNTs in water. Poly(organophosphazene) was prepared by sequential treatment of poly(dichlorophosphazene) with sodium 4-phenylphenoxide, sodium phenoxide, and sodium trifluoroethoxide in THF. Their substitution percentages were 60, 24, and 16%, respectively. A water-soluble polyphosphazene polyelectrolyte was obtained by sulfonation of aromatic rings by using fuming sulfuric acid. SWNTs were dispersed in an aqueous polymer solution by sonication to give a black homogeneous dispersion. The supramolecular association between the nanotube and the sulfonated polyphosphazene was investigated by TEM, SEM, and AFM. The SEM image of the cleaved edge of the bucky paper, obtained by filtration of the dispersion of SWNTs, showed the nanotubes uniformly wrapped with the polymer. Their diameters were about 30 nm, suggesting small bundles of SWNTs rather than individual SWNTs. Individual SWNTs coated with the polymer were also observed by TEM. The total diameter of the coated tube was about 10 nm and a polymer layer thickness was lager than 4 nm.