Control of SWNT dispersion by block copolymers with a side-chain polarity modifier

The dispersion of single-walled carbon nanotubes (SWNTs) in a non-polar solvent is controlled with a series of polystyrene-b/ocfe-polybutadiene-b/ocfe- polystyrene (PSBS) block copolymers that contain cholesteryl chloroformate (CC) in side-chains. Esterification of CC with the partially hydroxylated polybutadiene (PB) blocks allows one to tune the polarity of the block copolymers, which decreases with the amount of CC attached. An excellent dispersion of weak polar SWNTs is observed with PSBS that contains a partially hydroxylated PB block. The dispersion is then significantly deteriorated when the amount of non-polar CC moieties increases in the block copolymers. A good dispersion is achieved with a polymer that gives rise to strong SWNT-polymer interactions, which ensures contact of the polymer molecules with the nanotube surface, rather than a good solubility of the polymer dispersant in solvent. The stability of the SWNTs in solution arises from unique needle-like nanowires of the block copolymer aligned perpendicular to the nanotube axis.