Water soluble multi-walled carbon nanotubes prepared via nitroxide-mediated radical polymerization

Nitroxide-mediated radical polymerizations of 4-vinylpyridine and sodium 4-styrenesulfonate were carried out on the surfaces of MWNT to afford poly( 4-vinylpyridine)-grafted MWNT (MWNT-P4VP) and poly( sodium 4-styrenesulfonate)-grafted MWNT (MWNT-PSS). The covalent bonding of polymers to the MWNT surface was confirmed by IR and TGA investigations. SEM, TEM and AFM investigations also showed a polymer-wrapped MWNT structure. Due to the presence of basic pyridine units in the structures, MWNT-P4VP exhibited good solubility in acidic aqueous solutions, but tended to aggregate in neutral or basic solutions. In comparison, MWNT-PSS could form stable dispersion solutions in aqueous solutions throughout the pH range from 1 to 14.