Synthesis of water-soluble PEGylated single-walled carbon nanotubes

Carbon nanotube salts prepared by treating single-wall carbon nanotubes (SWNTs) with lithium in liquid ammonia react with omega-bromocarboxylic acids to yield sidewall-derivatized SWNTs. These can be reacted with amine-terminated polyethyleneglycol (PEG) chains (e.g., H2N-mPEG-OMe, MW = 5000 Da) to yield water-soluble PEGylated SWNTs. Short nanotubes (average length similar to 60 nm) functionalized by PEGylation of the carboxylic acid groups at the end of the nanotubes exhibit greater solubility in water than the longer (average length similar to 300 nm) sidewall-PEGylated pristine nanotubes.