PEGylation of double-walled carbon nanotubes for increasing their solubility in water
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Polyethylene glycol (PEG) functionalized double-walled carbon nanotubes (DWNTs) have been synthesized by a [2 + 1] cycloaddition reaction and characterized by transmission electron microscopy, atomic force microscopy, Raman spectroscopy, thermal gravimetric analysis, and UV-visible spectroscopy. Functionalization affords a large increase in the aqueous solubility of DWNTs. The saturated concentrations of DWNTs functionalized with diazido-terminated PEG800 (with a molecular weight of 800) and azido-terminated PEG750 monomethylether (with a molecular weight of 750) are very similar—0.36 and 0.37 mg/mL (DWNTs equivalent concentration), respectively.