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Fabrication of pH- or temperature-responsive single wall carbon nanotubes via a graft from photopolymerization



An ultraviolet light initiated “graft from” polymerization method to fabricate polymer-functionalized single wall carbon nanotubes (SWNTs) with pendant pH- and temperature-responsive polymer chains is utilized. The attached polymer chains, formed from methacrylic acid and poly(ethylene glycol) methyl ether methacrylate monomers, are well established for its pH-responsive swelling/deswelling behavior. This special property was utilized here to control the aqueous dispersibility of the carbon nanotubes. Furthermore, poly(N-isopropylacrylamide), a temperature-responsive polymer, was utilized in the fabrication of SWNTs whose dispersibility was dependent on solution temperature. The morphology of the polymer-functionalized carbon nanotubes was characterized by scanning electron microscopy (SEM) before and after functionalization. Environmental SEM was used to further characterize the morphology of the functionalized SWNTs. In addition, covalent bonding of the polymer to the carbon nanotube surface was established using Raman and Fourier transform infrared spectroscopic techniques. The physical and chemical properties of the functionalized nanotubes were further characterized by energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2980–2986, 2012