(551e) Aligned Carbon Nanotube Films by Lyophilization

We have developed a novel method for assembling oxidized single-walled carbon nanotubes (SWNTs) into anisotropic films using lyophilization. The initial and final SWNT surface chemistry was characterized using attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The effect of oxidation treatment time was studied under scanning electron microscopy and Raman spectroscopy revealing the evolution into an ordered structure arising from an increased degree of oxidation and increased mobility by length shortening of the tubes. In addition, the use of HNO₃ and H₂SO₄ for nanotube oxidation is particularly attractive since unpurified carbon nanotubes can potentially be purified and assembled in one process. The resultant carboxylic acid functional groups provide a plethora of possibilities for further functionalization routes. Finally, lyophilization studies were also performed from surfactant stabilized dispersions using both ionic and steric surfactants. Potential film applications include layered nanocomposites, specifically those where anisotropic property enhancement is desired.