High-shear treatment of single-walled carbon nanotubesuperacid solutions as a pre-processing technique for the assembly of fibres and films
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Single-walled carbon nanotubes (SWNTs) show great promise for use in a wide range of applications. One of the most promising avenues for attaining these applications is the dispersion of SWNTs at high concentrations in superacids, and their processing into macroscopic articles such as fibres or films. Fibres spun from SWNT/superacid dispersions indicate that the morphology of the starting SWNT material is reflected in the final morphology of the as-spun fibre. Here, we describe a method (termed disentanglement) of dispersing SWNTs in superacids and treating them using a high-shear, rotor/stator homogenizer, followed by coagulation to recover the solid SWNT material for use in fibre spinning. Several lines of experimental evidence (rheology and optical microscopy of the SWNTs in solution, scanning electron microscopy (SEM) of the coagulated material, and SEM of fibres spun from the coagulated material) show that this treatment radically improves the degree of alignment in the SWNTs' morphology, which in turn improves the dispersibility and processability. Raman microscopy and thermogravimetric analysis (TGA) before and after homogenization show that the treatment does not damage the SWNTs. Although this technique is particularly useful as a pre-processing step for fibre spinning of neat SWNT fibres, it is also useful for neat SWNT films, SWNT/polymer composites, and surfactant- or polymer-stabilized SWNT dispersions.
