Dispersion of nanotubes

Carbon nanotubes are insoluble in water or other solvents but can be suspended or dispersed in liquids. As-received samples of CNTs being agglomerated into 

TABLE 6.2 Examples of composite polymer nanofibers filled with carbon nanotubes  

Polymer Filler Dispersant Solvent Fiber d (nm) Characterization Reference 

Silk (B. mori) SWCNT - Formic Acid 35 15-153 99 SEM, TEM, FTIR Ayntsede et al. (2006) 

The inclusion of CNTs in elecirospim nanofibers appear to increase the fraction of relatively thicker nanofibers in the collected mats (Mathew et al. 

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Dispersion of nanotubes in either a solvent or polymer solution by energetic agitation ... 

It should be pointed out that this method relies on the efficient dispersion of nanotubes in the relevant solvent. The choice of solvent is generally made based on the solubility of the polymer. However, pristine nanotubes usually cannot be well dispersed in most solvents. To get around this problem, Xia et al. (17) compared the dispersion of MWNT-graft-PU, MWNT-OH and raw MWNTs in 0.2% aqueous solution of sodium lauryl sulfate. The results showed that MWNT-graft-PU has a better dispersion stability compared to MWNTs and MWNT-OH. The incorporation of polyurethane-grafted carbon nanotubes had a better reinforcing effect compared to the raw carbon nanotubes. This should be attributed to the improved interfacial interaction between polyurethane matrix and carbon nanotubes. 

Chen et al. (67) reported the use of trifluoroacetic acid (TFA) as a cosolvent with tetrahydrofuran (THF) to improve dispersion and processability of the nanocomposites. They prepared MWCNT-PMMA composite films with varying CNT content by solvent casting method using 10 vol % TFA as a co-solvent with tetrahydrofuran (THF). SEM and optical microscopy revealed a good dispersion of nanotubes in solvent and PMMA. The composites showed low percolation... 

An example of the grafting from strategy is a treatment of SWNTs with sec-butyllithium that generates carbanions on the nanotube surface. These carbanions can serve as initiators of anionic polymerisation of styrene for in situ preparation of polystyrene-grafted tubes. This procedure allows the debundling of SWNTs and the production of a homogeneous dispersion of nanotubes in polystyrene solution. 

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