Debundling

Giordani S, Bergin SD, Nicolosi V, Lebedkin S, Kappes MM, Blau WJ, Coleman JN (2006) Debundling of single-walled nanotubes by dilution Observation of large populations of individual nanotubes in amide solvent dispersions. J. Phys. Chem. B 110 15708-15718. 

Ikeda A, Hayashi K, Konishi T, Kikuchi J (2004) Solubilization and debundling of purified single-walled carbon nanotubes using solubilizing agents in an aqueous solution by high-speed vibration milling technique. Chem. Commun. 1334-1335. 

Chemical modification, through addition of functional groups that disrupt the sp2 pattern or isolation of individual tubes by noncovalent wrapping of various compounds, comes to our aid as one of the simplest and most effective ways to debundle the aggregates, thus improving solubility and processability. 

As for the covalent type, modification of CNTs by this approach has as its first goal to lead to debundling of the tubes, thus increasing their solubility and facilitating their manipulation. However, while the covalent method destroys the extended aromatic framework, noncovalent interactions preserve the original regular carbon network. This is important in those applications requiring use of the nanotubes without alteration of their electronic and optical properties, a process that normally occurs when the aromatic periodicity is disrupted. 

Functionalization of carbon nanotubes becomes essential for multiple reasons. Firstly, chemical modification can allow debundling and therefore solubilization of the tubes, which is an important feature for their processability. Secondly, insertion of functional groups enables attachment of more complex moieties that find applications in several fields. 

One of the potential ways how to improve CNT dispersion in polymer matrixes is in-situ polymerization of monomers in presence of nanotubes. Monomers have very small shear viscosity in orders of about lO -lO"3 Pa.s, compared to relatively high viscosity of polymer melts, 103-106 Pa.s. This low viscosity helps to better impregnation and wetting of CNT material, which leads to more efficient dispersion and debundling of the nanotubes aggregates, especially when ultrasound is used as a dispersing agent. 

PA6 phase of the blends. This approach was further extended to PA6 based ternary and quaternary blends in an attempt to find the applicability of this strategy. Raman spectroscopy and transmission electron microscopy (TEM) have been performed to get more insights into the role of these modifiers in debundling the MWNTs. AC electrical conductivity measurements have been carried out to assess the state of dispersion of MWNTs in the blends. Further, the phase microstructures and the localization of MWNTs in the blends have been investigated using scanning electron microscopy (SEM). 

The flow chart of a typical purification and debundling procedure of carbon nanotubes is shown in Figure 3.37. It is evident there that only combining several of the methods presented here can lead to success. 

The mechanical properties of isolated SWNT in particular (Section 3.4.3) turn them into nothing short of a fiUer par excellence for polymer composites. However, the embedding of individual, completely debundled carbon nanotubes in the polymer matrix still poses large problems. This is why, for the time being, the materials produced do by far not reach the envisaged improvement of characteristics Bundles of nanotubes feature much worse mechanical properties as there... 

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. 

Billups and co-workers prepared PMMA-grafted SWCNTs by in situ anionic polymerization in the presence of debundled nanotube salts serving as... 

---