Covalent sidewall

Covalent sidewall nanotube functionalization, 17 55 Cover crops, allelopathic, 13 352-353 Covering power, 9 773 Coverstock, use of nonwoven goods in, 17 517... 

Dipolar cycloaddition of azomethine ylides, generated by the condensation of an a-amino acid and an aldehyde, is an efficient method for covalent sidewall functionalisation and has been successfully used to solubilise CNTs in most organic solvents (Tasis et al., 2003 Holzinger et al., 2003). This particular technique has also been utilised to obtain the first example of a bioactive peptide covalently linked to CNTs by the prospect for the potential applications in immunology (Bianco and Prato, 2003 Pantarotto et al., 2003a, b Bianco et al., 2005b). 

The effect of (presumably covalent) sidewall functionalization on the conductivity of SWCNTs was also reported recently in a theoretical study [61]. The authors found it important (and possible ) to distinguish between monovalent and divalent sidewall additions, the latter with or without sidewall opening. They concluded that the conductance of the monovalently functionalized tube decreases rapidly with the increasing addend concentration, and the nanotube loses its metallic-ity around 25% of modification, whereas for the divalent case, the CNTs remain substantially conductive. ... 

There are two types of surface modifications for CNTs noncovalent interactions (Figure 6.54) and covalent sidewall (Figure 6.55) or defect-sitet (Figure 6.56) functionalization.Both methods, as well as physical techniques such as sonica-tion, are successful in separating individual SWNTs from bundles - a process known as exfoliation. In general, it is most desirable to incorporate isolated SWNTs in a composite rather than bundles, since the latter features poor intertube interactions resulting in a lower overall strength - especially at low CNT concentrations. 

Figure 1.6 Several possible functionalization mechanisms for SWCNTs." (A) defect-group functionalization, (B) covalent sidewall functionalization, (C) noncovalent exohedral functionalization with surfactants, (D) noncova-lent exohedral functionalization with polymers, (E) endohedral functionalization with fullerene (C6o)-...

Wu X. F. and Shi G. Q., Synthesis of a carboxyl-containing conducting oligomer and non-covalent sidewall functionalization of single-walled carbon nanotubes,/ Mater. Chem., 2005,15,1833-1837. 

Figure 12.2 Several possible functionalization with polymers, (c) defect-group mechanisms for CNTs. (a) endohedral functionalization, (d) covalent sidewall...

The covalent sidewall functionalization of SWCNTs has been conducted by a number of researchers. Highly reactive addends are needed for the sidewall functionalization reactions. The outer surface of SWCNTs is more active than the inner surface. There are several methods for covalent side-wall functionalization of SWCNTs, including fluorination, diazonium, radical chemistry, nitrene, azomethine ylides and dichlorocarbene, as shown in Table 4.2. The added functional groups include aryl, fluorine, pyrrolidine, aziridine and cyclopropane. Multiple analytical techniques can be used to... 

We have found that SWNTs can be functionalized by electrochemical reduction of aryl diazonium salts in their presence. Using this method, about 1 in 20 carbon atoms of the nanotube framework are reacted. We have also found that the SWNTs can be functionalized by direct treatment with aryl diazonium tetrafluoroborate salts in solution, or by in situ generation of the diazonium moiety using an alkyl nitrite reagent. These functional groups give us handles with which we can direct further, more selective derivatization (Figure 5.2) and we recently reviewed the area of covalent sidewall derivatization of SWNTs. 

Zhao, J., Park, H., Han, J. et al. 2004. Electronic properties of carbon nanotubes with covalent sidewall functionalization. J. Phys. Chem. B 108 4227-4230. 

The basic route of CP-CNT composite offers two paths, either the polymer functionalizes the CNTs or the CPs are doped with CNTs, i.e., a charge transfer occurs between the two constituents [13]. The main functionalization possibilities of CNTs are (A) generation and functionalization of defect sites at the tube ends and side walls by oxidation and subsequent conversion into derivatives (B) covalent sidewall functionalization using addition reactions and subsequent... 

Chemical functionalization is based on the covalent bond of functional groups onto carbon form of CNTs. It can be performed at the terminal ends of the CNTs or at their sidewalls [45]. Direct covalent sidewall functionalization is associated with a change on hybridization from sp to sp and simultaneously, a loss of TT-conJimction system of graphene layer (Figure 7.4a). This process can be made by reaction with some molecules... 

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