MWCNTs functionalization method

A novel chemical functionalization method for MWCNTs through an oxidation and silylation process was reported in 2002. Purified and oxidatively functionalized MWCNTs were reacted with 3-mercaptopropyltrimethoxysilane, the CNT surface being joined to the organosilane moieties through OH groups [143], Similarly, MWCNTs were functionalized by KMn04 oxidation under PTC catalysis and subsequent reaction with the hydrolysis product of 3-methacryloxypropyltri-methoxysilane (3-MPTS) (Scheme 1.13). The O-silyl-functionalized MWCNTs were characterized by FT-IR spectroscopy and energy-dispersive spectroscopy... 

Yang et al. developed a green chemical functionalization method using water and room temperature ionic liquids as the reaction media. By in situ ROP of E-caprolactone from hydroxyl-modified MWCNTs in ionic liquids of l-butyl-3-methylimidazolium tetrafluoroborate, MWCNT-g-PCL was obtained. When the reaction time was increased from 2 to 8 h, the PCL fraction improved from 30.6 to 62.7 wt%. ... 

Prato and coworkers succeeded in the 1,3-dipolar addition of azomethine ylides to CNTs [161], Treatment of pristine SWCNTs with an aldehyde and an N-substi-tuted glycine derivative resulted in the formation of substituted pyrrolidine moieties on the SWCNT surface (Scheme 1.22). The approach works effectively with both SWCNTs, prepared by several different methods, and MWCNTs. The pyrro-lidino-functionalized CNTs were sufficiently soluble in common organic solvents and were characterized by several spectroscopic techniques and TEM [161]. The... 

A number of studies on CNT-polymer composites have focused on improving the dispersion and load transfer efficiency in other words the compatibility between the CNTs and polymer matrix through covalent chemical functionalization of CNT surface (12,40). Many of the studies reported above have used acid-functionalized CNTs to fabricate MWCNT-PMMA composites with improved mechanical properties using different processing methods (24,25,27,62). Yang et. al (68) modified the acid functionalized CNTs with octadecylam-ine (ODA) to obtain ODA-functionalized CNTs. These CNTs were reinforced in a copolymer P(MMA-co-EMA) to form composites with improved dispersion and mechanical properties. 

In addition, Song et al. (76) used a one-step condensation synthesis method to prepare the PLA-MWCNTnanocomposites. For detailed experimental conditions, refer to Song et al. (76). The nanocomposites were prepared using pure and carboxylic-acid-functionalized MWCNTs. As with the other studies, the carboxylic-acid-functionalized MWCNTs dispersed better in PLA compared with non-functionalized MWCNTs. Overall, it can be inferred from the studies described in this section that the functionalization of MWCNTs is a very important step in the process of making a nanocomposite, as it will help to disperse the nanotubes uniformly, which will eventually create the superior properties of the resulting nanocomposite. In addition, among the currently available methods for functionalization, carboxylic-functionalization is the best for uniform dispersion. 

The most common method for the production of carbon nanotubes is hydrocarbon-based chemical vapor deposition (CVD) [97] and adaptations of the CVD process [98, 99], where the nanotubes are formed by the dissolution of elemental carbon into metal nanoclusters followed by precipitation into nanotubes [100]. The CVD method is used to produce multiwalled carbon nanotubes (MWCNTs) [101] and double-walled carbon nanotubes (DWCNTs) [102] as well as SWCNTs [103], The biomedical applications of CNTs have been made possible through surface functionalization of CNTs, which has led to drug and vaccine delivery applications [104,105],... 

In particular, Hong et al. [137] developed a so-called IL-assisted sonochemical method (ILASM) to fabricate CNT-based nanohybrids functionalized with various NPs. As shown in Fig. 15.10, MWCNTs and BmimBF were first mixed by mechanical grinding to produce BmimBF -wrapped MWCNTs (BmimBF -MWCNTs) due to the self-assembly of BmimBF through cation-7i and/or n-n stacking interactions. After that, the precursors of NPs were mixed with BmimBF -MWCNTs, resulting in the electrostatic interaction with BF anions on the surface of MWCNTs. Finally,... 

As described above, ILs for functionalization of CNTs are generally low molecular organic salts. Recently, Chen et al. [146] have employed PIL-functionalized MWCNTs to serve as the templates for fabrication of metal NP hybrids. In this method, the IL of 3-ethyl-l-vinylimidazolium tetrafluoroborate (EVimBF ) was in situ polymerized to form a poly(EVunBF ) shell on the surface of MWCNTs (Fig. 15.11). This not only makes MWCNTs uniform dispersion in water but also serves as the medium to stabilize and grow metal NPs. It is noted that metal NPs (e.g., Pt, PtRu) are uniformly dispersed on the supported surface of poly(EVimBF )/... 

Another Rh complex, [Rh(cod)(NH2(CH2)2NH(CH2)3Si(OCH3)3)], was immobilized onto air-oxidized ACs and MWCNTs and characterized by several methods N2 adsorption at 77 K, TPD, and XPS [80], The complex has a diamine functionalized with trimethoxysilane groups that reacted with hydroxyl groups formed within the supports by air oxidation, leading to very stable Si-O-C bonds. 

Kessler and co-workers synthesized norbornene-functionalized MWCNT (f-MWCNTs) (Scheme 5.9), and prepared bulk composites of f-MWCNTs/poly(dicyclopentadiene) (DCPD) by in situ ROMP of f-MWCNTs in the presence of DCPD and Grubbs catalyst for 2 h at 70 °C followed by 90 min at 170 °C. A cross-linked polymeric network was instantaneously formed, and the mechanical properties with low loadings (<0.5 wt%) of f-MWCNTs were studied. A remarkable increase in tensile toughness (925% increase over the neat polyDCPD) with only 0.4 wt% f-MWCNTs was found, and the corresponding elongation at break significantly increased from 5.75 to 51.8%. The DSC results demonstrated an increase in with the addition of f-MWCNTs.Using the same method, they subsequently... 

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