Polymer Functionalized CNTs

It has been shown that CNTs seed the formation of oriented domains in a liquid crystalline polymer [82]. Using polarized light microscopy it was observed that the molecular alignment in large domains was homogeneous and controlled by the direction of the nanombes nucleus. CNT films have been generated by deposition 

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Alternatively, hydrophilic multi-hydroxyl poly(GMA-OH)-grafted MWCNTs could be converted into multicarboxyl polymer-functionalized CNTs by reaction with succinic anhydride and then used as templates to efficiently sequestrate metal ions such as Ag", Co ", Ni , Au , La and (Scheme 5.3), generating MWCNT-polymer/metal hybrid nanocomposites, nanowires or necklace-like nanostructures, depending on the grafted polymer content and the nature of the captured metals. The combination of SEM, TEM and energy dispersive spectroscopy (EDS) characterizations demonstrated the structure and elements of the hybrid nano-objects. 

Alternatively, hydrophilic multi-hydroxyl poly(GMA-OH)-grafted MWCNTs could be converted into multicarboxyl polymer-functionalized CNTs by reaction with succinic anhydride and then used as templates to... 

Table 7 List of polymer functionalized CNTs with different types and potential applications...

More recently, the Diels Alder cycloaddition was used as a single-step strategy for attaching diene-capped polymers onto CNTs sidewalls through grafting to methods (see Section 3.3.1.6 for more details). Examples include attachment of furfuryl-functionalized polystyrene [35] and cyclopentadienyl-functionalized polymethyl methacrylate [36]. 

Campidelli et al. have synthesized interesting linear and hyperbranched porphyrin polymers from CNTs via copper-catalyzed alkyne-azide cycloaddition (CuAAC) [122], Zinc porphyrin monomers containing an azide group and one or three alkyne groups were synthesized and chemically bound to alkyne functionalized SWCNTs via CuAAC. Depending upon the number of alkyne functionalities either linear (single alkyne) or dendrimer-like (triple alkyne) porphyrin polymers were produced (Fig. 5.9) [122],... 

Fig. 5.9 Covalent grafting of (a) linear polymer and (b) dendrimer-like hyperbranched polymer of azo-functional porphyrin groups from alkyne functionalized CNTs. Redrawn from [122].

A further approach to electrically wire redox enzymes by means of supramolecular structures that include CNTs as conductive elements involved the wrapping of CNTs with water-soluble polymers, for example, polyethylene imine or polyacrylic acid.54 The polymer coating enhanced the solubility of the CNTs in aqueous media, and facilitated the covalent linkage of the enzymes to the functionalized CNTs (Fig. 12.9c). The polyethylene imine-coated CNTs were covalently modified with electroactive ferrocene units, and the enzyme glucose oxidase (GOx) was covalently linked to the polymer coating. The ferrocene relay units were electrically contacted with the electrode by means of the CNTs, and the oxidized relay mediated the electron transfer from the enzyme-active center to the electrode, a process that activated the bioelectrocatalytic functions of GOx. Similar results were observed upon tethering the ferrocene units to polyacrylic acid-coated CNTs, and the covalent attachment of GOx to the modifying polymer. 

Many physical and chemical methods were used to functionalize CNTs for enhancing interactions between CNTs and polymer (11-12). Three general approaches have been adopted to modify the surface of CNTs to promote the interfacial interactions chemical,... 

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. 

Li et al. studied the quality and activity of a catal3Tic system used in carbon nanotube (CNT) growth process using pRS [11]. By localized Raman mapping, the variation of the active metallic species (Fe, Co) over the oxide surface (CaCOs) was quantified and analyzed. In this study, it was observed that the compositional variation in the active species over the oxide surface affected the yield and morphology of the CNT. Mayo et al. employed pRS to study the phase separation of polymer-functionalized single-walled carbon nanotubes (SWCNTs) within... 

Hitherto, there have also been some reports on the use of polymers containing ionic moieties except for polymeric ILs to functionalize CNTs [127-130]. For instance, Yoshida et al. [128] found that a slightly concentrated solution (20 g/L) of an ionic electrolyte of poly(pyridinium-l,4-diyl-iminocarbony 1-1,4-phenylene-methylene chloride) was most appropriate for stable dispersion of SWCNTs in water to form a SWCNT-containing gel. This ionic polymer, capable to act both as a dispersant and as a gelator, may contribute to the development of a novel hydrogel filled with CNTs for the biological, medical, and pharmaceutical applications. 

Fig. 6 Concept of a CNT functionalized with a plasma polymer coating, luminescent QDs, and loaded with anticancer drugs. The functionalized CNTs can be used as biomarkers and drug carriers...

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