Polymers nanotube wrapping

Fig. 1.14 (A) Single-wall carbon nanotubes wrapped by glyco-conjugate polymer with bioactive sugars. (B) Modification of carboxyl-functionalized single-walled carbon nanotubes with biocompatible, water-soluble phosphorylcholine and sugar-based polymers. (A) adapted from [195] with permission from Elsevier, and (B) from [35] reproduced by permission of Wiley-VCH.

H. Dohi, S. Kikuchi, S. Kuwahara, T. Sugai, and H. Shinohara, Synthesis and spectroscopic characterization of single-wall carbon nanotubes wrapped by gly-coconjugate polymer with bioactive sugars, Chem. Phys. Lett., 428 (2006) 98-101. 

F. Zhang, H. Zhang, Z. Zhang, Z. Chen and Q. Xu, Modification of carbon nanotubes water-soluble polymers nanocrystal wrapping to periodic patterning with assistance of supercritical CO, Macromolecules, 41 4519-4523,2008. 

In recent years, some progress has been made in obtaining well-dispersed polymer-nanotube composites using a variety of approaches. These include in situ polymerization, the addition of surfactants and compatibilizers, ° polymer wrapping, and functionalizing the ends and sidewalls of the tubes. The widespread implementation of these methods, however, is limited by the absence of a quantitative understanding of the thermodynamics associated with the breakup of the nanotube bundles and accommodation of the discrete tubes within the polymer matrix. 

Since the discovery of SWNTs, they have been expected to become the building blocks of the next generation of functional nanomaterials. However, their strong cohesive property and poor solubility have restricted the use of SWNTs for fundamental and applied research fields. One method to overcome these problems is to make the SWNTs more soluble by wrapping them with polymers [31]. At the same time, the fabrication of high-performance carbon nanotube (CNT)-based composites is driven by the ability to create anisotropy at the molecular level to obtain appropriate functions. 

R. E. (2001) Reversible water-solubilization of single-walled carbon nanotubes by polymer wrapping. Chem, Phys, Lett, 342, 265-271. 

Yonemura, H., Yamamoto, Y, Yamada, S., Fujiwara, Y. and Tanimoto, Y. (2008) Magnetic orientation of single-walled carbon nanotubes or their composites using polymer wrapping. Sci. Technol. Adv. Mater., 9 (024213), 1-6. 

As with fullerenes, carbon nanotubes are also hydrophobic and must be made soluble for suspension in aqueous media. Nanotubes are commonly functionalized to make them water soluble although they can also be non-covalently wrapped with polymers, polysaccharides, surfactants, and DNA to aid in solubilization (Casey et al., 2005 Kam et al., 2005 Sinani et al., 2005 Torti et al., 2007). Functionalization usually begins by formation of carboxylic acid groups on the exterior of the nanotubes by oxidative treatments such as sonication in acids, followed by secondary chemical reactions to attach functional molecules to the carboxyl groups. For example, polyethylene glycol has been attached to SWNT to aid in solubility (Zhao et al., 2005). DNA has also been added onto SWNT for efficient delivery into cells (Kam et al., 2005). 

Nanocarbon hybrids have recently been introduced as a new class of multifunctional composite materials [18]. In these hybrids, the nanocarbon is coated by a polymer or by the inorganic material in the form of a thin amorphous, polycrystalline or single-crystalline film. The close proximity and similar size domain/volume fraction of the two phases within a nanocarbon hybrid introduce the interface as a powerful new parameter. Interfacial processes such as charge and energy transfer create synergistic effects that improve the properties of the individual components and even create new properties [19]. We recently developed a simple dry wrapping method to fabricate a special class of nanocarbon hybrid, W03 /carbon nanotube (CNT) coaxial cable structure (Fig. 17.2), in which W03 layers act as an electrochromic component while aligned... 

Noncovalent approaches can usually preserve the structures and properties of carbon nanotubes after functionalization17 (though not necessarily the near-infrared absorption characteristics due to well-established doping effects), thus are equally important to the biocompatibilization and bioapplications of nanotubes.15 Among commonly employed noncovalent schemes are surfactant dispersion,18 tt-tt stacking with aromatic compounds,19 and polymer wrapping.20... 

Noncovalent functional strategies to modify the outer surface of CNTs in order to preserve the sp2 network of carbon nanotubes are attractive and represent an effective alternative for sidewall functionalization. Some molecules, including small gas molecules [195], anthracene derivatives [196-198] and polymer molecules [118, 199], have been found liable to absorb to or wrap around CNTs. Nanotubes can be transferred to the aqueous phase through noncovalent functionalization of surface-active molecules such as SDS or benzylalkonium chloride for purification [200-202]. With the surfactant Triton X-100 [203], the surfaces of the CNTs were changed from hydrophobic to hydrophilic, thus allowing the hydrophilic surface of the conjugate to interact with the hydrophilic surface of biliverdin reductase to create a water-soluble complex of the immobilized enzyme [203]. 

The wrapping of polymer ropes around MWCNTs occurs in a well-ordered periodic fashion [237]. The authors suggested that the polymer intercalated between the nanotubes, leading to unraveling of ropes and causing a decrease in interactions between the individual CNTs. Moreover, Raman and absorption studies suggested that the polymer interacts preferentially with CNTs of specific diameters or a specific range of diameters [238]. 

The nanotubes have been wrapped with hydrophilic polymer layers, which act as assembly templates for common phospholipids and provide a support surface to maintain the bilayer structure.37 The bilayers were stable enough to survive multiple bleaching-recovery cycles. 

A number of nanotube surface modification approaches have been reported in the recent years. Non-covalent surface modifications aim to physically wrap polymer chains around the nanotubes or adsorb various surfactant molecules on the surface of nanotubes. Thus,... 

Dai, " and coworkers, and others.Nanotubes have been known to adsorb gas molecules (H2, N2, O2, and H2O) through adsorption. " Some polymers have strong noncovalent interactions with the carbon nanotubes. High molecular weight ionic or electron-rich polymers coat or wrap themselves around the carbon nanotubes. Polyvinyl pyrrolidone and polystyrene sulfonate and their copolymers, polyvinyl sulfate, and poly (metaphenylene vinylene) have been used to wrap around The wrapping... 

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