Self-assembly Nanostructured materials

J.H. Fendler, Self-Assembled Nanostructured Materials , Chem. Mater., 8, 1616... 

Characterization of Nanophase Materials, ed. Z.-L. Wang, Wiley-VCH Verlag GmbH, Weinheim, Germany, 2000 R135 L.-Q. Wang, G. J. Exarhos and J. Liu, Nuclear Magnetic Resonance. Characterization of Self-Assembled Nanostructural Materials , p.243... 

Wang, L.-Q., Exarhos, G.J., and Liu, J., Nuclear magnetic resonance — characterization of self-assembled nanostructured materials, Arfv. Mater, 11, 1331, 1999. 

Fendler, J.H., 1996. Self-assembled nanostructured materials. Chem. Mater. 8, 1616—1624. 

The examples discussed above illustrate the importance of block copolymer chain segment incompatibilities for the phase separation of bulk materials, combined with the ability to perform chemistry within specific nanoscale domains to impose permanence upon those self-assembled nanostructured morphologies. Each is limited, however, to crosslinking of internal domains within the solid-state assemblies in order to create discrete nanoscale objects. To advance the level of control over regioselective crosslinking and offer methodologies that allow for the production of additional unique nanostructured materials, the pre-assembled structures can be produced in solution (Figure 6.4), as isolated islands with reactivity allowed either internally or on the external... 

As an extension of Ghadiri s study, a 12-residue cyclic peptide, cyclo[(Gln-D-Ala-Glu-D-Ala),], afforded self-assembled nanotube materials having a uniform 13-A tailored pore diameter. Specifically sized tubular nanostructures with channel structures can expect various applications. ... 

Although much of the interest in biological nanostructures has focused on relatively complex functionality, cells and organisms themselves can be considered as a collection of self-assembled materials lipid bilayers, the extracellular matrix, tendon and connective tissue, skin, spider silk, cotton fiber, wood, and bone are all self-assembled biological materials, with an internal structure hierarchically ordered from the molecular to the macroscopic scale. 

Self-assembled nanostructures of biopolymers play an important role in nature. For example, extracellular branched polysaccharides decorate bacterial surfaces and therewith mediate cell adhesion [11], aggrecans (protein-polysaccharide complexes) control mechanical stresses in synovial joints [12], whereas neurofilaments (neuron-specific protein assemblies) support the elongated cell shape and participate in the maintenance of the axonal caliber [13]. It is believed that these biological functions rest on the ability of bioassemblies to provide adequate responses to variations in the local environment. Therefore, a better understanding of the physical mechanisms that govern conformational rearrangements in (bio)nanostructures, is of key importance, not only for colloid and material sciences, but also for cell biology. 

In this chapter we study the overview of the various naturally and artificially prepared self-assembled nanostructures which are currently very important and in demand in biomedical applications, for example, bone tissues, natural laminated composites present in sea shells, peptide chain arrays and their derivatives and cell membranes are naturally self-assembled materials. And Langmuir—Blodgett films, surfactant-directed nonporous materials, and molecularly directed films, composites, nanombes, nanofibrils, nanowires, spherical vesicles, and template-assisted growth are artificially prepared self-assembled nanostructures. Here we discuss in brief the synthesis of those nanostructures which exist in nature and are prepared artificially to fulfill certain requirements (Figure 2.1). 

Joshi et al., in Chapter 2, Self-assembled nanostructure preparation and applications, discuss about the fabrication of nanostructures from biological building blocks. The self-assembly of such nanostructures is a spontaneous process by which molecules/nanophase entities will materialize into organized aggregates. Many biomolecules, such as proteins and peptides, can interact and self-assemble into highly ordered supramolecular architectures including nanotubes, nanofibrils, nanowires, spherical vesicles, and hybrids, the subsequent improvement of their properties and their possible applications. 

Another interesting nanoblending strategy is to blend the donor polymer with a sacrificial-insulating-polymer-based template that forms self-assembled nanostructures and acts as a PDA [438]. The chosen PDA polymer is soluble in a solvent that don t at all dissolve donor, so that once the film (active layer) has been deposited, the PDA can be selectively dissolved leaving behind a porous nanostructured pool of donor material, that... 

Molecular self-assembly has been recognized as a powerful approach to designer soft materials with a nanoscopic structural precision [llj. However, self-assembled nanostructures are inherently subject to disruption with heating and exposure to solvents. The HBC nanotubes are not exceptional. Thus, for practical applications of the nanotubes, one has to consider postmodification of their nanostructures for covalent connection of the assembled HBC units. Because the inner and outer surfaces of the nanotubes are covered with TEG chains, incorporation of a polymerizable functionality into the TEG termini allows for the formation of surface polymerized nanotubes with an enhanced morphological stability. 

There are a number of experimental techniques used to fabricate self-assembled nanostructures from ZnO and other materials. These techniques include the following vapor-liquid-solid, metalorganic chemical vapor deposition, template-assisted, chemical reaction, molecular beam epitaxy, and reactive sputtering. In this section we provide a brief overview of these techniques. 

In the past decade, there are a number of promising self-assembled nanostructures with attractive properties and great potential for bone tissue engineering applications. These nanostructures of interest are in the forms of hydrogels or scaffolds consisting of nanotubular or nanofibrous materials fabricated by the aforementioned methods. Here, some typical self-assembled nanostractures for bone tissue engineering are inhoduced. 

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