Fibrous assemblies

Requirements for space suits are more complex and frequently involve garments that can circulate water and/or air through the fibrous assembly. Laminated and/or coated garments with specific requirements to pressure, radiation, temperature, and humidity are more stmcturaHy complex as a textile product relative to the types of fibers used in this aerospace fabrication. 

Elucidation of the three-dimensional structures of / -structural fibrous proteins has attracted the interest of scientists for more than 50 years. In the early days, the objects of these studies were predominandy the naturally occurring fibrous assemblies obtained from jS-silk and stretched mammalian... 

Kimura, Shirai and coworkers used two chiral dimeric porphyrins 95 and 96 to investigate their self-assembling behavior [162,163]. While incorporation into fibers made of the alkylamide derivatives of (fl,fl)-DACH, 95 formed stable well-resolved fibrous assemblies as visualized by transmission electron microscopy, the fluorescence of which was not quenched by external electron acceptors [162]. However, the induced CD was not detected indicating an inability of 95 to form chirally orientated aggregates under the applied conditions. In contrast, 96 was able to produce optically active inter molecular self-assemblies with an enhanced chiroptical response through the //-oxo bridging in an alkali solution, while intramolecular //-oxo dimer formation was excluded on the basis of steric reasons [163]. 

In another study, Ragunathan and Bhattacharya described the formation of gels and fibrous assemblies from L-serine-based amphiphiles in chloroform [74], In this instance also, chiral purity was essential for the observed gelation. The microscopic examinations of these fibers reveal the existence of braided fibers and helices in these aggregates. 

Fabric A kind of planar fibrous assembly. It allows the high degree of anisotropy characteristic of yam to be minimized, although not completely eliminated. 

The most stable and diversified porphyrin assemblies were received from protoporphyrin IX derivatives. It is characteristic that no crystal structure of an amphiphilic porphyrin is known. Crystal structures of esters have frequently been solved (see section 7.5), but protoporphyrin IX or similar porphyrins with a hydrophilic and a hydrophobic edge withstood all attempts at crystallization. This may be because they prefer to occur in curved fibrous assemblies. 

Figure 5.31 Fibrous assembly of a planar cyc o-peptide in water. ...

Figure 2.5.16 Typical examples of fibrous assemblies made of water-insoluble am-phiphiles. (a) The fluid type with a time-dependent shape, which cannot be isolated from water. (b,c) The solid type of constant shape, which can be isolated by lyophilization and stored for years in the dry state.

The exciton effects observed in absorption spectra of porphyrin monolayers are often different from those in stacked or lateral fibrous assemblies. One usually finds exclusively long-wavelength shifts of the Soret bands or no effect at all. Porphyrins either lie parallel to each other on the subphase (no shift) or are oriented in a slipped stack-of-cards configuration tilted by 10-20° angles against the subphase surfaces, which produce file observed 20-100 nm red shifts (Fig. 6.8.2). 

The so-called synthetic fibres, e.g. nylon, show their peculiarities of wetting in the presence of surfactants of various nature. Capillary wetting rates of nylon fibrous assemblies were studied in [172] using conductivity measurements as well as contact angle measurements by the Wilhelmy method. For sodium dodecyl sulphate and dodecyl trimethyl ammonium chloride a minimum wetting rate was observed near pH 4, which coincided with the isoelectric point of the nylon fibre. When the surface charge increased, the wetting rate increased. 

The wear of fine monofilaments when they slide over one another has important practical consequences in the deformation behaviour and the durability of fibrous assemblies. The frictional forces at the internal micro-contacts provide the local restraints which generate the cohesive response of the assembly. The flexibility of ropes and the tactile properties of fabrics are in many respects governed by these local forces. The frictional work produces surface damage and wear hence the macroscopic response of an assembly is modified by deformation. Ultimately the damage is sufficient to undermine the strength of the fibres and the assembly strength is weakened. 

D fibrous assemblies Properties, applications and modelling of three-dimensional textile structures... 

Based on the yam volume description, the fibrous stmcture of the yarn, or, more generally, the fibrous stmcture of the unit cell, is described as follows. Consider a point P and the fibres in the vicinity of this point. The fibrous assembly can be characterised by physical and mechanical parameters of the fibres near the point (which are not necessarily the same in all points of the fabric), fibre volume fraction Vf and direction /of them. If the point does not lie inside a yam, then Ff = 0 and/is not defined. For a point inside a yam, fibrous properties are easily calculated, providing that the fibrous stmcture of the yam/ply in the virgin state is known and its dependency of local compression of the yarn/ply, bending and twisting of the yam are given. Searching the cross-sections of the yams, cross-sections S, = S(si) and S,+i =5 (s,+i) (s is a... 

Wang, X., Fan, J., 2014. Use of aluminum-coated interlayers to develop a cold-protective fibrous assembly. J. Appl. Polym. Sci. 131 (9), 40205... 

In a broad sense, the source of vegetable fibers, as the name suggests, is the rich plant life on planet Earth. In a narrower sense, different fibers come from different parts of different plants. In general, fibrous assemblies of various types are the structural components of plant life. The load-deformation characteristics of these assemblies are determined by the functional role played by the plant part in the total architecture of the plant, and the soil-climate environment in which it grows. 

Fibrous assemblies like nanofibers, nanopipes, and nanotubes may have applications in micro-/ nanofiuidic systems. Vertically aligned carbon... 

A. Zabetakis, A. Stamelaki and T. Teloniati in Proceedings of a Conference on Fibrous Assemblies at the Design and Engineering Interface - INTERDEC, 2003, Edinburgh, UK. 

Hu J. (2008) 3D fibrous assemblies, properties applications and modelling of three dimensional textile structures , WR textiles series no. 74, p. 115. Cambridge Woodhead Ihiblishing. 

In their preliminary communication, Newkome and co-workers reported that their arborols formed a gel in aqueous solution. They commented in particular on the low molecular weight (1052) compared to a typical gel . Using transmission electron microscopy (TEM) they illustrated that a fibrous assembly was formed, and noted that a lwt/vol% solution exhibited no steady-state flow— analogous to a traditional crosslinked polymer gel. The authors suggested that the polar head groups became crosslinked via hydro-... 

Fig. 24 Two-component approach to fibrous assemblies in which the initial complex is assembled as a consequence of coordination interactions between dendritic pyrazole ligands and metal ions. These complexes go on to assemble into columnar fibrous superstructures that precipitate from solution...

Multiple interactions between dendritic branches enable the formation of strong fibrous assemblies as a consequence of multivalency (multiple non-covalent interactions are stronger than isolated ones). 

The dendritic branching often forms the periphery of the fibrous assembly, and as such can be considered to play a role in the encapsulation of the centre of the fibre from the bulk solvent. This may lead to modification of, for example, electronic and optical properties within the assembled gel state. 

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