Liquid crystalline state fibers from

Two approaches to the attainment of the oriented states of polymer solutions and melts can be distinguished. The first one consists in the orientational crystallization of flexible-chain polymers based on the fixation by subsequent crystallization of the chains obtained as a result of melt extension. This procedure ensures the formation of a highly oriented supramolecular structure in the crystallized material. The second approach is based on the use of solutions of rigid-chain polymers in which the transition to the liquid crystalline state occurs, due to a high anisometry of the macromolecules. This state is characterized by high one-dimensional chain orientation and, as a result, by the anisotropy of the main physical properties of the material. Only slight extensions are required to obtain highly oriented films and fibers from such solutions. 

Polyarylates prepared from cyclohexyl-HQ (Ch-HQ) and PEC (Ch-HQ/PEC) did not show liquid crystallinity due to the more bulky substituent on the HQ unit compared to those on f Bu-HQ and Ph-HQ. As-spun fibers of Ch-HQ/PEC exhibited lower moduli than those of fBu-HQ/PEC and Ph-HQ/PEC. Therefore, in order to obtain high-modulus as-spun fibers, the stability of the liquid crystalline state (7j — 7j,) is an influential factor, as shown in Table 19.1. 

Liquid crystalline compounds are remarkable because of their ability to show spontaneous anisotropy and readily induced orientation in the liquid crystalline state. When polymers are processed in the liquid crystalline state, this anisotropy may be maintained in the solid state and can readily lead to the formation of materials of great strength in the direction of orientation. A particularly important example of the use of this property for polymers is in the formation of fibers from aromatic polyamides which are spun from shear oriented liquid crystalline solutions Solutions of poly(benzyl glutamate) also show characteristics of liquid crystalline mesophases, and both of these types of polymers are examples of the lyotropic solution behaviour of rigid rod polymers which was predicted by Flory... 

The spinning of fibers from the nematic liquid crystalline state may at least in principle result in fibrous structures exhibiting nearly perfect molecular orientation. Imperfections such as chain ends should then be randomly distributed. A large amount of work has been performed in recent years on semicommercialized LCP s and also on more research based LCP s (13-161. 

You can indeed make a super-strong fiber, even stronger than steel, from a polymer, but the polymer must be converted into a special liquid-crystalline state which is really a variety of the viscous state. If you think of a viscous polymer as of some polymeric liquid , then a liquid-crystalline polymer can be regarded as an anisotropic polymeric liquid . The anisotropy occurs spontaneously, with no help from outside (such as orientating fields, mechanical stresses or whatever). 

In order to obtain high modulus as-spun fibers,the stability of liquid crystalline state and the rigidity of polymer chain are influential factors.Therefore,we expected that the polyarylates derived from BB would show higher modulus than those from PEC or Cl-PEC.As-spun fiber of the polyarylate derived from Cl-HQ and BB modified with TA(Cl-HQ/BB/TA) showed the modulus of 95 GPa(m/n= 7/3) which was higher modulus compared with that of Me-HQ/Cl-PEC. However,as-spun fiber of Cl-HQ/BB/TA showed the modulus of only 11 GPa(m/n=8/2) in spite of the rigid chemical structure,and this is referred to the decreased elongational flow orientation as shown in Fig. 4(3). 

One of the best examples of a man-made fiber spun from a lyotropic liquid crystalline polymer is poly (p-phenylene terephthalamide) (PPTA, Kevlar ), which was commercialized by DuPont in 1972. The Kevlar fibers possess impressive mechanical properties. Some polysaccharides are able to form lyotropic liquid crystalline states. High performance fibers from liquid crystalline spinning of cellulose mesophases have gained much interest, and a considerable amoimt of work has been done on spinning cellulose, with some of the products commercialized. This will be further discussed below. 

Since organogelators are in crystalline or lyotropic aggregate states in a gel. the nature of their intermolecular interactions becomes a factor of paramount importance in determining the nature and the intensity of emitted radiation from a gelled sample. Molecular proximity opens possible reactive channels for the excited states that are not available in dispersed solutions. For example, it has been shown that CAB dimerizes in its neat solid, liquid-crystalline, and gelled (fiber) states when exposed to UV radiation [47,48]. (See Structure I.) In dilute isotropic solutions, no photoreaction is observed because the time required for an... 

Among the di-substituted alkylnaphthalene derivatives, 2,6-dimethylnaphtha-lene is important as it can also be used as a base material for the production of naphthalene-2,6-dicarboxylic acid. It is produced from the coal tar fraction boiling between 255 and 265 °C, by redistillation and crystallization. Oxidation of 2,6-dimethylnaphthalene is carried out in the same way as the oxidation of p-xylene, in the liquid phase with Co/Br-catalysts. Naphthalene-2,6-dicarboxylic acid, or its acid chloride and ester, are components in the production of high-value polymer films and fibers, with high temperature resistance these polymers can display liquid-crystalline character in the molten state. 

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