Liquid-crystalline polymers, ease

More simple solutions are found for special cases. Already in 1933 Kratky [248] has presented a method for the ease in which the observed orientation distribution has its maximum on the equator. In 1979 the problem treated by Kratky has been revisited by Leadbetter and Norris [254]. They present a different solution which is frequently applied in studies of liquid-crystalline polymers. Burger and Ruland [255] pinpoint the error in the deduction of Leadbetter and... 

The unique molecular packing of rod-like chains in liquid crystalline polymers (LCP) closely resembles the extended chain structure of highly oriented flexible chain polymers, suggesting that these materials are good candidates for barrier applications. Thermotropic LCP s, first developed in the early 1970 s, have been the object of much interest because of their excellent mechanical properties and ease of product fabrication. Preliminary observations have shown that a commercially available wholly aromatic thermotropic copolyester has gas permeability coefficients that are lower than those of polyacrylonitrile (4.). These results raise some fundamental questions as to the nature of the mechanism for transport of small molecules through a matrix of ordered rigid rod-like chains. 

The ease of forming the smectic mesophase by this class of side-group type liquid crystalline polymers has rendered a great possibility in synthesizing polymeric chiral smectic materials useful in non-linear optics, transducers, pyroelectric detectors and display devices (Chapter 6). The first polymer forming a chiral smectic-C phase was synthesized by Shibaev et al. (1984). It has a polymethacrylate main chain, a long polymethylene spacer, and a mesogenic unit attached at the end with a chiral moiety (polymer (3.60)). Since then, a lot of polymers with chiral mesophases have been synthesized and studied (Le Barny and Dubois, 1989). 

Liquid crystals (or plastic crystals as they are sometimes called) are low molecular mass materials that show molecular alignment in one direction but not three-dimensional crystalline order. During the last 20 years, liquid crystalline polymers have been developed where the polymer chains are so straight and rigid that small regions of almost uniform orientation (domains) separated by distinet boundaries are produeed. In the ease where these domains occur in solution, polymers are... 

The liquid crystalline polymers find more applications in smart composite materials. The popularity of LCP is growing very fast because of its ease of processing. It also helps other engineering thermoplastics to process very smoothly even at higher temperature. This happens mainly due to the fibril formations of LCP in presence of other polymer matrix. From the above mentioned areas of LCPs, it is clear that new results arise due to the incorporatiOTi of polymeric LCP in to the other polymer systems. It is very much clear that in future it will create its own vast area in the field of polymer blends and nanocomposites. 

Liquid crystalline polymers (LCP) have excellent mechanical properties in addition to dimensional and chemical stability. These materials form in-situ composites during processing under elongational flow and are starting to replace traditional fiber reinforced systems [1, 2]. Combined with their ease of processing, LCPs are ideal for applications in aerospace, automobile, marine and other markets requiring high performance composites [2, 3]. 

Liquid crystal polymers (LCP) are a recent arrival on the plastics materials scene. They have outstanding dimensional stability, high strength, stiffness, toughness and chemical resistance all combined with ease of processing. LCPs are based on thermoplastic aromatic polyesters and they have a highly ordered structure even in the molten state. When these materials are subjected to stress the molecular chains slide over one another but the ordered structure is retained. It is the retention of the highly crystalline structure which imparts the exceptional properties to LCPs. 

In conclusion then, we have synthesized a series of extended-chain, aromatic polyazomethlnes under on-degradatlve conditions. Fusible, tractable polymers were obtained by use of unsymmetrlcally placed substituents, copolymerization, and/or limited proportions of flexible chain units. Many of the polymers yield liquid crystalline melts which were spun Into oriented, high tenacity, high modulus fibers. The fibers were further strengthened by heat treatment. The ease of preparation of the aromatic polyazomethlnes and the outstanding tenacity and modulus range of the fibers make these products excellent candidates for use as reinforcing fibers In resins and rubber. 

---