Liquid crystal polymer structure-property relationship

The relationship between chemical structures and their physical performance is one of the central topics of polymer physics. lUPAC has recommended a whole set of names to describe the detailed chemical structures of polymer chains and their derivatives. However, in our daily communication, people prefer to use the popular names of polymers reflecting their characteristic physical performances, such as high-density polyethylene (HOPE), foamed polystyrene, thermoplastic elastomers, liquid crystal polymers, conductive polymers, and polyelectrolyte. Such terminology allows us to comprehend quickly the basic characteristics of chemical structures responsible for their specific physical properties. 

Kim J Y and Kim S H, (2006), Structure and property relationship of thermotropic liquid crystal polymer and polyester composite fibers . Journal of Applied Polymer Science, 99,2211-2219. 

La Mantia FP, Sain M, Valenza A, Pad M, Magagnini PL (1990a) Relationships between mechanieal properties and structure for blends of nylon 6 with a liquid crystal polymer. Eur Polym J 26 323... 

The degree of crystallinity has an important effect upon the physical properties of a polymer. If a polymer melt is allowed to crystallize the crystallinity clearly increases as the spherulites form and grow and so the analysis of the crystallization of a polymer is of profound importance in understanding structure/property relationships in polymers. The nucle-ation and growth of spherulites in a polymer liquid can be readily analysed if a series of assumptions is made. 

Meng YZ, Tjong SC, Hay AS. Morphology, rheological and thermal properties of the melt blends of poly(phthalazinone ether ketone sulfone) with liquid crystalline copolyester. Polymer 1998 39 1845-50. Kim JY, Kang SW, Kim SH. Thermotropic liquid crystal polymer reinforced poly(butylene terephthalate) composites to improve heat distortion temperature and mechanical properties. Fibers Polym 2006 7 358-66. Kim JY, Kim SH. Structure and property relationship of thermotropic liquid crystal polymer and polyester composite fibers. J Appl Polym Sci 2006 99 2211-9. 

For synthetic macromolecules, NMR has been the most powerful method to characterize and to investigate the relationship between the structure and the physical properties at the atomic level. In the field of synthetic macromolecules, NMR is used not only as the routine analytical method but also as the method that has infinite possibility. In this chapter, NMR applications are reviewed by categorizing primary structure, liquid crystal, characterization of the synthetic macromolecules, dynamics of the synthetic macromolecules, gels and crosslinking macromolecules and polymer blends and diffusion of the synthetic macromolecules. 

An interesting area, which involves chiral liquid crystal properties, is that of temperature sensors, used, for example, in the diagnosis of skin cancer, as well as in peripheral blood circulation problems. Another application in the medical field is represented by nematic elastomer films or fibers of liquid crystalline polymers with mesogene in the side chain, that can be used in the manufacture of muscle prosthesis [28]. To optimize their performance for different applications, the current knowledge on the relationship between the structure and properties of liquid crystals should be extended. In addition to further development of liquid crystals and their applications, the liquid crystal theories represent a sound basis for other areas of interest. For example, liquid crystals can be used as model compounds for the study of molecular interactions and of their effects on self-organization in supramolecular chemistry. 

The recent work of Krigbaum on main-chain and Finkelmann, Ringsdorf, etc., on side-chain polymer liquid crystals has generated much interest in the potential of these systems for use in electro-optic devices. The combination of polymeric specific and monomeric liquid crystal specific properties leads to an interesting range of potential materials for new display devices. The majority of the research over the last five years has concentrated on synthesis and the establishment of the basic property-structure relationships. However in the last year or so papers have started appearing where the electro-optic properties of some of these materials have been examined." ... 

It is very often the commercial interest in novel materials which stimulates the growth in their study and eventual exploitation. This is certainly true in the case of thermotropic liquid crystals and their application in electro-optic displays. Indeed, the production of high-strength, high-modulus fibres has seen a wealth of interest in lyotropic main chain polymers. The use of lyotropic side chain polymers has, by comparison, been less well publicized. This is not to say that there are no applications. Alkyl polyoxyethylene surfactants attached to polysiloxane polymers have found uses in many personal care products such as liquid soaps, shampoos, skin creams, and hair mousses. Unfortunately the physical properties of these and other similar materials have been closely guarded secrets and the amount of information available in the literature is low. The limited data which does exist, however, provides us with some interesting structure - behaviour relationships. 

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