Definition of Liquid-Crystal Polymers

Lyotropic LCPs are polymers whose solutions exhibit liquid crystallinity, that is, anisotropic domains in a fluid system, over a characteristic range of concentrations. In more concentrated solutions the system may be multiphasic and contain crystalline particles, amorphous gel particles and anisotropic solution coexisting with one another. Upon dilution, the anisotropic liquid crystalline solution turns biphasic, where anisotropic and isotropic solutions of the same polymer in the same solvent coexist. Upon further dilution, the solution becomes fully isotropic. Polymers that exhibit lyotropic mesomorp-hicity are either stiff-backbone polymers with strong interchain interaction in the absence of solvent or polymers whose backbones are so extended and rigid that, upon breakup of their crystalline order by the addition of some solvent, the stiff polymer chains retain substantial measure of parallel alignment to remain in mobile anisotropic domains. 

A brief description of the structural features of LCPs owing their mesomorp-hicity to the presence in them of relatively stiff and slender structural units will now be given. It will be followed by a description of LCPs with more or less 

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When polymerization is effected at the air-water interface, monolayer polymer films may result. Such films have attracted a great deal of attention in recent years by virtue of their similarity to biological membranes. Polymeric films do not really fall within the strict definition of liquid crystal polymers. However, the molecular arrangement of the side chains resembles that found in many liquid crystal phases, most notably the lamellar phase, and could therefore realistically be described as one half of a lamellar sheet. Bilayer films, on the other hand, may be thought of as a single lamellar layer, and therefore the comparison becomes even more appropriate. The technical applications of polymer membranes are extremely diverse and for these reasons a short section will be devoted to their history, their uses and their current status. 

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