High polymers and liquid crystals

Practically all of the book so far has dealt with the properties of aggregations of simple molecules, that is, of molecules that consist of, at most, a few atoms or ions. From the point of view of their interactions, these simple molecules can be treated more or less as Newtonian particles. There are, however, many molecules that consist of a large number of component atoms or ions and consequently show some rather different properties from the simple solids and liquids. Some properties of two types of molecule, high polymers and liquid crystals, will be examined briefly in this chapter. 

PhotMefractive (PR) polymers are multifunctional field-responsive materials that combine photoconducting and electro-optic propoties. hi this charter, we will review the basics of photorefiactivity in polymers and liquid crystals and describe recent advances that have led to highly efficient materials. These advances in material development enable a variety of photonic aiqilications including optical correlators for security verification. 

In this composite film, the polymer structure must not disturb the liquid crystal alignment. That is, it needs to maintain the highly ordered liquid crystal alignment (that is indispensable for the high-contrast light modulation) in the dispersion structure of the polymer. Therefore, the composite film preparation uses the phase separation of polymer and liquid crystal materials with molecular alignment, as described below. 

A very high, price and performance family of polymers called liquid crystal polymers (LCPs) exhibit extremely high mechanical and thermal properties. As their ease of processing and price improve, they may find appHcation in thin-waH, high strength parts such as nails, bolts, and fasteners where metal parts cannot be used for reasons of conductivity, electromagnetic characteristics, or corrosion. 

---