Liquid crystalline polymeric defects

The liquid crystalline polymeric fibers exhibit high degree of order and orientation (greater than 0.9) compare to commodity polymeric fibers such as polyester, nylon, and polypropylene. The structure of commodity fibers is highly defective and contains chain folds and low amorphous orientation and typically crystallinity 30-65%, while the crystalline orientation is in the range of 0.9-0.98. 

Because of the additional translational order, the dislocations can exist in the cholesteric and smectic liquid crystals, which makes the texture of these liquid crystals even more complicated. Each liquid crystal phase shows characteristic textures and thus the optical texture becomes an important means to differentiate the phase of the liquid crystals. Liquid crystalline polymers have the same topologically stable defects as small molecular mass liquid crystals do, but the textures may be different due to the difference in the energetic stability of the same topological defects in both low molecular mass and polymeric liquid crystals (Kleman, 1991). In Chapter 3 we will discuss the textures in detail. 

In polymeric liquid crystals, not only the mobility in the liquid-crystalline phase but also the highly restricted dynamics of the probe in the frozen state can be studied by 2D ELDOR spectroscopy [ 140]. In high performance materials based on main chain liquid crystalline polymers, stable radicals are created during production and processing. The nature and the dynamics of these defects has been elucidated by pulsed electron-nuclear double resonance (ENDOR) spectroscopy [141],... 

Macro Crystals.—Nearly defect-free crystals of polymers have been produced by direct polymerization of monomer at gas-solid or liquid-solid interface. Poly-(diacetylene) single crystals have been produced from irradiation of the crystalline monomer and involves the instantaneous polymerization and crystallization of... 

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