Defect Associations and Textures at Rest

Textures correspond to various arrangements of defects. When the isotropic liquid is cooled, the nematic phase may appear at the deisotropization point in the form of separate small, round objects called droplets (Fig. 12). These can show extinction crosses, spiral structures, bipolar arrangements, or some other topology depending on boundary conditions. Theoretical studies based on a simple model confirm the stability of radial or bipolar orientation (Fig. 5) [22]. Considerations based on improved theoretical models yield stable twisted 

The marbled, threaded and Schlieren textures are the ones most often cited in the literature for thermotropic MCLCPs. Examples of typical polymeric textures are shown in Figs. 13-15. 

Nematic marbled texture consists of several areas with different molecular orientation. On observing the preparation between 

II Defects and Textures in Nematic Main-Chain Liquid Crystalline Polymers 

The threaded (or line) texture is observed in preparations where threads lie more or less horizontally, their ends being attached to the glass surfaces and the other parts floating freely in the liquid crystal. The threads may be extended and curved due to flow of the liquid. They can be closed in the form of loops (Fig. 16) and, in this case, generally shrink and disappear more or less rapidly (Fig. 17, s. page 107) [74, 75]. 

---