Liquid crystalline materials, design

First, we will consider the design of polyphosphazenes as side-chain liquid-crystalline materials.241 248 Side-chain liquid-crystalline polymers are a subclass of species described earlier as structure 3.72. Liquid crystallinity occurs when the rigid side groups become organized, usually in the semi-liquid state. The organization may be nematic (oriented but unlayered) or smectic (layered) as illustrated in Figure 3.25. 

Although the dielectric and optical anisotropies Ae and An are properties of the condensed nematic phase, they can be related to the physical properties of single molecules. This is of great importance for the targeted, rational design of liquid crystalline materials. 

Columnar phases could also be obtained by reacting disk-shaped molecules such as crown ethers with lanthanide salts. BiinzU and coworkers reported, for example, the preparation of thermotropic hexagonal columnar phases from nonmesogenic crown ethers and several different ions of the lanthanide family [76], An additional property of these compounds is a metal-centered emission, in the case of the liquid-crystalline phases containing Eu and Tb, making them attractive for the design of luminescent liquid-crystalline materials [76],... 

In view of sensitivity, the liquid crystal system is more improved than the previously mentioned systems. However, these liquid crystalline materials are viscous fluids and thus the long term image stability is not expected. To overcome this shortcoming, image amplification in a solid system has to be designed. 

In Chapters 1, 2, and 3 unconventional liquid crystalline molecules with complex structures based on covalent bonding are described. In Chapter 4, Rowan and Mather demonstrate that non-covalent bonding such as hydrogen bonds may be used for the design and construction of liquid crystalline materials. 

In this review, the design, preparation, and functionalization of hydrogen-bonded liquid-crystalline materials are described. These novel systems are... 

C. Tschierske, Micro-segregation, molecular shape and molecular topology partners for the design of liquid crystalline materials with complex mesophase morphologies, J. Mater. Chem. 11(11), 2647-2671, (2001). 

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