Question

In the nematic phase, only the long axes of the molecules are parallel, and the ends are staggered at random intervals. in the smectic phase, the long axes of the molecules are parallel, and the molecules are also arranged in planes. finally, in thecholesteric phase, the molecules are arranged in layers; each layer is rotated with respect to the ones above and below it to give it this?

Answer 1

spiral structure

In the nematic phase, only the long axes of the molecules are parallel, and the ends are staggered at random intervals. In the smectic phase, the long axes of the molecules are parallel, and the molecules are also arranged in planes. Finally, in thecholesteric phase, the molecules are arranged in layers; each layer is rotated with respect to the ones above and below it to give a spiral structure. The molecular order increases from the nematic phase to the smectic phase to the cholesteric phase, and the phases become increasingly opaque. Molecules that form liquid crystals tend to be rigid molecules with polar groups that exhibit relatively strong dipoledipole or dipoleinduced dipole interactions, hydrogen bonds, or some combination of both. Some examples of substances that form liquid crystals are listed in Figure 11.27 "Structures of Typical Molecules That Form Liquid Crystals*" along with their characteristic phase transition temperature ranges. In most cases, the intermolecular interactions are due to the presence of polar or polarizable groups. Aromatic rings and multiple bonds between carbon and nitrogen or oxygen are especially common. Moreover, many liquid crystals are composed of molecules with two similar halves connected by a unit having a multiple bond. Figure 11.27 Structures of Typical Molecules That Form Liquid Crystals*.