Photochemical phase chiral dopant

Scheme 25 Photochemical switching processes of LC-phase 41 and chiral dopants M-c/s-17a and P-trans-17b, representing a three position switch.

The photochemical control of phase change of antiferroelectric LCs was also achieved either by using azobenzenes possessing chiral side chains as dopants (A-6) in an antiferroelectric LC or by using azobenzene-containing chiral antiferroelectric LCs (A-7, A-8) [63,64]. 

Many of the compounds used as examples in this chapter to illustrate the three classes of chiral nematic structure are not necessarily compounds in which the presence of a chiral nematic phase or its properties were of primary importance to the researchers concerned in the work for instance some of the materials were developed as potential ferroelectric dopants, but happened to show a chiral nematic mesophase. Also in many cases, the synthetic techniques used and the hazardous nature of some of the reagents employed, along with the poor chemical or photochemical stabilities of the mesogens, would almost automatically preclude their use in any commercial applications (i.e., thermography). However, such materials are of scientific interest in that they help to illustrate the many potential variations of novel molecular structures which may result in a chiral nematic mesophase. 

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