Effects of Chiral Groups on Photochemical Change in HTP

In binary Ch LC systems consisting of the chiral compound and the host nematic LC, the intermolecular interaction between the chiral azobenzene molecule and LC molecule contributes to HTP of the chiral azobenzene compounds. In this section, photoswitching behavior of some chiral azobenzene compounds (Fig. 10.7) is examined in terms of the influence of the chiral groups on the photochemical change in HTP. 

Change In the orientation order S by replacing with different chiral dopant. 

The photoisomerization ratios determined by comparing H NMR spectra of azobenzene compounds before and after UV irradiation are given in Table 10.3. The yields of cis form of all chiral azobenzene compounds at the photostationary state were 90% (Alam et al., 2007). Therefore, it is assumed that there is no effect of the yield of cis form at photostationary state on the change in HTP under UV light. 

The photochromic chiral azobenzene compounds, azo-1, azo-4, azo-5, azo-6, azo-7, and azo-10, only differ in their chiral substituents as can be seen in Fig. 10.7. Their HTPs were decreased upon UV irradiation because of the trans-cis photoisomerization of the chiral azobenzene molecules (Table 10.3). 

TABLE 10.3. Characterization of Chiral Azobenzene Compounds and Chiral 

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