Liquid crystalline dimers containing a cholesteryl benzoate unit: smectic phase, chiral nematic phase and blue phase

Multiple mesophases, including the smectic A phase (Sm A), chiral nematic phase (N*), and blue phase (BP I), were seen in a series of non-symmetric bent mesogenic dimers containing a cholesteryl benzoate group. FTIR, 1H-NMR, DSC, POM, UV, and XRD were used to analyze the chemical structure and liquid crystal characteristics of the dimers. The phase transition occurred when the azobenzene structure was treated with UV light, changing the structure of the molecules. There is evidence that when the length of the terminal alkoxy chain is longer than the flexible spacer, it exhibits a smectic A phase as well as a chiral nematic phase; however, when the length of the flexible spacer is shorter than the length of the terminal alkoxy chain, it only exhibits a chiral nematic phase.