Synthesis and Properties of Dimesogenic Compounds Containing Cholesterol and 4‐(trans‐4‐n‐Alkylcyclohexyl)‐benzoic Acid Moieties

Abstract

A series of novel dimesogenic compounds containing cholesterol and 4-(trans-4-n-alkylcyclohexyl)benzoic acid moieties were synthesized. The two mesogenic units of these compounds are linked with ω-oxyalkanoyl spacers of varying lengths. The chemical structure and mesomorphic properties of this series of compounds were characterized by FT-IR, MS, 1 H NMR, polarizing optical microscopy (POM) and DSC techniques. The average viscosity and helical twisting power (HTP) in host liquid crystals of selected dimesogenic compounds were also measured. It was found that most of the present novel series of compounds exhibited only cholesteric mesophase with lower phase transition temperatures, and the average viscosity and HTP of selected compounds were similar to or superior to cholesteryl nonylate.

Synthesis and Characterization of a Series of Cholesterol-Based Liquid Crystalline Dimers with a Chiral (-)- Menthyl Terminal Group

“…In the previous studies of unsymmetric cholesterol-based LC dimers, mostly, they had only one chiral moiety in their molecular structure, another mesogenic group such as benzoate ester, Schiff's base, azobenzene, or biphenyl did not catch a chiral tail [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Only a few researches reported the tolane mesogenic moiety was attached chiral tails such as 2S-chloro-3S-methylpentanoyloxy or 1, 3-dioxalane on the unsymmetric cholesterol-based LC dimers [26].…”

“…Due to the great structural variety of unsymmetric compounds, the quantity of unsymmetric LC dimers is much more than that of symmetric LC dimers. In particular, unsymmetric cholesterol-based LC dimers which containing one cholesteryl moiety and another substituted aromatic mesogenic unit such as benzoate ester, Schiff's base, azobenzene, or biphenyl are especially interesting [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. This is because the chiral cholesteryl moiety entitles many unique optical properties such as selective reflection, circular dichroism, and thermo-optical effects besides the properties of conventional rigid aromatic LC dimers.…”