Preparation and Application of Cholesteryl‐Macrocyclic Polyether Liquid Crystals and Surfactants

Macrocyclic polyethers containing a cholesteryl moiety, e.g., cholesteryl benzo‐15‐crown‐5 (C₂₇H₄₅OOC‐B15C5) and cholesteryl cryptand22 (C₂₇H₄₅OOC‐Cryptand22), were synthesized. The cholesteryl crown ether C₂₇H₄₅OOC‐B15C5 showed liquid crystal characteristics which were observed by polarizing microscopy. In contrast, the cholesteryl cryptand C₂₇H₄₅OOC‐Cryptand22 showed no liquid crystal characteristics. The doping effect of inorganic salts on the liquid crystal formation of cholesteryl benzo‐15‐crown‐5 was also investigated, revealing that the addition of salts resulted in narrower liquid crystal temperature ranges. Both cholesteryl cryptand C₂₇H₄₅OOC‐Cryptand22 and cholesteryl crown ether C₂₇H₄₅OOC‐B15C5 also exhibited the distinctive characteristics of surfactants in solutions. Fluorescence probe of pyrene and surface tension measurement were applied as sensitive tools to study the formation of the micelles and determine the critical micellar concentration (CMC) of the cholesteryl cryptand and crown ether surfactants. The salt effect on the CMC of the cholesteryl cryptand surfactant was also investigated and is discussed. Furthermore, the cholesteryl benzo‐15‐crown‐5 was successfully employed as a quite good phase transfer catalyst for the oxidation of alcohols, e.g., benzhydrol, with NaMnO₄ as an oxidant. Effects of temperature, solvent and concentration of the crown ether catalyst on the oxidation of benzhydrol were also investigated.