The Synthesis Of Cholesterol Ester Liquid Crystals And Study On The Thermochromatic Liquid Crystal Mixture Compositions

Among general thermochromatic liquid crystals, cholesteryl ester liquid crystals have been used in showing color and displaying temperature due to their easy obtaining, low price and reversible fresh color change. There are usually some disadvantages such as more toxicity and low yield in the acetylating reaction which was used to synthesize cholesteryl ester liquid crystals.A super acylation catalyst, 4-Dimethylamino pyridine (DMAP), was prepared and used to synthesize cholesteryl ester compounds. Four kinds of cholesteryl ester compounds such as cholesteryl p-alkoxyl benzoate, cholesteryl dicarboxylate, cholesteryl lumequeic ester and coattail-like cholesteryl ester were synthesized by acylation method and super acylation catalyst method. Chemical structures and liquid crystal behaviors of the synthesized samples have been characterized by using Element Analysis, FTIR, DSC and polarized microscopy with a hot stage. The synthesized liquid crystal samples as a component were mixed with commercial cholesteryl liquid crystals to prepare thermochromatic liquid crystal mixture, respectively. Effects of different component proportions on showing color and displaying temperature of the liquid crystal mixture were studied. The cholesteryl liquid crystal mixture was microcapsulized by complex coacervation method using gelatin and acacia as membrane materials. The effects of the concentration and quantity of arabic gum on the microcapsule particle size and color showing were also studied.The research results showed that the DMAP is an effective catalyst to synthesize cholesteryl ester compounds. In the reactions, improving yield and purity, reducing toxicity as well as simplifying operation process can be carried out. For ten samples synthesized, six ones exhibit cholesteryl liquid crystal behaviors and four ones are not. Phenyl group introducing to cholesteryl ester molecules can enhance the phase transition temperatures of the liquid crystals and their stability. An increase in the chain length for cholesteryl dicarboxylate samples reduced stability of liquid crystal phases. While coattail-like structures on the ester group of the molecules have an adverse effect to form cholesteryl liquid crystal phase. Several cholesteryl liquid crystal samples synthesized are an excellent component for thermochromatic liquid crystal mixtures.