Synthesis And Characterization Of Novel Chiral Liquid Crystal Compounds

Liquid crystal has both crystal ordering and liquid mobility.Due to its good photoelectric properties andthermal properties,liquid crystal has attracted widespread attention in recent years.Cholesterol and diosgenin are natural biological liquid crystal groups which are derived from organisms.Cholesterol and diosgenin have good biocompatibility,liquid crystal properties and chiral carbon atoms(C*)in the molecular structure.At the same time,cholesterol and diosgenin are easy to interact with other functional groups to chemical modify,hence they are widely studied and applied in many fields.The main idea of this study is to synthesize novel chiral liquid crystal compounds with cholesteryl and diosgenin groups,whose liquid crystal performance can be tailored by changing the length of the methylene flexible spacer in the compound structure.The novel chiral liquid crystal compounds with biocompatibility will extend the application of liquid crystals as polymer materials in biomedical fields,which will supply a foundation for the synthesis of liquid crystal polycarbonate medical polymer materials.In the second chapter,four carboxylic acid compounds containing carboxyl groups were synthesized by the reaction of 5-hydroxy-1,3-dioxane with succinic anhydride,adipic acid,suberic acid,sebacic acid,respectively,and the obtained carboxylic acid compounds were named as 4-(2-phenyl-1,3-dioxane-5-oxy)-4-carbonyl butyric acid(A1),6-(2-phenyl-1,3dioxane-5-oxy)-6-carbonyl hexanoic acid(A2),8-(2-phenyl-1,3-dioxane-5-oxy)-8-carbonyl octanoic acid(A3),10-(2-phenyl-1,3-dioxane-5-oxy)-10-carbonyl decanoic acid(A4).The structures of the obtained compouds were characterized by fourier transform infrared spectrometer(FT-IR)and nuclear magnetic resonance(1H NMR).The thermal properties were characterized by differential scanning calorimeter(DSC)and Thermogravimetric Analyzer(TGA),and the influence of the methylene flexible spacer on theirthermal properties was discussed.The results showed that the melting point of the compounds decreased with the increase of the methylene flexible spacer length,but their thermal stability increased.In the third chapter,three new chiral liquid crystal monomers were synthesized by reaction of cholesterol with there carboxylic acid compounds(A2-A4).These cholesterol ester compounds were named as cholesteryl 6-(2-phenyl-1,3-dioxane-5-oxy)-6-carbonyl hexanoate(C1),cholesteryl 8-(2-phenyl-1,3-dioxane-5-oxy)-8-carbonyl octanoate(C2),cholesteryl 10-(2phenyl-1,3-dioxane-5-oxy)-10-carbonyl decanoate(C3)The structures of C1-C3 were characterized by FT-IR and 1H NMR,and the liquid crystal properties were characterized by polarizing optical microscopy(POM)and DSC.At the same time,the thermal stability properties were characterized by TGA,and the influence of the methylene flexible spacer number on their thermal properties were discussed.The results showed that C1-C3 were cholesteric thermotropic liquid crystal compounds,and exhibited focal-conic textures.With the increase of the methylene flexible spacer numbers,the glass transition temperature,clearing point,and thermal stability of compounds C1-C3 all decreased.In the forth chapter,three liquid crystal intermediates were synthesized by reacting diosgenin with succinic anhydride,adipic acid,suberic acid,sebacic acid..They were named as 4-diosgeninoxy-4-carbonyl butyric acid(D1),6-diosgeninoxy-6-carbonyl hexanoic acid(D2)and 8-diosgeninoxy-8-carbonyl octanoic acid(D3).Then their structures were characterized by FT-IR and 1H NMR.And their liquid crystal properties were characterized by POM and DSC.D1-D3 were cholesteric thermotropic liquid crystal compounds.Their liquid crystal properties appearred when the temperature were raised to the melting point and the focal-conic textures could be observed.At the same time,the influence of the methylene flexible spacer numbers on their thermal properties was discussed.The glass transition temperature and the melting point of the compounds decreased with the increase of the methylene flexible chain length.