Synthesis And Mesomorphism Of Ferrocenyl Calamitic And Triphenylene Discotic Liquid Crystals Containing Cholesteryl Moiety

Cholesteryl is a good chiral nematic phase mesogen because of its chirality. Its derivatives usually show chiral nematic phase, namely cholesteric phase, the molecules in cholesteric liquid crystal self-organize to a helical ordered structure. If the length of the pitch corresponds to the wavelength of light, then the light is reflected with different efficiency. The pitch is extremely sensitive to physical stimuli such as temperature,the electric field,the magnetic field,pressure and organic vapour, therefore the color of reflected light is changed. This makes cholesteric liquid crystals useful in many fields.There were many researches on calamitic liquid crystals with cholesteryl moiety. They showed cholesteric phase, some exhibited SC*, SA*, TGB, BP phase. Ferrocenyl have high thermol stability, and triphenylene is a good discotic mesogen. The combination of triphenylene or ferrocene with cholesteryl moiety in one molecule would result interesting physical properties. In this thesis, a series of ferrocenyl calamitic and triphenylene discotic liquid crystals containing cholesteryl moieties were synthesized, and studied on the organogel ability of triphenylene derivatives. The structure and purity characterization of these compounds were carried out with 1H NMR, EA. The thermotropic liquid crystal properties were studied through polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The structure-property relationship of these molecules was proposed, and it is hopefully to contribute to the molecular designing and practical application of these liquid crystals as new materials.The thesis consists of five chapters:1. Chapter one briefly introduced the elementary knowledge about liquid crystal materials, including the definition and classification of liquid crystals. Then mostly introduced the studies on calamitic liquid crystals with cholesteryl moiety.2. Five series of ferrocenyl derivatives Fc-(C6H4)i-COO-(C6H4)j-OCnH2nCOOCh (i = 0, 1, j = 1, 2, n = 5, 10) and phenyl analogues C6H5-COO-(C6H4)j-OCnH2nCOOCh (j = 1, 2, n = 5, 10) were synthesized in chapter two. Studi-es of DSC and POM texture observations revealed that, all of the compound-s showed thermotropic cholesteric phases. Their melting points and clearing points decreased with increasing of spacer in the same series.3. In chapter three, a series of triphenylene derivatives with three cholest-eryl moieties C₁₈H₆(OR)3(OCnH2nCOOCh)3 (R = C5H11, C7H15, C9H19, C11H23,n = 1, 5, 10) (6a⁶f), and C₁₈H₆(OC5H11)5(OC5H10COOCh) (2), C₁₈H₆(OC5H11)4(OC5H10COOCh)2 (4), C₁₈H₆(OC5H10COOCh)6 (8) were synthesized. The resultshowed that, compound 2 did not exhibit any mesophase; compounds 4 and 6 showed ND* phase; compound 8 showed SB phase. All of the compounds showed glass states except 2 and asym-6f, and stabilized a long time under room temperature.4. Chapter four studied on the gelling properties of triphenylene derivativ-es. The intermediates C₁₈H₆(OC₆H₁₃)5(OCH2CONHCnH2nNH2) (n = 2, 4) sho-wed columnar phase with high clearing points and can gel many kinds of or-ganic solvent such as alkane, arene, alcohol, ketone etc. But the mesomorphis-m of its derivatives C₁₈H₆(OC₆H₁₃)5(OCH2CONHCnH2nNHCOOCh) were disap-peared and can only gel nonpolar solvents such as hexane, octane.5. Chapter 5 gave the summary and conclusion of the thesis.