Synthesis of Fluorinated Bistolane Liquid Crystals
|關鍵字:||液晶;氟;三苯基雙乙炔基;向列型;liquid crystals;fluorine;bistolane;nematic phase|
Synthesis of a series of fluorinated bistolane was made in this reserch. We introduced the linking group of diacetylene and lateral substitution of difluoro, trying to obtain the liquid crystal with low melting point, low enthalpy, wide mesophase range, and negative dielectric anisotropic. The liquid crystal with these properties was suitable to be used in the formulation of liquid crystal mixture in the liquid crystal display with homeotropic alignment. The liquid crystal compounds in this study were with triphenyl as mesogene, diacetylene as linking group and alkyl as terminal. Their mesophase and transition temperature were characterized with DSC and OM. Their melting points were not as low as those expected, that would result from the symmetry of the molecular structure. Hence, we used more different alkyl chain as the terminal groups to destroy the molecular symmetry. With ethyl and pentyl groups as terminal groups, the compound had a melting point at 70.2 oC and lower isotropic temperature, but no obvious odd-even effect. Its mesophase range was up to 130 oC. Additionally, the enthalpies of these compounds were drastically down to 3.41 kcal/mole when their molecular symmetry reduced. The lower enthalpy will benefit the formulation of liquid crystal mixture. This series of liquid crystal was quite successful, even their melting points were a little higher. Their De up to -5 was due to the substitution of difluoro, and Dn between 0.3 and 0.4 was contributed from diacetylene. The relationship between the structure of the liquid crystal and their properties was also studied in this research.
|Appears in Collections:||Thesis|