Lateral Fluoride Synthesis And Properties Of Liquid Crystal Diaryl Substituted Acetylene

With the progress of liquid crystal display technology, new requirement of liquid crystal material with special properties arouse an attention. The liquid crystal materials with rapid response are dominating question. In order to achieve fast response speed, the various driving modes have been proposed. Dual frequency liquid crystal (DFLCs) has a unique advantage to improve the response speed of the liquid crystal. It can not only reduce the response time, but also can decrease the relaxation time. Usually, dual frequency liquid crystals contain a liquid crystal of negative dielectric anisotropy mixture as a basis of the mixture, by adding a liquid crystal material of positive dielectric anisotropy to adjust the performance. The traditional compound of negative dielectric anisotropy is mainly biphenyl and triphenyl compounds. Recent study found that the liquid crystals compound containing lateral multi-fluorine and internal triple bond exhibit lower melting point, wider phase transition interval, larger birefringence and negative dielectric anisotropy, which is favorable to be applied on DFLCs. Based on our previous research, the thesis emphasized on the synthesis and the nature of a internal alkynes liquid crystals, which could be a foundation significance in their application. The content includes the following aspects:(1) Two series of nmT and nmP, which involoved in thirty-two lateral multi-fluorine substituted internal alkynes liquid crystals were synthesized via substituted phenylboronic acid, Suzuki cross-coupling, Sonogashira cross-coupling and iodination.4-Bromo-alkylbenzene and4-bromo-2,3-difluoro-phenol were used as a starting substrates. The structures of all compounds were characterized by IR, NMR and MS. The Differential Scanning Calorimetric (DSC), Polarizing Microscope (POM) and Abbe Refractometer were used to perform the properties. The DSC analysis demonstrated that nmT series possesed wide phase transition interval, and the nmP series existed low melting point. Alkyl chain length can reduce the melting point, but it will lead to the emergence of a smectic phase. Introducing a F atoms can obviously reduce the melting point. Birefringence measurement indicated that the compounds nmT and nmP series exhibit highâ–³n values, andâ–³n for nmT series is over0.3.(2) Two series of n3X and n4X including eight lateral multi-fluorine substituted benzene and internal alkynes liquid crystals were synthesized via Sonogashira cross-coupling, Williamson reaction and iodination,4-bromo-2,3-difluoro-phenol was used as raw materials. The structures of the compounds were characterized by IR, NMR and MS. The DSC, POM and Abbe Refractometer were used to perform the properties. The results demonstrated that introduction of terminal olefins could effectively reduce the melting point of the compound. The allyoxyl can not only decline the melting point, but also can broaden the liquid crystal phase interval. The two series of compounds are high optical anisotropy value, which showed a promising application in the dual frequency liquid crystals.(3) Preliminary approach of the application nmT and nmP was carried out. The formulation showed that the basic mixture possess high optical anisotropy, low melting point, high clearing point. By optimizing the composition, a liquid crystal mixtune is obtained and its response time is about0.8ms, which has been proved to be a potential application in VA type LCoS projection display.