The Liquid Crystal Behavior And Luminescent Properties Of The Novel Cyano-stilbene Derivative Based On The Flexible Chain

In recent years, luminescent liquid crystals (LLCs) have received much attention due to their potential applications in optical waveguides, optically pumped lasers,chemical sensors, and organic light-emitting diodes. It is known that fluorescent liquid crystal materials exhibit unique linear or circular polarized fluorescent properties and liquid crystal properties. Thus, LLCs can be utilized to manufacture high concise emissive LCDs without a polarizer or color filter in the LC cell. A simple LCDs device design with a substantial increase in brightness, contrast, power efficiency, and viewing angle is possible. However, the design and synthesis of LLCs still have so great challenges that its species is very rare. Firstly, it is difficult to design the molecular nature of the liquid crystal and the luminous properties at the same time. On the other hand, aggregation-caused quenching (ACQ) often takes place in the condensed phases for luminescent molecules. The AIEE (aggregation induced enhanced emission effect)-active molecular can avoid the aggregation-caused quenching (ACQ) problem in the condensed phases. We designed and synthesized a series of novel AIEE effect cyanostilbene derivatives and researched its liquid crystal properties and luminescence properties. The main research works are concluded as follows:(1) It was fully reviewed on the recent development of the materials with aggregation induced enhanced emission and cyanostilbene derivative. On the basis of the research status of aggregation induced enhanced emission and cyanostilbene derivative, the new design idea was put forward in this dessertation A series of novel AIEE effect cyanostilbene derivatives was synthesized by Knoevenagel, nucleophilic substitution reaction. The structure and properties of thermal properties and the liquid crystal performance were characterized by H NMR?13C NMR?FT-IR?Tg and so on.(2) The liquid crystal properties of cyanostilbene derivatives with different alkyl chain lengths were studied. The liquid crystal performance was characterized by DSC and POM. The results show that the long alkyl chain molecules have multiple exothermic peaks in the cooling process. Further research shows the long alkyl chain molecules have a good liquid crystal performance.(3) The AIEE properties of cyanostilbene derivatives with different alkyl chain lengths were researched by absorption properties, fluorescence properties, and aggregation morphology, etc. The results show that it has aggregation induced enhanced emission effect, and can achieve aggregation induced luminescent properties with a variety of color.(4) The luminescent properties of this series of novel cyano-substituted stilbene derivatives were studied. It was found that the luminescent color of the long alkyl chain molecules changed with the change of the phase of the liquid crystal during the different cooling process. Based on this phenomenon, the long alkyl chain molecular films were cooled at different cooling rates and and then recovered to room terrperature to study its luminescence phenomenon. The results show that the C12 and C18 films can achieve continuous color changes which are expected to have potential application in fluorescent display.