Synthesis And Properties Of Liquid Crystal Molecules-based With Aggregation-induced Emission Feature

In this thesis, a series of tetraphenylethene(TPE) derivatives with different tail chain, and azobenzene derivatives with different alkoxy tail chain, and TPE derivatives with azobenzene, and tetraphenyl-1,3-butadiene derivatives, and tetraphenyl-1,3-butadiene derivatives with "dendritic" mesogens were designed and synthesized. The molecular structures of these compounds were characterized by nuclear magnetic resonance(1H NMR and 13 C NMR) and mass spectrometry(MS), the luminescent properties of compounds were studied by the ultraviolet-visible(UV-vis) absorption spectra and the fluorescence spectra, and the factors were discussed about the polar of solvent, and exposure time by UV light, and p H value affecting on the spectroscopic properties, the thermal stability and phase behavior of compounds were also characterized by thermo-gravimetric analysis(TGA), differential scanning caloriy(DSC) and polarizing microscope(POM).The specific content of this thesis as four following components:1. TPE derivatives with one or four and hydroxy or 1-bromo-hexyloxy tails chains were synthesized, and the chemical structures of target molecules were characterized. The UV-vis absorption and luminescent spectra of compounds in THF/H2 O mixtures with different water fractions(fw) were studied, and there were comfirmed that the target molecules had Aggregation-Induced Emission(AIE) effect. However, the molecules were proved to can not be formed liquid crystal phase by DSC and POM.2. Alkoxies with different length were connected to azobenzenes, and were researched on illumination time, polarity of solvent, p H value, which caused by the impact of its photochromic phenomenon and light-emitting properties. This study found out that the transition of trans-azobenzene was shifted to higher wavelengths and the transition of cis-azobenzene was shifted to shorter wavelengths with the increase the polarity of solvent in UV-vis absorption spectra. After irradiation with UV light, the trans-isomers were quickly transformed into the cis-isomers. Relative experiments suggested such photochromic transformation of azobenzenes were reversible. Moreover, all of these substances can form liquid crystal phase.3. TPE derivatives which containing a different number of parity azobenzene liquid crystal molecules were designed and synthesized to study the relevance between the effect of AIE and mesogenic azobenzenes. The trans and cis-isomer of molecules can switch reversibly after irradiation with UV light or room light. Particularly, the photochromic phenomenon is investigated by time-resolved 1H NMR. This study found out that the transition of trans-azobenzene was shifted to higher wavelengths and the transition of cis-azobenzene was shifted to shorter wavelengths with the increase the polarity of solvent in UV-vis absorption spectra. Molecules had red shift phenomenon with the increase of the polarity, and they were AIE-active molecules when introduced water caused the luminogens aggregated. Studies showed these materials can form LC phase in specific temperature range.4. Tetraphenyl-1,3-butadiene derivatives with "dendritic" mesogens by an ester bond were synthesized. Photoluminescent spectra indicate that they are typical AIE molecules due to their motifs. However only compound y of tetraphenyl-1,3-butadiene derivatives with "dendritic" mesogens can be excited from blue light to green light in the fluorescence emission spectra,this compound also can form liquid crystal phase.