| In this thesis,we successfully synthesized a series of compounds with “aggregation-induced emission”(AIE)effects while retaining the mesogenic properties through rational molecular design.The target molecules are consisting of a typical AIE-active core and peripheral mesogenic substituents or multi alkoxy groups.We finally realized that moleculars can self-assembly to form the novel luminescent liquid crystal by changing the length of spacer group,the number of the side chain,and the kind of end group.The structure of molecules were characterized by NMR and high resolution mass spectroscopy(MS).The photophysical properties were studied by using UV-vision(UV-vis)and photoluminescent(PL)spectroscopy.The thermal stability and mesomorphic properties were investigated by using polarized optical microscopy(POM),differential scanning calorimetry(DSC),and finally we identified the phase structure by using one-dimensional and two-dimensional wide-angle X-ray diffraction(1D/2D-WAXD).The main research content was as follows:1.In our work,we successfully designed and synthesized a series of compounds containing tetraphenylethylene(TPE)core and cyanobiphenyl mesogens with different spacer length and side chain.We have investigated the luminescence behavior ? mesogemic properties and mechanochromic behavior.The results revealed that all compounds possess an AIE effect,but only two molecules display mesomorphism.They are molecules which the length of spacer group is 12 canbons with 2 or 4 side chains.While the molecule linking four peripheral mesogenic substituents can self-assembly into hexagonal columnar mesophases with strong blue-green fluorescence,another displays lamellar mesophases with strong cyan-green fluorescence.In addition,the compounds with chain lengths C6 and molecule with both chain lengths C12 and 2 side chain exhibits reversible mechanochromic behavior.The 1D-WAXD studies of powder show that destruction of crystalline state into amorphous state is responsible for mechanochromism.2.We successfully designed and synthesized a series of compounds containing 1,1,2,2-tetrakis(4-(phenylethynyl)phenyl)ethane core which the degree of conjugate is higher than TPE.Their luminescence behavior?mesogemic properties and mechanochromic behavior were investigated.The results show that the compounds with multi alkoxy tails display no mesomorphism,regardless of the length of alkyl chain,but exhibits strong aggregation induced emission(AIE)and reversible mechanochromic effect at room temperature,and the longer chain lengths,the faster the recovery.Molecule with chain lengths C12 can self-recovery within 25 s after grinding.The loose packing environment make the transformation among different packing patterns easy,thus reversible switching the emission of luminogens among multiple colors is achieved.Molecules containing peripheral mesogenic substituents exhibit AIE effect while retaining the mesogenic properties.The molecule with disc-like mesogens can self-assembly into hexagonal columnar mesophases with strong yellow-green fluorescence.However,the molecule with cyanobiphenyl mesogens can form focal conic fan-shaped texture and emissive yellow fluorescence in mesophases.The results indicate that it is helpful to induce the twisted AIE core packing together in the liquid crystalline structure by combining the mesogens.To same extent,increasing the conjugate degree in center core makes contributions to extend the emissive wavelength of luminescent liquid crystal. |
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