Synthesis And Characterization Of New Liquid Crystal Compounds Based On Thiophene

As an important class of photovoltaic materials,thiophene derivatives have attracted more and more attentions because of their excellent performance such as moderate energy gap and wide spectral response.In addition,thiophene derivatives are not sensitive to oxygen,so they have good environment stability.At present,the development and utilization of thiophene derivatives are mostly limited to the crystalline and amorphous state.The study on thiophene derivatives with liquid crystal properties is not systematic.As functional materials,liquid crystal thiophene derivatives have great prospects due to the order structure and the response to external stimuli.Compared with the corresponding phenyl derivatives,liquid crystal thiophene derivatives have the asymmetric molecular structure,so they tend to exhibit lower melting point and viscosity,stronger anisotropy and lateral dipole moment.These characteristics make liquid crystal thiophene derivatives have special photoelectric properties.In the second chapter,five liquid crystal thiophene monomers were synthesized,and named as(E)-4'-(4-(3-(thiophen-3-yl)acryloyloxy)butoxy)-[1,1'-biphenyl]-4-ethoxybenzoate(M1),(E)-4'-(6-(3-(thiophen-3-yl)acryloyloxy)hexyloxy)-[1,1'-biphenyl]-4-ethoxybenzoate(M2),(E)-4'-(4-(3-(thiophen-3-yDacryloyloxy)butoxy)-[1,1',biphenyl]-4-pentylbenzoate(M3),(E)-4'-(6-(3-(thiophen-3-yl)acryloyloxy)hexyloxy)-[1,1'-biphenyl]-4-pentylbenzoate(M4)and(E)-4'-(6-(3-(thiophen-3-yl)acryloyloxy)hexyloxy)-[1,1'-biphenyl]-4-ethylbenzoate(M5).The chemical structures of the obtained monomers were characterized by FT-IR and 1H NMR.The mesomorphic properties and phase behavior were investigated by polarizing optical microscopy(POM)and differential scanning calorimetry(DSC).The optical properties were investigated by ultraviolet visible spectrophotometer(UV)and fluorescence spectrometer.The results showed that the melting temperatures(Tm)of the five monomers decreased gradually with increasing the length of flexible methylene chains in the molecular structures.The Tm and isotropic temperatures(Ti)of the monomers decreased with increasing the length of flexible terminal methylene chains in the molecular structures.In addition,M1-M5 exhibited threaded texture,schlieren texture and droplets texture of nematic phase on heating and cooling cycles.In the third chapter,four thiophene monomers with menthyl groups were synthesized and named as(E)-4'-(4-(3-(thiophen-3-yl)acryloyloxy)butoxy)-[1,1 '-biphenyl]-4--enthyloxy-acetate(M6),(E)-4'-(6-(3-(thiophen-3-yl)acryloyloxy)hexyloxy)-[1,1'-biphenyl]-4-menthyl-oxyacetate(M7),(E)-4'-(4-(3-(thiophen-3-yDacryloyloxy)butoxy)-[1,1'-bphenyl]-4-menthyl-oxyacetyloxyben-zoate(M8)and(E)-4'-(6-(3-(thiopen-3-yl)acryloyloxy)hexyloxy)-[1,1'-biphenyl]-4-menthyloxyacetyloxybenzoate(M9).Their chemical structures were characterized by FT-IR and 1H NMR.The mesomorphic properties and phase behavior were investigated with POM and DSC.The results showed that M6-M9 did not appear mesophase on heating and cooling cycles.With increasing the rigidity of monomer molecules,the corresponding Tm also increased.In the fourth chapter,four monomers containing diosgenyl groups were synthesized and named as 2-diosgenoxyethyl-3-(thiophen-3-yl)acrylate(M10),4-diosgenoxybutyl-3-(thiophen-3-yl)acrylate(M11),6-diosgenoxyhexyl-3-(thiophen-3-yl)acrylate(M12)and 8-diosgenoxy-octyl-3-(thiophen-3-yl)acrylate(M13).Their chemical structures were characterized by FT-IR and 1H NMR The mesomorphic properties and phase behavior were investigated using POM and DSC.The results showed that the intermediates containing diosgenyl groups all exhibited fan,shaped texture of a smectic phase on heating and cooling cycles.However,M10-M13 did not show any mesomorphism.In addition,with an increase of the flexible methylene chains in molecular structures,the Tm and Ti of the intermediates decreased,and the Tm of M10-M13 decreased.