A series of azobenzene liquid crystals with one or two terminal acrylate groups were synthesized and their polymers were fabricated.The azobenzene liquid crystals and their polymers achieved the photoisomerization fro...A series of azobenzene liquid crystals with one or two terminal acrylate groups were synthesized and their polymers were fabricated.The azobenzene liquid crystals and their polymers achieved the photoisomerization from the liquid crystalline trans-isomer to the isotropic cis-isomer with UV irradiation.Then,the cis to trans isomerization induced by an electric field was studied,the time required for electro-isomerization was measured,the texture change and absorption variation from cis to trans form induced by the electric field were observed clearly,and the time required for electro-isomerization was much shorter than that for thermal relaxation.The influence of the polar group（fluorine）,terminal acrylate group,and flexible alkyl chain on the time of electro-isomerization was studied.The results show that the compounds with polar fluorine group require shorter time for electro-isomerization and the polymerization of terminal acrylate group delays the electro-isomerization.展开更多
The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and characterized.The mesophase and photoswitching properties w...The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and characterized.The mesophase and photoswitching properties were determined by polarizing optical microscopy（POM）,differential scanning calorimetry（DSC） and UV-visible spectrometry.The rod-shaped compound 4a having an odd number of carbon atoms in the alkyl chains exhibits nematic phase and SmA type phase whereas compound 4b having an even number of carbon atoms showed only nematic phase.Both fluorinecontaining compounds 4c and 4d showed only SmA type phases.The photoswitching properties of these compounds showed a rate of trans to cis isomerization ranging 19-20 s,whereas reverse process took around 230 min in solution.These materials may be ideal in the field of optically rewritable applications where both on and off rates should be crucial.展开更多
Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorin...Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61435008 and 61575063)
文摘A series of azobenzene liquid crystals with one or two terminal acrylate groups were synthesized and their polymers were fabricated.The azobenzene liquid crystals and their polymers achieved the photoisomerization from the liquid crystalline trans-isomer to the isotropic cis-isomer with UV irradiation.Then,the cis to trans isomerization induced by an electric field was studied,the time required for electro-isomerization was measured,the texture change and absorption variation from cis to trans form induced by the electric field were observed clearly,and the time required for electro-isomerization was much shorter than that for thermal relaxation.The influence of the polar group（fluorine）,terminal acrylate group,and flexible alkyl chain on the time of electro-isomerization was studied.The results show that the compounds with polar fluorine group require shorter time for electro-isomerization and the polymerization of terminal acrylate group delays the electro-isomerization.
基金supported by UMP Research(No.RDU 100338)RAGS(No.RDU131408)
文摘The fluorine-substituted benzoate ester rod-shaped liquid crystals containing an azobenzene side chain linked with terminal double bonds were synthesized and characterized.The mesophase and photoswitching properties were determined by polarizing optical microscopy（POM）,differential scanning calorimetry（DSC） and UV-visible spectrometry.The rod-shaped compound 4a having an odd number of carbon atoms in the alkyl chains exhibits nematic phase and SmA type phase whereas compound 4b having an even number of carbon atoms showed only nematic phase.Both fluorinecontaining compounds 4c and 4d showed only SmA type phases.The photoswitching properties of these compounds showed a rate of trans to cis isomerization ranging 19-20 s,whereas reverse process took around 230 min in solution.These materials may be ideal in the field of optically rewritable applications where both on and off rates should be crucial.
基金The authors are grateful for the support and funding from National Scientific Research Project(Basis Strengthening Plan)State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202103).
文摘Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.
