A mesogen-jacketed liquid crystal polymer,poly{2,5 -bis［(4′-hexyloxyphenyl)oxycarbonyl］styrene}(PHPCS),with number-average d molecular weight of 1.28×１０5 and polydispersity of 1.48 was prepared vi a 2,2,6,6 ...A mesogen-jacketed liquid crystal polymer,poly{2,5 -bis［(4′-hexyloxyphenyl)oxycarbonyl］styrene}(PHPCS),with number-average d molecular weight of 1.28×１０5 and polydispersity of 1.48 was prepared vi a 2,2,6,6 -tetramethyl-piperidinyloxy mediated free radical polymerization.The thermotr opic behavior was studied by a combination of differential scanning calorimetry, thermogravimetry,polarized optical microscope and wide-angle X-ray diffracti on.PHPCS was not crystalline over the entire temperature region studied.On hea ting,PHPCS first became an isotropic melt at glass transition temperature (T g) and then a mesophase at temperatures much higher than T g.On subseq uent cooling,the formed ordered phase disappeared above T g.Contrary to t heoretical predictions and previous experimental observations,the transition fr om isotropic melt to liquid crystalline phase was an endothermic process and th e order-disorder transition took place with concurrence of heat release.展开更多
This paper describes the synthesis and free radical polymerization of 2,5 bis(4′ alkyloxyphenyl)styrene(M n ) for mesogen jacketed liquid crystal polymers(MJLCPs), where p terphenyl subsituted by alkoxy groups at bot...This paper describes the synthesis and free radical polymerization of 2,5 bis(4′ alkyloxyphenyl)styrene(M n ) for mesogen jacketed liquid crystal polymers(MJLCPs), where p terphenyl subsituted by alkoxy groups at both ends was used as mesogenic unit. Because of the absence of the polar linkage groups, such as —COO— or —CONH— as employed in the previous reported MJLCPs, M n is believed to be polymerized easily by both free radical polymerization and ionic polymerization. The chemical structure of M n was proved by 1H NMR, mass spectrometry and elementary analysis. Their phase transition and liquid crystallinity were characterized by DSC and POM. Although M 1, M 2, M 3 and M 4 exhibited monotropic nematic mesophase, M 5 displayed enantiotropic nematic mesophase presumably because of its decreased melting transition temperature. All monomers were easily polymerized to moderately high molecular weight polymers. At elevated temperature above T g, poly[2,5 bis(4′ alkoxyphenyl)styrene] showed a very stable mesophase. The formed birefrigence did not disappear until thermal decomposition started. Compared to other MJLCPs, the polymers reported here have much higher thermal stability. [WT5HZ]展开更多
Two monomers of 2,5 bis[( p methoxyphenoxy)carbonyl]benzyl acrylate and 2,5 bis[( p methoxyphenoxy)carbonyl] benzyl methacrylate and their corresponding polymers were successfully synthesized. The mesomorphic behavior...Two monomers of 2,5 bis[( p methoxyphenoxy)carbonyl]benzyl acrylate and 2,5 bis[( p methoxyphenoxy)carbonyl] benzyl methacrylate and their corresponding polymers were successfully synthesized. The mesomorphic behavior of both polymers was examined by using differential scanning calorimetry(DSC) and polarized optical microscopy(POM). It was found that both polymers are noncrystalline with a glass transition temperature of 67.1 ℃ for poly {2,5 bis[( p methoxyphenoxy)carbonyl]benzyl acrylate} and 95.1 ℃ for poly {2,5 bis[( p methoxyphenoxy)carbonyl]benzyl methacrylate}, above which the former can form liquid crystalline state and the clearing temperature is 97.8 ℃ while the latter can not. This indicates that main chain rigidity will affect the liquid crystallinity of mesogen jacketed polymers.展开更多
Mesogen-Jacketed liquid crystalline polymers were synthesized in various chiral conditions using 1) (\|)\|menthol as a reaction solvent (additive),2) (\|)\|dimenthyl peroxydicarbonate as a chiral free radical initiato...Mesogen-Jacketed liquid crystalline polymers were synthesized in various chiral conditions using 1) (\|)\|menthol as a reaction solvent (additive),2) (\|)\|dimenthyl peroxydicarbonate as a chiral free radical initiator,3) menthyl methacrylate as a comonomer for copolymerization,4) (-)-sparteine-fluorenyllithium as a chiral anionic initiator and 5) a chiral monomer.In the polymerization using a chiral initiator or a chiral solvent,the helix-sense-selection was not found.In the case of the copolymerization,the chiral monomeric unit incorporated into the polymer chain was found to induce liquid crystallinity.Chiral mesogen-Jacketed polymer was also synthesized from chiral monomer 5.However,this polymer did not form a liquid crystal phase although it met the model of Mesogen-Jacketed liquid crystalline polymers.展开更多
文摘A mesogen-jacketed liquid crystal polymer,poly{2,5 -bis［(4′-hexyloxyphenyl)oxycarbonyl］styrene}(PHPCS),with number-average d molecular weight of 1.28×１０5 and polydispersity of 1.48 was prepared vi a 2,2,6,6 -tetramethyl-piperidinyloxy mediated free radical polymerization.The thermotr opic behavior was studied by a combination of differential scanning calorimetry, thermogravimetry,polarized optical microscope and wide-angle X-ray diffracti on.PHPCS was not crystalline over the entire temperature region studied.On hea ting,PHPCS first became an isotropic melt at glass transition temperature (T g) and then a mesophase at temperatures much higher than T g.On subseq uent cooling,the formed ordered phase disappeared above T g.Contrary to t heoretical predictions and previous experimental observations,the transition fr om isotropic melt to liquid crystalline phase was an endothermic process and th e order-disorder transition took place with concurrence of heat release.
文摘This paper describes the synthesis and free radical polymerization of 2,5 bis(4′ alkyloxyphenyl)styrene(M n ) for mesogen jacketed liquid crystal polymers(MJLCPs), where p terphenyl subsituted by alkoxy groups at both ends was used as mesogenic unit. Because of the absence of the polar linkage groups, such as —COO— or —CONH— as employed in the previous reported MJLCPs, M n is believed to be polymerized easily by both free radical polymerization and ionic polymerization. The chemical structure of M n was proved by 1H NMR, mass spectrometry and elementary analysis. Their phase transition and liquid crystallinity were characterized by DSC and POM. Although M 1, M 2, M 3 and M 4 exhibited monotropic nematic mesophase, M 5 displayed enantiotropic nematic mesophase presumably because of its decreased melting transition temperature. All monomers were easily polymerized to moderately high molecular weight polymers. At elevated temperature above T g, poly[2,5 bis(4′ alkoxyphenyl)styrene] showed a very stable mesophase. The formed birefrigence did not disappear until thermal decomposition started. Compared to other MJLCPs, the polymers reported here have much higher thermal stability. [WT5HZ]
文摘Two monomers of 2,5 bis[( p methoxyphenoxy)carbonyl]benzyl acrylate and 2,5 bis[( p methoxyphenoxy)carbonyl] benzyl methacrylate and their corresponding polymers were successfully synthesized. The mesomorphic behavior of both polymers was examined by using differential scanning calorimetry(DSC) and polarized optical microscopy(POM). It was found that both polymers are noncrystalline with a glass transition temperature of 67.1 ℃ for poly {2,5 bis[( p methoxyphenoxy)carbonyl]benzyl acrylate} and 95.1 ℃ for poly {2,5 bis[( p methoxyphenoxy)carbonyl]benzyl methacrylate}, above which the former can form liquid crystalline state and the clearing temperature is 97.8 ℃ while the latter can not. This indicates that main chain rigidity will affect the liquid crystallinity of mesogen jacketed polymers.
文摘Mesogen-Jacketed liquid crystalline polymers were synthesized in various chiral conditions using 1) (\|)\|menthol as a reaction solvent (additive),2) (\|)\|dimenthyl peroxydicarbonate as a chiral free radical initiator,3) menthyl methacrylate as a comonomer for copolymerization,4) (-)-sparteine-fluorenyllithium as a chiral anionic initiator and 5) a chiral monomer.In the polymerization using a chiral initiator or a chiral solvent,the helix-sense-selection was not found.In the case of the copolymerization,the chiral monomeric unit incorporated into the polymer chain was found to induce liquid crystallinity.Chiral mesogen-Jacketed polymer was also synthesized from chiral monomer 5.However,this polymer did not form a liquid crystal phase although it met the model of Mesogen-Jacketed liquid crystalline polymers.
