Four novel copoly（ester-imide）s based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride, bis（trimellitic acid anhydride） phenyl ester and di-p-aminophenyl ester of dicarboxylic acids were synthesized via two-step...Four novel copoly（ester-imide）s based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride, bis（trimellitic acid anhydride） phenyl ester and di-p-aminophenyl ester of dicarboxylic acids were synthesized via two-step method in order to investigate whether two imide mesogenic units with different conformation and polarity could control the formation of LC-phase. Polarizes light microscopy （PLM） and differential scanning calorimetry （DSC） have shown that three polymers formed the nematic phase with ＂thread schlieren texture＂ and a polymer formed the nematic phase with ＂Inversion walls texture＂.展开更多
The lamellar structure of a thermotropic aromatic polyester with flexible spacer has beenstudied by using transmission electron microscopy. It was found that the lamellar structure couldbe observed in the crystalline ...The lamellar structure of a thermotropic aromatic polyester with flexible spacer has beenstudied by using transmission electron microscopy. It was found that the lamellar structure couldbe observed in the crystalline samples of this semirigid polymer crystallized from different states.The thickness of lamellae is around 10 nm, which is similar to that of the conventional polymersof flexible chain molecules. The molecular chains in the lamellae are oriented in the thicknessdirection as determined by electron diffraction. The possibility of molecular chains folding in the lamellae has been discussed.展开更多
A novel engineering thermoplastic, phenolphthalein poly(ether ether sulfone)(PES C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheom...A novel engineering thermoplastic, phenolphthalein poly(ether ether sulfone)(PES C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS Ⅱ) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone and plate geometry give a temperature independent correlation for both blend and PES C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.展开更多
With the help of differential scanning calorimetry, cone-plate and capillary rheometry andscanning electron microscopy, a research has been conducted on rheological behavior,crystallization and morphology of poly (but...With the help of differential scanning calorimetry, cone-plate and capillary rheometry andscanning electron microscopy, a research has been conducted on rheological behavior,crystallization and morphology of poly (butylene terephthalate) (PBT) blends containing athermotropic LCP. The blend has zero entrance pressure loss, although the LCP has rather largeone. The viscosity curve of the blend lies between those of the LCP and PBT. The crystallizationof PBT is not affected by the presence of the LCP together with no indication oftransesterification between the two ingredients. LCP spheres and ellipsoids with the size of 0. 5--1. 5 μm disperse in PBT matrix uniformly, which is related to the viscosity ratio of the two components.展开更多
Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation aftercessation of shear flow was used to study the rheological behavior and internal structure of thermot...Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation aftercessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystallinepolymer(TLCP).There are two kinds of intermittent shear flow:all start-up flows are in the same direction(intermittent flowforward:IFF)and start-up flows change their directions alternately(intermittent flow reversal:IFR).The results show thatthe stress of start-up flow of IFF and IFR in the test process is not superposed,indicating different changes of internalstructure of thermotropic LCP(TLCP).Two main factors affect structure changes in the experimental time scale.One relatesto long-term texture relaxation process,the other is an interchain reaction that becomes important after 30 min.The twofactors raise the stress of IFF,but express complex effects for the stress of IFR.The latter factor becomes very important atlong time annealing process.The relaxation behavior was also studied by the application of wide range relaxation spectrumcalculated from the combined dynamic modulus,which gave three characteristic relaxation times(0.3,10 and 600 s)ascribable to the relaxations of less-phase orientation,domain orientation,and domain deformation,respectively.The resultalso shows that the domain coalescence(texture relaxation),a long relaxation time,is a much slow process and lasts beyond2400 s of the test time.展开更多
A new aromatic thermotropic liquid crystalline polyester-ether sulfone(PEES)was prepared from 4,4-bis(4-hydroxyphenoxy)diphenyl sulfone(BHPDS),terephthalic acid(TPA)and p-hydroxybenzoic acid(P-HBA).Some factors that a...A new aromatic thermotropic liquid crystalline polyester-ether sulfone(PEES)was prepared from 4,4-bis(4-hydroxyphenoxy)diphenyl sulfone(BHPDS),terephthalic acid(TPA)and p-hydroxybenzoic acid(P-HBA).Some factors that affected melting viscosity of polymer such as prepolymerization reaction medium and post-polymerization etc,were discussed.The liquid crystalline properties were characterized by DSC,polarizing microscope with a hot stage and WAXD measurements.展开更多
A new series of thermotropic liquid crystalline poly(ester- imide)s were synthesized via a solution polycondensation process.The polymers were also characterized by IR,DSC,polarizing microscopy and WAXD measurements.
Thermotropic liquid crystalline VHE terpolyesters made from vanillic acid (V),p-hydroxybenzoic acid (H) and poly(ethylene terephthalate) (E) were studied by 400 MHz NMR spectra, wide angle X-ray diffraction,scanning e...Thermotropic liquid crystalline VHE terpolyesters made from vanillic acid (V),p-hydroxybenzoic acid (H) and poly(ethylene terephthalate) (E) were studied by 400 MHz NMR spectra, wide angle X-ray diffraction,scanning electron and polarizing microscopes.It was found that the VHE terpolyesters had random sequence distribution.The VHE terpolyester films exhibited highly oriented fibrillar structure.展开更多
A new all aromatic thermotropic liquid crystalline polyester from acetylhydroquinone was prepared by nucleophilic substitution reaction and characterized for its thermotropic liquid crystalline property. The new polye...A new all aromatic thermotropic liquid crystalline polyester from acetylhydroquinone was prepared by nucleophilic substitution reaction and characterized for its thermotropic liquid crystalline property. The new polyester was amorphous which had glass transition at 274 degrees C. Above Tg, the sample exhibited typical nematic texture. It showed high thermal stability (Td=487 degrees C).展开更多
BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible...BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible from renewable resources in the form of pure enantiomers. Thus it is used to synthesize main chain cholesteric thermotropic liquid crystalline polymers. Incorporation of phenyl hydroquinone into the backbone of the main chain frustrates chain packing, thus lowering the crystallinity and depressing the melting point below the degradation temperature, also improves the solubility due to disruption of packing and maintains the mechanical and thermal performance. RESULTS: Optical microscopy study reveals that more than 50% of isosorbide content with phenyl hydroquinone and terephthalic acid showed “yellow iridescent oily streaks” with a background of mosaic/marble texture. These are the typical textures of cholesteric liquid crystalline phase. Copolyesters based on phenyl hydroquinone, isosorbide and terephthalic acid are soluble in aprotic solvents like N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Solubility increases with the content of isosorbide percent. Thermal stability of all copolyesters was more than 300?C on the basis of 10% wt loss. CONCLUSIONS: It was found that main chain cholesteric thermotropic liquid crystalline polymers can be prepared form chiral cycloaliphatic diol such as isosorbide. Main chain cholesteric thermotropic liquid crystalline polyesters are prepared from phenyl hydroquinone, isosorbide and terephthalic acid showed thermal stability more than 300?C. Main chain cholesteric thermotropic liquid crystalline polymers are soluble in aprotic solvents like DMAC, DMSO, DMF and NMP.展开更多
The present work concerns the crystallization of PET accelerated by addition of thermotropic liquid crystalline polymers (TLCP)based on two aromatic copolyesters: PHB/PET (60:40 ) and PHB/HDA/2,6-DNA /IPA ( 50:25 : 12...The present work concerns the crystallization of PET accelerated by addition of thermotropic liquid crystalline polymers (TLCP)based on two aromatic copolyesters: PHB/PET (60:40 ) and PHB/HDA/2,6-DNA /IPA ( 50:25 : 12.5 : 12.5 ). The investigation has been made by measurements of the cold-crystallization and melt-crystallization temperatures by DSC and of the changes of density and depolarizing light intensity during the isothermal process. In addition, the morphology of selectively etched surface of compressing pellets proved the presence of crystalline fibrillar structure, it can be supposed to have grown up from the micelle nucleus based on bundle of rigid TLCP chains.展开更多
基金supported by the National Science Foundation of China(No.50433010).
文摘Four novel copoly（ester-imide）s based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride, bis（trimellitic acid anhydride） phenyl ester and di-p-aminophenyl ester of dicarboxylic acids were synthesized via two-step method in order to investigate whether two imide mesogenic units with different conformation and polarity could control the formation of LC-phase. Polarizes light microscopy （PLM） and differential scanning calorimetry （DSC） have shown that three polymers formed the nematic phase with ＂thread schlieren texture＂ and a polymer formed the nematic phase with ＂Inversion walls texture＂.
文摘The lamellar structure of a thermotropic aromatic polyester with flexible spacer has beenstudied by using transmission electron microscopy. It was found that the lamellar structure couldbe observed in the crystalline samples of this semirigid polymer crystallized from different states.The thickness of lamellae is around 10 nm, which is similar to that of the conventional polymersof flexible chain molecules. The molecular chains in the lamellae are oriented in the thicknessdirection as determined by electron diffraction. The possibility of molecular chains folding in the lamellae has been discussed.
文摘A novel engineering thermoplastic, phenolphthalein poly(ether ether sulfone)(PES C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS Ⅱ) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone and plate geometry give a temperature independent correlation for both blend and PES C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.
基金Supported by the National Natural Science Foundation of China
文摘With the help of differential scanning calorimetry, cone-plate and capillary rheometry andscanning electron microscopy, a research has been conducted on rheological behavior,crystallization and morphology of poly (butylene terephthalate) (PBT) blends containing athermotropic LCP. The blend has zero entrance pressure loss, although the LCP has rather largeone. The viscosity curve of the blend lies between those of the LCP and PBT. The crystallizationof PBT is not affected by the presence of the LCP together with no indication oftransesterification between the two ingredients. LCP spheres and ellipsoids with the size of 0. 5--1. 5 μm disperse in PBT matrix uniformly, which is related to the viscosity ratio of the two components.
基金This work was supported by the National Natural Science Foundation of China(Nos.201740242020400750290090).
文摘Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation aftercessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystallinepolymer(TLCP).There are two kinds of intermittent shear flow:all start-up flows are in the same direction(intermittent flowforward:IFF)and start-up flows change their directions alternately(intermittent flow reversal:IFR).The results show thatthe stress of start-up flow of IFF and IFR in the test process is not superposed,indicating different changes of internalstructure of thermotropic LCP(TLCP).Two main factors affect structure changes in the experimental time scale.One relatesto long-term texture relaxation process,the other is an interchain reaction that becomes important after 30 min.The twofactors raise the stress of IFF,but express complex effects for the stress of IFR.The latter factor becomes very important atlong time annealing process.The relaxation behavior was also studied by the application of wide range relaxation spectrumcalculated from the combined dynamic modulus,which gave three characteristic relaxation times(0.3,10 and 600 s)ascribable to the relaxations of less-phase orientation,domain orientation,and domain deformation,respectively.The resultalso shows that the domain coalescence(texture relaxation),a long relaxation time,is a much slow process and lasts beyond2400 s of the test time.
文摘A new aromatic thermotropic liquid crystalline polyester-ether sulfone(PEES)was prepared from 4,4-bis(4-hydroxyphenoxy)diphenyl sulfone(BHPDS),terephthalic acid(TPA)and p-hydroxybenzoic acid(P-HBA).Some factors that affected melting viscosity of polymer such as prepolymerization reaction medium and post-polymerization etc,were discussed.The liquid crystalline properties were characterized by DSC,polarizing microscope with a hot stage and WAXD measurements.
文摘A new series of thermotropic liquid crystalline poly(ester- imide)s were synthesized via a solution polycondensation process.The polymers were also characterized by IR,DSC,polarizing microscopy and WAXD measurements.
文摘Thermotropic liquid crystalline VHE terpolyesters made from vanillic acid (V),p-hydroxybenzoic acid (H) and poly(ethylene terephthalate) (E) were studied by 400 MHz NMR spectra, wide angle X-ray diffraction,scanning electron and polarizing microscopes.It was found that the VHE terpolyesters had random sequence distribution.The VHE terpolyester films exhibited highly oriented fibrillar structure.
文摘A new all aromatic thermotropic liquid crystalline polyester from acetylhydroquinone was prepared by nucleophilic substitution reaction and characterized for its thermotropic liquid crystalline property. The new polyester was amorphous which had glass transition at 274 degrees C. Above Tg, the sample exhibited typical nematic texture. It showed high thermal stability (Td=487 degrees C).
文摘BACKGROUND: Generally main chain cholesteric thermotropic liquid crystalline polymers are prepared form chiral diacid or diol monomer. But these monomers are costly. Isosorbide is chiral cycloaliphatic diol accessible from renewable resources in the form of pure enantiomers. Thus it is used to synthesize main chain cholesteric thermotropic liquid crystalline polymers. Incorporation of phenyl hydroquinone into the backbone of the main chain frustrates chain packing, thus lowering the crystallinity and depressing the melting point below the degradation temperature, also improves the solubility due to disruption of packing and maintains the mechanical and thermal performance. RESULTS: Optical microscopy study reveals that more than 50% of isosorbide content with phenyl hydroquinone and terephthalic acid showed “yellow iridescent oily streaks” with a background of mosaic/marble texture. These are the typical textures of cholesteric liquid crystalline phase. Copolyesters based on phenyl hydroquinone, isosorbide and terephthalic acid are soluble in aprotic solvents like N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). Solubility increases with the content of isosorbide percent. Thermal stability of all copolyesters was more than 300?C on the basis of 10% wt loss. CONCLUSIONS: It was found that main chain cholesteric thermotropic liquid crystalline polymers can be prepared form chiral cycloaliphatic diol such as isosorbide. Main chain cholesteric thermotropic liquid crystalline polyesters are prepared from phenyl hydroquinone, isosorbide and terephthalic acid showed thermal stability more than 300?C. Main chain cholesteric thermotropic liquid crystalline polymers are soluble in aprotic solvents like DMAC, DMSO, DMF and NMP.
文摘The present work concerns the crystallization of PET accelerated by addition of thermotropic liquid crystalline polymers (TLCP)based on two aromatic copolyesters: PHB/PET (60:40 ) and PHB/HDA/2,6-DNA /IPA ( 50:25 : 12.5 : 12.5 ). The investigation has been made by measurements of the cold-crystallization and melt-crystallization temperatures by DSC and of the changes of density and depolarizing light intensity during the isothermal process. In addition, the morphology of selectively etched surface of compressing pellets proved the presence of crystalline fibrillar structure, it can be supposed to have grown up from the micelle nucleus based on bundle of rigid TLCP chains.
