Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure f...Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure from the living environment.This study included 1311 women in late pregnancy from the Zunyi birth cohort and measured the urinary concentrations of 10 hydroxylated PAH metabolites(OH-PAHs).Risk assessment was conducted based on the estimated daily intake to calculate the hazard quotient and hazard index(HI).A linear regression model was used to analyze the relationship between creatinine-adjusted OH-PAHs concentrations and living environment and lifestyle factors,while principal component analysis was applied to trace the sources of PAHs exposure.1-OHPYR was detected in all participants’urine,with naphthalene metabolites having the highest concentrations among creatinine-adjusted PAHs.OH-PAHs concentrations were associated with housing type,room number,cooking frequency,household size,exercise frequency,fuel type,distance from main road,and drinking water source.Pregnant women using traditional fuels and living in bungalows had higher health risks than those using clean energy and living in buildings.Those living within 100 m of a main road had higher HI than those farther away.Coal combustion was identified as the primary source of PAHs exposure.The study emphasizes the importance of reducing PAHs exposure,especially for pregnant women living in polluted environments.It recommends public health interventions such as improving indoor ventilation and providing clean energy to reduce related health risks.展开更多
The crystalline morphology of a thermotropic aromatic polyester has been studied by microscopy techniques. Spherulites with ringed structure under polarizing micioscope were observed for solution cast specimens, They ...The crystalline morphology of a thermotropic aromatic polyester has been studied by microscopy techniques. Spherulites with ringed structure under polarizing micioscope were observed for solution cast specimens, They were composed of radially growing crystalline lamellae of thickness around 100. It was found that the molecules were packed in the thickness direction. Banded texture was observed in randomly packed domains for melt cast specimens. The bands have the same width and internal structure as those usually observed in oriented specimens of these polymers obtained by shearing their mesomorphic melt.展开更多
An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of t...An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of the AB(2) monomer, 5-acetoxyisophthalic acid. Polymer P1 was converted into the polymeric acid chloride by reaction with thionyl chloride. The acid chloride was reacted with ethanol and glycidol to form a poly(ethyl ester) (P2) and an epoxy terminated material (P3), respectively. The reaction conditions in each step of these processes had to be controlled very carefully to avoid unwanted cross-linking reactions. The characterization of products and intermediates, including molecular weight distributions and thermal properties, are reported.展开更多
A novel polyester containing ferrocenyl was prepared by low-temperature interface polycondensation of 1,1'-ferrocenedicarboxylic acid chloride with 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ),which is a twisted...A novel polyester containing ferrocenyl was prepared by low-temperature interface polycondensation of 1,1'-ferrocenedicarboxylic acid chloride with 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ),which is a twisted non-coplanar heterocyclic bisphenol-like monomer.The newly generated polymer was evaluated based on characterization of its solubility,viscosity measurements,elemental analysis,FTIR spectroscopy,differential scanning calorimetric and thermogravimetric studies.展开更多
Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solu...Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solution and in the presence of pyridine as a base. The polycondensation reactions produce a series of new polyesters （4a-f） in high yields, and inherent viscosity between 0.30 and 0.55 dL/g. The resulting polyesters were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis （TGA and DTG）, solubility test, Fourier transform infrared （FT-IR） spectroscopy and gel permeation chromatography （GPC）. C 2009 Khalil Faghihi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.展开更多
Six aromatic polyesters were prepared for gas separation membranes, and their permeation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane were measured at 30 degrees C and 1 atmosphere by low pre...Six aromatic polyesters were prepared for gas separation membranes, and their permeation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane were measured at 30 degrees C and 1 atmosphere by low pressure manometric method. The correlation between the gas transport behavior and molecular structure of aromatic polyester membrane is discussed. These data are interpreted qualitatively in terms of the calculated packing density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.展开更多
Infrared spectra at different temperatures have been studied for fractions ofa liquid crystal tormmg aromatic polyester. The molecular interactions in different phases and their changes duringthe transitions were disc...Infrared spectra at different temperatures have been studied for fractions ofa liquid crystal tormmg aromatic polyester. The molecular interactions in different phases and their changes duringthe transitions were discussed. Abrupt frequency shift was found for bands of groups both in mesogens and flexible spacers during fusion and isotropization transitions. It may imply that both the mesogens and the flexible spacers are included in the same crystalline phase and give their contributions to the formation of the mesophase. The splitting into doublet of the C—O stretching vibrations was observed for both the aromatic and aliphatic esters and was attributed to the existence of local regions for ester groups different in ordering. The more ordered regions do not disappear completely even in the isotropic liquid phase.展开更多
Crystalline morphology in a series of CH_(3)-substituted main chain thermotropic aromatic polyesters with even and odd numbered methylene spacers has been studied by polarizing optical microscopy(POM),scanning electro...Crystalline morphology in a series of CH_(3)-substituted main chain thermotropic aromatic polyesters with even and odd numbered methylene spacers has been studied by polarizing optical microscopy(POM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).On crystallization from solution evaporation spherulites of radial structure were observed in the polymers with even numbered spacers,but spherulites with concentric rings form in the polymer with odd numbered spacers.Both spherulites have a lamellar structure,which is about 10 nm in thickness.On crystallization from nematic glassy state spherulites can not be grown;lamellar structure was only observed around disclinations in a specimen during crystallization.Ln the case of crystallization from nematic melt two types of spherulites can be observed far the sample with even numbered spacers.For the sample with add numbered spacers spherulites can not be formed,but only irregular crystallites.展开更多
Six new polyesters 7a-f were synthesized through the solution polycondensation reaction of diacid chloride 5 with six aromatic diols 6a-f in N,N-dimethyl acetamide(DMAc) as solvent in the presence of pyridine as base....Six new polyesters 7a-f were synthesized through the solution polycondensation reaction of diacid chloride 5 with six aromatic diols 6a-f in N,N-dimethyl acetamide(DMAc) as solvent in the presence of pyridine as base.The polycondensation reaction produced a series of novel polyester containing pyridyl moiety in the main chain in high yields with inherent viscosities between 0.35 and 0.54 dL/g.The resulted polymers were fully characterized by means of FT-IR spectroscopy,elemental analyses,inherent viscosity ...展开更多
Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalli...Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.展开更多
A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic...A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BG) and ethylene glycol (EG) through direct esterification and polycondensation. The sequence structure and crystallinity of the copolyester were investigated by 1H NMR spectroscopy and the wide-angle X-ray diffractometry (WAXD). The analytical results showed that the PBATE copolyester was a random copolymer and the composition of PBATE copolyester was almost consistent with the feed molar ratios. The crystal structure of PBATE copolyester belonged to the triclinic crystalline system; The variation in melting point of the synthesized PBATE copolyester agreed well with the estimation obtained by the Flory equation and was applicable to the random copolymer.展开更多
The radiative curable dendritic acrylated aromatic/aliphatic polyesters based on pentaerythritol, 1,2,4 benzenetricaboxylic anhydride and epoxy propane modified with acryloyl chloride were synthesized via a diver...The radiative curable dendritic acrylated aromatic/aliphatic polyesters based on pentaerythritol, 1,2,4 benzenetricaboxylic anhydride and epoxy propane modified with acryloyl chloride were synthesized via a divergent procedure, and their photopolymerization kinetics was studied by photo differential scanning calorimetry. The mechanical properties and the morphology of the fracture surface of the cured dendritic polyester films were investigated by means of dynamic mechanical thermal analysis and scanning electron microscopy, respectively.展开更多
The crystallinities, thermal properties, liquid crystal properties and rheologic properties oftwo series of the aromatic copolyesters are studied. One of them is composed of IPA, 2,6-NDA,CLHQA, PABA and. the other com...The crystallinities, thermal properties, liquid crystal properties and rheologic properties oftwo series of the aromatic copolyesters are studied. One of them is composed of IPA, 2,6-NDA,CLHQA, PABA and. the other composed of TPA, 2.6-NDA, CLHQA, IPA. The results showthat the crystallinities of the aromatic copolyesters are relatively low and the melting point of thecopolyesters decreases with an increase of the unsymmetrical contents. These two series of aro-matic copolyesters are both suitable for the conventional melt spinning process and have a goodfiber forming property and a good thermal stability. The viscosities of aromatic copolyestermelts are greatly affected by the shear rate, hence the so-called" thinning under shearing" phe-nomenon. The melts have a rather high viscosity flow activation energy and a relatively lowelasticity.展开更多
A new spherulite-like structure of main chain thermotropic aromatic copolyesters formed in solution cast specimens was observed and was studied by means of polarizing microscopy, X-ray diffraction, SEM and IR spectrom...A new spherulite-like structure of main chain thermotropic aromatic copolyesters formed in solution cast specimens was observed and was studied by means of polarizing microscopy, X-ray diffraction, SEM and IR spectrometry. Results indicate that the spherulite-like structure of main chain thermotropic aromatic copolyesters formed from the casting solution (phenol/Cl2CH2CH2Cl2) is not a real crystal but only a high oriented arrangement of the macromolecular chains as a spherulite. This resulted from the interaction between the needle-like crystal of phenol and the rigid mesomorphic groups of molecular chain. The parallel packing of extended copolyester molecules along the needle-like crystal of phenol leads to the formation of the spherulite-like structure.展开更多
Several novel aromatic liquid crystalline copolyesters with regular sequence structure were prepared by melt Sehotten-Baumann polycondensation via complex monomer. Polarizing microscope with hot stage, thermal analysi...Several novel aromatic liquid crystalline copolyesters with regular sequence structure were prepared by melt Sehotten-Baumann polycondensation via complex monomer. Polarizing microscope with hot stage, thermal analysis and X-ray diffraction were used to investigate the structure and properties of the copolyesters. The effects of structural units, such as flexible spacer, noncolinear meta-linked phenylene unit, crankshaft unit, kink with flexible bridging unit and various substituted benzene rings on melting temperature of aromatic copolyesters were studied and discussed on the basis of crystalline structure of the polymers.展开更多
Biodegradable aliphatic/aromatic copolyesters, poly（butylene terephthalate-co-lactate） （PBTL） were prepared via direct melt polycondensation of terephthalic acid （TPA）, 1,4-butanediol （BDO） and poly（L-lactic ...Biodegradable aliphatic/aromatic copolyesters, poly（butylene terephthalate-co-lactate） （PBTL） were prepared via direct melt polycondensation of terephthalic acid （TPA）, 1,4-butanediol （BDO） and poly（L-lactic acid） oligomer （OLLA）. The effects of polymerization time and temperature, as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated. The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃ for 6 h. DSC, XRD, DMA and TGA analysis clearly indicated that the degree of crystallinity, glass-transition temperature, melting point, decomposition temperature, tensile strength, elongation and Young＇s modulus were influenced by the ratio between TPA and OLLA in the final copolyesters. Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.展开更多
A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl di...A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.展开更多
In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid （TPA）, poly（L-lactic acid） oligomer （OLLA）, 1,4-butanediol （BDO）...In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid （TPA）, poly（L-lactic acid） oligomer （OLLA）, 1,4-butanediol （BDO） and nano-SiO2. TEM and FT-IR characterizations confirmed that TPA, OLLA and BDO copolymerized to obtain biodegradable copolyesters, poly（butylene terepbthalate-co-lactate） （PBTL）, and the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted PBTL. The nano-SiO2 particles were chemically wrapped with PBTL to form PBTL/nano- SiO2 hybrids. Due to the good dispersion and interfacial adhesion of nano-SiO2 particles with the copolyester matrix, the tensile strength and the Young＇s modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO2 hybrids with 5 wt.% nano-SiO2, respectively. The mechanical properties of PBTL/nano-SiO2 hybrids were substantially improved.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
In order to explore new substitutes for 2,5 furandicarboxylic acid(FDCA)or poly(ethylene 2,5 furandicarboxylate)(PEF)and try to develop more ideal bio based polyesters,several thiophene aromatic polyesters(PETH,PPTH,P...In order to explore new substitutes for 2,5 furandicarboxylic acid(FDCA)or poly(ethylene 2,5 furandicarboxylate)(PEF)and try to develop more ideal bio based polyesters,several thiophene aromatic polyesters(PETH,PPTH,PBTH,and PHTH)were synthesized from dimethyl thiophene 2,5-dicarboxylate(DMTD)and different diols,including ethylene glycol,1,3-propanediol,1,4-butanediol,and 1,6-hexanediol.The chemical structures of obtained polyesters were confirmed by nuclear magnetic resonance spectroscopy(H-NMR and 1'C-NMR).Determined by GPC measurement,their average molecular weight(M.)varied from 5.22 x 10*g/mol to 7.94 x 10*g/mol with the molar-mass dispersity of 1.50-2.00.Based on the DSC and TGA results,the synthesized polyesters PETH,PPTH,and PBTH displayed comparable or even better thermal properties when compared with their FDCA-based analogues.From PETH to PHTH,their Tg varied from 64.6°Cto-1°C while Tsm ranged from 409 C to 380°C in nitrogen atmosphere,PETH showed elongation at break as high as 378%,tensile strength of 67 MPa,and tensile modulus of 1800 MPa.Meanwhile,the CO2 and O2 barrier of PETH was 12.0 and 6.6 folds higher than those of PET,respectively,and similar to those of PEF.Considering the overall properties,the synthesized thiophene aromatic polyesters,especially PETH,showed great potential to be used as an excellent bio based packaging material in the future.展开更多
基金supported by the National Key R&D Program of China(Nos.2018YFC1004300 and 2018YFC1004302)the Science&Technology Program of Guizhou Province(Nos.QKHHBZ[2020]3002,QKHPTRC-GCC[2022]039-1 and QKHPTRCCXTD[2022]014)the Scientific Research Program of Guizhou Provincial Department of Education(No.QJJ[2023]019).
文摘Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure from the living environment.This study included 1311 women in late pregnancy from the Zunyi birth cohort and measured the urinary concentrations of 10 hydroxylated PAH metabolites(OH-PAHs).Risk assessment was conducted based on the estimated daily intake to calculate the hazard quotient and hazard index(HI).A linear regression model was used to analyze the relationship between creatinine-adjusted OH-PAHs concentrations and living environment and lifestyle factors,while principal component analysis was applied to trace the sources of PAHs exposure.1-OHPYR was detected in all participants’urine,with naphthalene metabolites having the highest concentrations among creatinine-adjusted PAHs.OH-PAHs concentrations were associated with housing type,room number,cooking frequency,household size,exercise frequency,fuel type,distance from main road,and drinking water source.Pregnant women using traditional fuels and living in bungalows had higher health risks than those using clean energy and living in buildings.Those living within 100 m of a main road had higher HI than those farther away.Coal combustion was identified as the primary source of PAHs exposure.The study emphasizes the importance of reducing PAHs exposure,especially for pregnant women living in polluted environments.It recommends public health interventions such as improving indoor ventilation and providing clean energy to reduce related health risks.
文摘The crystalline morphology of a thermotropic aromatic polyester has been studied by microscopy techniques. Spherulites with ringed structure under polarizing micioscope were observed for solution cast specimens, They were composed of radially growing crystalline lamellae of thickness around 100. It was found that the molecules were packed in the thickness direction. Banded texture was observed in randomly packed domains for melt cast specimens. The bands have the same width and internal structure as those usually observed in oriented specimens of these polymers obtained by shearing their mesomorphic melt.
基金The project is supported by the EPSRC and the Youth Science Foundation of Shanghai Higher Education.
文摘An epoxy-terminated hyperbranched aromatic polyester (P3) was synthesized from a hyperbranched aromatic polyester containing carboxylic acid end groups (P1), which was derived from the condensation polymerization of the AB(2) monomer, 5-acetoxyisophthalic acid. Polymer P1 was converted into the polymeric acid chloride by reaction with thionyl chloride. The acid chloride was reacted with ethanol and glycidol to form a poly(ethyl ester) (P2) and an epoxy terminated material (P3), respectively. The reaction conditions in each step of these processes had to be controlled very carefully to avoid unwanted cross-linking reactions. The characterization of products and intermediates, including molecular weight distributions and thermal properties, are reported.
基金supported by Education Office of Liaoning Province(No.2008567)
文摘A novel polyester containing ferrocenyl was prepared by low-temperature interface polycondensation of 1,1'-ferrocenedicarboxylic acid chloride with 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ),which is a twisted non-coplanar heterocyclic bisphenol-like monomer.The newly generated polymer was evaluated based on characterization of its solubility,viscosity measurements,elemental analysis,FTIR spectroscopy,differential scanning calorimetric and thermogravimetric studies.
文摘Six new thermally stable polyesters （4a-f） were synthesized through the solution polycondensation reaction of 2,5-pyridine dicarbonyldichloride （2） with six aromatic diols in N,N＇-dimethyl acetamide （DMAc） solution and in the presence of pyridine as a base. The polycondensation reactions produce a series of new polyesters （4a-f） in high yields, and inherent viscosity between 0.30 and 0.55 dL/g. The resulting polyesters were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis （TGA and DTG）, solubility test, Fourier transform infrared （FT-IR） spectroscopy and gel permeation chromatography （GPC）. C 2009 Khalil Faghihi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
文摘Six aromatic polyesters were prepared for gas separation membranes, and their permeation properties for hydrogen, oxygen, nitrogen, carbon dioxide, and methane were measured at 30 degrees C and 1 atmosphere by low pressure manometric method. The correlation between the gas transport behavior and molecular structure of aromatic polyester membrane is discussed. These data are interpreted qualitatively in terms of the calculated packing density, gas-polymer interaction, concentration of aryl bromine on backbone, and effect of silane group on main chain of polymer.
文摘Infrared spectra at different temperatures have been studied for fractions ofa liquid crystal tormmg aromatic polyester. The molecular interactions in different phases and their changes duringthe transitions were discussed. Abrupt frequency shift was found for bands of groups both in mesogens and flexible spacers during fusion and isotropization transitions. It may imply that both the mesogens and the flexible spacers are included in the same crystalline phase and give their contributions to the formation of the mesophase. The splitting into doublet of the C—O stretching vibrations was observed for both the aromatic and aliphatic esters and was attributed to the existence of local regions for ester groups different in ordering. The more ordered regions do not disappear completely even in the isotropic liquid phase.
基金This work was supported by the National Key Prject of Fundamental Research"Maromolcular Condensed State"Ministy of Scicncc and Technology,China and by Polymer Physics Laboratory,Chinesec Academy of Science.
文摘Crystalline morphology in a series of CH_(3)-substituted main chain thermotropic aromatic polyesters with even and odd numbered methylene spacers has been studied by polarizing optical microscopy(POM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).On crystallization from solution evaporation spherulites of radial structure were observed in the polymers with even numbered spacers,but spherulites with concentric rings form in the polymer with odd numbered spacers.Both spherulites have a lamellar structure,which is about 10 nm in thickness.On crystallization from nematic glassy state spherulites can not be grown;lamellar structure was only observed around disclinations in a specimen during crystallization.Ln the case of crystallization from nematic melt two types of spherulites can be observed far the sample with even numbered spacers.For the sample with add numbered spacers spherulites can not be formed,but only irregular crystallites.
文摘Six new polyesters 7a-f were synthesized through the solution polycondensation reaction of diacid chloride 5 with six aromatic diols 6a-f in N,N-dimethyl acetamide(DMAc) as solvent in the presence of pyridine as base.The polycondensation reaction produced a series of novel polyester containing pyridyl moiety in the main chain in high yields with inherent viscosities between 0.35 and 0.54 dL/g.The resulted polymers were fully characterized by means of FT-IR spectroscopy,elemental analyses,inherent viscosity ...
文摘Polyesters consisting of substituted aromatic type Schiff base mesogenic unit andpolymethylene spacers were synthesized and their thermal transitions and liquid crystallineproperties were studied. The liquid crystalline behaviour has been characterized by differentialscanning calorimetry (DSC) and optical polarizing microscopy. Structural broadening bysubstitution of methoxy group in 2, 2' positions of the mesogenic core produce polymers withlower transition temperatures. Polymers synthesized from ortho and meta substituted phenylenediamine did not form a liquid crystal phase.
文摘A series of biodegradable aliphatic-aromatic copolyesters, poly(butylene terephthalate-co-butylene adipate-co- ethylene terephthalate-co-ethylene adipate) (PBATE), were synthesized from terephthalic acid (PTA), adipic acid (AA), 1,4-butanediol (BG) and ethylene glycol (EG) through direct esterification and polycondensation. The sequence structure and crystallinity of the copolyester were investigated by 1H NMR spectroscopy and the wide-angle X-ray diffractometry (WAXD). The analytical results showed that the PBATE copolyester was a random copolymer and the composition of PBATE copolyester was almost consistent with the feed molar ratios. The crystal structure of PBATE copolyester belonged to the triclinic crystalline system; The variation in melting point of the synthesized PBATE copolyester agreed well with the estimation obtained by the Flory equation and was applicable to the random copolymer.
基金Supported by the National Natural Science Foundation of China(No. 2 0 0 74 0 34)
文摘The radiative curable dendritic acrylated aromatic/aliphatic polyesters based on pentaerythritol, 1,2,4 benzenetricaboxylic anhydride and epoxy propane modified with acryloyl chloride were synthesized via a divergent procedure, and their photopolymerization kinetics was studied by photo differential scanning calorimetry. The mechanical properties and the morphology of the fracture surface of the cured dendritic polyester films were investigated by means of dynamic mechanical thermal analysis and scanning electron microscopy, respectively.
文摘The crystallinities, thermal properties, liquid crystal properties and rheologic properties oftwo series of the aromatic copolyesters are studied. One of them is composed of IPA, 2,6-NDA,CLHQA, PABA and. the other composed of TPA, 2.6-NDA, CLHQA, IPA. The results showthat the crystallinities of the aromatic copolyesters are relatively low and the melting point of thecopolyesters decreases with an increase of the unsymmetrical contents. These two series of aro-matic copolyesters are both suitable for the conventional melt spinning process and have a goodfiber forming property and a good thermal stability. The viscosities of aromatic copolyestermelts are greatly affected by the shear rate, hence the so-called" thinning under shearing" phe-nomenon. The melts have a rather high viscosity flow activation energy and a relatively lowelasticity.
基金This work was supported by the National Key Project for Fundamental Research"Macromolecular Condensed State",The State Science and Technology Commission of China.
文摘A new spherulite-like structure of main chain thermotropic aromatic copolyesters formed in solution cast specimens was observed and was studied by means of polarizing microscopy, X-ray diffraction, SEM and IR spectrometry. Results indicate that the spherulite-like structure of main chain thermotropic aromatic copolyesters formed from the casting solution (phenol/Cl2CH2CH2Cl2) is not a real crystal but only a high oriented arrangement of the macromolecular chains as a spherulite. This resulted from the interaction between the needle-like crystal of phenol and the rigid mesomorphic groups of molecular chain. The parallel packing of extended copolyester molecules along the needle-like crystal of phenol leads to the formation of the spherulite-like structure.
文摘Several novel aromatic liquid crystalline copolyesters with regular sequence structure were prepared by melt Sehotten-Baumann polycondensation via complex monomer. Polarizing microscope with hot stage, thermal analysis and X-ray diffraction were used to investigate the structure and properties of the copolyesters. The effects of structural units, such as flexible spacer, noncolinear meta-linked phenylene unit, crankshaft unit, kink with flexible bridging unit and various substituted benzene rings on melting temperature of aromatic copolyesters were studied and discussed on the basis of crystalline structure of the polymers.
基金supported by the Natural Science Foundation of Ningbo(No.2007A610030)Scientific Special Fund of Zhejiang Province(No.2008C11092-2)
文摘Biodegradable aliphatic/aromatic copolyesters, poly（butylene terephthalate-co-lactate） （PBTL） were prepared via direct melt polycondensation of terephthalic acid （TPA）, 1,4-butanediol （BDO） and poly（L-lactic acid） oligomer （OLLA）. The effects of polymerization time and temperature, as well as aliphatic/aromatic moiety ratio on the physical and thermal properties were investigated. The largest molecular weight of the copolyesters was up to 64100 with molecular weight distribution index of 2.09 when the polycondensation was carried out at 230℃ for 6 h. DSC, XRD, DMA and TGA analysis clearly indicated that the degree of crystallinity, glass-transition temperature, melting point, decomposition temperature, tensile strength, elongation and Young＇s modulus were influenced by the ratio between TPA and OLLA in the final copolyesters. Hydrolytic degradation results demonstrated that the incorporation of biodegradable lactate moieties into the aromatic polyester could efficiently improve hydrolytic degradability of the copolymer even though it still had many aromatic units in the main chains.
基金The work was supported by the National Natural Science Foundation of China.
文摘A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.
基金support from the Natural Science Foundation of Ningbo(No.2007A610030)Science and Technology Department of Zhejiang Province(No.2008C11092-2)
文摘In situ melt polycondensation was proposed to prepare biodegradable aliphatic-aromatic copolyesters/nano-SiO2 hybrids based on terephthalic acid （TPA）, poly（L-lactic acid） oligomer （OLLA）, 1,4-butanediol （BDO） and nano-SiO2. TEM and FT-IR characterizations confirmed that TPA, OLLA and BDO copolymerized to obtain biodegradable copolyesters, poly（butylene terepbthalate-co-lactate） （PBTL）, and the abundant hydroxyl groups on the surface of nano-SiO2 provided potential sites for in situ grafting with the simultaneous resulted PBTL. The nano-SiO2 particles were chemically wrapped with PBTL to form PBTL/nano- SiO2 hybrids. Due to the good dispersion and interfacial adhesion of nano-SiO2 particles with the copolyester matrix, the tensile strength and the Young＇s modulus increased from 5.4 and 5.6 MPa for neat PBTL to 16 and 390 MPa for PBTL/nano-SiO2 hybrids with 5 wt.% nano-SiO2, respectively. The mechanical properties of PBTL/nano-SiO2 hybrids were substantially improved.
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).
基金This work was finanially supported by the National Natural Science Foundation of China(No.21975270)Zhejiang Provincial Natural Science Foundation of China(No.LR20E030001)+2 种基金Ningbo 2025 Key Scientific Research Programs(No.2018810015)National Key Research and Development Program of China(No.2018YFD0400700)Research Project of Ningbo Natural Science Foundation(No.2019A610141).
文摘In order to explore new substitutes for 2,5 furandicarboxylic acid(FDCA)or poly(ethylene 2,5 furandicarboxylate)(PEF)and try to develop more ideal bio based polyesters,several thiophene aromatic polyesters(PETH,PPTH,PBTH,and PHTH)were synthesized from dimethyl thiophene 2,5-dicarboxylate(DMTD)and different diols,including ethylene glycol,1,3-propanediol,1,4-butanediol,and 1,6-hexanediol.The chemical structures of obtained polyesters were confirmed by nuclear magnetic resonance spectroscopy(H-NMR and 1'C-NMR).Determined by GPC measurement,their average molecular weight(M.)varied from 5.22 x 10*g/mol to 7.94 x 10*g/mol with the molar-mass dispersity of 1.50-2.00.Based on the DSC and TGA results,the synthesized polyesters PETH,PPTH,and PBTH displayed comparable or even better thermal properties when compared with their FDCA-based analogues.From PETH to PHTH,their Tg varied from 64.6°Cto-1°C while Tsm ranged from 409 C to 380°C in nitrogen atmosphere,PETH showed elongation at break as high as 378%,tensile strength of 67 MPa,and tensile modulus of 1800 MPa.Meanwhile,the CO2 and O2 barrier of PETH was 12.0 and 6.6 folds higher than those of PET,respectively,and similar to those of PEF.Considering the overall properties,the synthesized thiophene aromatic polyesters,especially PETH,showed great potential to be used as an excellent bio based packaging material in the future.
