Thermotropic polyesters. 2: Synthesis, characterization and thermal transitions of copolyesters containing 4,4′-bis (ω-alkyloxy) biphenyl isophthalate units

Thermotropic copolyesters containing an isophthalate unit and mesogenic 4, 4′-bis (ω-hydroxyalkyloxy) biphenyls (n = 3, 4, 6) with different numbers of methylene units have been synthesized by melt polymerization. The number-average molar mass (M_n) was estimated from end group analysis by ¹H NMR. The copolymer compositions were also obtained from ¹H NMR. The thermal behavior of the copolymers containing even-even (n = 4, 6) and odd-even (n = 3, 4) pairings has been investigated and is also compared with that of the analogous homopolymers. The copolymers exhibit reduced melting point and extending liquid crystalline range identified using polarizing microscopy and DSC. All of the obtained compounds were characterized by conventional spectroscopic methods.     

Synthesis,physical properties and enzymatic degradation of bio-based poly(butylene adipate-co-butylene furandicarboxylate) copolyesters

A series of bio-based poly(butylene adipate-co-butylene furandicarboxylate) (PBAFs) copolyesters were synthesized from 2,5-furandicarboxylic acid (FDCA), adipic acid (AA), and 1,4-butanediol (BDO) through a two-step polycondensation reaction. The copolyesters were characterized by ¹H NMR, GPC, DSC, XRD and tensile tests, and their enzymatic degradation behaviors were also investigated. They were random copolymers whose composition was well controlled and the weight average molecular weight (M_w) ranged from 54,100 to 76,800 g/mol. By combining the results of DSC and XRD, with increasing FDCA content, PBAFs changed from semi-crystalline polymers to nearly amorphous polymers, then to semi-crystalline polymers again. Specifically, the crystallizability and melting temperature (T_m) decreased with FDCA content 0–50 mol%, but rose again at FDCA content 75–100 mol%. And, the glass transition temperature (T_g) increased continuously with increasing FDCA content. Consequently, the tensile modulus and strength decreased but the ultimate elongation increased at lower FDCA content (0–50 mol%), which were converse at higher FDCA content (75–100 mol%). Especially, the P(BA-40 mol% BF) shows outstanding elasticity and rebound resilience. In addition, the influences of FDCA content on the enzymatic degradation by lipase from porcine pancreas were studied in terms of the weight loss and morphological change. At FDCA content of 0–50 mol%, the copolyesters showed biodegradability but only the degradation rate of P(BA-10 mol% BF) was faster than PBA. When the FDCA content were 75–100 mol%, they were actually un-degradable. Thus, depending on their composition, PBAFs might find applications from biodegradable elastomers to thermoplastics.     

Thermal Properties and Crystallinity of Thermotropic Liquid Crystalline Copolyesters Prepared from Poly(ethylene terephtalate) (PET) and Rigid Aromatic Units

A series of copolyesters were synthesized by melt‐polycondensation reaction of poly(ethylene terephtalate) (PET) with various proportions of equimolar compositions of p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephtalic acid (TPA). Viscosity, liquid crystallinity, thermal properties, degree of crystallinity and thermal stabilitiy of these copolyesters were investigated by Ubbelohde viscometer, hot‐stage polarized light microscopy (PLM), differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD) and thermogravimetric analysis (TGA), respectively. On the basis of viscosity measurement, it was observed that intrinsic viscosity values of the copolyesters are increased regularly with increasing amounts of aromatic units (p‐ABA, HQDA and TPA) in the polymer chain. Thermotropic liquid crystalline behavior was observed in the copolyesters containing over 50 mol% of rigid p‐ABA/HQDA/TPA aromatic units. DSC analysis of the anisotropic copolyesters revealed broad and weak endotherms associated with the nematic phases, and the melting temperatures were found to be in the processable region. As the mol% of PET in the polymer chain increased, the specific enthalpies of fusion and the degree of crystallinity of the copolyesters were also increased regularly.     

Synthesis and characterization of amorphous poly(ethylene terephthalate) copolymers containing bis[4-(2-hydroxyethoxy)phenyl]sulfone

Poly(ethylene terephthalate) copolymers (abbreviated as PETS) that contain bis[4-(2-hydroxyethoxy)phenyl]sulfone (BHEPS) were prepared from dimethyl terephthalate (DMT), ethylene glycol (EG) (5-95%) and BHEPS (5-95%). The compositions and microstructures of the copolyesters were determined by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy, respectively. The thermal behaviors were studied over the entire range of copolymer compositions, using X-ray analysis, differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The molecular weights, optical characteristics and tensile properties of these polymers were also determined. Experimental results indicated that the copolymers had a random microstructure. The intrinsic viscosities of the copolymers ranged from 0.65 to 0.69 dL/g. The copolyesters with BHEPS of <10 mol% were crystallizable, whereas the copolyesters with BHEPS of ?10 mol% were amorphous. Incorporating BHEPS affected the glass-transition temperature (T_g) values of those polymers, from about 81 °C for PETS₅ to 126 °C for PETS₉₅. The optical transmissions exceeded 86% for λ = 400 nm for all of the amorphous polyesters. The tensile modulus and strength of the copolyesters increased with BHEPS. However, they also became brittle and their elongation at break decreased.     

Synthesis and characterization of isomeric polyesters based on sebacic acid and hexanediols

Isomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6-hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a T_g of ?62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2-methyl-2-ethyl-1,3-propanediol and 2,5-hexanediol were amorphous tacky fluids with glass temperatures of ?69 and ?66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6-diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point.     

STUDIES ON THERMOTROPIC LIQUID CRYSTALLINE COPOLYESTERS:POLY (ARYLENE TEREPHTHALATECO-HEXAMETHYLENE TEREFHTHALATE)

A series of copolyesters based on terephthaloyl chloride, hexamethylene glycol and hydroquinone or chlorohydroquinone were prepared. The copolymers showed composition-dependent liquid crystalline properties as verified by visual observation of stir-opalescence, polarizing microscope and DSC. The copolyesters with aromatic diol contents over a certain extent (x≥0.2) were thermotropic with wide liquid crystalline temperature ranges. Comparing with the copolyesters based on butylene glycol or ethylene glycol, the minimum fraction of aromatic diol (x value) used to get the liquid crystallinity for all these copolyesters is around 0.2 regardless of the chain lengths of aliphatic glycols. ~1H-NMP studies revealed that copolyesters have microstructure of block sequence distribution and the mesogenie segments shorter than triad with three phenyl nuclei will not provide the liquid crystallinity.     

Thermal and structural investigation of random ethylene/1-hexene copolymers with high 1-hexene content

Random ethylene/1-hexene copolymers with the 1-hexene content in the range from 2 to 28 mol% were produced with a novel post-metallocene catalyst and analyzed by three techniques, FTIR, ¹³C NMR, and DSC. The 1-hexene content and the sequence distribution in the copolymers were determined by means of FTIR-M and ¹³C NMR. The crystallization behavior of the copolymers was studied by DSC under dynamic and isothermal conditions; the Avrami model was used to analyze the crystallization kinetics. It was found that both the 1-hexene content and the crystallization temperature affect the relative crystallinity. The bulk crystallization rate decreases with the 1-hexene content and reduces exponentially with an increase of T _c. The melting behavior of isothermally crystallized samples was also investigated and it was found that the melting temperatures of the copolymers under equilibrium conditions were related to the composition.     

Preliminary communication - The synthesis and thermotropic liquid crystalline behaviour of novel main chain poly(aryl ether ketone)s containing a lateral phenyl group

Novel main chain poly(aryl ether ketone)s containing a lateral phenyl group were synthesized by nucleophilic substitution reactions of 4,4-biphenol and phenylhydroquinone with either 4,4-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 50 and 70 mol% biphenol. Melting (Tm) and isotropization (Ti) transitions both appeared on the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline nematic state. As expected, each of the copolymers had a relatively lower melting transition than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer phenylhydroquinone.     

Preliminary communication - The synthesis and thermotropic liquid crystalline behaviour of novel main chain poly(aryl ether ketone)s containing a lateral phenyl group

Novel main chain poly(aryl ether ketone)s containing a lateral phenyl group were synthesized by nucleophilic substitution reactions of 4,4-biphenol and phenylhydroquinone with either 4,4-difluorobenzophenone or 1,4-bis(4-fluorobenzoyl)benzene and their thermotropic liquid crystalline properties were characterized by a variety of experimental techniques. Thermotropic liquid crystalline behaviour was observed in the copolymers containing 50 and 70 mol% biphenol. Melting (Tm) and isotropization (Ti) transitions both appeared on the DSC thermograms. A banded texture was formed after shearing the sample in the liquid crystalline nematic state. As expected, each of the copolymers had a relatively lower melting transition than the biphenol-based homopoly(aryl ether ketone)s because of the copolymerization effect of the crystal-disrupting monomer phenylhydroquinone.     

热致性液晶嵌段共聚酯的合成及表征

以对羟基苯甲酸甲酯和乙二醇为原料，通过熔融酯交换反应合成中间体（Ⅰ）：双（对一羟基苯甲酸）乙二醇酯．用溶液缩合法合成了三种不同嵌段长度的液晶嵌段共聚酯（Ｐ２４７、Ｐ２７７、Ｐ２７４）作为液晶聚合物与热塑性聚合物的“增容剂”．ＦＴＩＲ，Ｈ ＮＭＲ分析表明，嵌段共聚酯的结构和组成与分子设计基本相符；偏光显微镜证实，嵌段共聚酯在一定温度范围内为热致性向列型液晶，在较低温度为均相，在较高温度为两相结构．     

SYNTHESIS AND CHARACTERIZATION OF MAIN CHAIN AROMATIC LIQUID CRYSTAL COPOLYESTERS WITH X-SHAPED AND ROD-SHAPED MESOGENIC UNITS

A series of main chain liquid crystal aromatic copolyesters with X-shapedand rod-shaped mesogenic units were synthesized via solution condensation polymerizationsof 4, 4'-(α,ω-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystallinebehaviors through observations using DSC, polarized microscopy and X-ray diffraction.The melting point (T_m) and the isotropization temperature (T) change regularly withvarying the content of diphenol unit in the copolymers.     

Effect of Polycondensation Reaction Conditions on the Properties of Thermotropic Liquid‐Crystalline Copolyester

In this study a range of wholly aromatic copolyesters based on kink m‐acetoxybenzoic acid (m‐ABA) monomer (33 mol%) and equimolar‐linear p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephthalic acid (TPA) monomers (67 mol%) have been synthesized by melt polycondensation reaction process at 280°C and 260°C for different time intervals. Characterization of copolyesters were performed by solution viscosity measurement, wide–angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), hot‐stage polarized light microscopy, proton‐nuclear magnetic resonance analysis (¹H‐NMR). According to the results obtained, copolyesters showed thermotropic liquid crystalline behavior in an appropriate temperature range. The copolyesters were prepared in high yields. It was observed that the intrinsic viscosities of the copolyesters are increased regularly with increasing polymerization time and temperature. All the copolyesters were soluble in a trifluoroacetic acid/dichloromethane (30:70 v/v) except the copolyesters which were synthesized at 280°C in 5 h. According to the WAXD results; the degree of crystallinity of copolyesters were found to be between 5–15%. DSC and hot stage polarized light microscopy results showed that all the copolyesters are melt processable and a significant molecular interaction exist in a very broad temperature range (160°C and 165°C) in the nematic mesophase. The T_g values are increased with an increasing polycondensation reaction time and temperature and they were observed between 93–126°C. Fibers prepared by a hand‐spinning technique from the polymer melt exhibit well‐developed fibrillar structure parallel to the fiber axis.     

Development of poly(ε-caprolactone-co-l-lactide) and poly(ε-caprolactone-co-δ-valerolactone) as new degradable binder used for antifouling paint

Copolyesters containing ε-caprolactone and l-lactide or ε-caprolactone and δ-valerolactone at different compositions were synthesized by using tetrabutoxytitane Ti(OBu)₄ at high temperature in bulk. A series of copolyesters were prepared by varying the compositions of both comonomers. These copolymers were characterized by using ¹H NMR, ¹³C NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and MALDI-TOF mass spectrometry. ¹³C NMR analysis gave an insight on their microstructure. Structural parameters of the copolymers were obtained by calculating the triad sequence fractions. Poly(ε-caprolactone-co-l-lactide) has a more alternate structure than poly(ε-caprolactone-co-δ-valerolactone). The potential use of these copolyesters in antifouling coatings was examined because of their solubility in aromatic solvent and their hydration and hydrolytic degradation. Paints based on these new degradable binders had a good antifouling activity in Atlantic Ocean (France).     

Biodegradable poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-butylene dimerized fatty acid)s: Synthesis,crystallization, mechanical properties,and rheology

Poly(butylene succinate-co-butylene dimerized fatty acid) (P(BS-co-BDFA)) copolyesters were synthesized from succinic acid (SA) and dimerized fatty acid (DFA) with 1,4-butanediol (BDO) through a two-step process of esterification and polycondensation. The polyester compositions and physical properties of copolyesters were investigated by GPC, ¹H NMR and ¹³C NMR, DSC, WAXD, DMA, TGA, tensile and rheology test. The melting temperature (T_m), and crystallization temperature (T_c) decreased gradually as the content of DFA monomer increased. P(BS-co-BDFA) copolyesters showed the same crystal structure as the PBS homopolyester. Besides, TGA results indicated that P(BS-co-BDFA)s were of higher thermal stabilities. Moreover, it was found that the synthesized P(BS-co-BDFA)s showed the maximum elongation at break (591%) as the DFA contents were 10 mol%. Rheology analysis indicated that the viscoelastic behavior of the polyesters greatly depended on the molecular weight of polyesters.     

Synthesis and characterization of fully aromatic thermotropic liquid‐crystalline copolyesters containing m‐hydroxybenzoic acid units

A series of fully aromatic copolyesters based on p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m‐acetoxybenzoic acid (m‐ABA) were prepared by a modified melt‐polycondensation reaction. The copolyesters were characterized by DSC, thermogravimetric analysis, ¹H NMR, polarized optical microscopy, X‐ray diffraction, and intrinsic viscosity measurements. The copolyesters exhibited nematic liquid‐crystalline phases in a broad temperature range of about 150 °C, when the content of linear (p‐ABA, HQDA, and TPA) units was over 67 mol %. DSC analysis of the anisotropic copolyesters revealed broad endotherms associated with the nematic phases, and the melting or flow temperatures were found to be in the processable region. The flow temperatures and crystal‐to‐nematic and nematic‐to‐isotropic transitions depend on the type of linear monomer units, and these transitions increased as the content of the p‐ABA units increased, as compared to the HQDA/TPA units. When the content of the p‐ABA units increased, as compared to other linear units (HQDA and TPA), the intrinsic viscosity and degree of crystallinity of the copolyesters also increased, implying a higher reactivity for p‐ABA in the p‐ABA/HQDA/TPA/m‐ABA polymer system. The aromatic region in the ¹H NMR spectra of the copolyesters containing equal molar compositions of p‐ABA, HQDA, and TPA units were sensitive to the sequence distribution of aromatic rings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3263–3277, 2001     

Biodegradable liquid crystalline aromatic/aliphatic copolyesters. Part I: Synthesis, characterization, and hydrolytic degradation of poly(butylene succinate-co-butylene terephthaloyldioxy dibenzoates)

To increase the thermal and mechanical properties of the aliphatic polyester poly(butylene succinate) (PBS), a series of potentially biodegradable liquid crystalline aromatic/aliphatic random copolyesters were prepared by melt polycondensation of new mesogenic monomers dimethyl 4,4′-(terephthaloyldioxy) dibenzoate (MTB), dimethyl succinate, and 1,4-butanediol. The synthesized copolyesters were characterized by means of proton nuclear magnetic resonance spectroscopy (¹H NMR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction (XRD), polarizing light microscopy (PLM) and mechanical property measurements. The MTB content was varied so that the effects of the mesogen content on the thermal and mechanical properties, degradable behaviours and mesophase were examined. It was found that introducing the rigid rod mesogens could increase the thermal stability and the mechanical properties, while it reduced the melting temperature (T_m), the crystallization temperature (T_c), the degree of relative crystallinity (X_c) and the hydrolytic degradation rate. Only the homopolyester poly(butylenes terephthaloyldioxy dibenzoates) was able to show the schlieren texture characteristic of nematics.     

Dynamic DSC,SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20°C min^?1 using synchrotron radiation. An EP copolymer with a density of 896 kg m^?3 (about 89 mol % ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [w ^c (T)] calculated from these reflections using the two-phase model was in good agreement withw ^c (T) calculated fromc _p measurements using DSC. Thec _p measurements also enabled calculation of the baselinec _p and the excessc _p. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO copolymers with densities of about 871 kg m^?3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these copolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems — vanadium and metallocene — did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the microchain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed crystallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol %), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied.     

Synthesis and properties of poly(ethylene oxide)‐grafted polyethylene copolymer and terpolymer

A series of graft copolymers were synthesized based on ethylene‐co‐m,p‐methylstyrene (EMS) (backbone copolymer), ethylene‐1‐hexene‐m,p‐methylstyrene (EHMS) (backbone terpolymer), and polyethylene glycol monomethyl ethers (PEGM) (grafts) in this study. The PEGMs with molecular weights of 750 and 2000 were used. The chemical composition of the graft copolymers was analyzed by NMR and DSC measurements. The graft copolymers exhibited a phase‐separated morphology with the backbone and the methoxy polyethylene glycol (MPEG) grafts forming separate crystalline phases. The MPEG phase had a melting temperature lower than the corresponding MPEG homopolymer, as determined by DSC. The melting point of the crystalline phase formed by the EMS and EHMS main chains was lower than that of pure polymer backbone. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystallization and melting behavior of liquid crystalline copolyesters based on poly(ethylene terephthalate)

A series of copolyesters were prepared by the incorporation of p‐hydroxybenzoic acid (HBA), hydroquinone (HQ), and terephthalic acid (TA) into poly(ethylene terephthalate) (PET). On the basis of viscosity measurements, high molar mass copolyesters were obtained in the syntheses, and ¹H‐NMR analyses indicated the total insertion of comonomers. They exhibit nematic phase above melting temperature, as observed by polarized light microscope (PLM). Their crystallization and melting behaviors were also studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). It was found that these copolyesters are more crystalline than copolyesters prepared from PET and HBA. Introduction of HQ/TA disrupts longer rigid‐rod sequences formed by HBA, and thus enhances molecular motion and increases crystallization rate and crystallinity. Isothermal crystallization at solid phase polymerization conditions (up to 24 h at 200°C) resulted in increased copolymer randomness (by NMR) and higher melting point, the latter attributed to structural annealing. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 369–377, 1999     

Synthesis and characterization of biodegradable poly(butylene succinate-co-butylene fumarate)s

A series of aliphatic biodegradable polyesters modified with fumaric residues was synthesized by transesterification in the melt of dimethyl succinate, dimethyl fumarate and 1,4-butanediol. The amount of unsaturation, originating from the fumaric acid residues in the polyesters chains was varied from 5 to 20 mol%. The molecular structure and composition of the polyesters were determined by ¹H NMR spectroscopy. The effects of the content of fumaric residues on the thermal and thermo-oxidative properties of the synthesized polyesters were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis. The degree of crystallinity was determined by DSC and wide angle X-ray scattering. The degrees of crystallinity of the unsaturated copolyesters were reduced, while the melting temperatures were higher in comparison to poly(butylene succinate). Biodegradation of the synthesized copolyesters was estimated in enzymatic degradation tests using a buffer solution with Rhizopus arrhizus lipase at 37 °C. Although the degree of crystallinity of the copolyesters decreases slightly with increasing unsaturation, the biodegradation is not enhanced suggesting that not only the chemical structure and molecular stiffness but also the morphology of the spherulites has an influence on the biodegradation properties. The highest biodegradability was observed for the copolyesters containing 5 and 10 mol% of fumarate units.