New polymer syntheses: 59. Homo-and copolyesters of 4-(4′-hydrophenoxy)benzoic acid

The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, ¹H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt.     

Synthesis and characterization of polyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane

Aromatic polyesters are of considerable interest because of their excellent mechanical properties, chemical resistance and thermal stability. However, most aromatic polyesters are difficult to process due to their high glass transition temperatures coupled with their insolubility in common organic solvents. The present article describes a series of organosoluble polyesters and copolyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane. A series of new aromatic polyesters containing pendant pentadecyl chains was synthesized by interfacial polycondensation of 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane with terephthalic acid chloride (TPC), isophthalic acid chloride (IPC) and a mixture of TPC and IPC. A series of copolyesters was synthesized from 4,4′‐isopropylidenediphenol with TPC by incorporating 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane as a comonomer. Inherent viscosities of the polyesters and copolyesters were in the range 0.72–1.65 dL g^?1 and number‐average molecular weights were in the range 18 170–87 220. The polyesters and copolyesters containing pendant pentadecyl chains dissolved readily in organic solvents such as chloroform, dichloromethane, pyridine and m‐cresol and could be cast into transparent, flexible and apparently tough films. Wide‐angle X‐ray diffraction data revealed the amorphous nature of the polyesters and copolyesters. The formation of loosely developed layered structure was observed due to the packing of pendant pentadecyl chains. The temperature at 10% weight loss, determined using thermogravimetric analysis in nitrogen atmosphere, of the polyesters and copolyesters containing pendant pentadecyl chains was in the range 400–460 °C. The polyesters and copolyesters exhibited glass transition temperatures in the range 63–82 °C and 177–183 °C, respectively. Copyright © 2010 Society of Chemical Industry     

Preparation and characterizations of thermotropic copolyesters of p-hydroxybenzoic acid,sebacic acid,and hydroquinone

A series of copolyesters of p-hydroxybenzoic acid (HBA), sebacic acid and hydroquinone were prepared by melt polycondensation of p-acetoxybenzoic acid, sebacic acid and p-phenylene diacetate. The copolyesters were characterized by IR, NMR, DSC, polarized microscopy, and X-ray diffraction. It was found that the copolyesters exhibited liquid crystallinity when the HBA content was 25–67 mol %. The copolyesters with an HBA content of 25–43 mol % showed a nematic phase and a biphasic range, and the isotropization temperature increased as the HBA content increased. The copolyesters with an HBA content of 54–67 mol % showed a nematic phase up to above 400°C. The liquid crystalline order increased as the HBA content increased due to the increased of the average length of the rigid moieties. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(ethylene‐co‐trimethylene terephthalate)s

Taking advantage of a melt polycondensation process, a series of copolyesters composed of pure terephthalate acid (PTA), ethylene glycol (EG), and 1,3‐propanediol (1,3‐PDO) were synthesized. The component, molecular weight, molecular weight distribution, and thermal properties of the copolymers were characterized. The results show that the contents of trimethylene terephthalate (TT) units in the resulting copolyesters are higher than PDO compositions in original diol. Oligomer content in the copolyesters varies with the compositions and attains a minimum value when the TT ingredient is 49.52 mol %. The glass transition temperature (T_g) of the copolyesters varies from 78.5°C for PET (polyethylene terephthalate) to 43.5°C for PTT (polytrimethylene terephthalate) and decreases monotonically with the components. The copolyesters are amorphous copolymers when TT content is in the range of 32.4–40.8 mol %, as calculated from the melting enthalpy (ΔH_m) measured via differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1511–1521 2006     

Glas- und tieftemperaturrelaxation von copolyestern der terephthalsäure

The relaxation mechanisms of linear saturated copolyesters of terephthalic acid are influenced by the chemical structure of the used aliphatic, aromatic, and cyclic diols or dicarbonic acids. The glass transition temperatures of the copolyesters are in the range from -30 to 90°C. The numerical value of T_G can be calculated by the increment method with a mean error of ±5°C. Since this method can be applied also to other polymer systems or some other physical parameters a general procedure for optimizing the increments is given. With reference to known relaxation criterions the molecular motions of the copolyesters above and below T_G are identified. The two relaxation mechanisms below T_G show a statistical distribution of the different components of acids and diols along the chain. The γ′-relaxation is caused by orientational motions of carbonyl groups and depends on the chemical structure of the neighbouring segments. On the contrary the γ″-process is not influenced by the molecular environment and is caused by hindered rotation of CH₂-groups.     

Semiflexible random thermotropic copolymers from 8‐(3‐hydroxy phenyl) octanoic acid and 3‐chloro‐4‐hydroxy benzoic acid/3,5‐dibromo‐4‐hydroxy benzoic acid

Two series of semiflexible random thermotropic copolymers containing 8‐(3‐hydroxy phenyl) octanoic acid (HPOA) with either 3‐chloro‐4‐hydroxy benzoic acid or 3,5‐dibromo‐4‐hydroxy benzoic acid were prepared by melt polycondensation techniques. The copolyesters were characterized with Fourier transform infrared spectroscopy, dilute solution viscometry, hot‐stage polarized light microscopy, differential scanning calorimetry, thermogravimetric analysis, and wide‐angle X‐ray diffraction. Studies revealed that the amount of HPOA as a disruptor incorporated into the backbone of substituted 4‐hydroxy benzoic acids had a detrimental effect on the liquid‐crystalline behavior. Mesophase‐transition temperatures were observed between 210 and 250°C, and the optical textures were of typical nematic phases. The degree of crystallinity decreased with an increase in the HPOA content. The thermal stability of the copolymers was in the range of 310–370°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthese und charakterisierung von flüssigkristallinen hauptkettenpolyestern zur verwendung in mischungen mit thermoplasten

The melting points of liquid-crystalline main chain polyesters made from hydroquinone derivatives and substituted terephthalic acids can be lowered strongly by attaching flexible side chains or voluminous side groups. The solid state of poly(2′-phenyl-1′,4′-phenylene-2,5-dihexyloxyterephthalate) is even amorphous with a glass transition at 47°C and a phase transition to isotropic melt at 184°C. Beside the low phase transition temperatures, this polyester is readily soluble in toluene and tetrahydrofuran. Up to 40 mol-% of 2,5-dihexyloxyterephthalic acid may be replaced by unsubstituted terephthalic acid without a strong influence on the phase transition temperatures and the solubility of the polyester. The E-modulus of the copolyester with 40 mol-% of terephthalic acid reaches 7700 MPa.     

Poly(ethylene terephthalate) copolymers that contain 5‐tert‐butylisophthalic acid and 1‐3/1‐4‐cyclohexanedimethanol: Synthesis,characterization, and properties

The effects of incorporating 5‐tert‐butylisophthalic acid (^tBI) and 1‐3/1‐4 cyclohexanedimethanol (CHDM) in the polymer chain of poly(ethylene terephthalate) (PET) on the crystallization behavior and thermal, optical and tensile properties of this polyester (PETGB) were evaluated. These random copolyesters that contained between 0 and 20 mol % of CHDM and between 0 and 10 mol % of ^tBI units were prepared by esterification followed by melt copolycondensation. The compositions and molecular weights of the copolyesters were determined by ¹H‐NMR spectroscopy and viscometry, respectively. The composition of the polyester was consistent with the composition of the feed. The intrinsic viscosities of the copolymers ranged between 0.62 and 0.74 dL/g. The thermal behaviors were investigated over the entire range of copolymer compositions, using DSC under the heating and cooling rate of 20°C/min and TGA. The copolyesters with ^tBI and CHDM of < 20 mol % were crystallizable, whereas the copolyesters with ^tBI and CHDM of ≥ 20 mol % were amorphous. They appeared to be stable up to 395°C. The optical transmissions of the amorphous polyesters were more than 88% in the visible region. The mechanical behavior was investigated by performing a tensile test. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 279–285, 2007     

The crystallinity of poly(phenylene sulfide) and its effect on polymer properties

The crystallinity and crystallizability of poly(phenylene sulfide) have been examined by a number of common techniques. Several provided qualitative information, but only one, x-ray diffraction, was considered sufficiently reliable and reproducible to allow quantitative comparisons. Based on x-ray measurements, an approximate degree of crystallinity, termed crystallinity index (C_i), could be readily assigned. According to this method, virgin polymer possesses significant crystallinity (C_i ≈ 65%). Curing (crosslinking) the resin below its melting point did not change the crystallinity but did affect the crystallizability. Lightly cured resin suitable for molding and film extrusion was easily quenched from the melt to give amorphous polymer. The amorphous samples crystallized rapidly when heated to temperatures > 121°C (250°F). At mold temperatures below 93°C (200°F), moldings with very low surface crystallinity were produced. Annealing (204°C, 400°F) caused rapid crystallization of such moldings, and changes in crystallinity were correlated with observed changes in physical properties. The resin crystallizes so rapidly that these quenched moldings possessed a crystallinity gradient, the internal crystallinity being substantially greater. At high mold temperatures (121–204°C, 250–400°F), moldings very similar to fully annealed specimens were obtained.     

Soluble asymmetric bismaleimide with low molten viscosity and its high glass transition temperature polymer

Three novel bismaleimide monomers (MBA‐BMI, EBA‐BMI, and PBA‐BMI) with unsymmetrical backbone and different pendant groups were synthesized using asymmetric diamine and maleic anhydride as the precursors. The prepared bismaleimide monomers show good solubility in common organic solvents such as acetone and tetrahydrofuran. The EBA‐BMI melt treated at 180 °C also shows low viscosity about 190–934 mPa s at the temperature range of 160–139 °C below its melting point (166 °C). In addition to the good processability, all three cured bismaleimides show high storage moduli at high temperatures (2.0 GPa at 400 °C), high glass transition temperatures over 400 °C, and good thermal stability with the 5% weight loss temperatures around 470 °C under nitrogen atmosphere. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43491.     

Phase stability and melting behavior of the α and γ phases of nylon 6

The phase stability and melting behavior of nylon 6 were studied by high‐temperature wide‐angle X‐ray diffraction and differential scanning calorimetry (DSC). The results show that most of the α phase obtained by a solution‐precipitation process [nylon 6 powder (Sol‐Ny6)] was thermodynamically stable and mainly melted at 221°C; the double melting peaks were related to the melt of α crystals with different degrees of perfection. The γ phase formed by liquid nitrogen quenching (sample LN‐Ny6) melted within the range 193–225°C. The amorphous phase converted into the γ phase below 180°C but into the high‐temperature α phase at 180–200°C. Both were stable over 220°C. α‐ and γ*‐crystalline structures were formed by annealing but were not so stable upon heating. Typical double melting peaks were shown on the DSC curve; melt recrystallization happened within the range 100–200°C. The peak at 210°C was mainly due to the melting of the less perfect crystalline structure of the γ phase and a fraction of the α phase; the one at 219°C was due to the high‐temperature α‐ and γ‐phase crystals. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradable polymers based on renewable resources. III. copolyesters composed of 1,4:3,6‐dianhydro‐D‐glucitol, 1,1‐bis(5‐carboxy‐2‐furyl)ethane and aliphatic dicarboxylic acid units

Various copolyesters were synthesized by bulk polycondensation of the respective combinations of 1,4;3,6‐dianhydro‐D ‐glucitol (1) as the diol component and 1,1‐bis[5‐(methoxycarbonyl)‐2‐furyl]ethane (3b) and seven dimethyl dialkanoates with methylene chain lengths of 4, 5, 6, 7, 8, 10, and 12 (4a–4g) as the dicarboxylic acid components. Most of the copolyesters were amorphous, while a copolyester composed of 1, 3b, and dodecanedioic acid (4g) (3b:4g = 25:75) units as well as homopolyesters derived from 1 and azelaic acid (4d), sebacic acid (4e), and dodecandioic acid (4g), respectively, were partially crystalline. All these homo‐ and copolyesters were soluble in chloroform, dichloromethane, pyridine, trifluoroacetic acid, and m‐cresol. The number‐average molecular weights of these polyesters were estimated to be in the range of 10,000–20,000 by SEC using chloroform as an eluent and standard polystyrene as a reference. The biodegradability of these copolyesters was assessed by enzymatic degradation using four different enzymes in a phosphate buffer solution at 37°C and by soil burial degradation tests in composted soil at 27°C. In general, biodegradability of the copolyesters decreased with increase in the difuran dicarboxylate 3b content. Copolyesters containing sebasic acid 4e units showed higher biodegradability. Soil burial degradation in the soil that was treated with antibiotics, together with electron microscopic observation, indicated that actinomycetes are mainly responsible for the degradation of the copolyesters containing 3b units in the present soil burial test. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3342–3350, 1999     

Poly(amide‐ester)s derived from dicarboxylic acid and aminoalcohol

A series of alternating aliphatic poly(amide‐ester)s, derived from dicarboxylic acid and aminoalcohols, were obtained by polycondensation in melt. All poly(amide‐ester)s were characterized by FTIR and ¹H/¹³C‐NMR spectroscopies. The synthesized polymers showed an inherent viscosity ranging from 0.4 to 1.0 dL g^?1. Thermal analysis showed melting points within the range 100–115°C and glass transition within the range 30–60°C. Decomposition temperatures were more than 200°C higher than the corresponding melting temperatures. The polymers can thus be processed from the melt. The processed polymers were partially crystalline with good thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 362–368, 2005     

Relationship between physical properties and chemical structures of poly(ethylene terephthalate-co-ethylene isophthalate)

A series of copolyesters based on different ratios of polyethylene terephthalate (PET) to polyethylene isophthalate (PEI) have been synthesized. With the involvement of PEI, the copolyesters become less crystallizable and even amorphous when PEI content is above 20%. The WAXD profiles of the crystallizable copolyesters infer that the crystals come from PET homopolymer. DSC cooling runs indicated that the copolyesters with PEI no more than 15% are easily crystallizable, while the copolyester with 20% PEI is not easily crystallized at a cooling rate above 5°C/min. Heating runs indicated that the copolyesters with PEI below 20% show melting processes. Nonuniform results were provided by WAXD and DSC, however, the effect of PEI on the ability of crystallization was deduced similarly from WAXD and DSC. Glass transition temperatures have been measured by DSC. Due to the flexibility of PEI chain, glass transition temperatures of the copolyesters decrease linearly with increasing composition of PEI as predicted by the principle of additive contribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1191–1195, 1999     

Synthesis,characterization, and hydrolytic degradation of copolyesters of 3‐(4‐hydroxyphenyl) propionic acid and p‐hydroxybenzoic acid,vanilic acid,or syringic acid

A series of copolyesters were prepared by a direct polycondensation of 3‐(4‐hydroxyphenyl) propionic acid and p‐hydroxybenzoic acid (HBA), vanilic acid (VA), or syringic acid (SGA) of different composition in pyridine using diphenyl chlorophosphate and lithium bromide as condensing agents. The effects of methoxy substitution in the benzene ring and copolymer composition on the synthesis and thermal properties as well as hydrolytic degradation were examined. The methoxy substitution increased a glass transition temperature and a solubility, while it decreased a crystallinity and a thermal stability. The HBA series copolyesters showed a homogenous nematic phase, while the VA and SGA series copolyestes neither revealed an anisotropic melt nor formed a mobile melt below around 350°C. The hydrolytic degradation of melt‐pressed films was performed in a 5% sodium hydroxide aqueous solution at 40°C to test a biodegradability of the copolyesters. HBA‐50 and HBA‐30 exhibited the much higher degradation rate than HBA‐70, showing that the aliphatic ester linkage was more degradable than aromatic one. The degradation rates of VA‐50 and SGA‐50 were remarkably slower than that of HBA‐50 due to the steric hindrance of the methoxy group in the ortho position. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2474–2481, 2000     

Processing characteristics and structure development in solid-state extrusion of bacterial copolyesters: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The bacterial copolyesters poly(3-hydroxybutyrate-co-3-hydroxyvalerate) have been successfully commercialized by ICI and are currently being distributed worldwide. Because of their bacterial origin, they are completely biodegradable. This has opened up numerous opportunities to develop new environmentally friendly products. The solid-state extrusion of a series of biodegradable copolyesters (P(3HB-3HV)) was performed in our laboratory with the aim of gaining fundamental understanding about their processability below their melting temperatures. The extrudability windows were found to span the temperature range from 135 to 150°C, depending on the composition of the samples under our experimental setup. The solid-state extrudates were found to exhibit an extra melting endotherm about 15–20°C above their normal melting temperature. This high temperature melting peak increasingly became dominant at lower extrusion temperatures. Wide angle X-ray diffraction studies did not indicate any phase change that might be responsible for this increase in the melting point. Contrary to the expectations, the solid-state extruded samples did not show significant chain orientation along the extrusion direction. This might be a result of fracture of the mass in the barrel into smaller pieces and their randomization during the course of their passage through the die. When the extrusion temperature was raised closer to the melting temperature, the quality of the extrudates was improved, and this was reflected in improvement of their mechanical properties. © 1996 John Wiley & Sons, Inc.     

Smart Wearable Textiles with Breathable Properties and Repeatable Shaping in In Vitro Orthopedic Support from a Novel Biomass Thermoplastic Copolyester

In this study, materials with low melting temperatures and high toughness are developed for orthopedic applications. A series of an aliphatic copolyester based on sebacic acid (SeA), a green resource, is copolymerized with ethylene glycol, trimesic acid, aminocaproic acid, and adipic acid (AA) to produce poly(ethylene sebacate‐co‐ethylene adipate) (PESA) with various molar ratios through melt polymerization. Thermal characterizations of the PESA copolyesters are tuned with SeA and AA in varying molar ratios, exhibiting a crystalline phase with a lower degree of perfection. The melting point (T_m) and crystallization temperature (T_c) of the copolyesters are observed at 60–70 and 30–40 °C, respectively. Furthermore, a high Young's modulus ranging between 140 and 200 MPa is observed, which could be attributed to the 3D network structure formed by the trimesic acid unit used as a cross‐linking agent. Within the authors' research group, the PESA copolyesters are adopted to reinforce the mechanical properties of a 3D air mesh fabric as a composite application. Also, the highly breathable and low‐weight characteristics of 3D fabric with PESA copolyesters render them suitable for replacing traditional plaster in the future.     

Synthesis and properties of poly(ethylene-1,4-cyclohexanedimethylene naphthalate)

Copolyesters were synthesized from bis(hydroxyethyl) naphthalate/bis(hydroxymethylcyclohexane)naphthalate (BHEN/BHCN) with various compositions. Copolyesters having intrinsic viscosities of 0.58–0.65 dL g were obtained by melt polycondensation in the presence of metallic catalysts. The optimum condition for polyethylene-1,4-cyclohexanedimethylene naphthalate (PECN) copolyester manufacturing is the transesterification under a nitrogen atmosphere for 4 h at a temperature of 245 ± 5°C followed by polymerization under 2 mmHg for 50 min at a temperature of 290–320°C. Most copolyesters have better thermal stability than has poly(ethylene naphthalate) (PEN) and the effect of the cyclohexane–dimethylene structure on the thermal and crystalline properties of the resulting copolyesters was investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Glass transition temperatures of the copolyesters were in the range of 115.2–138.4°C, and 10% weight losses in nitrogen were all above 453°C. The solubility, crystallinity, and moisture absorption of the copolyesters were also investigated. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2245–2252, 1998     

Aromatic liquid crystalline copolyesters with low Tm and high Tg: Synthesis,characterization, and properties

In this study, a series of aromatic copolyesters P‐BPAx with lower melting temperature and higher glass transition temperature derived from hydroxybenzoic acid (HBA), 6‐hydroxy‐2‐naphthoic acid (HNA), bisphenol A (BPA) and terephthalic acid (TA) were synthesized via melt polymerization. The copolyesters were characterized by FTIR, solid state ¹³C NMR, DSC, TGA, polarized optical microscopy, X‐ray diffraction, and rheometry measurements. With addition of BPA, the resulting copolyester's melting temperature decreased from 260 to 221°C and its glass transition temperature increased from 70 to 135°C, compared with the parent copolyester P‐HBA70 (HBA/HNA copolymer). With exception of copolyester P‐BPA5.0 (225–280°C), the copolyesters could maintain liquid crystalline behavior in a broad temperature range from 230°C to higher than 410°C. The ability to form nematic liquid crystalline phase disappeared when BPA concentration became higher than 15 mol %. X‐ray diffraction analysis showed crystallinity decreased as the BPA content increased. A slightly distorted O" and a substantially distorted O′ orthorhombic phase was observed for P‐BPA2.5. Upon annealing at 220°C, the O" phase disappeared and the O′ phase became stronger gradually. Rheology study data showed the ability to process the copolyesters improved in those compositions containing <2.5 mol % BPA. Continuing to increase concentrations of BPA, they became intractable. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40487.     

Secondary crystallization and premelting endo‐ and exotherms in oriented polymers

Crystallization in polyamide 6 (nylon 6) fibers during annealing was studied in detail by following the changes that occurred in the neighborhood of crystalline relaxation temperatures, by using wide‐ and small‐angle X‐ray scattering and differential scanning calorimetry (DSC). Two distinct crystallization regimes were observed depending on whether annealing was carried out below or above onset of crystalline relaxation at ～190°C. In fibers annealed below 190°C, minor melting peaks were followed by exothermic transitions. These were attributed to ～1.5% (by weight) of microcrystals formed during annealing that melt and recrystallize during the DSC scan. These microcrystals are nucleated from unoriented amorphous chains between the lamellar stack within a fibril, and are shown to account for the observed increase in the crystalline orientation and decrease in permeability. Fibers annealed above 190°C did not show the exotherm and had significantly fewer microcrystals. The crystallization in this regime was attributed to the growth of existing lamellae, as evidenced by the increase in crystallite size, crystalline density, crystalline orientation, lamellar spacing, and lamellar intensity. The changes at annealing temperatures >190°C are accompanied by increased dyeability, indicative of more open amorphous regions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 447–454, 2006