Series Of Copolyesters Research Articles

Synthesis of Renewable and Seawater-degradable Polyesters Based on a Fully Biobased Diester

The design and development of biobased plastics that can degrade in seawater is a potential approach to address the seawater pollution of fossil plastics. Herein, N,N'-pentamethylene-bis(pyrrolidone-4-methyl carboxylate) (PBPC), a biobased diester with two pyrrolidone rings, was synthesized from renewable 1,5-pentanediamine and dimethyl itaconate. PBPC was polymerized with three α,ω-diols to prepare biobased homopolyesters with number-average molecular weight (Mn) around 25 kDa. These amorphous homopolyesters presented remarkable UV shielding abilities compared with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS). Incubation experiments in artificial seawater for 150 days indicated that the homopolyesters based on PBPC exhibited rapid seawater-degradability. Then, PBPC was copolymerized with 1,4-butanediol and terephthalic acid to prepare a series of copolyesters with Mn around 20 kDa. The introduction of PBPC into poly(butylene terephthalate) (PBT) resulted in the elevated toughness and sensitivity to seawater degradation. Depending on the composition of PBPC, the thermal, mechanical, and degradation rate of the copolyesters were adjustable. Overall, the PBPC-based polyesters are promising alternatives to commercial packaging materials in improving the renewability of raw materials and achieving seawater degradation.

Synthesis, Characterization and Thermal Study of Some new Copolyesters from mono-carbonyl analogues of Curcumin and Thymol blue dye

A series of copolyesters were prepared from a dicarboxylic acid, curcumin analogues (monocarbonyl) and thymol blue dye in the mole ratio of 2:1:1 by direct polycondensation using triethylamine (Et3N) as the condensation agent. The dicarboxylic used is 2,6-Pyridine dicarbonyl dichloride acid. The curcumin analogues were prepared by acid catalyzed Aldol condensation reaction. These copolyesters were characterized by FT-IR. The fluorescence of the synthesized copolyesters was also investigated. Furthermore, Thermo gravimetric analysis (TGA) was used to investigate the thermal stability of these copolymers

Effect of side group and crosslinking on the copolyesters as solvent-free pressure-sensitive adhesives

Pressure-sensitive adhesives (PSAs) are extensively employed in various applications due to their ability to instantly adhere upon the application of light pressure. Towards a sustainable future is the major driving force for the development of PSAs without solvent. In this study, a two-step melt polycondensation method was used to synthesize a series of copolyesters with varying contents of propanediol (PDO), 2-methyl-1,3-propanediol (MPO), and glycerol. These copolyesters were composed of different molar ratios of PDO/MPO (80/20, 50/50, and 20/80, respectively) and varying glycerol loading in polymer backbone (0, 0.5, and 1.0 mol%, respectively). The influence of the short side group from MPO and the slight crosslinking from glycerol on the thermal and rheological behavior of the copolyesters was investigated. The glass-transition temperature of these copolyesters range from −58.0 to −52.1 °C. Furthermore, the adhesive strength of these copolyesters was evaluated through T-peel and 180° peel testing. The 180° peel strength ranged from 81.1 to 600.6 Pa, while the T-peel strength ranged of 52.5–156.6 Pa. By adjusting the balance of side group and crosslinking content, it was possible to control the relationship between cohesion, adhesion, and tack. This study provides a potential material design for polyester-based and solvent-free PSAs.

Synthesis, Properties, and Biodegradability of Novel Sequence-Controlled Copolyesters Composed of Glycolic Acid, Dicarboxylic Acids, and C3 or C4 Diols

We have previously reported that sequence-controlled copolyesters such as poly((ethylene diglycolate) terephthalate) (poly(GEGT)) showed higher melting temperatures than those of the corresponding random copolymers and high biodegradability in seawater. In this study, to elucidate the effect of the diol component on their properties, a series of new sequence-controlled copolyesters composed of glycolic acid, 1,4-butanediol or 1,3-propanediol, and dicarboxylic acid units was studied. 1,4-Butylene diglycolate (GBG) and 1,3-trimethylene diglycolate (GPG) were prepared by the reactions of 1,4-dibromobutane or 1,3-dibromopropane with potassium glycolate, respectively. Polycondensation of GBG or GPG with various dicarboxylic acid chlorides produced a series of copolyesters. Terephthalic acid, 2,5-furandicarboxylic acid, and adipic acid were used as the dicarboxylic acid units. Among the copolyesters bearing terephthalate or 2,5-furandicarboxylate units, the melting temperatures (Tm) of the copolyesters containing 1,4-butanediol or 1,2-ethanediol units were substantially higher than those of the copolyester containing the 1,3-propanediol unit. Poly((1,4-butylene diglycolate) 2,5-furandicarboxylate) (poly(GBGF)) showed a Tm at 90 °C, while the corresponding random copolymer was reported to be amorphous. The glass-transition temperatures of the copolyesters decreased as the carbon number of the diol component increased. Poly(GBGF) was found to show higher biodegradability in seawater than that of poly(butylene 2,5-furandicarboxylate) (PBF). On the other hand, the hydrolysis of poly(GBGF) was suppressed in comparison with that of poly(glycolic acid). Thus, these sequence-controlled copolyesters have both improved biodegradability compared to PBF and lower hydrolyzability than PGA.

Supramolecular structure, relaxation behavior and free volume of bio-based poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone) copolyesters.

In the present study, a fully plant-based sustainable copolyester series, namely poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone)s (PBF-block-PCL)s were successfully synthesized by melt polycondensation combining butylene 2,5-furandicarboxylate with polycaprolactone diol (PCL) at different weight ratios. Differential scanning calorimetry (DSC) showed that only PBF underwent melting, crystallization from the melt, and cold crystallization. Thermogravimetric analysis (TGA) revealed outstanding thermal stability, exceeding 305 °C, with further improvement in thermal and thermo-oxidative stability with increasing PCL content. Broadband dielectric spectroscopy (BDS) revealed that at low temperatures, below the glass transition (Tg) all copolyesters exhibited two relaxation processes (β1 and β2), whereas the homopolymer PBF exhibited a single β-relaxation, which is associated with local dynamics of the different chemical bonds present in the polymer chain. Additionally, it was proved that an increase in PCL content affected the dynamics of the chain making it more flexible, thus providing an increase in the value of the room temperature free volume fractions (fv) and the value of elongation at break. These effects are accompanied by a decrease in hardness, Young's modulus, and tensile strength. The described synthesis enables a facile approach to obtain novel fully multiblock biobased copolyesters based on PBF and PCL polyesters with potential industrial implementation capabilities.

Degradation performances of CL-modified PBSCL copolyesters in different environments

In order to improve the poor degradability of polybutylene succinate (PBS) in marine environment, a series of copolyesters called poly(butylene succinate-co-ε-caprolactone)s (PBSCLs) were synthesized by one-pot melt polycondensation technique. Such copolyesters had excellent mechanical properties, with tensile strengths from 26.4 MPa to 47.6 MPa and elongation at break around 450%. In addition, the introduction of CL segment decreased the crystallinity and increased the hydrophilicity. Furthermore, four different degradation environments were settled to investigate the enzymatic hydrolysis, compost degradation, non-enzymatic hydrolysis, and natural seawater degradation performances of PBSCL copolyesters. The biodegradation and hydrolysis performances of the copolyesters were significantly different compared with PBS. Faster degradation of the copolyesters was detected not only in buffer solution with CALB and compost, but also in buffer solution and natural seawater. Besides, different degradation mechanisms, namely bulk erosion and surface erosion, coexisted during non-enzymatic hydrolysis and natural seawater degradation process. The higher CL content, the more the degradation mechanism of the copolyester was inclined to the latter.

Effects of a symmetrical inorganic-organic monomer on the flame retardancy and mechanical properties of polyethylene terephthalate copolymers

In this paper, a kind of symmetric functionalized monomer is presented, and a polyester with flame retardancy and mechanical properties is obtained. Magnesium hydroxide was modified with phenylphosphonic acid to give a novel inorganic–organic monomer (MH-PPOA) with intrinsic flame retardancy. MH-PPOA was incorporated into the main chain of polyethylene terephthalate (PET) in varying amounts (n, wt% relative to terephthalic acid) to give a series of co-polyesters (MH-PPOAn-co-PET), and the effects of the monomer on their flame retardancy and mechanical properties were determined. The structure and morphology of the hybrid monomer was confirmed by Fourier transform infrared spectroscopy, and scanning electron microscopy, and its successful introduction into the polyester chain of PET was verified by proton nuclear magnetic resonance spectroscopy. The thermal characteristics, flame retardancy and burning behavior of the synthesized copolymers were evaluated by differential scanning calorimetry, thermogravimetric analysis, measurement of the limiting oxygen index (LOI), Underwriters Laboratory vertical burning (UL-94) test, and cone calorimetry. The mechanical properties were measured by tensile testing. This study provides a new direction for the introduction of intrinsic flame retardants anddemonstrates that the incorporation of a symmetrical phenylphosphonic acid modified magnesium hydroxide monomer can also improve the mechanical properties of the PET copolymer.

Tuning thermal properties and biodegradability of poly(isosorbide azelate) by compositional control through copolymerization with 2,5-furandicarboxylic acid

A new fully biobased poly(isosorbide furanoate-co-azelate) (PISFAz) copolyester series was synthesized through melt polycondensation. Incorporation of 2,5-furandicarboxylic acid (FDCA), a rigid comonomer, at different molar ratios in poly(isosorbide-azelate) homopolymer led to tuning of the thermal properties and biodegradability of the resulting copolyesters. The PISFAz copolyesters with various FDCA molar content spanning from 10 to 70% were prepared and characterized by FTIR, GPC, 1D/2D NMR and viscosity measurements. It was found that PISFAz were totally amorphous materials with high thermal stability. NMR results indicated that random microstructures were obtained for the prepared copolymers with high azelaic acid content (⩾ 60 mol%). Most notably, the inclusion of FDCA units into the copolymer molecular chains induced a significant increase in the glass transition temperatures (Tg) that varied from 9.2 to 91.1 °C depending on FDCA content, leading to copolyesters with tunable Tg over a wide temperature window. The enzymatic hydrolysis behavior of PISFAz was assessed using lipases from Pseudomonas cepacia and Rhizopus oryzae revealing different susceptibility to enzymatic attack depending on the comonomer ratio, with a maximum degradation rate up to 61% after 30 days. These novel furanoate-based copolyesters show great potential to serve as promising green thermoplastic materials for applications requiring high Tg values.

Kilogram-scale preparation of sustainable PETG modified with a biobased cyclic diol derived from 5-hydroxymethylfurfural: From synthesis to properties

• Kilogram-scale novel PETT copolyesters were successfully synthesized in 5L reactor. • The cyclic structure and ether group of THFDM reach a balance to the influence on T g . • Kwei’s equation evaluated the T g of copolyesters better than other theories. • The introduction of THFDM provides better processability and hydrophilicity. • PETT copolyester with outstanding properties is an ideal candidate in replacing PETG. Poly(ethylene terephthalate-co-cyclohexanedimethanol terephthalate) (PETG) which could perform good mechanical and transparency properties have been commercialized for decades. While, such good properties presented only when the copolyesters is unable to crystallize for a narrow window of compositions. Moreover, considering the unsustainability of 1,4-cyclohexanedimethanol (CHDM) which was mainly obtained from fossil resources, incorporating novel biobased monomer into poly(ethylene terephthalate) (PET) to obtain the excellent properties have arisen researchers’ attentions. Novel biobased 2.5-tetrahydrofurandimethanol (THFDM), an alicyclic diol containing similar structure with CHDM, was successfully introduced into PET and obtained a series of copolyesters with outstanding tunable properties. The process was conducted in 5L stainless steel reactor, which maintained the stability of properties of samples and provided the prospect of being large scale production. The cyclic structure and ether group contained by THFDM reached a balance to the influence on the T g of copolyesters, resulting only slight change of T g (ranging from 76.1 °C to 69.4 °C). Three equations, namely Fox’s, Gordon–Taylor’s and Kwei’s equations, were employed to evaluate the T g of copolyesters. According to the statistics analysis, the value calculated by Kwei’s equation performed the best fitting the experimental results comparing to the other two theories, due to the peculiar dielectric properties. The (co)polymers performed as amorphous materials with excellent transparency at room temperature. As expected, the introduction of highly electronegative ether-oxygen atoms increased the hydrophilicity. It was worthy noting that the rheology property determining the processability was significantly influenced by the polarity which could be adjusted by the content of THFDM. As for the mechanical property, the yield strength increased form 52.7 MPa (PET) to 63.6 MPa (poly(tetrahydrofurandimethanol terephthalate), PTT), while the elongation at break decreased from 205.0% (PET) to 43.3% (PTT) in consistent with the decrease tendency of impact strength (200.6–78.0 J/m). Overall, the PETTs copolyesters performed outstanding transparency, comparable T g , broader processing window and better mechanical properties comparing with PETG, and it could be potentially used in sheet material, high-performance shrink film, bottle and profile markets. Therefore, the PETT copolyesters is an ideal candidate in replacing PETG to realize the concept of “carbon neutral” and “sustainable development”.

Low‐crystallinity to highly amorphous copolyesters with high glass transition temperatures based on rigid carbohydrate‐derived building blocks

AbstractThe current trend of developing novel biobased polymeric materials is focused more on utilizing the unique structural/physical properties of renewable building blocks towards niche market applications. In this work, with the aim of developing low‐crystallinity to amorphous polyesters with enhanced thermal properties, a series of copolyesters based on rigid and structurally asymmetric carbohydrate‐derived building blocks, namely furan‐2,5‐dicarboxylic acid and isosorbide, and 1,4‐butanediol were successfully synthesized using melt polycondensation. The copolyesters were obtained with varied chemical compositions and rather high molecular weights (Mn = 24 000–31 000 g mol−1) and intrinsic viscosities ([η] = 0.56–0.72 dL g−1). Incorporation of both building blocks significantly enhances the glass transition temperatures (Tg = 38–107 °C) of polyesters, and also efficiently inhibits the crystallization of the copolyesters. A low content of isosorbide (ca 10 mol%) leads to complete transition of the homopolyester to nearly fully amorphous materials. Detailed characterizations of the chemical structures and thermal properties of the synthesized copolyesters were conducted using various analytical techniques. In addition, hydrolytic and enzymatic degradations of the copolymers in the presence of porcine pancreatic lipase and cutinase were also investigated. © 2020 Society of Industrial Chemistry

Partially bio-based copolyesters poly(ethylene 2,5-thiophenedicarboxylate-co-ethylene terephthalate): Synthesis and properties

The aim of this study was to investigate the feasibility of replacing petroleum-based terephthalic acid (PTA) with renewable 2,5-thiophenedicarboxylic acid (TDCA) in poly(ethylene terephthalate) (PET), a series of copolyesters were synthesized from PTA, TDCA and ethylene glycol (EG). The effects of composition on structures, thermal properties, mechanical properties and β relaxation were studied. With the increase of the TDCA content, the esterification reaction time is noticeably shorter in the first step because the acidity of TDCA is stronger. PET, PETF and PETTF25 are semi-crystalline materials. However, no melting and crystallization peaks were observed for PETTF49 and PETTF74. All polyesters exhibit high tensile strength (56.0–68.8 MPa) and good toughness (elongation at break: 190–508%). With the increase of the TDCA content, β relaxation peak is shifted to a higher temperature. For all PET, PETF, and PETTFs, high peak intensity of the β relaxation can be achieved, indicating that the motions of more units are believed to contribute to the relaxation behavior.

Synthesis, Life Cycle Assessment, and Polymerization of a Vanillin-Based Spirocyclic Diol toward Polyesters with Increased Glass-Transition Temperature

Bio-based rigid diols are key building blocks in the development and preparation of high performance bioplastics with improved thermal and dimensional stability. Here, we report on the straightforward two-step synthesis of a diol with a spirocyclic acetal structure, starting from bio-based vanillin and pentaerythritol. According to a preliminary life cycle assessment (LCA), the greenhouse gas emissions of this bio-based diol are significantly lower than that of bio-based 1,3-propanediol. Copolymerization of the rigid spiro-diol with 1,6-hexanediol and dimethyl terephthalate by melt polymerization yielded a series of copolyesters, which showed improved glass transition temperature and thermal stability upon the incorporation of the spiro-acetal units. The crystallinity and melting point of copolyesters decreased with increasing content of the spirocyclic backbone structures. The copolyesters containing 10% of the new diol was semicrystalline while those with 20 and 30% spiro-diol incorporated were completely amorphous. Moreover, dynamic mechanical analysis indicated that the copolyesters showed comparable storage moduli as AkestraTM, a commercial fossil-based high-performance polyester.

Intrinsic high thermal conductive co-polyester based on offset π-π stacking

It has been known that phonon mean free path along polymer chains is much larger than in transverse directions because weak interaction between polymer chains leads to chain distortion and entanglement. In order to improve intensity of intermolecular interaction, a series of co-polyesters (CPE) containing different content of offset π-π stacking structure in side chains were synthesized by means of polycondensation and transesterification in this work. WAXD patterns unfolded diffraction peak at 2θ of 27.6°, standing for structure of offset π-π stacking. On enlarging intensity of offset π-π stacking interaction, specific heat capacity of CPE increased from 1.140 Jg−1K−1 to 1.410 Jg−1K−1 and thermal diffusivity rose from 0.194mm2s−1 to 0.245mm2s−1. As a result, CPE sample exhibited excellent thermal conductivity (TC) of 0.381 Wm−1K−1, which is around twice that of traditional thermoplastics. Hence offset π-π stacking interaction could strengthen capacity of heat absorption and thermal conduction at the same time, which might be a good candidate for enhancing thermal conductivity of intrinsic polymers. Furthermore, strong π-π interaction in side chains could maintain modulus when temperature is over glass temperature. And the Young modulus grew from 0.14 GPa to 0.44 GPa with the augment of offset π-π stacking structure.

New bio-based copolyesters poly(trimethylene 2,5-thiophenedicarboxylate-co-trimethylene terephthalate): Synthesis, crystallization behavior, thermal and mechanical properties

A series of copolyesters based on poly(trimethylene terephthalate) derived from 2,5-thiophenedicarboxylic acid (TFDCA) have been successfully synthesized by the melting polymerization. Microstructures and molecular weights were characterized by 1H NMR and size exclusion chromatography (SEC), respectively. Meanwhile, thermal properties, crystallization behaviors, and crystal structures were investigated by DSC, TGA, and WAXD. The results confirmed the copolymer compositions were nearly equal to the feed compositions. The weight molecular weights were all higher than 21000 g/mol for all polyesters synthesized. With increasing the TFDCA content, the glass transition temperature decreased slightly due to the weaker rigidity of the thiophene ring. DSC and WAXD results demonstrated that the isodimorphic behavior occurred for poly(trimethylene 2,5-thiophenedicarboxylate-co-trimethyleneterephthalate)s (PTTTFs). When TFDCA content was 25%, PTTTF25 exhibited the moderate tensile strength (53.1 MPa). However, the high elongation at break (396%) was observed due to the β relaxation and strain-induced crystallization.

Effect of Ethylenediaminetetraacetic Acid on Unsaturated Poly(Butylene Adipate-Co-Butylene Itaconate) Copolyester with Low-Melting Point and Controllable Hardness.

A series of copolyesters, poly(butylene adipate-co-butylene itaconate) (PBABI), was synthesized using melt polycondensation from adipic acid (AA), itaconic acid (IA), 1,4-butanediol (1,4-BDO), and ethylenediaminetetraacetic acid (EDTA). 1H-NMR, FT-IR, GPC, DSC, TGA, DMA, XRD, Shore D, and tensile test were used to systematically characterize the structural and composition/physical properties of the copolyesters. It was found that the melting point (Tm) and crystallization temperature (Tc) of the copolyesters were, respectively, between 21.1 to 57.5 °C and −6.7 to 29.5 °C. The glass transition (Tg) and the initial thermal decomposition (Td-5%) temperatures of the PBABI copolyesters were observed to be between −53.6 to −55.8 °C and 313.6 and 342.1 °C at varying ratios of butylene adipate (BA) and butylene itaconate (IA), respectively. The XRD feature peak was identified at the 2θ values of 21.61°, 22.31°, and 23.96° for the crystal lattice of (110), (020), and (021), respectively. Interestingly, Shore D at various IA ratios had high values (between 51.3 to 62), which indicated that the PBABI had soft plastic properties. The Young’s modulus and elongation at break, at different IA concentrations, were measured to be at 0.77–128.65 MPa and 71.04–531.76%, respectively, which could be attributed to a close and compact three-dimensional network structure formed by EDTA as a crosslinking agent. There was a significant bell-shaped trend in a BA/BI ratio of 8/2, at different EDTA concentrations—the ∆Hm increased while the EDTA concentration increased from 0.001 to 0.05 mole% and then decreased at an EDTA ratio of 0.2 mole%. Since the PBABI copolymers have applications in the textile industry, these polymers have been adopted to reinforce 3D air-permeable polyester-based smart textile. This kind of composite not only possesses the advantage of lower weight and breathable properties for textiles, but also offers customizable, strong levels of hardness, after UV curing of the PBABI copolyesters, making its potential in vitro orthopedic support as the “plaster of the future”.

Synthesis and characterization of two new biobased poly(pentylene 2,5-furandicarboxylate-co-caprolactone) and poly(hexamethylene 2,5-furandicarboxylate-co-caprolactone) copolyesters with enhanced enzymatic hydrolysis properties

Herein, two fully renewable copolyester series, namely poly(pentylene 2,5-furandicarboxylate-co-caprolactone) (PPeCFs) and poly(hexamethylene 2,5-furandicarboxylate-co-caprolactone) (PHeCFs) were successfully synthesized with combining ε-caprolactone (CL) with poly(pentylene 2,5-furandicarboxylate) (PPeF) and poly(hexamethylene 2,5-furan dicarboxylate) (PHeF) with different molar ratios. These materials, with a CL content ranging from 10 to 50 mol%, were synthesized for first time using stannous octoate as catalyst via ring opening polymerization (ROP). Their chemical structures and molar composition were evaluated by 1H NMR, 13C NMR and FTIR spectroscopies, while their thermal properties were investigated in detail using Fast Scanning Calorimetry (FSC), Differential scanning calorimetry (DSC) and Thermogravimetric analysis (TGA). The obtained results, in combination with Wide-Angle-X-ray diffractometry (WAXD), showed that copolymerization of CL with PHeF and PPeF led to semi-crystalline and partially amorphous copolyesters respectively, providing the basis for significant thermal properties enhancement with respect to the polycaprolactone (PCL) homopolymer, and therefore a much wider range of melting points (Tm) and glass transition temperatures (Tg) were obtained. TGA of the new copolymers showed excellent thermal stability, exceeding 310 °C and 360 °C for PHeCFs and PPeCFs respectively, while their decomposition mechanism was evaluated by pyrolysis-gas chromatography/mass spectroscopy (Py-GC/MS). Almost all copolyesters and mainly the ones with 40 and 50 mol% CL content showed accelerated enzymatic hydrolysis rate.

Systematic Study of Thermal and (Bio)Degradable Properties of Semiaromatic Copolyesters Based on Naturally Occurring Isosorbide

Here we present a series of copolyesters of poly(butylene terephthalate) (PBT) with the renewable building block isosorbide (1,4:3,6-dianhydro-d-glucitol, IS), designated PBIT. The aim of this work is to systematically elucidate how the inherent properties (reactivity, structural asymmetry, structural rigidity, and hydrophilicity) of IS would affect the synthesis and thermal/(bio)degradable performance of PBIT copolyesters. The target copolyesters containing 0–50 mol % IS units were successfully synthesized by melt polycondensation and were afforded in fully random microsequential structures. Their number-average molecular weights and intrinsic viscosities are in the ranges of 22 400–31 000 g/mol and 0.5–0.65 dL/g, respectively. The thermal properties determined by differential scanning calorimetric analysis firmly confirmed the remarkable Tg-enhancing effect of IS. Comprehensive degradation study further revealed that IS incorporation promotes remarkable hydrolytic degradation in a relatively harsh acidi...

Polyol Structure and Ionic Moieties Influence the Hydrolytic Stability and Enzymatic Hydrolysis of Bio-Based 2,5-Furandicarboxylic Acid (FDCA) Copolyesters.

A series of copolyesters based on furanic acid and sulfonated isophthalic acid with various polyols were synthetized and their susceptibility to enzymatic hydrolysis by cutinase 1 from Thermobifida cellulosilytica (Thc_Cut1) investigated. All copolyesters consisted of 30 mol % 5-sulfoisophthalate units (NaSIP) and 70 mol % 2,5-furandicarboxylic acid (FDCA), while the polyol component was varied, including 1,2-ethanediol, 1,4-butanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, or tetraethylene glycol. The composition of the copolyesters was confirmed by 1H-NMR and the number average molecular weight (Mn) was determined by GPC to range from 2630 to 8030 g/mol. A DSC analysis revealed glass-transition temperatures (Tg) from 84 to 6 °C, which were decreasing with increasing diol chain length. The crystallinity was below 1% for all polyesters. The hydrolytic stability increased with the chain length of the alkyl diol unit, while it was generally higher for the ether diol units. Thc_Cut1 was able to hydrolyze all of the copolyesters containing alkyl diols ranging from two to eight carbon chain lengths, while the highest activities were detected for the shorter chain lengths with an amount of 13.6 ± 0.7 mM FDCA released after 72 h of incubation at 50 °C. Faster hydrolysis was observed when replacing an alkyl diol by ether diols, as indicated, e.g., by a fivefold higher release of FDCA for triethylene glycol when compared to 1,8-octanediol. A positive influence of introducing ionic phthalic acid was observed while the enzyme preferentially cleaved ester bonds associated to the non-charged building blocks.

Miscibility and competition of cocrystallization behavior of poly(hexamethylene dicarboxylate)s aliphatic copolyesters: Effect of chain length of aliphatic diacids

Four series of random aliphatic copolyesters derived from 1,6-hexanediol and different diacids were designed and synthesized to investigate the effect of chain length of aliphatic diacids on miscibility and competition of cocrystallization behavior. Isodimorphic behaviors were observed from DSC, WAXD and SAXS analyses for the four series of copolyesters. Crystal type transition point at isodimorphism depended on the chain length of comonomeric diacid units in copolyesters, which presented a crystallization competition effect between the two crystal types of parent homopolyesters. The comonomeric diacids with longer chain length had stronger competitive ability in controlling the cocrystallization even when they were present in a minor proportion. Then, the cocrystallization miscibility was qualitatively analyzed by WAXD and SAXS, and further quantificatively investigated by the defect Gibbs energy calculated from the Wendling-Suter method. For HS unit (hexamethylene succinate) incorporated into the crystal type of HL unit (HA, HSu, HSe or HD unit whose chain length of comonomeric diacids gradually lengthens compared to HS unit), the HL with longer chain length has bettermiscibility with the inserted HS unit. For HL unit squeezed into the crystal lattice of HS unit, HS unit has worse miscibility with the longer inserted HL unit. Moreover, the chain length inclusion-exclusion model on the basis of the Wendling and Suter theory is proposed to give an insight into the mechanism of how does the chain length of comonomers regulate the cocrystallization behavior.

Aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups: synthesis and characterization

A new bisphenol, 1,1-bis-[(4-hydroxyphenyl)-1-(4-phenylsulfonyl)phenyl)]ethane (DPSBP) was synthesized starting from diphenylsulfide and was characterized by spectroscopic methods. DPSBP was polycondensed with isophthalic acid chloride (IPC), terephthalic acid chloride (TPC) and a mixture of IPC and TPC (50:50 mol%) by phase-transfer catalysed interfacial polymerization method to obtain aromatic polyesters containing pendent 4-(phenylsulfonyl)phenyl groups. A series of copolyesters was also obtained by polycondensation of varying molar proportions of DPSBP and bisphenol-A (BPA) with TPC. (Co)polyesters exhibited inherent viscosities in the range 0.56–1.57 dLg−1 and number average molecular weights (Mn) were in the range 28,650–80,230 g/mol. Polyesters dissolved readily in common organic solvents such as dichloromethane, chloroform, tetrahydrofuran and aprotic polar solvents such as N-methylpyrrolidone, and N,N-dimethylacetamide. Tough, transparent and flexible films of polyesters could be cast from their chloroform solutions. X-Ray diffraction studies indicated amorphous nature of aromatic polyesters. Polyesters showed Tg values in the range 223–257 °C while T10 values were in the range of 469–484 °C indicating their excellent thermal stability.