Biodegradable network elastomeric polyesters from multifunctional aromatic carboxylic acids and poly(ϵ‐caprolactone) diols

Novel biodegradable network polyesters were prepared from multifunctional aromatic carboxylic acids [trimesic acid (Y), pyromellic acid (X), and mellic acid (Y_M)] and poly(?‐caprolactone) (PCL) diols with molecular weights of 530, 1250, and 2000. Prepolymers prepared by a melt polycondensation method were cast from dimethylformamide solutions and postpolymerized at 220 °C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density measurements, differential scanning calorimetry, thermomechanical analysis, and tensile testing. Some network polyester films, including YPCL_1250, XPCL₁₂₅₀, and Y_MPCL₂₀₀₀, showed elastomeric properties with high ultimate elongation and low tensile modulus. The enzymatic degradation was measured by the weight loss of the network polyester films in a buffer solution with Rhizopus delemar lipase at 37 °C. The degree and rate of degradation increased with the increasing molecular weight of the PCL diols, but they decreased in the order of YPCL > XPCL > Y_MPCL because of the increase in the crosslinking densities of the network films. The degraded products after enzymatic degradation showed that the ester linkage of the PCL component and the aromatic ester linkage between Y and PCL diols were hydrolyzed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4523–4529, 2002     

Synthesis and Enzymatic Degradation of Aliphatic Polyesters Copolymerized with Trimesic Acid

Abstract

Network copolyesters were made from adipic acid and ethylene glycol with 10–40 mol% trimesic acid (Y). Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and postpolymerized at 260°C for various times to form a network. The degree of reaction (D _R), estimated from the infrared absorbance of hydroxyl and methylene groups, increased with increasing postpolymerization time and leveled out at about 90% after 4–6 hours. Heat distortion temperatures (T _h) measured by thermomechanical analysis increased greatly from ?83 to 48°C upon the incorporation of Y. Wide-angle x-ray diffraction patterns showed that the copolymer films are amorphous. Density, tensile strength, and Young's modulus decreased for the copolymers with 10–30 mol% Y, whereas they increased drastically for the copolymer with 40 mol% Y. The enzymatic degradation was estimated by the weight loss of the copolymer films in buffer solutions with a lipase at 37°C. The weight loss decreased remarkably with increasing Y and showed no weight loss for the copolymer with 40 mol% Y. On the other hand, the weight loss by alkali hydrolysis increased for the copolymers with 10 and 20 mol% Y, implying a difference in the degradation mechanism between enzymatic degradation and alkali hydrolysis.     

Synthesis,characterization, and biodegradability of novel regular‐network polyester‐amines based on 1,1,1‐triethanolamine

Regular‐network polyester‐amines were prepared from 1,1,1‐triethanolamine (Y_N) and various dicarboxylic acids [HOOC? (CH₂)_n?2? COOH, n = 6–14]. A prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 220 °C in a nitrogen flow for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyester‐amines obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density, DSC, and thermomechanical analysis. The biodegradation experiments for the network polyester‐amine films were carried out in enzymatic solution with Rhizopus delemar or Pseudomonas cepacia lipase and in an activated sludge. The degree and rate of biodegradation were estimated by the weight loss of the films. After incubation in Rhizopus delemar lipase solution for 24 h, weight loss was hardly observed for Y_N6–7, whereas it increased greatly for Y_N8–13 (13–51 g/m²), and then it decreased rapidly for Y_N14. The methylene‐chain dependence of degradation was essentially the same as in the case of network polyesters from glycerol and various aliphatic dicarboxylic acids reported previously. Psedomonas cepacia lipases also degraded Y_Nn films, but the rate of degradation was much slower than Rhizopus delemar lipase. In the exposure to activated sludge for 30 days, the network polyester films with medium methylene‐chain lengths (Y_N7–11) showed the lager weight loss, as in the case of the enzymatic degradation, whereas the rate of biodegradation was much slower than that of the enzymatic degradation with Rhizopus delemar lipase. The effect of the protonation of the film with hydrochloric acid on the enzymatic degradation was also examined. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2896–2903, 2001     

Enzymatic degradation of aliphatic polyesters copolymerized with various diamines

Poly(hexamethylene adipate) copolymers with 10–40 mol-% (in feed) of aliphatic diamines of various methylene chain lengths were prepared by melt polycondensation. In vitro degradation was performed in buffer solution at 37°C with a lipase and was evaluated by weight loss of the films. The weight loss increased greatly by the copolymerization and showed a maximum at 10 mol-% of comonomer content. Degradation also increased in a zig-zag fashion with decreasing number of methylene chains in the diamine comonomers. Both effects on the enzymatic degradation are discussed.     

Comparison of the catalytic activity of PHB–depolymerase,yeast lipase,and papain on poly(ethylene adipate), poly(ethylene succinate), and poly (3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)

PHB-depolymerase degraded poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] (PHB/V) significantly. No other enzyme used in this study showed activity toward PHB/V. Weight loss and gel permeation chromatography (GPC) studies suggested that enzymatic degradation takes place by a surface erosion mechanism. pH studies demonstrated that enzymatic degradation occurs even when little weight loss is observed. Differential scanning calorimetry (DSC) analysis demonstrated that the enzymes studied prefer to degrade amorphous regions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2581–2585, 1999     

Synthesis and properties of photocurable biodegradable multiblock copolymers based on poly(ε‐caprolactone) and poly(L‐lactide) segments

Photocurable biodegradable multiblock copolymers were synthesized from poly(ε‐caprolactone) (PCL) diol and poly(L ‐lactide) (PLLA) diol with 4,4′‐(adipoyldioxy)dicinnamic acid (CAC) dichloride as a chain extender derived from adipoyl chloride and 4‐hydroxycinnamic acid, and they were characterized with Fourier transform infrared and ¹H NMR spectroscopy, gel permeation chromatography, wide‐angle X‐ray diffraction, differential scanning calorimetry, and tensile tests. The copolymers were irradiated with a 400‐W high‐pressure mercury lamp from 30 min to 3 h to form a network structure in the absence of photoinitiators. The gel concentration increased with time, and a concentration of approximately 90% was obtained in 90–180 min for all the films. The photocuring hardly affected the crystallinity and melting temperature of the PCL segments but reduced the crystallinity of the PLLA segments. The mechanical properties, such as the tensile strength, modulus, and elongation, were significantly affected by the copolymer compositions and gel concentrations. Shape‐memory properties were determined with cyclic thermomechanical experiments. The CAC/PCL and CAC/PCL/PLLA (75/25) films photocured for 30–120 min showed good shape‐memory properties with strain fixity rates and recovery rates of approximately 100%. The formation of the network structure and the crystallization and melting of the PCL segments played very important roles for the typical shape‐memory properties. Finally, the degradation characteristics of these copolymers were investigated in a phosphate buffer solution at 37 °C with proteinase‐k and Pseudomonas cepacia lipase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2426–2439, 2005     

Synthesis and characterization of functional aliphatic copolyesters

Functional aliphatic copolyesters of succinic acid (SA) and citric acid (CA) were synthesized via direct copolycondensation in the presence of 1,4‐butanediol, with titanium(IV) butoxide as a catalyst. The effects of the comonomer and comonomer ratio on the polycondensation and the melting and glass‐transition temperatures were investigated. The melting temperature was very sensitive to the molar ratio of the SA–CA comonomer units. The chain extension of this poly(butylene succinate citrate) was carried out with hexamethylene diisocyanate. The intrinsic viscosity, crystallinity percentage, and rheological properties of these copolyesters were also studied. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3232–3239, 2002     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. III. Methanolytic degradation

The methanolysis of poly(ethylene terephthalate) (PET) copolymers containing 5‐nitroisophthalic units was investigated. Random copolyesters containing 10 and 30 mol % of such units were prepared via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate (BHET) and bis(2‐hydroxyethyl) 5‐nitroisophthalate (BHENI) in the presence of tetrabutyl titanate as a catalyst. First, the susceptibility of these two comonomers toward methanolysis was evaluated, and their reaction rates were estimated with high‐performance liquid chromatography. BHENI appeared to be much more reactive than both BHET and bis(2‐hydroxyethyl) isophthalate. The methanolysis of PET and the copolyesters was carried out at 100 °C, and the degradation process was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the rate of degradation increased with the content of nitrated units. The products resulting from methanolysis were concluded to be dimethyl terephthalate, dimethyl 5‐nitroisophthalate, ethylene glycol, and small, soluble oligomers. For both PET and the copolyesters, an increase in crystallinity was observed during the degradation process, indicating that methanolysis preferentially occurred in the amorphous phase. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 76–87, 2002     

Effects of comonomer sequential structure on thermal and crystallization behaviors of biodegradable poly(butylene succinate‐co‐butylene terephthalate)s

In this work, new investigations on the effect of comonomer sequential structure on the thermal and crystallization behaviors and biodegradability have been implemented for the biodegradable poly(butylene succinate‐co‐butylene terephthalate) (PBST) as well as aliphatic poly(butylene succinate) (PBS). At first, these copolyesters were efficiently synthesized from dimethyl succinate and/or dimethyl terephthalate and 1,4‐butanediol via condensation polymerization in bulk. Subsequently, their molecular weights and macromolecular chain structures were analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. By means of differential scanning calorimeter (DSC) and wide‐angle X‐ray diffractometer (WAXD), thermal and crystallization behaviors of these synthesized aromatic–aliphatic copolyesters were further explored. It was demonstrated that the synthesized copolyesters were revealed to have random comonomer sequential structures with thermal and crystallization properties strongly depending on their comonomer molar compositions, and that crystal lattice structures of the new crystallizable copolyesters shifted from the monoclinic crystal of semicrystalline PBS to triclinic lattice of the poly(butylene terephthalate) (PBT) with increasing the terephthalate comonomer composition, and the minor comonomer components were suggested to be trapped in the crystallizable component domains as defects. In addition, the enzymatic degradability was also characterized for the copolyesters film samples. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1635–1644, 2006     

Synthesis and characterization of new cardo polyimides prepared from 5,5-Bis[4-(4-aminophenoxy)phenyl]-4,7-methanohexahydroindane

A new cardo diamine monomer, 5,5-bis[4-(4-aminophenoxy)phenyl]-4,7-methanohexahydroindane (II), was prepared in two steps with high yield. The monomer was reacted with six different aromatic tetracarboxylic dianhydrides in N,N-dimethylacetamide (DMAc) to obtain the corresponding cardo polyimides via the poly(amic acid) precursors and thermal or chemical imidization. All the poly(amic acid)s could be cast from their DMAc solutions and thermally converted into transparent, flexible, and tough polyimide films which were further characterized by x-ray and mechanical analysis. All of the polymers were amorphous and the polyimide films had a tensile strength range of 89–123 MPa, an elongation at break range of 6–10%, and a tensile modulus range of 1.9–2.5 GPa. Polymers V_c, V_e, and V_f exhibited good solubility in a variety of solvents such as N-methyl-2-pyrrolidinone (NMP), DMAc, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, γ-butyrolactone, and even in tetrahydrofuran and chloroform. These polyimides showed glass-transition temperatures between 274 and 299°C and decomposition temperatures at 10% mass loss temperatures ranging from 490 to 521°C and 499 to 532°C in nitrogen and air atmospheres, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2815–2821, 1999     

Synthesis,characterization, and in vitro degradation of thermotropic polyesters and copolyesters based on terephthalic acid, 3‐(4‐hydroxyphenyl)propionic acid,and glycols

A new series of thermotropic liquid‐crystalline (LC) polyesters were prepared from a diacyl chloride derivative of 4,4′‐(terephthaloyldioxy)‐di‐4‐phenylpropionic acid (PTP) and glycols with a different number of methylene groups (n) [HO(CH₂)_n OH, n = 6–10, 12] by high‐temperature solution polycondensation in diphenyl oxide. PTP6/10 and PTP6/hydroquinone (H) LC copolyesters were also prepared according to a similar procedure. The chemical structure, LC, phase‐transition behaviors, thermal stability, and solubility were characterized by elemental analysis, Fourier transform infrared spectroscopy, ¹H and ¹³C NMR spectra, differential scanning calorimetry (DSC), thermogravimetric analysis, and a polarizing light microscope. The melting and isotropization temperatures decreased in a zigzag manner as the number of n increased. All of the polyesters formed a nematic phase with the exception of PTP8. The temperature ranges of the mesophase (ΔT) were much wider for the polyesters with an odd number of n's than those with an even number. ΔT increased markedly for the PTP6/10 and PTP6/H copolyesters. The in vitro degradations of the polymers were ascertained by enzymatic hydrolysis and alkaline hydrolysis. The model compound, PTP dihexylester, was synthesized and found to be degraded into terephthalic acid, 3‐(4‐hydroxyphenyl)propionic acid, and 1‐hexanol by Rhizopus delemar lipase, but PTPn homopolyesters and PTP6/10 and PTP6/H copolyesters were resistant to Rhizopus delemar hydrolysis. They were degradable in a sodium hydroxide buffer solution of pH 12 at 60 °C, depending on the number of n's and the copolymer composition. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3043–3051, 2001     

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     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. I. Synthesis and characterization

Poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers, abbreviated as PETNI, were synthesized via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate and bis(2‐hydroxyethyl) 5‐nitroisophthalate mixtures with molar ratios of these two comonomers varying from 95/5 to 50/50. Polymerization reactions were carried out at temperatures between 200 and 270 °C in the presence of tetrabutyl titanate as a catalyst. The copolyesters were characterized by solution viscosity, GPC, FTIR, and NMR spectroscopy. They were found to be random copolymers and to have a comonomer composition in accordance with that used in the corresponding feed. The copolyesters became less crystalline and showed a steady decay in the melting temperature as the content in 5‐nitroisophthalic units increased. They all showed glass‐transition temperatures superior to that of PET with the maximum value at 85 °C being observed for the 50/50 composition. PETNI copolyesters appeared stable up to 300 °C and thermal degradation was found to occur in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1934–1942, 2000     

Synthesis and properties of new polyarylates from 1,4‐bis(4‐carboxyphenoxy)naphthyl or 2,6‐bis(4‐carboxyphenoxy)naphthyl and various bisphenols

New 1,4‐naphthyl and 2,6‐naphthyl‐containing polyarylates having inherent viscosities up to 1.28 dL/g were synthesized by the high‐temperature solution polycondensation from the acid chloride of 1,4‐bis(4‐carboxyphenoxy)naphthyl or 2,6‐bis(4‐carboxyphenoxy)naphthyl and various bisphenols. Most of the resulting polyarylates showed amorphous characteristics and were readily soluble in common organic solvents such as N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), o‐chlorophenol, and chloroform. Transparent, flexible, and colorless films of these polymers could be cast from the DMAc solutions. Their cast films had tensile strengths ranging from 54.9 to 84.2 MPa, elongations at break from 5.3% to 19.0%, and initial modulus from 2.0 to 2.8 GPa. These polymers had glass transition temperatures in the range of 172–280°C and began to lose weight around 400°C, with 10% weight loss being recorded at about 450°C in air. Dynamic mechanical analysis (DMA) reveals that the polyarylates containing isopropylidene linkages have three transitions on the temperature scale between −100 and 300°C. However, only two transitions were observed in the other polyarylates without isoproylidene linkage. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 645–652, 1999     

Synthesis and characterization of photocrosslinked poly(ε‐caprolactone)s showing shape‐memory properties

Poly(ε‐caprolactone) (PCL) with a pendent coumarin group was prepared by solution polycondensation from 7‐(3,5‐dicarboxyphenyl) carbonylmethoxycoumarin dichloride and α, ω‐dihydroxy terminated poly(ε‐caprolactone) with molecular weights of 1250, 3000, and 10,000 g/mol. These photosensitive polymers underwent a rapid reversible photocrosslinking upon exposure to irradiation with alternating wavelengths (>280/254 nm) without a photoinitiator. The thermal and mechanical properties of the photocrosslinked films were examined by means of differential scanning calorimetry and stress–strain measurements. The crosslinked films exhibited elastic properties above the melting temperature of the PCL segment along with significant decrease in the ultimate tensile strength and Young's modulus. Shape‐memory properties such as strain fixity ratio (R_f) and strain recovery ratio (R_r) were determined by means of a cyclic thermomechanical tensile experiments under varying maximum strains (ε_m = 100, 300, and 500%). The crosslinked ICM/PCL‐3000 and ‐10,000 films exhibited the excellent shape‐memory properties in which both R_f and R_r values were 88–100% for tensile strain of 100–500%; after the deformation, the films recovered their permanent shapes instantaneously. In vitro degradation was performed in a phosphate buffer saline (pH 7.2) at 37 °C with or without the presence of Pseudomonas cepacia lipase. The presence of the pendent coumarin group and the crosslinking of the polymers pronouncedly decreased the degradation rate. The crosslinked biodegradable PCL showing a good shape‐memory property is promising as a new material for biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2422–2433, 2009     

Synthesis and characterization of novel poly(amide-imide)s containing hexafluoroisopropylidene linkage

A series of novel soluble poly(amide-imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl]hexafluoropropane, with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl₂ using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.78–1.63 dL g⁻¹. The polymers were amorphous and readily soluble in aprotic polar solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide as well as in less polar solvents such as pyridine and γ-butyrolactone, and also in tetrahydrofuran. The polymer films had tensile strength of 84–129 MPa, an elongation at break range of 6–22%, and a tensile modulus range of 2.0–2.7 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 240–282°C. These polymers were fairly stable up to a temperature around or above 400°C, and lose 10% weight in the range of 450–514°C and 440–506°C in nitrogen and air, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2629–2635, 1999     

Preparation and characterization of colorless alternate poly(amide-imide)s based on trimellitic anhydride and 2,2-bis[4-(3-aminophenoxy)phenyl]sulfone

Alternate poly(amide-imide) [P(A-alt-I)] was synthesized from two aromatic diamines and trimellitic anhydride (TMA). When the diamine was 2,2-bis[4-(3-aminophenoxy)phenyl]sulfone (BAPS), the resulted P(A-alt-I) was found to be of light color. Specifically, when BAPS was located between two amide groups in the P(A-alt-I) chain, the P(A-alt-I) was almost colorless. A series of P(A-alt-I)s (Series III) containing BAPS was synthesized through direct polycondensation of an aromatic dicarboxylic acid prepared from various aromatic diamines and TMA, as well as BAPS. Polymers of Series III were much lighter in color than those of the isomeric series (BAPS was located between two imide group). The series of P(A-alt-I)s III had inherent viscosities ranging 0.69–1.35 dL/g and good solubility in various solvents. The tensile strengths, elongations to break, and initial moduli of the films were 72–107 MPa, 7–12% and 1.93–2.39 GPa, respectively, and most of the films had no yielding. Polymers of Series III had glass transition temperatures 210–272°C and 10% weight loss temperatures in nitrogen 518–545°C, indicating excellent thermal stability. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2421–2428, 1999     

Pseudohexagonal crystallinity and thermal and tensile properties of ethene–propene copolymers

Structural (X‐ray diffraction), melting (differential scanning calorimetry), as well as mechanical (tensile tests) characterizations on uncrosslinked ethene–propene copolymer samples, obtained using a metallocene‐based catalytic system and having an ethene content in the range 80–50% by mol, are reported. Samples with an ethene content in the range 80–60% by mol present a disordered pseudohexagonal crystalline phase, whose melting moves from ≈ 40°C down to ≈ −20°C as the ethene content is reduced. The dramatic influence of the crystalline phase on tensile properties of uncrosslinked ethene–propene copolymers is shown. In particular, highest elongation at break values are obtained for samples being essentially amorphous in the unstretched state and partially crystallizing under stretching. On the other hand, lowest tension set values (most elastic behavior) are observed for samples presenting, already in the unstretched state, microcrystalline domains acting as physical crosslinks in a prevailing amorphous phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1095–1103, 1999     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. III. Methanolytic degradation

The methanolytic degradation of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units was investigated. Random poly(ethylene terephthalate‐co‐nitroterephthalate) copolyesters (PETNT) containing 15 and 30 mol % nitrated units were prepared from ethylene glycol and a mixture of dimethyl terephthalate and dimethyl nitroterephthalate. A detailed study of the influence of the nitro group on the methanolytic degradation rate of the nitrated bis(2‐hydroxyethyl) nitroterephthalate (BHENT) model compound in comparison with the nonnitrated bis(2‐hydroxyethyl) terephthalate (BHET) model compound was carried out. The kinetics of the methanolysis of BHENT and BHET were evaluated with high‐performance liquid chromatography and ¹H NMR spectroscopy. BHENT appeared to be much more reactive than BHET. The methanolytic degradation of PET and PETNT copolyesters at 80 °C was followed by changes in the weight and viscosity, gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and ¹H and ¹³C NMR spectroscopy. The copolyesters degraded faster than PET, and the degradation increased with the content of nitrated units and occurred preferentially by cleavage of the ester groups placed at the meta position of the nitro group in the nitrated units. For both PET and PETNT copolyesters, an increase in crystallinity accompanied methanolysis. A surface degradation mechanism entailing solubilization of the fragmented polymer and consequent loss of mass was found to operate in the methanolysis of the copolyesters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2276–2285, 2002     

Polyterephthalates made from Ethylene glycol, 1,4‐cyclohexanedimethanol,and isosorbide

Three series of terephthalate polyesters (copolyesters and terpolyesters) containing 70, 80, and 90 mol % of ethylene glycol respectively, 1,4‐cyclohexanedimethanol (CHDM) and isosorbide in varying ratios, were synthesized by melt polycondensation. It was found that only ～75 mol % of the feeding isosorbide was incorporated in the resulting polyesters and that their content in diethylene glycol oscillated between 2 and 4 mol %. The polyesters had weight‐average molecular weights in the 25,000–33,000 g mol^?1 range and polydispersities between 2 and 2.5. The combined ¹H and ¹³C NMR analysis revealed that the microstructure of all these polyesters was at random. They showed good thermal stability with decomposition temperatures above 400 °C. Their glass‐transition temperatures were observed to increase with the content in cyclic diols, this effect being more pronounced when isosorbide was the replacing comonomer. Only the series containing 90 mol % of ethylene terephthalate units was able to crystallize upon cooling from the melt. Compared isothermal crystallizations revealed that isosorbide was more effective than CHDM in repressing the crystallizability of PET. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011