Adipate Units Research Articles

Non-isothermal crystallization and thermo-mechanical properties of poly(butylene adipate-co-ethylene terephthalate) random copolyesters

Random aliphatic-aromatic copolyesters are synthesized through melt polycondensation of bis(2-hydroxybutyl) adipate (BHBA) with 0–15 mol% of bis(2-hydroxyethyl) terephthalate (BHET) oligomers. Regarding the random ester-interchange reactions, the sequence length distribution of butylene adipate (BA) units reduces with increasing BHET. Crystallization of copolyesters is investigated by differential scanning calorimetry. Crystallization peak temperatures (Tc) and melting peaks (Tm1, Tm2, and Tm3) of all samples decrease with increasing cooling rate. Moreover, increasing BHET results in the reduction of crystallinity. Regarding the results of Avrami, Tobin, Ozawa, and Mo's models for non-isothermal crystallization, the crystallization rate decreases as the BHET content increases. Using the isoconversional method of Friedman, it is revealed that copolymerization leads to a reduction of the absolute enthalpy of crystallization. According to the wide-angle X-ray diffraction (WAXD) results, the crystalline dimensions reduce with copolymerization, and flawed crystals are developed in copolyesters.

Synthesis and properties of poly(hexamethylene 2,5-furandicarboxylate-co-adipate) copolyesters

Through a two-stage transesterification/esterification and polycondensation method, three biobased poly(hexamethylene 2,5-furandicarboxylate-co-adipate) (PHFA) copolyesters with low contents of hexamethylene adipate (HA) units were synthesized in this research. The thermal properties, crystal structure, and tensile properties of PHFA copolyesters and poly(hexamethylene 2,5-furandicarboxylate) (PHF) homopolymer were extensively studied and compared with each other. All PHFA copolyesters still maintained good thermal stability. The glass transition temperatures, melting point temperatures, and equilibrium melting point temperatures of PHFA copolyesters gradually decreased with the increase of HA units. PHFA copolyesters displayed the same crystal structures as PHF. The elongation at break remarkably increased to 498.3 ± 12.0% for the PHFA copolyester containing 30 mol% of HA units (PHFA30) from 197.3 ± 12.2% for PHF; moreover, PHFA30 still showed a relatively high melting point temperature of 116.4 °C, similar to that of biodegradable poly(butylene succinate) (about 114 °C).

Isothermal Crystallization Kinetics and Crystalline Morphologies of Poly(butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate) Copolymers

In this study, the isothermal crystallization kinetics and crystalline morphology of poly(butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate) (PBAC), which refers to a copolyester containing a non-planar ring structure, were investigated by differential scanning calorimetry and polarized optical microscopy, and compared with those of neat poly(butylene 1,4-cyclohexanedicarboxylate) (PBC). The results indicate that the introduction of butylene adipate (BA) unit into PBAC did not change the intrinsical crystallization mechanism. But, the crystallization rate and ability, and equilibrium melting temperature of PBAC copolymers were reduced. All PBC and PBAC copolymers could only form high density of nucleation from melt at given supercooling, while no Maltese cross or ring-banded spherulites could be observed. PBAC copolymers with a high amount of BA unit became amorphous after quenching with liquid nitrogen from melt, while PBC and PBAC copolymers with a low amount of BA unit could still form a large amount of nuclei under the same treatment.

Preparation of random poly(butylene alkylate-co-terephthalate)s with different methylene group contents: crystallization and degradation kinetics

Random copolyesters having 1,4-butanediol units were synthesized from a transesterification process between homopolymers constituted by aliphatic dicarboxylates (i.e. succinate, adipate or sebacate) and the aromatic therephthalate derivative, as verified by NMR spectroscopy. Biodegradability of resulting copolyesters was studied via enzymatic hydrolysis using Pseudomonas cepacia lipase at pH = 7.2 and 37 °C. Kinetics of degradation showed that in all cases the degradation rate decreased after 19 days of exposure. The observed glass transition temperatures, T g, of the random copolyesters showed a non-linear dependence on composition, a feature that was explained in terms of the internal stiffening effect of butylene terephthalate units. Copolymers with higher aliphatic (i.e. 50 and 70 mol-%) and methylene (i.e. adipate and sebacate units) contents showed double melting peaks in DSC thermograms. These copolyesters resulted in two different crystalline rich phases after melt-crystallization and subsequent cooling. The ratio between these phases logically depended on the predominant aliphatic or aromatic dicarboxylate content. The copolymers initially crystallized via the aromatic units through a heterogeneous nucleation and a spherulitic growth. The presence of aliphatic dicarboxylate units hindered the beginning of the crystallization process, but the overall growth kinetic constant was similar for all samples. The secondary nucleation constants were determined and showed higher values for samples with higher adipate and sebacate contents.

Synthesis of porous CdO sheet-like nanostructure based on soft template model and application in dye pollutants adsorption

In this work, the synthesis of porous structure of cadmium oxide with multilayered sheet-like morphology in nano-meter size using adipic acid as soft template by solvothermal/thermal decomposition process is reported. Chemical analyses exhibited that the formation of porous sheet-like structure is originated from bidentate coordination mode of adipate units to Cd-center. It was found that the change of reaction conditions can vary final morphology of product due to the different coordination modes of adipate units. The structural and morphological characterizations of product were discussed in detail. Brunauer-Emmett-Teller (BET) analysis indicated a specific surface area of 52.08 m 2 g - 1 with pore size distribution centered at 11.7 nm for prepared CdO sheet-like nanostructure. The capability of the as prepared product for adsorption of dye pollutants from aqueous solution was also studied. The results showed a maximum adsorption capacity (q max ) of 500 mg g -1 for adsorption of Congo Red (CR) dye in water revealing a superior ability of this product for adsorption of dye pollutants.

Structural analysis of biodegradable low-molecular mass copolyesters based on glycolic acid, adipic acid and 1,4 butanediol and correlation with their hydrolytic degradation

Copolyesters of glycolic acid combined with adipic acid and 1,4 butanediol were synthesized, their in vitro hydrolytic degradation was studied and correlated with their structure. The hydrolytic degradation of the copolyesters was directly related with the degree of crystallinity and the diameter of the crystallites. It was found that glycolate units disturb the ordering of the butylene adipate units, which results in a decrease of the crystallinity. By comparing the hydrolysis parameters of synthesized copolyesters with those of similar aliphatic copolyesters a hydrolysis mechanism was proposed. According to this mechanism, the degradation takes place not only by the loss of end units, but also through the removal of larger segments. MALDI-TOF MS data showed that the possibility of a copolyester macromolecule forming cyclic structures correlates with the arrangement of ester groups in the macromolecules and the structure of the linear segments.

Carbohydrate‐based copolyesters made from bicyclic acetalized galactaric acid

AbstractMixtures of the dimethyl esters of adipic acid and 2,3:4,5‐di‐O‐methylene‐galactaric acid (Galx) were made to react in the melt with either 1,6‐hexanediol or 1,12‐dodecanediol to produce linear polycyclic copolyesters with aldarate unit contents varying from 10 up to 90 mole %. The copolyesters had weight–average molecular weights in the ∼35,000–45,000 g mol−1 range and a random microstructure, and were thermally stable up to nearly 300 °C. They displayed Tg in the ‐50 to ‐7 °C range with values largely increasing with the content in galactarate units. All the copolyesters were semicrystalline with Tm between 20 and 90 °C but only those made from 1,12‐dodecanediol were able to crystallize from the melt at a crystallization rate that decreased as the contents in the two comonomers approached each other. Copolyesters containing minor amounts of galactarate units adopted the crystal structure characteristic of aliphatic polyesters but a new crystal polymorph was formed when the cyclic sugar units became the majority. Stress–strain parameters were sensitively affected by composition of the copolyesters with the mechanical behavior changing from flexible/ductile to stiff/brittle with the replacement of adipate units by the galactarate units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Evaluation of Biodegradability of Poly(Butylene succinate-co-butylene Adipate) on the Basis of Copolymer Composition Determined by Thermally Assisted Hydrolysis and Methylation-Gas Chromatography

Biodegradability of poly(butylene succinate-co-butylene adipate) (PBSA) was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) using trace amounts (20 µg) of the film samples. The copolymer compositions of butylene adipate (BA) units gradually decreased with soil burial degradation time, reflecting preferential biodegradation of BA moieties during soil burial due to their lower crystallinity. Furthermore, local differences in biodegradability of a given PBSA film after soil burial were also successfully evaluated.

Chain extension of adipic acid and (or) succinic acid/butanediol polyesters with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoylbiscaprolactamate combined chain extenders

AbstractThis paper provided an easy and flexible method to synthesize high molecular weight polyesters by polycondensation and chain extension. Low molecular weight polybutylene adipate, polybutylene succinate, and poly(butylene succinate‐co‐butylene adipate) (PBSA) were synthesized through melt condensation polymerization from adipic acid and/or succinic acid with butanediol. The prepolyesters obtained had different amount of COOH and OH terminal groups. Chain extension of them was carried out at 180–240°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The influencing factors of the chain extension were studied. At the optimal conditions, chain‐extended polybutylene adipate with Mn up to 39,100, polybutylene succinate with intrinsic viscosity of 0.99 dl/g, and PBSA with intrinsic viscosity from 0.73 to 0.81 dl/g were synthesized. The chain‐extended polyesters were characterized by IR spectrum, 1H NMR spectrum, differential scanning calorimetry, thermogravimetric analysis (TGA), wide angle X‐ray scattering, and tensile test. The thermal analysis showed that chain extension often led to slight decrease of the regularity, the crystallinity, and the melting point. This deterioration of the properties is not harmful enough to impair their thermal properties and obstruct them from being used as biodegradable thermoplastics. The TGA showed that the chain‐extended polyesters were stable with initial decomposition temperature over 354.7°C. The tensile strength of the chain extended PBS and PBSAs with butylene adipate units less than 20 mol% was in the range of 18.95–31.22 MPa. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis and characterization of novel poly(propylene terephthalate-co-adipate) biodegradable random copolyesters

Novel aromatic/aliphatic poly(propylene terephthalate-co-adipate) (PPTAd) random copolymers were synthesized. Copolymer composition varied over the whole range from that of neat poly(propylene terephthalate) (PPT) to that of neat poly(propylene adipate) (PPAd). Interestingly, the copolymers showed that they can degrade via hydrolysis, especially in presence of enzymes, even for a terephthalate content as high as 66 mol%. Thermal behaviour and solid state as well as mechanical properties were studied. In contrast to hydrolysis rates, mechanical properties increase with terephthalate content. WAXD patterns indicate some extent of co-crystallization of both comonomers, especially for intermediate compositions. The thermodynamic analysis of the melting point depression showed that some portion of the adipate comonomer units participate in the formation of crystals, although the major portion of them is rejected from crystals and remain in the amorphous phase. WAXD patterns showed that even for a 60 mol% or more adipate content, the copolymers form PPT like crystals. Thus, the amorphous phase is enriched in adipate units, as is also shown by a lowering of the glass transition temperature of the crystallized copolymer samples, compared to glassy ones. Finally, multiple melting behaviour of the melt crystallized copolymer samples, as well as, banded spherulitic morphology was observed.

μ-Adipato-κ2O1:O4-bis{[2,6-bis(1H-benzimidazol-2-yl-κN3)pyridine-κN](nitrato-κO)lead(II)}

The dinuclear title compound, [Pb2(C6H8O4)(NO3)2(C19H13N5)2], lies with the mid-point of the butyl chain of the bridging adipate unit on a center of inversion. The PbII ion is covalently bonded to the nitrate anion and is bonded to a carboxyl­ate group of the adipate unit by another covalent bond. The N-heterocycle functions in a chelating tridentate mode. The metal atom exists in a Ψ-octa­hedral coordination environment. When weaker Pb⋯O inter­actions are also considered, the geometry is a Ψ-tricapped trigonal prism in which the lone-pair electrons occupy one face of the trigonal prism. Adjacent mol­ecules are linked into a layer structure by N—H⋯O hydrogen bonds.

Composition, thermal properties, and biodegradability of a new biodegradable aliphatic/aromatic copolyester

AbstractA series of new aliphatic/aromatic copolyesters [poly(hexylene terephthalate‐co‐hexylene adipate) (PHTA)] were synthesized on the bases of 1,6‐hexanediol, adipic acid, and dimethyl terephthalate and characterized by gel permeation chromatography, 1H‐NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and compost testing. 1H‐NMR results show that the compositions of the copolyesters were in accordance with the feed molar ratios. The WAXD patterns indicated that the crystal structures of the PHTA copolyesters were determined by the dominant crystal units, and the copolyesters became less crystallizable, even amorphous, with increasing comonomer content. The DSC curves showed that the glass‐transition temperatures (Tg′s) of the PHTA copolyesters decreased linearly, and both the melting temperature (Tm) and heat of fusion decreased first and then increased with increasing hexylene adipate unit content. Under compost conditions, PHTA copolyesters with less than 60 mol % aromatic units were biodegradable. Particularly, compared with the copolyester poly(butylene terephthalate‐co‐butylene adipate), the PHTA copolyester with the same aliphatic/aromatic composition possessed a lower Tg and Tm and better biodegradability. Additionally, the biodegradability of the copolyesters could be predicted by the number‐average sequence length of aromatic units, Tg, and the temperature difference between Tm and the temperature at which biodegradation took place. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and Characterization of Branched Polymers from Lipase-Catalyzed Trimethylolpropane Copolymerizations

Lipase-catalyzed terpolymerizations were performed with the monomers trimethylolpropane (B3), 1,8-octanediol (B2), and adipic acid (A2). Polymerizations were performed in bulk, at 70 degrees C, for 42 h, using immobilized lipase B from Candida antartica (Novozyme-435) as a catalyst. To determine the substitution pattern of trimethylolpropane (TMP) in copolymers, model compounds with variable degrees of acetylation were synthesized. Inverse-gated 13C NMR spectra were recorded to first determine the chemical shift positions for mono-, di-, and trisubstituted TMP units and, subsequently, to determine substitution of TMP units along chains. Variation of TMP in the monomer feed gave copolymers with degrees of branching (DB) from 20% to 67%. In one example, a hyperbranched copolyester with 53 mol % TMP adipate units was formed in 80% yield, with Mw 14 100 (relative to polystyrene standards), Mw/Mn 5.3, and DB 36%. Thermal and crystalline properties of the copolyesters were studied by thermogravimetric analysis and differential scanning calorimetry.

Characterization of Poly(ethyleneoxyethylene terephthalate‐co‐adipate) using NMR Spectroscopy

Comonomer sequence distribution and 1H‐NMR chemical shifts were determined for poly(ethyleneoxyethylene terephthalate‐co‐adipate) (PEOETA) copolyester. The sequence distribution of terephthalate (T) and adipate (A) residues was found to be random, which is typical for copolyesters synthesized via bulk polycondensation. The inner methylene protons of EOE residues appeared as a pair of doublets due to chemical shift differences among the EOE‐centered dyad sequences TT, TA, AT, and AA. The four equivalent phenylene protons of T residues appeared as a triplet due to chemical shift differences among the T‐centered triad sequences TTT, TTA (˭ATA), and ATA. Higher‐order tetrad and pentad sensitivity were also observed for the inner methylene and phenylene protons, respectively, especially for TT‐ and TTT‐centered sequences. The sequence sensitivity of the phenylene protons was attributed to unique spatial interactions between themselves and protons within adjacent adipate and EOE units. These spatial interactions were confirmed using Nuclear Overhauser Enhancement Spectroscopy (NOESY).

Novel random poly(propylene isophthalate/adipate) copolyesters: Synthesis and characterization

Poly(propylene adipate) (PPA) and poly(propylene isophthalate/adipate) (PPI–PPA) random copolymers of various compositions were synthesized in bulk and characterized in terms of chemical structure and molecular weight. Furthermore, the thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers showed a good thermal stability. At room temperature they appeared as semicrystalline materials, except the copolymers containing 20 and 30 mol% of PI units: the main effect of copolymerization was a lowering in the amount of crystallinity and a decrease of melting temperature with respect to homopolymers. The crystalline phase of PPI and PPA was evidenced at high content of propylene isophthalate or propylene adipate units, respectively. Amorphous samples were obtained after melt quenching and an increment of T g as the content of PI units is increased was observed. This behavior was explained as due to the stiff phenylene groups in the polymeric chain. The Wood equation was found to describe well T g-composition data. Lastly, the presence of a rigid-amorphous phase was evidenced in the copolymers, differently from PPA homopolymer.

Biodegradable aliphatic polyesters. Part I. Properties and biodegradation of poly(butylene succinate- co-butylene adipate)

A series of aliphatic homopolyesters and copolyesters was prepared from 1,4 butanediol and dimethylesters of succinic and adipic acids through a two-step process of transesterification and polycondensation. The synthesized polyesters were characterized by means of nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), viscosity measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and mechanical property measurements. The homopolymer poly(butylene succinate) exhibited the highest tensile strength, which decreased with increasing adipate unit content, passed through a minimum at copolyester composition close to equimolarity and then increased towards the value of poly(butylene adipate). It is interesting to note that in contrast to tensile strength, the elongation at break increased for adipate unit content of 20–40 mol%. The biodegradation of the polymers was investigated by soil burial and enzymatic hydrolysis using three enzymes, Candida cylindracea lipase, Rhizopus delemar lipase, and Pseudomonas fluorescens cholesterol esterase. It appears that the key factor affecting material degradation was its crystallinity.

Biodegradation of poly(butylene succinate- co-butylene adipate) by Aspergillus versicolor

We have studied the biodegradation behaviour and mechanism of poly(butylene succinate- co-butylene adipate) (PBSA) by Aspergillus versicolor isolated from compost. Analysis of weight loss showed that more than 90% of PBSA film was assimilated within 25 days. There was also a rapid decrease in molecular weight characterized by gel permeation chromatography (GPC). A number of cracks and round holes were observed on the eroded film surface through scanning electron microscopy (SEM). These results revealed the fast degradation of PBSA film in the presence of A. versicolor. As a comparison, the hydrolysis of the same sample was much slower in the corresponding abiotic medium. The analyses of 1H NMR and differential scanning calorimetry (DSC) indicate that the preferred degradation takes place in the adipate units and the succinate units are relatively recalcitrant to A. versicolor.

Glycerol Copolyesters: Control of Branching and Molecular Weight Using a Lipase Catalyst

Immobilized Lipase B from Candida antartica (Novozyme 435) catalyzed bulk polycondensations at 70 °C for 42 h that resulted in hyperbranched polyesters with octanediol-adipate and glycerol-adipate repeat units. Instead of using organic solvents, the monomers adipic acid (A2), 1,8-octanediol (B2), and glycerol (B‘B2) were combined to form monophasic ternary mixtures. During the first 18 h of a copolymerization with monomer feed ratio (A2 to B2 to B‘B2) 1.0:0.8:0.2 mol/mol, the regioselectivity of Novozyme 435 resulted in linear copolyesters. Extending the reaction to 42 h gave hyperbranched copolymers with dendritic glycerol units. The % regioselectivity for esterifications at the primary glycerol positions ranged from 77 to 82% and was independent of glycerol content in the monomer feed. Variation of glycerol in the monomer feed gave copolymers with degree of branching (DB) from 9 to 58%. In one example, a hyperbranched copolyester with 18 mol % glycerol−adipate units was formed in 90% yield, with Mw 75 6...

Lipase Catalysis. A Direct Route to Linear Aliphatic Copolyesters of Bis(hydroxymethyl)butyric Acid with Pendant Carboxylic Acid Groups

Immobilized Lipase B from Candida antartica (CAL-B, Novozyme 435) catalyzed terpolymerizations of bis(hydroxymethyl)butyric acid, BHB (AB2) and 1,8-octanediol (B2) with adipic acid (A2). The copolymerizations of these AB2, B2, and A2 monomers were conducted in bulk, at 80 °C, without activation of the acid groups. Carbon (13C) NMR studies using a series of model BHB derivatives showed that CAL-B was strictly selective for esterification of BHB hydroxyl groups while leaving the carboxylic acid unchanged. Thus, all polymerizations were conducted as if BHB were a B2 monomer and then formulating a 1 to 1 ratio of carboxylic acid to hydroxyl groups in the monomer feed. By varying the monomer feed ratio, copolyesters with 9−45 mol % BHB−adipate units were formed with Mw values between 21 900 and 2300 g/mol. By this direct polymerization without protection−deprotection chemistry, a series of linear aliphatic copolyesters with controlled quantities of pendant free acid groups was prepared. Thermal and crystalline properties of the copolyesters were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and wide-angle X-ray scattering (WAXS). Increasing the BHB content in the copolyesters resulted in melting temperature depressions that were well described by Baur's equation for random copolymers where BHB−adipate units are excluded from the crystal phase of the crystallizable 1,8-octanediol−adipate units.

Isolation and Characterization of Poly(Butylene Succinate-co-Butylene Adipate)-Degrading Microorganism

Poly(butylene succinate-co-butylene adipate) (PBSA)-degrading bacterium, strain 1-A, was isolated from soil. Strain 1-A was identified as Bacillus pumilus on the basis of its physiological properties and partial 16S rRNA gene sequence. Strain 1-A also degraded poly(butylene succinate) (PBS) and poly(ε-caprolactone). On the other hand, poly(butylene adipate terephthalate) and poly(lactic acid) were minimally degraded by strain 1-A. The NMR spectra of degradation products from PBSA indicated that the adipate units were more rapidly degraded than 1,4-butanediol and succinate units. This seems to be one of the reasons why strain 1-A degraded PBSA faster than PBS.