Unsaturated Aliphatic Polyesters Research Articles

Enzymatic synthesis and characterization of muconic acid‐based unsaturated polymer systems

AbstractThe design of unsaturated aliphatic (co)polyester systems, based on different diester‐modified muconic acid isomers, was performed via an eco‐friendly pathway by utilizing enzymatic polymerization using Candida antarctica lipase B (CALB) as catalyst. The obtained fully unsaturated oligoesters and polyesters reached lower molecular weights from 2210 to 2900 g mol−1 for the cis,cis‐(Z,Z)‐muconate isomer, and higher molecular weights of up to 21 200 g mol−1 for the polymers with cis,trans‐(Z,E) isomeric structures. The obtained (co)polyesters were thoroughly characterized and compared with their saturated polyester analogues. The applied biobased catalyst Novozym®435 (an immobilized form of CALB) showed higher selectivity towards the open cis,trans‐muconate compared to the more closed‐structure cis,cis‐muconate. Results of 1H NMR analysis showed that alkene functionality is present, and no stereo conformational changes were detected in the resulting polymers. The thermal properties of the muconate‐based polyesters showed a glass transition between −7 and 12 °C, and a one‐step degradation process with a maximum rate of weight loss between 415 and 431 °C, depending both on the conformation of the applied diester derivatives and on the segment lengths of the polyoxyalkylenes. Mass spectrometric analysis of the resulting saturated and unsaturated polyesters revealed five different microstructures with different terminal end groups, such as ester/hydroxyl, acid/ester, ester/ester and acid/hydroxyl, and cyclic polyesters without functional end groups. Overall, this study demonstrates that enzymatic polymerization is a robust approach for the synthesis of unsaturated polyesters. © 2020 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

ABA triblock copolyesters composed of poly(l-lactide) A hard blocks: comparison of amorphous and crystalline unsaturated aliphatic polyesters as B soft blocks

The property profiles of ABA triblock copolymers can be precisely customized by changing the chemical structure of the components. The identification of the midblock is the key point in the development of PLLA-containing ABA triblock copolymers. Two kinds of unsaturated aliphatic polyesters, crystalline poly(cis-butene succinate) (PcBS) and amorphous poly(cis-butene glutarate) (PcBG) with dihydroxyl end groups were prepared by polycondensation reactions. Then, dihydroxyl-terminated PcBS and PcBG were used as macroinitiators to initiate ring opening of polymerization of L-lactide toward two series of fully biobased biodegradable PLLA-b-PcBS-b-PLLA and PLLA-b-PcBG-b-PLLA triblock copolymers with PLLA as hard end-blocks. The influences of the midblocks and the endblocks length on microstructure, thermal and tensile properties of the triblock copolymers were studied. Compared to homopolymer PLLA, all the triblock copolymers had a much higher elongation at break with lower tensile strength and tensile modulus, depending on the length of PLLA blocks. It was found that the amorphous PcBG midblock plays a greater role than the crystalline PcBS midblock in enhancing the tensile toughness of ABA triblock copolymers. PLLA-b-PcBG-b-PLLA composed of shorter PLLA hard block displayed typical elastomeric behavior without yield, which is a promising aliphatic polyester-based thermoplastic elastomer. The unsaturated carbon–carbon double bonds in these polyesters backbone provide a variety of opportunities for further modifications.

Crosslinking of Electrospun Fibres from Unsaturated Polyesters by Bis-Triazolinediones (TAD).

Crosslinking of an unsaturated aliphatic polyester poly(globalide) (PGl) by bistriazolinediones (bisTADs) is reported. First, a monofunctional model compound, phenyl–TAD (PTAD), was tested for PGl functionalisation. 1H-NMR showed that PTAD–ene reaction was highly efficient with conversions up to 97%. Subsequently, hexamethylene bisTAD (HM–bisTAD) and methylene diphenyl bisTAD (MDP–bisTAD) were used to crosslink electrospun PGl fibres via one- and two-step approaches. In the one-step approach, PGl fibres were collected in a bisTAD solution for in situ crosslinking, which resulted in incomplete crosslinking. In the two-step approach, a light crosslinking of fibres was first achieved in a PGl non-solvent. Subsequent incubation in a fibre swelling bisTAD solution resulted in fully amorphous crosslinked fibres. SEM analysis revealed that the fibres’ morphology was uncompromised by the crosslinking. A significant increase of tensile strength from 0.3 ± 0.08 MPa to 2.7 ± 0.8 MPa and 3.9 ± 0.5 MPa was observed when PGI fibres were crosslinked by HM–bisTAD and MDP–bisTAD, respectively. The reported methodology allows the design of electrospun fibres from biocompatible polyesters and the modulation of their mechanical and thermal properties. It also opens future opportunities for drug delivery applications by selected drug loading.

Biobased polyester obtained from bifunctional monomers through metathesis of fatty acids as precursor to synthesis of polyurethanes

ABSTRACTBiobased unsaturated aliphatic polyesters and polyurethanes were obtained from fatty acid monomers with double functionality synthesized through cross‐metathesis of oleic acid and oleic alcohol. The chemical structure and thermal behavior of the monomers and polymers were analyzed by several physicochemical tests, and oscillatory rheometry and optical microscopy were used to determine their rheological properties and to observe the crystal formation of the obtained polyesters, respectively. It has been found that the polyesterification reaction depends on reaction temperature and to a lesser degree on both the reaction time and catalyst addition. The melt temperature and enthalpy of the obtained biobased polymers show that the monomer chain length has an effect on both the crystallinity and thermal transitions of the polymers, as can be explained by a group contribution analysis showing excellent correlation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47095.

Thermally Degradable Polyesters with Tunable Degradation Temperatures via Postpolymerization Modification and Intramolecular Cyclization

We report the novel synthesis of thermally degradable polyesters through the postpolymerization modification of an unsaturated aliphatic polyester from maleic acid via Michael addition reaction with β-amino mercaptans. A high molecular weight polyester (P0) was synthesized by the acyclic diene metathesis (ADMET) polymerization of a diene monomer, di(10-undecenyl) maleate. Postpolymerization modification of P0 with three β-amino mercaptans (2-aminoethanethiol, l-cysteine methyl ester, and 2-(butylamino)ethanethiol) and 2-mercaptoethanol via the selective and quantitative thiol–Michael addition reaction with the maleate vinylic double bonds afforded four polyesters (P1–P4). All the polyesters were characterized by 1H NMR, GPC, and MALDI-TOF-MS, and their thermal properties were studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The three polymers with pendant amino groups (P1–P3) subjected to thermal-induced degradation in the solid state, the driving force of which i...

Poly(diol fumarates); A new class of tunable antimicrobial polymers

Event Abstract Back to Event Poly(diol fumarates); A new class of tunable antimicrobial polymers Alexander M. Tatara1, Emma Watson1*, Tejus Satish1, Dimitrios P. Kontoyiannis2* and Antonios G. Mikos1* 1 Rice University, Bioengineering, United States 2 University of Texas MD Anderson Cancer Center, Infectious Diseases, United States Introduction: Due to the tremendous healthcare burden of device-related infections, novel biomaterials and strategies for prevention of pathogenic device colonization are warranted. There is in vitro and clinical evidence that diols, or carbon chains featuring two alcohol groups, have inherent antimicrobial properties[1],[2]. These molecules have been demonstrated to have a broad spectrum of efficiency, including inhibition of both bacterial and fungal pathogens[2]. This antimicrobial effect can be modulated by the length of the diol carbon chain[1]. Therefore, we have designed a novel class of diol-based, unsaturated, aliphatic polyesters that biodegrade into monomers capable of mitigating infection (Fig. 1). This new class of polymers, the poly(diol fumarates) (PDFs), can be crosslinked to form networks of scaffolds with antimicrobial degradation products. Both the diol carbon length as well as degree of available double bonds are tunable, resulting in a highly controllable class of antimicrobial polymers. In this work, we first investigated the effects of diol carbon length on synthesis and polymer physicochemical properties. We next measured the effects of double bond density on PDF physicochemical properties. Lastly, PDFs were crosslinked into a network structure to create scaffolds that were evaluated for swelling and mechanical properties as a function of diol length and crosslinking density. Materials and Methods: PDFs were synthesized by a condensation reaction between equimolar concentrations of diol (hexanediol, octanediol, or decanediol) and dicarboxylic acid (fumaric acid and/or succinic acid). A multifactorial design approach was taken to create 15 unique formulations of PDF (Table 1). The resulting polymers were characterized, based on altering diol carbon length and amount of double bonds, via proton-nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, and rheology to confirm synthesis, measure chain length, characterize transition temperatures, and evaluate polymer viscosities, respectively. Scaffolds of crosslinked PDF networks were fabricated by mixing the polymers with crosslinker (n-vinyl-2-pyrrolidinone, 1:1 mass ratio) and photoinitiator (Irgacure 819, 0.3 wt%)[3]. The effects of different diols and availability of double bonds on the resulting Fourier Transform Infrared spectra, swelling ratios, and compressive properties of these networks were measured as previously described[3]. For compressive testing, a mixture of PDF, crosslinker, and photoiniator was poured into cylindrical molds (3 mm in diameter, 6 mm in height), exposed to blue light for 160 seconds to initiate crosslinking, and then compressed at a crosshead speed of 1 mm/min[3]. Results and Discussion: The PDFs were successfully synthesized from a variety of diols with different densities of double bonds, dependent on the ratio of fumaric acid to succinic acid. Analysis is ongoing, but preliminary data indicate significant differences in physicochemical properties of polymers and networks formed by PDFs (Fig. 2). Conclusion: PDFs are a new class of biodegradable unsaturated aliphatic polyesters. Different PDFs can be synthesized with a variety of diols and tunable physicochemical properties. Due to its flexibility, this new class of polymers has potential for a variety of anti-infection applications. Barrow Scholars Program; Armed Forces Institute of Regenerative Medicine II (Award No. W81XWH-14-2-0004); John S. Dunn Foundation; Baylor College of Medicine Medical Scientist Training Program (NIH T32 GM007330); Frances King Black Endowment for Cancer Research

Potential Application of a Visible Light-Induced Photocured Hydrogel Film as a Wound Dressing Material

The objective of this work was to prepare hydrogel films, as semi-interpenetrating polymer networks (semi-IPN), based on polyethylene glycol-co-fumarate (PEGF) and chitosan (Ch) blends. Hydrogel films were prepared by free radical cross-linking of PEGF, an unsaturated aliphatic polyester, in the presence of N-vinyl pyrrolidone (NVP), camphorquinone (CQ), and N,N-dimethyl-p-toluidine (DMPT) as a cross-linking, photoinitiating, and accelerating agent, respectively. The effect of NVP concentration on physicochemical and biological properties of semi-IPN film properties was evaluated. The sol fraction, water vapor transmission rate, and swelling degree of the hydrogel films were also investigated. Antibacterial activity against S. aureus was observed for the photocured blend hydrogels of Ch/PEGF with no toxicity to L929 cells according to the cell viability assays. Blend hydrogel films showing 600 ± 88% of equilibrium swelling degree in water and the lowest sol fraction (3.14 ± 1.22%) were obtained at 20 wt% of NVP content whilst preserving their own cytocompatibility and antibacterial activity. Therefore, this formulation was considered as an optimal semi-IPN blend hydrogel film composition with potential application for wound dressing.

Environmentally benign synthesis of saturated and unsaturated aliphatic polyesters via enzymatic polymerization of biobased monomers derived from renewable resources

Biobased saturated aliphatic polyesters and photo-curable unsaturated aliphatic polyesters are enzymatically polymerized, and their structure–property relationships are systematically studied.

Fully biobased and supertough polylactide-based thermoplastic vulcanizates fabricated by peroxide-induced dynamic vulcanization and interfacial compatibilization.

A fully biobased and supertough thermoplastic vulcanizate (TPV) consisting of polylactide (PLA) and a biobased vulcanized unsaturated aliphatic polyester elastomer (UPE) was fabricated via peroxide-induced dynamic vulcanization. Interfacial compatibilization between PLA and UPE took place during dynamic vulcanization, which was confirmed by gel measurement and NMR analysis. After vulcanization, the TPV exhibited a quasi cocontinuous morphology with vulcanized UPE compactly dispersed in PLA matrix, which was different from the pristine PLA/UPE blend, exhibiting typically phase-separated morphology with unvulcanized UPE droplets discretely dispersed in matrix. The TPV showed significantly improved tensile and impact toughness with values up to about 99.3 MJ/m(3) and 586.6 J/m, respectively, compared to those of 3.2 MJ/m(3) and 16.8 J/m for neat PLA, respectively. The toughening mechanisms under tensile and impact tests were investigated and deduced as massive shear yielding of the PLA matrix triggered by internal cavitation of VUPE. The fully biobased supertough PLA vulcanizate could serve as a promising alternative to traditional commodity plastics.

Fully Biobased Unsaturated Aliphatic Polyesters from Renewable Resources: Enzymatic Synthesis, Characterization, and Properties

Fully biobased saturated and unsaturated aliphatic polyesters and oligoesters are successfully prepared by Candida antarctica lipase B (CALB)‐catalyzed polycondensations of succinate, itaconate, and 1,4‐butanediol. The effects of monomer substrates and polymerization methods on enzymatic polycondensation are investigated. The CALB‐catalyzed polycondensations of succinic acid, itaconic acid, and 1,4‐butanediol only yield oligomers. By replacing the unactivated dicarboxylic acids with the alkyl diesters, polyesters with various chemical compositions are successfully obtained. The molar compositions and molecular weights of poly(butylene succinate‐co‐itaconate) (PBSI) are significantly affected by the applied polymerization method. Compared with the two‐stage enzymatic polymerization in bulk and in diphenyl ether, the enzymatic azeotropic polymerization in the mixture of cyclohexane and toluene is the best method to synthesize high‐molecular‐weight PBSI with tunable molar compositions. The 13C NMR study reveals that CALB is capable of producing more I‐B‐I‐3 microstructures in the mixture of cyclohexane and toluene by azeotropic distillation. Moreover, the crystalline properties of the obtained polyesters are characterized by wide‐angle X‐ray diffraction (WAXD) and DSC. Furthermore, the thermal and mechanical properties of the crosslinked PBSI are studied. image

Enzyme-catalyzed synthesis of unsaturated aliphatic polyesters based on green monomers from renewable resources.

Bio-based commercially available succinate, itaconate and 1,4-butanediol are enzymatically co-polymerized in solution via a two-stage method, using Candida antarctica Lipase B (CALB, in immobilized form as Novozyme® 435) as the biocatalyst. The chemical structures of the obtained products, poly(butylene succinate) (PBS) and poly(butylene succinate-co-itaconate) (PBSI), are confirmed by 1H- and 13C-NMR. The effects of the reaction conditions on the CALB-catalyzed synthesis of PBSI are fully investigated, and the optimal polymerization conditions are obtained. With the established method, PBSI with tunable compositions and satisfying reaction yields is produced. The 1H-NMR results confirm that carbon-carbon double bonds are well preserved in PBSI. The differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results indicate that the amount of itaconate in the co-polyesters has no obvious effects on the glass-transition temperature and the thermal stability of PBS and PBSI, but has significant effects on the melting temperature.

Preparation and biodegradation of hydroxyl terminated poly(fumaric acid-co-diethylene glycol) and its segmented polyurethane

Hydroxyl terminated poly(fumaric acid-co-diethylene glycol), poly(FA-co-DEG) was prepared by melt polycondensation. The resultant unsaturated aliphatic polyester was characterized by Fourier transform infrared (FTIR) spectroscopy, hydroxyl value, acid value, and intrinsic viscosity. Its enzymatic degradation and crosslinking behavior as well as the effect of crosslinking degree on enzymatic degradation were also investigated. The crosslinking degree and reduction of carbon–carbon double bonds revealed excellent self-crosslinking nature of poly(FA-co-DEG) at high temperature. The results of enzymatic degradation showed that poly(FA-co-DEG) has excellent biodegradability and that the biodegradation can be controlled by the crosslinking degree. Polyurethane was prepared by the reaction of poly(FA-co-DEG), 2,4-toluene diisocyanate (TDI), and 1,4-butanediol (BD). It was found that the biodegradation of the obtained polyurethane was slower than that of the original unsaturated aliphatic polyester poly(FA-co-DEG). The peeling strength of the polyurethane was very high, supporting better adhesion property with enhanced crosslinking. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Design of Elastomeric Homo- and Copolymer Networks of Functional Aliphatic Polyester for Use in Biomedical Applications

An unsaturated aliphatic polyester was synthesized by condensation polymerization to yield the pre-polymer, poly(but-2-ene-1,4-diyl malonate) (PBM), which is applicable as an elastomeric network and as a macroinitiator for the polymerization of cyclic ester monomers. The method of preparation was simple and straightforward with no need to purify the monomers or add a potentially harmful catalyst. The number average molecular weight of the pre-polymer could easily be increased from 5000 to 12000 by extending the reaction time. The pre-polymer PBM was successfully cross-linked with UV-radiation to form a clear, transparent, colorless, flexible, and strong film. PBM as a macroinitiator for l-lactide (LLA) and ε-caprolactone (CL) polymerizations highly increased the ductility of the LLA-polymer, while maintaining the strength, compared to PLLA polymerized with common initiators. The tensile properties of PCL were also improved. The linear PCL-PBM and PLLA-PBM polymers were easily cross-linked to give polymers with greater strength and higher modulus as the result.

Synthesis and preparation of biodegradable and visible light crosslinkable unsaturated fumarate‐based networks for biomedical applications

AbstractBiodegradable polymers have currently attracted high interest as ideal carriers in drug delivery and tissue engineering applications. In situ forming devices based on these materials will synergistically provide the advantages of the customary prefabricated devices as well as ease of administration. To acheive these objectives, optically transparent and biodegradable macromers based on poly(ethylene glycol) and fumaric acid copolymers were synthesized using propylene oxide as a different proton scavenger to enhance in situ photocrosslinking capability. The macromers in different compositions were then photocured for 300 sec in the presence of a visible light initiator/accelerator couple and also a reactive diluent. Characterization of the macromers and the resulting networks were performed using different spectroscopic, chromatographic, physical, and thermal analysis techniques. The resulted shrinkage strain of the macromers upon photocuring was studied using the bounded disk technique, and initial shrinkage strain rates were obtained by numerical differentiation. Our results suggest that the compositions based on these unsaturated aliphatic polyesters are potentially useful to develop injectable, in situ photocrosslinkable carriers for drug and cell delivery applications. Copyright © 2008 John Wiley & Sons, Ltd.

Amorphous Unsaturated Aliphatic Polyesters Derived from Dicarboxylic Monomers Synthesized by Diels−Alder Chemistry

A versatile method for synthesizing functionalized amorphous degradable polyesters via step growth polycondensation was investigated. A series of dicarboxylic acids and anhydrides were synthesized by Diels−Alder reactions of fumaric acid and maleic anhydride, respectively, with various dienes. The resulting difunctional monomers were reacted with 1,8-octanediol in the presence of tin octanoate catalyst at 160 °C and 30 mmHg for 24 h to form new unsaturated aliphatic polyesters. Each polyester had molecular weight 〈Mn〉 between 1.0 × 104 and 2.0 × 104 g mol-1 and a polydispersity index near 2.0. All of the materials were amorphous and had glass transition temperatures between −30 and −15 °C. Each polymer repeat unit necessarily featured a double bond, which was exploited to cross-link the materials yielding degradable elastomers. Amine- and ether-containing polyesters were synthesized by using monomers formed from the corresponding polar functionalized dienes. Using this broad cycloaddition scheme, a variet...

Preparation of Unsaturated Linear Aliphatic Polyesters Using Condensation Polymerization

A versatile method for preparing linear, unsaturated polyesters through condensation polymerization of trans-β-hydromuconic acid (HMA) with a variety of diols using Sn(Oct)2 and Novozyme-435 as catalysts was explored. Poly(1,8-octanediol hydromuconoate) was the highest molecular weight homopolymer prepared with a 〈Mn〉 of 10.5 × 103 g/mol and polydispersity of 2.0. These materials showed unique melting behavior that was dependent on the number of carbons in the diol. Melting points ranged from 40 to 70 °C. Copolymers where the amount of HMA was diluted by adipic acid were prepared and had a 〈Mn〉 as high as 13.0 × 103 g/mol and polydispersities below 2.0. The double bonds of these materials were chemically modified through epoxidation in yields greater than 93% and with no degradation of the polymer backbone. Materials with hydroxyl end groups were prepared through stoichiometric mismatch. Unsaturated poly(ester ether)s that are amorphous liquids with Tg below −40 °C were prepared using diethylene glycol as...

Novel unsaturated ε-caprolactone polymerizable by ringopening and ring-opening metathesis mechanisms

AbstractRing-opening polymerization (ROP) and ring-opening metathesis polymerization (ROMP) of an unsaturated ε-caprolactone, 6,7-dihydro-2(3H)-oxepinone (DHO2), are alternative routes to produce unsaturated aliphatic polyesters with the same molecular structure. Polymerization of DHO2 initiated by Al isopropoxide in toluene at room temperature or at 0°C proceeds by a coordination-insertion mechanism, although intramolecular transesterification takes place beyond complete monomer conversion. The molecular weight distribution is narrow as long as monomer conversion does not exceed 90%. Ring-opening metathesis polymerization of DHO2 initiated by Schrock’s Mo-based catalyst, 1, at 60°C allows higher molecular weight unsaturated polyester to be prepared, even though an intramolecular side reaction also operates. The structure of poly(DHO2) synthesized by ROP and ROMP is the same, as confirmed by 1H, 13C NMR, and FT-IR spectra. Copolymers of DHO2 with norbornene, cis-cyclooctene, and 1,5-cyclooctadiene have been successfully prepared.

Effects of Geometrical Difference of Unsaturated Aliphatic Polyesters on Their Biodegradability III. Cross Effects of Molecular Weight and Geometric Structure of Poly(ethylene maleate/fumarate) and Its Model Compounds

Unsaturated polyesters, P1a and P2a, having different molecular weight were synthesized by solution polycondensation of maleic anhydride (MAn) with ethylene glycol (EG). Furthermore, unsaturated polyesters, poly(ethylene maleate/fumarate) (P1b-e and P2b-e), which have various ratios of different Z-/E-configuration at the C=C double bond were readily delivered from P1a and P2a, respectively, in 1,2-dichloroethane by using morpholine as a catalyst for isomerization. In order to discuss separately the effects of molecular weight of the samples on their biodegradability from the effects due to configuration of C=C double bond, several Z- or E-rich oligomeric model compounds having methyl esters as the terminal groups were prepared. The biodegradability of these polyester samples and oligomeric model compounds was evaluated from biochemical oxygen demand (BOD) values in the presence of an activated sludge. As the number-average molecular weight of both oligomeric model compounds and unsaturated polyesters was higher, their biodegradability was lowered by introducing C=C double bond, especially, by that of Z-configuration.

Controlled synthesis and chemical modification of unsaturated aliphatic (Co)polyesters based on 6,7‐dihydro‐2(3H)‐oxepinone

AbstractA pure unsaturated cyclic ester, 6,7‐dihydro‐2(3H)‐oxepinone (DHO2), was prepared by a new synthetic route. The copolymerization of DHO2 with ϵ‐caprolactone (ϵCL) was initiated by aluminum isopropoxide [Al(OiPr)3] at 0 °C as an easy way to produce unsaturated aliphatic polyesters with nonconjugated CC double bonds in a controlled manner. The chain growth was living, as certified by the agreement between the experimental molecular weight at total monomer conversion and the value predicted from the initial monomer/initiator molar ratio. The polydispersity was reasonably low (weight‐average molecular weight/number‐average molecular weight ≤ 1.2). The homopolymerization of DHO2 was, however, not controlled because of fast intramolecular transesterification. Copolymers of DHO2 and ϵCL were quantitatively oxidized with the formation of epoxides containing chains. The extent of the epoxidation allowed the thermal properties and thermal stability of the copolyesters to be modulated. The epoxidized copolyesters were successfully converted into thioaminated chains, which were then quaternized into polycations. No degradation occurred during the chemical modification. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2286–2297, 2002

Effects of Geometrical Difference of Unsaturated Aliphatic Polyesters on Their Biodegradability II. Isomerization of Poly(maleic anhydride-co-propylene oxide) inthe Presence of Morpholine

Ring-opening copolymerizations of succinic anhydride (SAn, 1) or maleic anhydride (MAn, 2) with propylene oxide (PO) were carried out by using magnesium diethoxide (Mg(OEt)2) as a catalyst. The unsaturated polyester (P2a) was found to have only Z-configuration around a C=C double bond from its 1H and 13C NMR spectra. Isomerization reaction of P2a from Z- to E-configuration was performed in 1,2-dichloroethane with a catalytic amount of morpholine. Thus unsaturated polyesters, P2b-e, having the same molecular weight but the different ratio of Z-/E-configuration could be optionally prepared from one original polymer P2a by controlling isomerization reaction time. Biodegradability of these polyester samples was evaluated from their biochemical oxygen demand (BOD) values in the presence of an activated sludge. Polyester P2a was hardly degraded during measurement. However, polyesters P2b-e, partially containing E-configuration of the C=C double bond, degraded considerably faster than P2a itself. The biodegradability of saturated polyester P1 was also examined to compare with the P2-series.