Biological basis of enzyme-catalyzed polyester degradation: 59 C-terminal amino acids of poly(3-hydroxybutyrate) (PHB) depolymerase a from pseudomonas lemoignei are sufficient for PHB binding

Biodegradable polyesters such as biologically produced poly[(R)-3-hydroxybutyric acid], (PHB) other polyhydroxyalkanoic acids and related chemosynthetic polyesters have attracted industrial interest, and bacterial produced PHB is commercially available since 1990. A large variety of polyester degrading microorganisms have been found to be present in environment. The microorganisms decompose the polymers by secretion of extracellular polyester depolymerases and utilize low molecular weight degradation products for growth. Microbial polyester depolymerases have the unique property to be water soluble and to be able to bind specifically to polyester surfaces. The objective of this contribution is a functional analysis of a bacterial PHB depolymerase polyester binding domain. In addition, a detailed summary of the present knowledge on the biochemistry of enzymatic polyester hydrolysis is provided.     

Synthesis of Polymers by Using Divalent Metal Salts of Mono(hydroxyethyl)phthalate: Metal-Containing Unsaturated Polyesters

Syntheses of metal-containing unsaturated polyesters based on divalent metal salts (I) of mono (hydroxyethyl)phthalate were investigated by the polycondensation reactions of I-glycols with maleic anhydride (MA)-phthalic anhydride (PA). Among various combinations of components, the systems of MA-PA-diethylene glycol (DEG)-Mg salt, and MA-PA-ethylene glycol (EG)-propylene glycol (PG)-Mg salt gave polyesters soluble in styrene. Viscosities of styrene solutions of the polyesters obtained showed a tendency to increase with increase in metal content in the polyester. The styrene solutions could be cured. The cured polyester resins were evaluated for physical properties. Generally, the polyesters of MA-PA-EG-PG-Mg salt have good physical properties. Further, resistance to chemical attack and boiling water, and thermal behavior are also discussed.     

Study on the Synthesis and Biodegradation of Aliphatic Polyester

With the increasing use of one-off plastic products, the environmental pollution resulted from the plastic waste has become more and more serious. So many scientists have focused their attention on developing biodegradable polymers to substitute the traditional unbiodegradable polymers in the manufacture of disposable products. Thus the plastic waste can be treated by landfill or composting technique. It has been found that aliphatic polyesters possess better biodegradability compared with oth…     

Water absorption and degradation characteristics of chitosan-based polyesters and hydroxyapatite composites

Blends of chitosan and biodegradable synthetic aliphatic polyesters (polycaprolactone, poly(butylene succinate), poly[(butylene succinate)-co-adipate], poly[(butylene terephthalate)-co-adipate], and poly(lactic acid)) were injection-molded. These samples were immersed in isotonic solution at 37 degrees C for a period of 60 d. The water uptake and the degradation properties, as measured by the loss in tensile strength, were evaluated as a function of time. In this study, the rate and the equilibrium water uptake were proportional to the amount of chitosan in the blend. The addition of HA to chitosan and polyester significantly reduced the equilibrium water uptake. The water uptake did not follow the classical Fickian phenomena and could be expressed by a two-stage sorption non-Fickian diffusion model. Contact angle measurement was used to quantify the changes in surface hydrophilicity as a function of chitosan and polyester composition. The glycerol contact angle decreased with increasing synthetic components in the blend. The blends and composites also showed increased degradation, as quantified by a loss in their mechanical properties, with increase in natural content. The degradation of properties was directly related to the water uptake of the blends; the higher the water uptake, the higher the degradation. Pure polyesters, while having low water uptake, nevertheless showed significant degradation by a precipitous drop in the strain at break. Among the polyesters, poly(lactic acid) displayed maximum degradation, while polycaprolactone displayed the least.     

2,4-二氯苯甲酸改性饱和聚酯的合成及其聚氨酯阻燃涂料

用2,4-二氯苯甲酸改性三羟甲基丙烷制得含氯的多元醇中间体（NHDB）,用改性的中间体合成含氯的聚酯。用红外、核磁表征了中间体和聚醇的结构,TGA分析表明,含氯量增高,聚酯热稳性下降。将聚酯同异氰酸酯预聚体常温固化,各种性能良好。阻燃测试表明：含30%的2,4-二氯苯甲酸的聚酯具有自熄功能。提出了阻燃机理。     

Synthesis of Polymers by Using Divalent Metal Salts of Mono(hydroxyethyl)phthalate: Metal-Containing Unsaturated Polyesters with Pendent Methacrylate Groups

Syntheses of novel metal-containing unsaturated polyesters having pendent methacrylate groups obtained by use of divalent metal salts of mono(hydroxyethyl)phthalate-maleic anhydride (MA)-glycidyl methacrylate (GMA) reactions were investigated. The yields were generally high. The metal-containing polyesters obtained were slightly yellow-brown solids, and the molecular weights ranged from 1546 to 2174, depending on the mole ratio of feed. Among them, the polyesters obtained at a feed mole ratio of metal salt:MA:GMA of 1:8:8 were miscible with methyl methacrylate (MMA), giving homogeneous solutions suitable for copolymerization, and the polyesters could be easily cross-linked with MMA to give cured resins. The metal-containing cured polyester resins showed excellent physical properties. Resistance of the resins to chemical attack and boiling water and thermal behavior are also discussed.     

Synthesis and Characterization of Soluble Polyester Based on Calixarene Dicarboxylic Acid with Tertiary Butyl Pendant Groups

A series of new polycalixesters(PCES) were synthesized by polyesterification of calixarene dicarboxylic acid derivatives having tertiary butyl pendant groups at the upper rim using five different diols. All polyesters were readily soluble in polar solvents such as NMP(N-methylpyrrolidone), DMF(dimethylformamide), DMSO(dimethylsulfoxide), pyridine, THF(tetrahydrofurane), HMPA(hexamethylenephosphoramide) and DMAC(dimethylacetamide). The PCES were also partially soluble in TCE(tetrachloroethane) and ethanol and they were unsoluble in aceton. The glass transition temperatures of polyesters were between 80-184 °C, the crystallinity temperatures of polyesters were between 130–212 °C and the melting temperatures of polyesters were between 185–234 °C, as determined by differential scanning calorimeter(DSC). The inherent viscosities of polyesters were obtained from 0.55 dL/mg to 0.61 dL/mg. The temperatures at 10% weight loss of polyesters ranged from 182 °C to 237 °C. The temperatures at 25% weight loss of polyesters ranged from 258 °C to 331 °C. The half weight loss(50%) temperatures of polyesters were among 315 °C to 371 °C and the char yields at 600 °C were determined within 13% to 22.3% in N2 atmosphere, as determined by thermo gravimetric analysis(TGA). The polyester, PES3, has the higher melting point(234 °C) and higher inherent viscosity(molecular weight) than the other polyesters.     

Miscibility and surface segregation in PVC/polyester blends—The influence of chain architecture and composition

Four poly(butylene adipate) (PBA) polyesters, the structure ranging from linear to highly branched, were synthesized and solution casted with poly(vinyl chloride) (PVC) in 20 or 40 wt % concentrations to evaluate the influence of polyester chain architecture on miscibility, surface segregation, and mechanical properties. The miscibility of PVC and polyesters is based on specific interactions between the carbonyl group in the polyester and PVC. These interactions cause a shift in the carbonyl absorption band in the FTIR spectra. The shifting of the carbonyl absorption band was more significant for all the 40 wt % blends compared with the blends containing 20 wt % of the same polyester. In the 20 wt % blends surface segregation and enrichment of polyester at the blend surface increased as a function of branching. However, all the films containing 40 wt % of polyester had similar surface composition. This is explained by better miscibility and stronger intermolecular interactions in the 40 wt % blends, which counteract the effect of branching on the surface segregation. High degree of branching resulted in poor miscibility with PVC and poor mechanical properties. A linear or slightly branched polyester structure, however, resulted in good miscibility and desirable blend properties. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1552–1563, 2007     

Surface activity of new invertible amphiphilic polyesters based on poly(ethylene glycol) and aliphatic dicarboxylic acids

The surface active properties of aqueous solutions of invertible amphiphilic alternated polyesters differing by hydrophilic-lipophilic balance (HLB) and molecular weight have been determined over the wide concentration range. The polyesters are based on poly(ethylene glycol) (PEG) of two molecular weights and aliphatic dicarboxylic acids (decanedioic and dodecanedioic). The surface activity of the polyesters and their ability to form micellar assemblies (which was recently shown for organic solvents) has been confirmed in water. The central role of the balance of hydrophilic to hydrophobic groups ratio in the formation of polymeric arrangements having hydrophobic pockets and external hydrophilic shell has been shown. The effect of molecular weight has been found considerable as well. Two changes in slope have been observed for the more hydrophobic polyesters in the surface tension vs log concentration curve. The change at low concentration is believed to originate from the formation of polyester assemblies with a hydrophobic interior and hydrophilic exterior due to the interaction of hydrophobic fragments and macromolecular flexibility. The higher concentration region exhibits behavior consistent with a cmc, which was confirmed by additional dye solubilization experiments. Molecular structure of the polyester micelles is determined by the solubilization of a solvatochromic dye. The experiment confirmed that micellization of polyesters is accompanied by the association of more hydrophobic (aliphatic) constituents forming the micelle interior. The hydrophilic fragments (ethylene oxide groups) are involved in the formation of micelle exterior.     

Synthesis and characterization of 1,3-bis(2-hydroxyethoxy) benzene based saturated and unsaturated polyesters

Polyesterification of adipic acid and maleic anhydride with 1,3-bis(2-hydroxyethoxy)benzene (HER) in the presence of toluene-4-sulphonic acid was carried out using melt condensation technique. The structural characterization of the synthesized polyesters had been carried out using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopic methods. The thermal properties of the polyesters were studied using differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The activation energies for the thermal degradation of the polyesters were calculated by the method of Dharwadkar and Kharkhanavala and discussed. The char residue value at 600 °C indicated maleic anhydride based polyester is thermally more stable compared to the adipic acid based polyester. The mechanism of degradation of these polyesters is discussed.     

Synthesis,characterization, and biological evaluation of new polyester containing Schiff base metal complexes

The production of new biocidal polyester Schiff base metal complexes [PESB–M(II)] via polycondensation reaction between chelated Schiff base diol and adipoyl chloride is reported. The resulting polyesters were characterized by physico-chemical and spectroscopic methods. The analytical data of all the synthesized polyesters were found to be in good agreement with 1:1 molar ratio of chelated Schiff base diol to adipoyl chloride. Thermogravimetric analyses of synthesized polyesters were studied by TG in nitrogen atmosphere up to 1073 K and results indicate that Cu(II) polyester complex exhibited better heat resistant properties than the other polyesters complexes. Magnetic moment and UV–visible spectra were examined to explain the structure of all the polyesters which reveled that Mn(II), Co(II), Ni(II) have octahedral geometry while Cu(II) possess a distorted octahedral geometry. These newly developed polyesters were also tested for their antibacterial activity against several bacteria and fungi. Among all the tested compounds PESB–Cu(II) possess the highest bactericidal and fungicidal activity.     

Influence of hyperbranched polyesters on the surface tension of polyols

The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements.     

Nanocomposites of aliphatic polyesters: An overview of the effect of different nanofillers on enzymatic hydrolysis and biodegradation of polyesters

In the present review the findings concerning the effect of nanofillers to biodegradation and enzymatic hydrolysis of aliphatic polyesters were summarized and discussed. Most of the published works are dealing with the effect of layered silicates such as montmorillonite (unmodified and modified with organic compounds), carbon nanotubes and spherical shape additives like SiO₂ and TiO₂. The degradation of polyester due to the enzymatic hydrolysis is a complex process involving different phenomena, namely, water absorption from the polyesters, enzymatic attack to the polyester surface, ester cleavage, formation of oligomer fragments due to endo- or exo-type hydrolysis, solubilization of oligomer fragments in the surrounding environment, diffusion of soluble oligomers by bacteria and finally consumption of the oligomers and formation of CO₂ and H₂O. By studying the published works in nanocomposites, different and sometimes contradictory results have been reported concerning the effect of the nanofillers on aliphatic polyesters biodegradation. Most of the papers suggested that the addition of nanofillers provokes a substantial enhancement of polyester hydrolysis due to the catalyzing effect of the existed reactive groups (–OH and –COOH), to the crystallinity decrease, to the higher hydrophilicity of nanofillers and thus higher water uptake, to the higher interactions, etc. However, there are also some papers that suggested a delay effect of nanofillers to the polyesters degradation mainly due to the barrier effect of nanofillers and the lower available surface for enzymatic hydrolysis.     

STUDY ON THE SYNTHESIS AND PHYSICOCHEMICAL PROPERTIES OF SUCROSE POLYESTER

Orthogonal test was used to evaluate the effects of synthetic such as temperature (120～140 ℃), reaction time (4-6) and substrate molar ratio of methyl oleate to sucrose (8:1-12:1) on the percent quantity conversion to sucrose polyester. Sucrose polyester was synthesized by a solvent-free one-stage interesterification. The optimum reaction conditions are as follows: methyl oleate/sucrose = 10∶1 (mol/mol); reaction temperature is 140 ℃;yield reaches 88.15%, and the degree of esterification (DE) is over 7 in the conditions. Thin layer chromatography (TLC), column chromatography (CC), High-performance liquid chromatography (HPLC) were used to analyze the product, the results show that the percent of sucrose polyoleate is over 70% in the product. The physicochemical properties of sucrose polyesters were compared with cooking oil. The results show that the qualities of sucrose polyesters are all up to the triglyceride.     

Blends of an epoxy thermosetting polymer with aromatic liquid-crystalline polyesters

A series of aromatic liquid-crystalline polyesters with different composition have been synthesized to adjust transition temperatures and molecular weight. Miscibility of polyesters with bisphenol-A-diglycidyl ether (DEGBA), 4,4′-methylene-bis(3-chloro-2,6-dimethylaniline) (MCDEA) and the influence on transition temperatures has been studied. Miscibility of binary and ternary mixtures was found over the whole range of composition depending on the temperature. Thermoset formation by curing of LC-polyester / DEGBA / MCDEA mixtures containing different amounts of polyester resulted in reaction-induced phase separation with polyester content from 30 to 50 wt.%. Cloud point techniques, scanning electron microscopy (SEM) and dynamic mechanical thermal analysis (DMTA) have been applied.     

The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene copolymers

The influence of chemical modification of unsaturated polyesters on viscoelastic properties and thermal behavior of styrene copolymers has been investigated by DMA and TG analyses. Chemical modification of unsaturated polyesters obtained in polycondensation of cyclohex-4-ene-1,2-dicarboxylic anhydride (THPA), maleic anhydride (MA) and suitable glycol: diethylene glycol (DEG) or triethylene glycol (TEG) was performed using 38–40% peracetic acid. It allowed to selective and successful oxidation of carbon-carbon double bonds in unsaturated polyesters giving modified unsaturated polyesters/unsaturated epoxypolyesters/containing both carbon-carbon double bonds in polyester chain and new functional groups-epoxy groups in cycloaliphatic rings. Both unsaturated polyesters and unsaturated epoxypolyesters were used as a component of styrene copolymers cured with different hardeners. It has been demonstrated that the use of modified unsaturated polyesters as a component of styrene copolymers allowed obtaining more stiffness and more cross-linked network structure compared to styrene copolymers based on unmodified polyesters. The higher values of storage modulus, glass transition temperatures and better thermal stability for styrene copolymers based on unsaturated epoxypolyesters were obtained.     

Influence of Residual Polyesterification Catalysts on the Curing of Polyesters

 Unsaturated polyesters are synthesized by means of polyesterification, often with catalysts like strong acids, metal oxides and metal-organic salts. Most often, the catalysts used cannot be separated from the bulk of the polyester. Also, some organic or inorganic additives – called fillers – which are used with the polyester in order to decrease cost, affect the curing of the polyester. In this work the effect of residual catalyst on the curing of unsaturated polyester is studied. Unsaturated polyesters were prepared using propylene glycol with a 10% molar excess over stoichiometry and a mixture of dicarboxylic acids, namely maleic acid (unsaturated) adipic acid (saturated) and phthalic anhydride (saturated) at a molar ratio 1:2:2. Lead dioxide, p-toluenesulfonic acid and zinc acetate were used as catalysts, at 0.1% w/w. After the polyesterification, the polymers were diluted with styrene at a proportion of 100:30 w/w. The resins were cured by using MEKP (methylethylketone peroxide) as initiator and CoNp (cobalt naphthenate) as accelerator. Catalysts affect the final color of the polyester. The kinetics of curing of the resins was studied by DSC analysis based on the exothermic peak due to the double bonds breaking to give crosslinked macromolecules. The heat released ΔH is decreased by the presence of catalyst, while activation energy, the frequency factor and the order of reaction are increased.     

聚酯在超临界甲醇中的降解特性

研究在间歇高压反应器中聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)及聚碳酸酯(PC)在超临界甲醇中的降解反应;通过建立聚酯在超临界甲醇中的降解反应模型,探讨了聚酯在甲醇中降解的机理。结果表明:PET、PBT和PC在甲醇溶液中的降解具有共性,均可分为超临界区、非临界区和中间过渡区三个区域。在超临界区聚酯完全溶于甲醇并降解为原料单体,且对苯二甲酸二甲酯(DMT)和碳酸二甲酯(DMC)的收率均大于90%;聚酯的降解是在聚合物分子链的无规断裂和聚酯进行酯交换反应的双重作用下发生的。     

Syntheses of functional condensation polymer. I. Polyesters having pendant functional groups such as hydroxyl,formyl, aldoxime,aminomethyl and hydroxymethyl

Unsaturated polyesters having pendant functional groups such as hydroxyl, formyl, aldoxime, aminomethyl and hydroxymethyl, have been prepared and characterized, and some of their properties were investigated. Reaction conditions for the epoxidation of unsaturated polyesters and hydrolysis of the epoxy groups in the polyesters were established to control the amount of pendant diol groups. It was possible to incorporate up to 90 mole-% of formyl side groups into the unsaturated polyester by the hydroformylation with the rhodium catalyst. In addition, the formyl side groups of the modified polyester were converted into hydroxymethyl or aldoxime groups and were then converted to amino groups. The melting points of the modified polyesters decreased with increasing the pendant group content of the polyesters, as expected. Aliphatic polyesters having pendant hydroxyl or amino groups had a high affinity for moisture, which might be ascribed to the participation of the hydrophilic pendant groups in the modified polyesters.     

Investigation of Conversion of Styrene and Fumarate Double Bonds in Unsaturated Polyester Resins

The conversion of styrene and fumarate double bonds in the copolymerization of unsaturated polyesters and styrene was investigated. Several commercial polyester resins including Bisphenol-type, Iso-type and G-type resins were used. The initial fumarate double bond, the equivalent double bond per 100 g of the polyesters, was determined by the hydrogenation procedure which was developed for the present study. Using palladium-carbon catalyst and benzene-acetone (1:1) mixture, polyester resin can be hydrogenated satisfactorily.

The cured resin was extracted with chloroform. The styrene in the chloroform was determined by ASTM D-1159, bromine index method. The conversion of the fumarate double bond was calculated from the soluble part of polyester resin using the theoretical equations which were derived from the basic theory of Flory. The validity of the equations was examined by application of Funke et al.'s experimental results and found to be satisfactory. With the confidence of these results, commercial polyester resins were investigated to determine the effect of the condition of polymerization on the conversion of styrene and fumarate double bonds.

For all the polyesters the conversion of styrene was at least over 80% after a room temperature cure of 24 hr with a dimethyl anilin-cobalt naphthenate-methyl ethyl ketone peroxide three component catalyst system, and it reached approximately 100% after postcure of 100[ddot]C for 2 hr. On the other hand, the conversion of the fumarate double bond depended greatly upon the type of the resin. Bisphenol-type resin gave the highest conversion, and the conversion for Iso-type resin was higher than that for G-type resin. In the case of Bisphenol-type resin, there was no difference in the conversion of fumarate double bond between the room temperature cure and the postcure, but the conversions of fumarate double bond for G- and Iso-type resins were increased remarkably by postcure. The Barcol hardness is applicable to determine the conversion of styrene for the specified polyesters based on the relationship between the conversion of styrene and the Barcol hardness.