Structure Of Polyesters Research Articles

Controllable Synthesis of Stereoregular Polyesters by Organocatalytic Alternating Copolymerizations of Cyclohexene Oxide and Norbornene Anhydrides

A facile strategy has been demonstrated for the selective synthesis of highly stereoregular polyesters with cis-2,3-(exo, exo) or trans-2,3-(exo, endo) repeating units by the organocatalysts mediated alternating copolymerization of cyclohexene oxide and norbornene anhydride (NA) stereoisomers. The geometrical structure of polyester can be tuned simply by modulating the type of NA isomers (endo- or exo-NA), monomer feed ratio, and reaction temperature. The cis- (>99%) and trans-polyesters (>99%) exhibit high glass transition temperature up to 129.8 and 115.9 °C, respectively. The resulting polyesters provide a versatile platform to incorporate various functional groups through the robust thiol–ene reaction of the pendant norbornenyl groups.

Prebiotic alternatives to proteins: structure and function of hyperbranched polyesters.

Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins' three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.

Influence of ceria nanoparticles on chemical structure and properties of segmented polyesters.

In this work, we present new nanocomposite materials derived from segmented copolyesters, comprising ethylene terephthalate (PET) segments and dimerized linoleic acid (DLA), and nanometric cerium oxide particles (CeO2). Nanoparticles were incorporated in situ during polycondensation in various concentrations, from 0.1 up to 0.6 wt.%. It was found that preparation of nanocomposites in situ, during polycondensation, had no significant influence on changes in segmental composition as determined from (1)H and (13)C, as well as 2D NMR. Thermal analysis and calculated degree of crystallinity showed that increasing concentration of ceria nanoparticles lead to an increase in mass content of PET crystallites in hard segments. The XRD investigations also showed an increased intensity of characteristic signals with increasing ceria concentration. Simultaneously, the incorporation of CeO2 led to an increase in tensile strength and elongation at break, indicating a reinforcing and plasticizing effect of ceria nanoparticles. However, the modulus at 10% strain decreased with increasing amount of nanoparticles. The in vitro culture of human cardiac progenitor cells (hCPCs) on the new materials indicated a homogenous cell displacement across the samples after 5 days with no signs of cytotoxicity, indicating good biocompatibility in vitro of CeO2-based nanocomposites and a potential for biomedical applications.

Pyrolysis versus hydrolysis behavior during steam decomposition of polyesters using18O-labeled steam

A method was developed to distinguish between hydrolysis and pyrolysis pathways in the steam degradation of various polyesters. Selectivity was shown to be strongly influenced by the polyester structure.

Synthesis of Novel Hyperbranched Polyurethane Acrylate Based on Pentaerythritol

To study the structure and properties of hyperbranched polyesters as well as the modified ones. Three generations of hyperbranched polyesters named HBPE-1, HBPE-2 and HBPE-3 were synthesized by the reactions from pentaerythritol and 2,2-dihydroxy-methyl-propionic acid by single-step polycondensation. They were characterized by 1H NMR, 13C NMR and the results indicated they possessed a high degree of branching. Then homemade urethane acrylate prepolymer reacted with three generations of hydroxyl-terminated hyperbranched polyesters introducing C=C contents, the product was characterized by FT-IR, DSC, TGA techniques. The results of TGA showed well thermal stability of all the products. TGA curves of the modified HBPES showed two stages, 280-350°C means pyrolysis of main chain ester section and 400-450°C means pyrolysis of urethane acrylate section. The results of DSC indicated that glass transition temperature increased with the number of the hyperbranched polyester units’ increment. What’s more, glass transition temperature of HBPE-3 was 48.13°C. HPUA-3 was semi-crystalline material, its glass transition temperature was-12.59°C, cold crystallization temperature Tc 110.92°C, melting temperature Tm 134.74°C. Since the introduction of a large number of unsaturated units to the end, the resin can be introduced into the UV-curable systems for paints, inks, adhesives and some other fields.

The Research on the Dielectric Constant of Polyester Knitted Fabrics

The influence on polyester knitted fabrics’ dielectric constant of each fabric organization structure of knitted fabrics were discussed by a single factor test method, and made a good choice from various polyester knitted fabric knitting parameters so as to the polyester knitted fabric was provided with the maximum real part and imaginary part of the dielectric constant. The results showed that when the structure of polyester knitted fabric was 2+2 rib, polyester knitted fabric had a good microwave absorbing property in these knitting parameters.

Synthesis and Thermal-Stability Study of Polybutylene Itaconate Modified with Divinyl Benzene and Glycerol

Polybutylene itaconate (PBI) for modification with divinyl benzene (DVB) and glycerol has been synthesized at 180 °C for 3 h via polycondensation of itaconic acid (IA) and butanediols using catalyst of Ti(OBu)4. Modification on PBI was done with addition of 15%, 20% and 25% DVB (w/w) using benzoyl peroxide. With glycerol, weight variations of glycerol:1,4-butanediol (BDO) in the synthesis were 10%, 30%, and 50% (mole/mole). PBI and PBI modified with DVB and glycerol were characterized with FTIR and TG-DTA. PBI showed a wavenumber shift from 1703 cm-1 to 1728 cm-1 of the C=O functional group from acid to esther. The DVB modification on PBI also showed that the intensity decrease of C=C stretching was due to the formation of crosslinking on the double bond. In the modification with glycerol, three dimensional networking on the polyester occurred through bonding between hydroxyl of glycerol and acid group of IA. Constant intensity of C=C stretching on polyester was seen. The thermal stability of PBI modified with DVB increased, accompanied by rigidity change of the structure. The thermal stability of PBI modified with glycerol decreased, caused by the decrease of regularity degree and the elasticity increase of the three dimensional structure of polyester.

Resisting protein adsorption on biodegradable polyester brushes

The protein adsorption and degradation behaviors of poly(lactic acid), poly(glycolic acid) (PGA) and poly(ε-caprolactone) (PCL) brushes and their co-polymer brushes with oligo(ethylene glycol) (OEG) were studied. Both brush structure and relative amount of OEG and polyester were found to be important to the protein resistance of the brushes. A protein-resisting surface can be fabricated either by using OEG as the top layer of a copolymer brush or by increasing the amount of OEG relative to polyester when using a hydroxyl terminated OEG (OEG-OH) and a methoxy terminated OEG (OEG-OMe) mixture as the substrate layer. The degradation of single polyester brushes and their co-polymer brushes using OEG-OH as a substrate layer or using OEG as a top layer was hindered. This phenomenon was rationalized by the inhibition of the proposed back-biting process as the hydroxy end groups of polyester were blocked by OEG molecules. Among these brushes tested, PGA co-polymer brushes using the methoxy/hydroxyl OEG mixture as the substrate layer proved to be both protein-resistant and degradable due to the relatively large amount of OEG moieties and the good biodegradability of PGA.

Synthesis and processability into textile structures of radiopaque, biodegradable polyesters and poly(ester‐urethanes)

Radiopaque biodegradable polymers have been synthesized by ring‐opening polymerization of l/dl‐lactide and caprolactone with the iodine‐containing starter molecule 2,2‐bis(hydroxymethyl)propane‐1,3‐diyl bis(2,3,5‐triiodobenzoate) followed by chain elongation with a diacid chloride or diisocyanates. The resulting polyesters and poly(ester‐urethanes) exhibited a radiopacity of 60−124% relative to an aluminium sample of the same thickness. The polymers were processed into monofilament fibres by melt‐spinning and into fibre meshes by electrospinning. All polymers were biodegradable in simulated body fluid medium under in vitro conditions and showed an excellent in vitro cytocompatibility even after several months of hydrolytic degradation. A current drawback is the relatively low tensile strength of the polymer monofilaments, which needs to be improved for applications as textile structures. Nevertheless, the new radiopaque and biodegradable polymers are promising candidates in fields of application where radiopacity of implants is an important parameter.

Fire‐retardant hybrid thermosetting resins from unsaturated polyesters and polysilazanes

ABSTRACTThis introduces an organic–inorganic thermosetting hybrid resin system based on unsaturated polyester and polysilazanes. It shows the chemical modification of unsaturated polyester structures by end capping to enable the combination of both components. In general, halogen‐free unsaturated polyesters are not fire‐retardant and have to be equipped with additives. Fillers and intumescent additives are preponderantly used in today's fire‐retardant formulations. In contrast to these fire‐retardants, polysilazanes act as ceramizing agents. Polysilazanes are suitable fire‐retardants for resin transfer molding due to their low viscosity. Both burning behavior and glass transition temperature (Tg) are investigated as important application properties. In contrast to state‐of‐the‐art fire‐retardant formulations polysilazane‐based thermosetting hybrid resins burn with high intensity and fast extinction. Therefore, total heat and smoke emission is decreased. The formation of ceramic structures during burning results in high residual mechanical properties and a low mass loss. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40375.

Behaviour of a New Composite Mesh for the Repair of Full-Thickness Abdominal Wall Defects in a Rabbit Model

IntroductionComposite biomaterials designed for the repair of abdominal wall defects are composed of a mesh component and a laminar barrier in contact with the visceral peritoneum. This study assesses the behaviour of a new composite mesh by comparing it with two latest-generation composites currently used in clinical practice.MethodsDefects (7x5cm) created in the anterior abdominal wall of New Zealand White rabbits were repaired using a polypropylene mesh and the composites: PhysiomeshTM; VentralightTM and a new composite mesh with a three-dimensional macroporous polyester structure and an oxidized collagen/chitosan barrier. Animals were sacrificed on days 14 and 90 postimplant. Specimens were processed to determine host tissue incorporation, gene/protein expression of neo-collagens (RT-PCR/immunofluorescence), macrophage response (RAM-11-immunolabelling) and biomechanical resistance. On postoperative days 7/14, each animal was examined laparoscopically to quantify adhesions between the visceral peritoneum and implant.ResultsThe new composite mesh showed the lowest incidence of seroma in the short term. At each time point, the mesh surface covered with adhesions was greater in controls than composites. By day 14, the implants were fully infiltrated by a loose connective tissue that became denser over time. At 90 days, the peritoneal mesh surface was lined with a stable mesothelium. The new composite mesh induced more rapid tissue maturation than PhysiomeshTM, giving rise to a neoformed tissue containing more type I collagen. In VentralightTM the macrophage reaction was intense and significantly greater than the other composites at both follow-up times. Tensile strengths were similar for each biomaterial.ConclusionsAll composites showed optimal peritoneal behaviour, inducing good peritoneal regeneration and scarce postoperative adhesion formation. A greater foreign body reaction was observed for VentralightTM. All composites induced good collagen deposition accompanied by optimal tensile strength. The three-dimensional macroporous structure of the new composite mesh may promote rapid tissue regeneration within the mesh.

Effect of Thermal Treatment on the Morphological Structure and Properties of Polyester Hollow Staple Fibers

The effect of thermal treatment conditions namely water pick-up, temperature and time on the morphological structure, bursting strength and wearabilities of polyester (PET) hollow staple fiber were investigated. The results show that changes in water pick-up, temperature and time may lead to an obvious change in bursting strength, warmth retention and water-vapor permeation of fabric. Scanning Electronic Microscope (SEM) analysis indicates that both thermal treatment temperature and time have a significant effect on the morphological structure and hollow structure, and the critical maximum time mostly depends on the applied temperature. Furthermore, the bursting strength, warmth retention and water-vapor permeation of polyester (PET) hollow staple fiber knitted fabric are determined by its morphological and hollow structure.

Stretch sensing properties of conductive knitted structures of PEDOT-coated viscose and polyester yarns

Wearable textile-based stretch sensors for health-care monitoring allow physiological and medical evaluation without interfering in the daily routine of the patient. In our previous work, we successfully coated viscose and polyester (PES) fibers with the conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT), using a chemical vapor deposition (CVD) process. In the present paper we report the possibility of producing a large quantity of PEDOT-coated conductive fibers with acceptable mechanical strength and frictional properties, so that knitted stretch sensors can be produced. In utilizing these knitted structures we have demonstrated the possibility of producing a textile-based monitoring device which is more readily integrated into wearable clothing than the previous metal-containing structures. The performance of viscose and PES knitted structures as stretch sensors has been investigated using a cyclic tester of our own design. For imitation of respiratory and joint movement, the variation in electrical properties of the knitted structures was examined at 5 to 50% elongation, and the performance of knitted viscose and PES structures was then compared on the basis of the cyclic testing results. In order to determine the effect of washing on PEDOT coatings and the knitted structures, two washing cycles were performed. After washing, the persistence of PEDOT coating on knitted structures was investigated using FT–IR spectroscopy and thermogravimetric analysis. In the case of PES fiber, it was revealed that stretch sensing behavior persisted even after the washing cycles. These structures thus have the potential to be utilized in medical textiles for monitoring the physiological activities of patients, such as breathing rate and joint movement.

Optical characteristics of injection-molded fluorene polymers

Abstract Digital cameras are small, but they must be able to take images with numerous pixels. To use few lenses in devices, aspheric lenses have been used. Fluorene-based polymers (FBPs) have a high refractive index and low birefringence. Because optical lenses must be manufactured as designed with low optical retardation, FBP optical lenses are widely used. This study assessed optical and flow characteristics of polycarbonate (PC) and two kinds of FBP. Molded specimen characteristics of PC and two FBPs revealed these properties of the FBPs. The results show that the unique structure of FBPs eliminated birefringence, because of the cardo structure part, including the fluorene ring. Differences in optical properties are attributable to structural differences of the part which is polymerized with the fluorene structure (the X part). The temperature dependence of FBPs in the flow characteristics and optical properties was smaller than that of PC; the slight temperature dependence is particularly obvious above the glass transition temperature (Tg). The benzene ring content of FBP affects the resin optical and physical properties. The influence of the difference between the fluorene polyester structure and the PC structure was greater than that of the benzene ring content in the X part, in the molecular structure of FBP.

Polyester-Containing α-Cyclodextrin-Based Polyrotaxane: Synthesis by Living Ring-Opening Polymerization, Polypseudorotaxanation, and End Capping Using Nitrile N-Oxide

The first synthesis of polyrotaxanes consisting of polyester axles and α-cyclodextrin (α-CD) wheels was achieved by the catalyst-free click end-capping reaction of polypseudorotaxanes using nitrile N-oxide. The polypseudorotaxanes contain acrylate-functionalized polyesters that are obtained by the living ring-opening polymerization of lactones. The yield and coverage ratio of polyrotaxanes are highly dependent on the reaction time, molecular weight of the polyester, polyester structure, and solvent used. From the thermal properties of the resulting polyrotaxanes, it was found that coverage with α-CDs efficiently suppresses the crystallization of the polyester main chain.

Effect of X-ray irradiation on the structure, thermal and mechanical properties of polyester

Samples from sheets of the polymeric material polyester have been exposed to X-rays from a 50 kV X-ray tube in the dose range 10–100 kGy. The resultant effect of X-rays has been investigated using different techniques such as X-ray diffraction XRD, thermogravimetric analysis TGA, differential thermal analysis DTA and stress-strain measurements. The results indicate that the polyester decomposes in one weight loss stage. Also, the X-ray irradiation in the dose range 30–100 kGy led to a more compact structure of polyester, which resulted in an improvement in its thermal stability. The variation of transition temperatures with the X-ray dose has been determined using DTA. The polyester thermograms were characterized by the appearance of an endothermic peak due to the melting of the crystalline phase. The melting temperature of the polymer T m was investigated to probe the crystalline domains of the polymer. At the dose range 30–100 kGy, the defect generated destroys the crystalline structure, thus reducing the melting temperature. In addition, the stress-strain measurements indicate that the X-ray irradiation at the same dose range 30–100 kGy yields crosslinked polyester of high resilience that is suitable for manufacturing protective clothes that reduce heat stress.

The development and the study of cyanourethane laquer compositions and coatings based on them

A procedure was developed for preparing cyanourethane laquer compositions based on polyisocyanates, polyesters of various structures, and dicyanodiamide. The influence of the polyester structure and component ratio on the properties of the cured laquer coatings was examined, and the compositions allowing preparation of corrosion- and heat-resistant laquer coatings were determined.

Poly(butylene 2,5-furan dicarboxylate), a Biobased Alternative to PBT: Synthesis, Physical Properties, and Crystal Structure

This paper describes the synthesis, crystal structure, and physicomechanical properties of a biobased polyester prepared from 2,5-furandicarboxylic acid (FDCA) and 1,4-butanediol. Melt-polycondensation experiments were conducted by a two-stage polymerization using titanium tetraisopropoxide (Ti[OiPr]4) as a catalyst. Polymerization conditions (catalyst concentration, reaction time and second stage reaction temperature) were varied to optimize poly(butylene-FDCA), PBF, and molecular weight. A series of PBFs with different Mw were characterized by DSC, TGA, DMTA, X-ray diffraction and tensile testing. Influence of molecular weight and melting/crystallization enthalpy on PBF material tensile properties was explored. Cold-drawing tensile tests at room temperature for PBF with Mw 16K to 27K showed a brittle-to-ductile transition. When Mw reaches 38K, the Young modulus of PBF remains above 900 MPa, and the elongation at break increases to above 1000%. The mechanical properties, thermal properties and crystal st...

微生物産生ポリエステルの構造, 物性および生分解性

微生物産生ポリエステルの構造, 物性および生分解性

Fully Isohexide-Based Polyesters: Synthesis, Characterization, and Structure–Properties Relations

Here we present a novel series of biobased polyesters solely based on renewable isohexide building blocks, synthesized via melt polymerization. The recently developed isoidide dicarboxylic acid (IIDCA) was polymerized with rigid renewable diols such as isosorbide (IS), isomannide (IM), isoidide (II), and the novel 2,5-methylene-extended isoidide dimethanol (IIDML). Both IIDCA and IIDML were developed to increase the reactivity of the isohexide building block, while retaining rigidity and hence the beneficial effects on Tg. Compared to the parent isohexides, IIDML showed a markedly higher reactivity, resulting in three to four times higher weight-average molecular weight (Mw) values of the synthesized polyesters. The molecular structure of the novel polyesters was analyzed by 1H, 13C and 2D-COSY NMR techniques, confirming that the stereoconfigurations of the isohexide moieties were preserved under the applied polymerization conditions. The II/IS-based polyesters have high Tg values noted of 70 and 85 °C, r...