Polyester Copolymers Research Articles

Ring-opening polymerization of 6-hydroxynon-8-enoic acid lactone: Novel biodegradable copolymers containing allyl pendent groups

This article reports the synthesis and copolymerization of 6-hydroxynon-8-enoic acid lactone. The ring-opening polymerization of this lactone-type monomer bearing a pendant allyl group led to new homopolymers and random copolymers with e-caprolactone and L,L-lactide. The copolymerizations were carried out at 110 °C with Sn(Oct)2 as a catalyst. The introduction of unsaturations into the aliphatic polyester permitted us to carry out different chemical transformations on this family of polymers. For example, this article reports the bromination, epoxidation, and hydrosylilation of the allyl group in the new polyester copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 870–875, 2000

The Molecular Basis for the Relationship between the Secondary Relaxation and Mechanical Properties of a Series of Polyester Copolymer Glasses

A correlation between the yield behavior of copolymers based on poly(ethylene terephthalate) and poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their secondary relaxation motions is est...

Influence of sterilization on injectable bone biomaterials

Injectable biomaterials used in bone surgery include acrylic bone cements, calcium phosphate cements, and new composite-type biomaterials with a mineral content and an organic phase dispersed or dissolved in water. Cellulose derivatives, chitosan solutions, alginates, and other polymers are studied as useful modifiers and binding agents in calcium phosphate cements. We have developed proprietary polyester copolymers including lactic acid moieties and present here results concerning the effect of sterilization on the physico-chemical properties of derived bone biomaterials. Chitosan solutions show a dramatic decrease in viscosity after 25-kGy gamma sterilization. Aqueous copolylactic solutions also show, by capillary electrophoresis, that hydrolysis occurs to liberate monomers after 25-kGy gamma sterilization. Heat sterilization also degrades chitosan solutions, and ultrafiltration is difficult because of high viscosity. However, apatite-copolylactic solids can be steam sterilized without deterioration. Gelatin has been used as a natural polymer to bind apatite particles. Gel exclusion chromatography reveals crosslinking of the chains by irradiation. Standard acrylic cements contain monomers sterilized by ultrafiltration because they do not tolerate irradiation. We have used ultrafiltration to prepare aqueous copolylactic solutions without polymer hydrolysis. Implantation of calcium phosphate cement modified by copolylactic acid in a rabbit metaphyseal model defect shows progressive substitution of the biomaterial by new bone tissue. At 3 months, a mild inflammatory reaction still remains associated with the continuing resorption of the biomaterial. These results show that interesting biological properties can be obtained with products not sterilized by irradiation. Undoubtedly, many biopolymers are fragile and, like reactive monomers, need to be sterilized by special methods if they are to be used in injectable, liquid form.

Thermally crosslinkable thermoplastic PET-co-XTA copolyesters

A series of thermally crosslinkable polyester copolymers were synthesized by incorporation of a benzocyclobutene-containing terephthalic acid derivative (XTA) into polyethylene terephthalate (PET). The cyclobutene moiety on the XTA monomer allows for reactive crosslinking at temperatures ∼350°C requiring no catalyst and causing no change in mass. Copolymers were synthesized containing 1, 5, 10, 20, 50, and 100 mol%o XTA. Crosslinking occurred above the melting temperature (∼250°C) yet below the degradation temperature (∼400°C), providing a window for melt processing of the copolymer. To demonstrate this point fibres were melt spun. The PET-co-XTA copolymers show systematic variations in the glass transition, recrystallization, melting and degradation temperatures as a function of benzocyclobutene content. The degradation and melting temperature both decrease slightly with increased XTA, while the recrystallization and glass transition temperature were relatively insensitive to XTA content. Thermal gravimetric analysis (TGA) indicated a decrease in the degradation temperature as higher amounts of XTA were incorporated, although an increase in the %char at 800°C was seen. This decrease in degradation temperature may be due to the generation of free radicals. Limiting Oxygen Index (LOI) measurements showed an increase in the oxygen content required to maintain a stable flame in copolymers with increasing amounts of XTA. LOI values ranged from 18 for neat PET to 35 for the copolymer containing 20 mol % XTA. Wide-angle X-ray scattering data showed little change in the crystalline structure, but decreasing crystallinity for PET for blends containing up to 20 mol% XTA. The 50 mol% XTA copolymer was amorphous, while the 100% XTA homopolymer (PEXTA) showed evidence of a new crystalline structure. Crystalline diffraction peaks showed reduced intensities in data recorded for heat treated samples, and there was evidence for new peaks in the copolymer containing 20 mol% XTA when heated near 300°C. Transmission electron microscopy of cross-sections through burned samples showed a highly crystalline char at the surface of XTA copolyesters. This crystalline char appeared to protect the underlying copolymer from further flame-induced degradation. Evidence for significantly increased adhesion of the copolymers to polyimide films was also obtained.

The Mesogenic Index: An Empirical Method for Predicting Polymeric Liquid Crystallinity

An empirical method for predicting the chemical compositions of random or partially ordered copolymers that exhibit mesophases was devised by the authors in 1989, while working on liquid crystal copolymer synthesis for BP Chemicals. A brief description of the method and its application to the chemical synthesis of amorphous thermotropic polyamides was given by the authors in a previous paper. Thermotropic polyimides were also synthesized by the authors as a result of the use of the predictive method. Subsequently, the method has been updated and applied to polycarbonates and polyimides. The new approach has been termed ‘the mesogenic index’ (MI) and has successfully been applied to 23 copolymer systems in which the critical compositions for mesophase formation have been established by means of varying constituent monomer concentrations. It is also consistent in predicting liquid crystalline behaviour in several hundred main-chain polymer systems containing amide, ester, carbonate, ether and urethane groups. It is inherent in the MI system that the mesogenic length is defined in terms of the number of monomer units for a given polymer class. From published work in the literature, it was first established that ester and amide groups need at least two and three aromatic rings in the mesogen respectively. Using these values to define mesogen length in polyester and polyamide copolymers, the condition MI > 10 has been determined for mesophase formation. This rule has been applied to other linking groups, such as carbonate or imide, with the surprising result that the corresponding mesogen lengths for these condensation polymers are simple numbers. Moreover, the rule has been applied successfully to mixed systems, by simply averaging the contributions of the different groups to the mesogen length in strictly molar proportions. The mesogenic index is based upon summing functional group contributions towards rigidity and/or resonance stabilization of the mesogen. To the best of our knowledge, this is the first simple method to be published that successfully correlates chemical composition with mesophase formation.

Molecular Structure Effects on the Secondary Relaxation and Impact Strength of a Series of Polyester Copolymer Glasses

The secondary relaxations of a series of glassy copolymers based on poly(ethylene terephthalate) (PET) and poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) involve cooperative motions of the cyclohexylene rings. The cooperativity gives rise to longer range motions which create significant volume fluctuations that can facilitate macroscopic shear yielding. Comparison of the secondary loss peaks and activation energies by dynamic mechanical spectroscopy between the copolyesters and poly(cyclohexyl methacrylate) and poly(1,4-cyclohexylenedimethylene 2,5-dimethylterephthalate) indicates that the secondary relaxation of the copolyesters involve motions of the cyclohexylene ring. Dipolar rotational spin−echo 13C NMR confirmed large amplitude motions of the cyclohexylene ring faster than 10 kHz at 300 K. By examining feasible ring conformations, we conclude that transitions between chair and twist−boat conformations are possible for trans-cyclohexylene rings and cis-rings that prefer chair conformations. (Cis-rings that reside in boat conformations are more restricted.)

Nanolithographic Determination of Brittleness at Polymer Surfaces

AFM techniques were used to interrogate the mechanical properties of weathered polyester copolymer sheets near the exposed surface. Tapping mode tips, as well as a diamond tip mounted on a high spring constant cantilever, were used to scratch overlapping quadrilateral patterns into the polymer. The marred sites were micrographed and the RMS roughness was used as an index of brittleness. Propagation speed and normal force of the test cycle were optimized.

New epoxy-unsaturated polyester resin copolymers

Some fire-resistant epoxy resins known in literature and practice were reviewed. New unsaturated polyester resins with decreasing flammability was reviewed. The main monomers were dibromobutendiol and diallylic ether of dibromoneopentylglycol. The new idea of epoxy resin fire-retardance by creating new epoxy resin-unsaturated polyester copolymers was put forward and then obtained. The reagents were as follows: low-molecular epoxy resin, polyamine curing agent, special diazo-epoxy resin, brominated unsaturated polyester resins, styrene or diallylic ether of dibromoneopentylglycol as diluent to obtain optimum viscosity. The proposed mechanism to form three-dimensional copolymer network was presented.

BAMO/NMMO Copolymer with Polyester Initiation

AbstractIn order to improve of mechanical properties at low temperature region, 3,3‐bis(azidomethyl)oxetan (BAMO), 3‐nitratomethyl‐3‐methyloxetane (NMMO) and polyester (PE) copolymer were synthesized by using polyester initiator with boron trifluoride etherate. The molar ratio of each units in the BAMO/NMMO/PE copolymer was 7.4/2.6/0.39 according to the 1H‐NMR spectrum analysis and was almost exactly the same composition as the monomer fed (7/3/0.33). The relative composition of triad microstructures was same as theoretical value and they were randomly arranged. The PE, which was a replacement of 1,4‐butanediol, acted as an excellent soft segment in the copolymer, and the glass transition point of the elastomer was 4.8 degrees lowered by the replacement. This effect was also verified in the mechanical properties of the composite propellant and the tensile elongation was increased from 15% to 40%percnt; at −40 °C.

Effect of copolymer composition on free volume and gas permeability in poly(ethylene terephthalate)-poly(1,4 cyclohexylenedimethylene terephthalate) copolyesters

The gas permeability and free volume of a series of polyester copolymers were studied. The free volume was studied using the positron annihilation lifetime spectroscopy (PALS) technique to indicate the relative size and concentration of free volume cavities in the copolymers. The homopolymers were poly(ethylene terephthalate) (PET) and poly(1,4 cyclohexamethylene terephthalate) (PCT). The copolymers were prepared by reacting terephthalic acid with varying amounts of ethylene glycol and 1,4 cyclohexanedimethanol to produce a copolymer series containing 11.8, 30.8, 31.8, 60.9, 68.9, and 80.8 mol% PCT. The logarithm of the permeability to oxygen and carbon dioxide was found to increase linearly with vol% PCT. The mean free volume cavity size and relative concentration (as indicated by the PALS parameters τ 3 and I 3, respectively) were found to increase approximately linearly with vol% PCT. The results are modelled using the Cohen-Turnbull theory for transport in polymers and discussed in terms of various methods of calculating, from PALS data, the free volume fraction that is important to transport properties.

Nanoporous Polyimide Films from Polyimide-Aliphatic Polyester or Polyimide-Aliphatic Polycarbonate Copolymers

AbstractWe have explored polyimide foams created using a block copolymer approach as part of our research efforts to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range thus the term “nanofoam”, The polyimide foams are prepared from phase separated block copolymers consisting of thermally stabile and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the labile block leaving pores the size and shape corresponding to the initial copolymer morphology. Polyimide nanofoams generated from thermolysis of polyimidealiphatic polyester and polyimide-aliphatic polycarbonate copolymers were investigated. The aliphatic co-blocks were synthesized by ring opening polymerization of the cyclic monomers, such as E-caprolactone, valerolactone, trimethylene carbonate, and L-lactide. The aliphatic blocks were designed in such a way as to allow for incorporation into polyimide copolymers. The foams were characterized by a variety of techniques including, TEM, SAXS, WAXD, DMTA, density and refractive index measurements.

Studies of the effect of fiber surface and matrix rheological properties on nonwoven reinforced elastomer composites

AbstractThe influence of fiber type and fiber‐surface properties on matrix flow behavior was investigated using structural reaction injection‐molding (SRIM). The influence of fiber type, fiber‐surface properties, and matrix type on strength properties in elastomeric composites reinforced with nonwoven fibrous structures was investigated using tensile tests on elastomer composite samples from SRIM and latex coagulation (LC) fabrication methods and the microbond strength method on individual fibers. The fibers used were PET, LLDPE, and p‐aramid. Fibers were treated with epoxy, styrene, and isocyanate derivatives, which make the surface chemically reactive. Treatments were also made with NaOH and a copolymer of polyester and polyol ether, causing a change in the fiber surface energy. The matrix types were polyurethane elastomer and natural rubber. The results show that the surface treatments which produced a change in the surface energy influenced the flow rate of the matrix polymer during the composite fabrication process. The treatments resulted in chemically reactive fiber surfaces which improved the fiber‐matrix bond strength without affecting the Young's modulus of the composite material. Good correlation was found between bond strength and surface energy including the dispersive component of surface energy in the case of polyurethane elastomer and surface‐modified PET fibers. The age of the polyurethane matrix has a marked influence on the bond strength. The fiber volume fraction in composites has a strong influence on the Young's modulus of the elastomer composite. © 1995 John Wiley & Sons, Inc.

Homogeneous polyesters of predetermined length, composition, and sequence: Model synthesis of alternating glycolic‐acid‐co‐(L)‐lactic‐acid oligomers

AbstractMethods for making monodisperse polyester copolymers of predetermined length, com‐position, and sequence are reported. Alternating oligomers of (L)‐lactic‐co‐glycolic acid (La‐co‐Gl), isosteric with polypeptides, are prepared by solution methods of protecting, coupling, and deprotecting alcohol and acid groups. The carboxylic acid is protected by benzyl ester formation and released by hydrogenation. The hydroxyl group is protected as the methoxyethoxyethyl ether and deprotected with sodium iodide and trimethylsilyl chlo‐ride. Coupling uses dicyclohexylcarbodiimide. End‐capped alternating oligomers containing (GILa)4 and (GILa)8 show polymer properties. They are noncrystalline oils that exhibit discernable Tg. The conformation of GILa and LaGl diads in the polyesters is shown to be similar to isosteric peptide diads GlyAla and AlaGly. Exactly structured, monodisperse polyesters suggest a chemical parallel to proteins. Designed struc‐tural templates combining sheet‐form (Gl)n and helical (La)n segments are at‐tractive synthesis targets. The solution preparations reported here can be applied, but it is suggested that biosynthetic methods for introducing single ester units into peptide chains be adapted to synthesize precisely fashioned polyesters. © 1995 John Wiley & Sons, Inc.

Viscosimetric Investigation of Plasticized Epoxy Resin

Abstract Blends of diglycidyl ether of bisphenol-A epoxy resin and adipic acid, ethylene glycol, diethylene glycol polyester copolymer have been studied regarding viscosity behavior. Both the rheological measurements carried out on the molten mixtures over a large interval of shear rates and the intrinsic viscosity of the blend solutions pointed to an immiscibility at temperatures ranging from 30° to 90°C. The rheological parameters evaluated on the flow of the mixtures against temperature and the shear rate led to the conclusion that the tested blends have a non-Newtonian rheological behavior of the pseudoplastic type.

Biodegradation of Polyester Copolymers Containing Aromatic Compounds

Abstract For investigation of the microbial accessibility of polyesters based on 1,3-propanediol, a series of different polymer structures (homo, random, and block copolymers) were synthesized by polycondensation of terephthalic acid, adipic acid, sebacic acid, and 1,3-propanediol. The alcohol component, 1,3-propanediol, can be obtained from a biotechnological process from glycerol, a surplus product of the oleochemical industry. Aliphatic dicarbonic acids can be derived from vegetable oils. Biodegradation was performed in different test systems. 1) Polyester films were exposed to an aerated liquid medium inoculated with eluates from soil. 2) For this test system, polymer films were buried in soil. Copolyesters exhibited significant differences in both tests. Furthermore, a clear influence of the polymeric structure as well as of the chain length of the aliphatic dicarbonic acids on the microbial accessibility was observed.

Shrinkage modeling of polyester shrink film

AbstractA model was developed to quantify the thermal shrinkage behavior of polyester shrink film under isothermal and nonisothermal conditions. This model employs the straightforward first order reaction kinetics to an otherwise microscopically complex relaxation process. It offers three unique parameters for quality control and material specification of shrink film. In the isothermal condition, the induction time, the shrink constant, and the ultimate shrinkage are the three parameters used by the model to quantify the shrinkage of shrink film under an elevated but constant temperature. In the nonisothermal condition, the shrink film is heated using a constant heating rate. Three parameters, which are the onset shrink temperature, the shrink constant, and the ultimate shrinkage, characterize the shrinkage of shrink film. The model fits the experimental data very well. The thermal shrinkage of several polyester homopolymers, copolymers, and polyester blends was investigated and compared to that of poly(vinly chloride) (PVC) shrink film. Two polyester blends containing glycol modified poly(ethylene terephthalate) (PETG) copolyester behave similar to PVC in shrinkage behavior. The effect of stretch temperature, stretch ratio, and stretch rate on the shrinkage characteristics of oriented PETG film was also studied. The stretch temperature has the highest influence on the shrinkage behavior of oriented film.

Synthesis of Diblock Polyolefin and Polyester Copolymers Using Zirconium and Aluminum Catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of Diblock Polyolefin and Polyester Copolymers Using Zirconium and Aluminum CatalystsAnne-Lise Mogstad and Robert M. WaymouthCite this: Macromolecules 1994, 27, 8, 2313–2315Publication Date (Print):April 1, 1994Publication History Published online1 May 2002Published inissue 1 April 1994https://doi.org/10.1021/ma00086a050RIGHTS & PERMISSIONSArticle Views234Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (328 KB) Get e-Alerts Get e-Alerts

Degradable polyurethane networks based on d,l-lactide, glycolide, ε-caprolactone, and trimethylene carbonate homopolyester and copolyester triols

Several trifunctional, hydroxy-telechelic polyester and poly(ester-carbonate) homopolymers and copolymers were synthesized by the triol-initiated, ring-opening bulk polymerization of d,l-lactide, glycolide, ε-caprolactone, and/or trimethylene carbonate. The molar compositions of the copolymers were determined from 13C n.m.r. spectra; hydroxy equivalent weights were determined by acetylation titration, and the glass transition temperatures ( T g) and melting points were determined by differential scanning calorimetry (d.s.c.). Crosslinked polyurethane networks were prepared by reacting the hydroxy-telechelic prepolymers with tolylene diisocyanate. Network characterization included determination of sol content by solvent extraction, T g by d.s.c., tensile properties by stress-strain measurements, and degradation properties by hydrolytic degradation studies. Equilibrium swelling results indicated that the per cent weight gains correlated well with the prepolymer hydroxy equivalent weights, with the exception of the poly(glycolide- co-trimethylene carbonate) network. The poly( d,l-lactide) and poly( d,l-lactide- co-trimethylene carbonate) (PLTMC) networks had the highest tensile strengths of 49.60 and 41.27 MPa, respectively, and glass transition temperatures of 51.3 and 21.3°C, respectively. All other networks were highly flexible with tensile strengths of 12 MPa or less. Hydrolytic degradation studies were conducted by placing network samples in a solution of phosphate-buffered saline (pH = 7.4) at 37°C. Weight uptake of buffer and weight loss of the networks were monitored gravimetrically over time. Tensile properties, monitored as a function of degradation time, indicated that the poly(ε-caprolactone- co- d,l-lactide) and PLTMC networks displayed a linear loss of strength with respect to weight during the first 30 days of degradation; the other networks degraded either too slowly or too quickly to establish such a linear relationship.

Degradation methods and degradation kinetics of polymer films

Two accelerated degradation systems are described for the marine and soil exposures of polymer films. The systems were designed to provide controlled environments in which rates of degradation could be accelerated. The goal in developing these systems was to provide a standardized basis for comparing degradation kinetics of the films. Polymer film degradation kinetics are illustrated with two bacterial polyester copolymers (8% valerate and 24% valerate in butyrate-co-valerate polyester polymers) and cellophane. Initial data on weight loss per surface area, changes in molecular weight, and changes in mechanical properties of the films are described. The long-term goals are to correlate this type of data to environmental exposure conditions and to polymer morphology and chemistry.

The behavior of alloplastic tympanic membranes in Staphlococcus aureus‐induced middle ear infection. II. Morphological study of epithelial reactions

Epithelial reactions to Silastic, Estane polyether urethane, polypropylene oxide, and a poly(ethylene oxide hydantoin) and poly(tetramethylene terephthalate) segmented polyether polyester copolymer were investigated after implantation in tympanic membranes and submucosa of noninfected and Staphylococcus aureus-infected rat middle ears. Porous implants made of Estane and polypropylene oxide were completely covered by tympanic-membrane connective tissue, epidermis, and epithelium in 2 weeks and those made of copolymer in between 2 and 4 weeks postoperatively. Silastic implants, which were dense, were not enveloped by tympanic-membrane tissue but rejected. Starting in the 6th postoperative month the proliferative activity and structure of both the tympanic membrane epithelium and epidermis became normal except for the presence of iron-containing secretory epithelium near polypropylene oxide. After initial swelling caused by the surgical trauma, neither the proliferative activity nor the composition of the epithelium covering submucosal implants was affected by the presence of any of the biomaterials. Infection of middle ears bearing implants induced epithelial reactions similar to those associated with infected middle ears without an implant.