Aliphatic Polyesters (aliphatic + polyester)

Distribution by Scientific Domains


Selected Abstracts


Synthesis and Characterization of a Novel Degradable Aliphatic Polyester that Contains Monomeric Lactate Sequences

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2006
Congming Xiao
Abstract Summary: A novel degradable aliphatic polyester that contains monomeric lactate sequences is synthesized via melt-polycondensation of ethylene glycol lactate diol (EGLD) with succinic anhydride without the use of catalyst. The structure of the EGLD precursor and the polyester are verified with FT-IR and 1H NMR spectra. Gel permeation chromatography reveals that the weight-average molecular weight of the polyester is 5.5,,104 with a polydispersity index (PDI) of 1.7. Differential scanning calorimetry profiles reveal that the polyester is a semicrystalline polymer with a glass transition temperature of ,12,C and melting temperature of 101,C. The weight loss percentage of the polyester after immersing for 208 d in active sludge is 2.7%, which suggests degradation has occurred. The synthesis route of the polyester synthesized here (see inset for structure). [source]


Synthesis and characterization of amphiphilic block copolymer of polyphosphoester and poly(L -lactic acid)

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008
Xian-Zhu Yang
Abstract Aliphatic polyesters and polyphosphoesters (PPEs) have received much interest in medical applications due to their favorable biocompatibility and biodegradability. In this work, novel amphiphilic triblock copolymers of PPE and poly(L -lactic acid) (PLLA) with various compositions were synthesized and characterized. The blocky structure was confirmed by GPC analyses. These triblock copolymers formed micelles composed of hydrophobic PLLA core and hydrophilic PPE shell in aqueous solution. Critical micellization concentrations of these triblock copolymers were related to the polymer compositions. Incubation of micelles at neutral pH followed by GPC analyses revealed that these polymer micelles were hydrolysized and resulted in decreased molecular weights and small oligomers, whereas its degradation in basic and acid mediums was accelerated. MTT assay also demonstrated the biocompatibility against HEK293 cells. These biodegradable polymers are potential as drug carriers for biomedical application. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6425,6434, 2008 [source]


A Novel Micellar PEGylated Hyperbranched Polyester as a Prospective Drug Delivery System for Paclitaxel

MACROMOLECULAR BIOSCIENCE, Issue 9 2008
Christina Kontoyianni
Abstract A hyperbranched aliphatic polyester has been functionalized with PEG chains to afford a novel water-soluble BH40-PEG polymer which exhibits unimolecular micellar properties, and is therefore appropriate for application as a drug-delivery system. The solubility of the anticancer drug paclitaxel was enhanced by a factor of 35, 110, 230, and 355 in aqueous solutions of BH40-PEG of 10, 30, 60, and 90 mg,,mL,1, respectively. More than 50% of the drug is released at a steady rate and release is almost complete within 10 h. The toxicity of BH40-PEG was assessed in vitro with A549 human lung carcinoma cells and found to be nontoxic for 3 h incubation up to a 1.75 mg,,mL,1 concentration while LD50 was 3.5 mg,,mL,1. Finally, it was efficiently internalized in cells, primarily in the absence of foetal bovine serum, while confocal microscopy revealed the preferential localization of the compound in cell nuclei. [source]


Synthesis and Characterization of a Novel Degradable Aliphatic Polyester that Contains Monomeric Lactate Sequences

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2006
Congming Xiao
Abstract Summary: A novel degradable aliphatic polyester that contains monomeric lactate sequences is synthesized via melt-polycondensation of ethylene glycol lactate diol (EGLD) with succinic anhydride without the use of catalyst. The structure of the EGLD precursor and the polyester are verified with FT-IR and 1H NMR spectra. Gel permeation chromatography reveals that the weight-average molecular weight of the polyester is 5.5,,104 with a polydispersity index (PDI) of 1.7. Differential scanning calorimetry profiles reveal that the polyester is a semicrystalline polymer with a glass transition temperature of ,12,C and melting temperature of 101,C. The weight loss percentage of the polyester after immersing for 208 d in active sludge is 2.7%, which suggests degradation has occurred. The synthesis route of the polyester synthesized here (see inset for structure). [source]


Compatibilization of starch,polyester blends using reactive extrusion

POLYMER ENGINEERING & SCIENCE, Issue 3 2006
R.B. Maliger
Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator respectively for blending starch and a biodegradable synthetic aliphatic polyester using reactive extrusion. Blends were characterized using dynamic mechanical and thermal analysis (DMTA). Optical micrographs of the blends revealed that in the optimized blend, starch was evenly dispersed in the polymer matrix. Optimized blends exhibited better tensile properties than the uncompatibilized blends. X-ray photoelectron spectroscopy supported the proposed structure for the starch,polyester complex. Variation in the compositions of crosslinking agent and initiator had an impact on the properties and color of the blends. POLYM. ENG. SCI. 46:248,263, 2006. 2006 Society of Plastics Engineers [source]


Surface modification of poly(glycolic acid) (PGA) for biomedical applications

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2003
Kyung-Bok Lee
Abstract The immobilization of biological ligands (such as biotin and peptides) onto biodegradable polymer surfaces, including poly(glycolic acid) (PGA) sutures, is complicated by the absence of functional groups on the polymer backbone. We demonstrate a method for overcoming this problem, by attaching (+)-biotinyl-3,6,9-trioxaundecanediamine to the surface of PGA sutures, which immobilizes the ligand through an amide bond between amine (ligands) and carboxylic acid groups (surface-hydrolyzed PGA sutures). Fluorescence microscopy was used to verify the attachment of the biotin ligand to the surface of the PGA suture after a complexation with fluorescein-conjugated streptavidin. The strategy can be generalized to surface modifications of other biodegradable aliphatic polyesters, which would improve the properties of the polymers in biomedical applications such as active targeting of drugs based on ligand-attached, polymeric drug delvery systems. 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:933,937, 2003 [source]


Mapping the characteristics of the radical ring-opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyester

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009
Peter Plikk
Abstract Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4587,4601, 2009 [source]


Syntheses of aliphatic polyesters catalyzed by lanthanide triflates

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2009
Mazen Garaleh
Abstract Polycondensations of 1,6-hexane diol and sebacic acid were conducted in bulk with addition of a lanthanide triflate as acidic catalyst. With exception of promethium triflate all lanthanide triflates were studied. A particularly low molecular weight was obtained with neodym triflate and the best results with samarium triflate. With Sm(OTf)3 weight average (Mw) values up to 65 kDa (uncorrected SEC data) were achieved after optimization of the reaction conditions. Comparison of these results with those obtained from bismuth, magnesium, and zinc triflates, on the one hand, and comparison with the acidities of all catalysts, on the other, indicates that the esterification mechanism involves complexation of monomer by metal ions. Preparation of multiblock copoly(ether ester)s failed due to insufficient incorporation of poly(tetrahydrofuran) diols. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 170,177, 2009 [source]


One-pot synthesis of star-shaped aliphatic polyesters with hyperbranched cores and their characterization with size exclusion chromatography

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2006
Tadeusz Biela
Star-shaped aliphatic polyesters with hyperbranched cores were prepared by a two-step synthesis with the one-pot, arms-first core method. First, the polymerization of ,-caprolactone (CL) or L,L -lactide (LA) was initiated with aluminum isopropoxide trimer. Then, the resulting poly(CL),OAl< or poly(LA),OAl< living chains were employed as initiators for 5,5,-bis(oxepan-2-one) or 1,6-dioxaspiro[4,4]nonane-2,7-dione) polymerization. A sequence of chain growth and branching reactions led to the formation of starlike macromolecules. The progress of the polymerization was followed with size exclusion chromatography, and the products of the model reaction were also analyzed with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. [source]


Nerve conduits and growth factor delivery in peripheral nerve repair

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2007
Lukas A. Pfister
Abstract Peripheral nerves possess the capacity of self-regeneration after traumatic injury. Transected peripheral nerves can be bridged by direct surgical coaptation of the two nerve stumps or by interposing autografts or biological (veins) or synthetic nerve conduits (NC). NC are tubular structures that guide the regenerating axons to the distal nerve stump. Early synthetic NC have primarily been made of silicone because of the relative flexibility and biocompatibility of this material and because medical-grade silicone tubes were readily available in various dimensions. Nowadays, NC are preferably made of biodegradable materials such as collagen, aliphatic polyesters, or polyurethanes. Although NC assist in guiding regenerating nerves, satisfactory functional restoration of severed nerves may further require exogenous growth factors. Therefore, authors have proposed NC with integrated delivery systems for growth factors or growth factor,producing cells. This article reviews the most important designs of NC with integrated delivery systems for localized release of growth factors. The various systems discussed comprise NC with growth factors being released from various types of matrices, from transplanted cells (Schwann cells or mesenchymal stem cells), or through genetic modification of cells naturally present at the site of injured tissue. Acellular delivery systems for growth factors include the NC wall itself, biodegradable microspheres seeded onto the internal surface of the NC wall, or matrices that are filled into the lumen of the NC and immobilize the growth factors through physical-chemical interactions or specific ligand-receptor interactions. A very promising and elegant system appears to be longitudinally aligned fibers inserted in the lumen of a NC that deliver the growth factors and provide additional guidance for Schwann cells and axons. This review also attempts to appreciate the most promising approaches and emphasize the importance of growth factor delivery kinetics. [source]


Water Absorption and Degradation Characteristics of Chitosan-Based Polyesters and Hydroxyapatite Composites

MACROMOLECULAR BIOSCIENCE, Issue 3 2007
Vitor M. Correlo
Abstract 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,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. [source]


Enzymatic Synthesis of Chitin- and Chitosan- graft -Aliphatic Polyesters

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004
Masayori Fujioka
Abstract Summary: The title polymers, in which both the stem and the graft are biodegradable, have been synthesized for the first time in a one-pot, lipase-catalyzed, graft-polymerization reaction (in bulk, at 70,C) of , -butyrolactone (, -BL) and , -caprolactone (, -CL) onto chitin and chitosan. The reactivity order of the lactones was found to be , -CL,>,, -BL,,,, -BL (no reaction). All the graft polymers prepared are insoluble in common organic solvents. Synthesis of chitin- or chitosan- graft -aliphatic polyesters. [source]


Viscoelastic properties of extrusion cast sheets of natural and synthetic aliphatic polyesters

POLYMER ENGINEERING & SCIENCE, Issue 10 2005
Mrinal Bhattacharya
The objective of this study was to determine the viscoelastic properties of natural (starch and protein) blends and synthetic biodegradable aliphatic copolyester blends. Blends of natural and synthetic biodegradable poly(butylene succinate) were cast into sheets using a coathanger die and then subjected to stress relaxation and creep tests at various temperatures. The natural content was varied at 10%, 30%, and 50% by weight. In some formulations a small (5% by weight) amount of compatibilizer was added. The materials were blended using a twin screw-extruder, pelletized, and sheeted using a coathanger die. The decay of stress upon the imposition of constant strain showed two regions, an exponential and power law; the stresses relaxed sharply at the initial stage and then decayed at a reduced rate for the duration of the experiment. The addition of compatibilizers increased the time required for the stress to relax compared to uncompatibilized blends of the same composition. Similarly, as the natural content increased the time taken to relax to a specified stress level decreased. Increased temperature enhanced the relaxation process. The initial strain of the creep curves was affected by the natural content; the higher the natural content, the lower the initial strain for the samples upon imposition of a constant stress. Similarly, the presence of compatibilizer in the blend reduced the initial strain for samples containing the same natural content. As the natural content of the blend decreases, the time required to attain the plateau compliance is reduced. The equilibrium compliance increased with temperature. These behaviors are described in terms of blend morphology. The empirical Struik and power law models can be used to fit the compliance data well. POLYM. ENG. SCI., 45:1452,1460, 2005. 2005 Society of Plastics Engineers [source]


UV curing behaviors and hydrophilic characteristics of UV curable waterborne hyperbranched aliphatic polyesters,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2003
Anila Asif
Abstract A series of waterborne hyperbranched polyesters (WBHPs) endcapped with methacrylic and salt-like groups in different ratios have been investigated as UV curable resins. The kinetic studies of the drying step and UV curing were carried out by FT-IR measurements. The drying of the film of 100,,m thickness was completed in less than 6,hr at 70C or within 10,hr at 50C in an oven. The influence of different photoinitiators and their concentrations, extent of unsaturation and acid content of WBHP on final unsaturation conversion was studied. The surface free energy is a critical character, which affects the surface properties of a cured film. So one method based on the measurement of contact angle of a pure liquid on a solid surface was applied to determine the polar and dispersive components of the surface energy of UV cured films. The investigations of surface energy of WBHPs illustrated that those with more acid content and thus higher polar component are more sensitive to water, while those containing less acid content and thus lower polar term are less water sensitive. Moreover, the UV cured films of WBHPs and their blends with commercial waterborne resins (trade name EB 210, EB 2002, EB 11 and IRR 160) have acceptable pendulum hardness varying from 55 to 180,sec. Copyright 2003 John Wiley & Sons, Ltd. [source]