Biodegradable Aliphatic Polyesters Research Articles

Crystallization Behavior of Reactive Blends between PBS and PA6IcoT

A biodegradable crystalline aliphatic polyester, poly(butylene succinate) (PBS), and an amorphous semiaromatic nylon, poly(hexamethylene isophthalamide-co-terephthalamide) (PA6IcoT), were melted an...

Pengaruh Massa Awal Poli (trimetilen-sebasat) Terhadap Laju Biodegradasi dalam Media Cair Menggunakan Mucor miehei Secara Aerob

The author has conducted research about the effect of poly(trimethylene-sebacate) mass toward the rate of biodegradation using Mucor miehei in aerobic liquid media. Poly(trimethylene-sebacate) is a biodegradable linear aliphatic polyester, that can be degraded by Mucor miehei lipase. To determine the effect of poly(trimethylene-sebacate) mass in the biodegradation, the mass of poly(trimethylene-sebacate) were varied 0.06 g, 0.08 g, 0.1 g, 0.12 g and 0.14 g. Biodegradation process carried out for 12 hours, using liquid of Complex media, which was nutrient rich for Mucor miehei growth, and solution at pH 5. The resulting CO2 gas was flowed into the 50 mL reservoir of 0.1 M NaOH, followed by titration using 0.05 M HCl and MO (methyl orange) and PP (phenolptalein) indicator. The rate of CO2 gas were 0.287 x 10-3 M/h; 0.102 x 10-3 M/h; 0.137 x 10-3 M/h; 0.016 x 10-3 M/h; and 0.039 x 10-3 M/h respectively. The greater rate of CO2 produced the lower mass of poly(trimethylene-sebacate).

ChemInform Abstract: Precision Synthesis of Biodegradable Polymers

AbstractReview: 36 refs.

Poly(ethylene-co-methyl acrylate)/poly(caprolactone) triol blends for drug delivery systems: characterization and drug release

Poly(ethylene-co-methyl acrylate) (EMA) and poly (caprolactone) triol (PCL-T) blends, a biodegradable aliphatic polyester with low molecular weight and moderate water solubility containing diltiazem hydrochloride (DZ) were studied in terms of the thermal and morphological properties, and drug release mechanism. An increase in the PCL-T content in the EMA/PCL-T/DZ films decreased the degree of DZ crystallinity. Drug release from these films is temperature-dependent, and it is possible to modify the drug release rate by adjusting the EMA/PCL-T composition of the blends. The mechanism of drug release is governed by PCL-T melting and PCL-T leaching from EMA matrix.

Homogeneous Chitosan/Poly(L-Lactide) Composite Scaffolds Prepared by Emulsion Freeze-Drying

The combination between chitosan (CS)-based hydrophilic extracellular matrix polysaccharide and polylactide (PLA)-based hydrophobic biodegradable aliphatic polyester is a challenge in the biomaterials field. This study investigated the formation of homogeneous chitosan/poly(L-lactide) (CS/PLLA) porous composite scaffold using a novel emulsion freeze-drying technique. An oil-in-water (O/W) emulsification system was used in the presence of surfactant Tween-80, in which CS solution was used as the water phase and PLLA solution was used as the oil phase. The composite scaffolds showed well interconnected pore structures and homogenous distribution of CS and PLLA when the PLLA volume fraction was not higher than 50%. Once the PLLA content increased to 75%, SEM micrographs demonstrated that the two components present phase separation region. FT-IR analysis revealed that there are strong hydrogen bond interactions between CS and PLLA components. The porosity of the CS/PLLA composites was in the range of 85–90% and showed a slight decrease with increasing PLLA dose. The mechanical properties of the composites lay between that of the pure CS and the PLLA scaffold. The compressive strength increased from 0.17 to 0.21 MPa, while the compressive modulus increased from 2.37 to 3.38 MPa as the PLLA contents increased from 25 to 75%. In vitro cytotoxicity was evaluated by MTT assay. The results indicated that MC3T3-E1 cell viability and proliferation in the CS/PLLA scaffold were comparable to that in the CS scaffold, and much higher than that in the PLLA scaffold. The successful hydrophilic polysaccharide and hydrophobic polyester system offers a new delivery method of growth factors and a novel scaffold design for tissue engineering.

Ionic liquids as foaming agents of semi-crystalline natural-based polymers

In this work, the ability to foam semi-crystalline natural-based polymers by supercritical fluid technology is evaluated. The application of this technique to natural polymers has been limited due to the fact that they are normally semi-crystalline polymers, which do not plasticize in the presence of carbon dioxide. This can be overcome by the use of plasticizers, such as glycerol, which is a commonly used plasticizer, or ionic liquids, which have recently been proposed as plasticizing agents for different polymers. Following the green chemistry principles, the main aim is, hereafter, the design and development of new 3D architectures of natural-based polymers, combining ionic liquids (IL) and supercritical fluid (SCF) technology. A polymeric blend of starch, one of the most abundantly occurring natural polymers, and poly-e-caprolactone, a synthetic polymer, which is a biodegradable aliphatic polyester commonly used in an array of biomedical applications (SPCL), was processed by supercritical fluid foaming, at different operating conditions, namely pressure (10.0 up to 20.0 MPa), temperature (35 up to 60 °C) and soaking time (30 min up to 3 h). The ionic liquid tested in this work was 1-butyl-3-methylimidazolium acetate ([bmim]Ac). The interactions between SPCL and [bmim]Ac or glycerol were analysed by Fourier transform infrared spectroscopy, differential scanning calorimetry and by mechanical tests, using both tensile and compressive modes. Morphological analysis, porosity, interconnectivity and pore size distribution of the matrixes were evaluated and the morphology was analyzed by scanning electron microscopy and by micro-computed tomography. To our knowledge the use of ionic liquids as foaming agents is reported here for the first time. The results obtained suggest that this approach can further promote the development of composite polymer–IL materials, particularly for catalysis, chromatography, extraction and separation purposes.

Easily synthesized novel biodegradable copolyesters with adjustable properties for biomedical applications

Current compositions of biodegradable aliphatic polyesters experience a number of limitations associated with the difficulty of customizing mechanical, physicochemical, and biological properties for different biomedical applications. In this study, we propose a new class of multiblock copolyesters made using butylene succinate (BS) and triethylene succinate (TES). In particular, four copolyesters with the same chemical composition but different block lengths – P(BS18TES18), P(BS9TES9), P(BS4TES4), and P(BS2TES2) – were synthesized by reactive blending. Physicochemical characterization (DSC, WAXS, tensile tests, WCA, hydrolysis experiments) demonstrated that, by simply varying block length, it is possible to control polymer crystallinity, thermal and mechanical properties, wettability, and degradation rate. Copolymers displayed different stiffness, depending on the crystallinity degree, a tunable range of degradation rates, and different surface hydrophilicity. In vitro drug release and cell culture experiments were performed to evaluate the potential of these new copolyesters in the biomedical field. In particular, fluorescein isothiocyanate (FITC) was used as a model molecule to study the release profile of small molecules, and polymer cytocompatibility and fibronectin absorption capability were assessed. Depending on comonomer distribution, the polyesters are capable of releasing FITC in a tailorable manner. Moreover, the newly developed biomaterials are not cytotoxic and they are able to absorb proteins and, consequently, to tailor cell adhesion according to their surface hydrophilicity.

Towards homogeneous dynamics in incompatible blends by selective transesterification

The evolution from two component dynamics towards homogeneous dynamics in originally incompatible blends of biodegradable aliphatic polyesters has been followed by dielectric spectroscopy. Transesterification reactions are responsible for the compatibilization process. However, our results indicate that the segmental dynamics are strongly modified even before any transesterification process is detected by 13C-NMR. This modification in the dynamics can be explained by incipient reactions at the interphase between the homopolymer rich regions, which further evolves to the interior of those phases by the formation of block copolymer of gradually decreasing block length. This process finally produces a random copolymer that forms a single phase with a single segmental relaxation.

Liquid chromatography under limiting conditions of desorption 4 separation of blends containing low-solubility polymers

Low solubility polymers, poly(ethylene terephthalate), PET and poly(butylene terephthalate), PBT were mutually separated at ambient temperature with help of a novel method, liquid chromatography under limiting conditions of desorption, LC LCD. The results demonstrate high selectivity of LC LCD, which enabled discrimination of macromolecules of well similar chemical structure, irrespectively of their molar mass. Above poly(terephthalate)s were also readily base-line separated from the aliphatic biodegradable polyesters poly( l-lactic acid) and poly(butylene adipate). The experimentally feasible LC LCD method produces narrow, focused peaks of polymers eluted behind the adsorption promoting barrier of appropriate liquid. This merit of LC LCD enables discrimination and identification of minor macromolecular constituents of multicomponent polymers and facilitates the application of method as an integral part of two-dimensional liquid chromatography for comprehensive molecular characterization of complex polymer systems.

Preparation of Fully Biodegradable Poly(L-lactide) and Poly(ethylene succinate) Blend and its Crystallization Property

Both poly(L-lactide) (PLLA) and poly(ethylene succinate) (PES) are biodegradable synthetic aliphatic polyesters with excellent biocompatibility. They are semicrystalline thermoplastic polymers processed by most conventional processing methods. In view of their complementary properties, blending PLLA with PES becomes a promising approach to improve the properties of PLLA without compromising its biodegradability. In the present work, fully biodegradable PLLA/PES blend(the weight ratio 90/10) was melt-blended in stainless steel chamber. The crystallization morphology was investigated using a polarized optical microscope (POM), showing more clear spherulites with typical crosslink extinction patterns and faster crystallization rate of PLLA in blend at the lower heating rate. It clearly showed that the addition of PES largely increased the crystallization rate of PLLA and improved the crystallinity of PLLA in blends.

生物可降解高分子形状记忆合金的研究和进展

Shape memory polymers have attracted increasing attention from researchers worldwide. Because of their low cost, remarkable recovery, advantageous mechanical and physical properties, and excellent processing performance, there has been rapid development of these materials in recent years. However, the usage of non-renewable petroleum-based chemicals for the synthesis and manufacture of commercial polymers has caused serious environmental pollution, and biodegradable and renewable materials are urgently required for industrial use. Poly(lactic acid) (PLA), a biodegradable aliphatic polyester, has the advantage of being not only biodegradable but also renewable because the raw material, lactic acid, can be produced by microbial fermentation of biomass. PLA has attracted increasing attention from both academic researchers and technologists because of its potential applications as both a biomedical material and an environmentally friendly polymer. This paper focuses mainly on the development of biodegradable shape memory polymers. The shape memory mechanism, materials selection, and the latest research progress in biodegradable shape memory polymer alloys are also discussed. In addition, we offer suggestions for future studies of PLA-based biodegradable shape memory polymer alloys.

Thermal decomposition of poly(propylene sebacate) and poly(propylene azelate) biodegradable polyesters: Evaluation of mechanisms using TGA, FTIR and GC/MS

The synthesis, characterization and thermal behavior of two biodegradable aliphatic polyesters poly(propylene azelate) (PPAz) and poly(propylene sebacate) (PPSeb) are described in the present work. The thermal degradation of both polyesters was studied using thermogravimetric analysis (TG) by the determination of their mass losses during heating. From the thermogravimetric curves it can be seen that both polyesters are thermally stable materials since PPAz has its highest decomposition rate at 411.3 while PPSeb at 413.6 °C. From the variation of activation energy ( E) with increasing degree of conversion it is found that the polyester's decomposition proceeds with a complex reaction mechanism with the participation of at least two different mechanisms. To evaluate these mechanisms the TG, FTIR and a combination of TG-gas chromatography–mass spectrometry (TG/GC–MS) methods were used. From mass ions detection of formed decomposition compounds, it was found that the decomposition of both polymers takes place, mainly, through β-hydrogen bond scission and secondarily through α-hydrogen bond scission. The main decomposition products are aldehydes, alcohols, allyl, diallyl, and carboxylic acids.

Design of reversibly core cross-linked micelles sensitive to reductive environment

Azido-functional amphiphilic macromolecules based on a biodegradable aliphatic polyester (poly-ε-caprolactone, PCL) and a bioeliminable hydrophilic poly(ethylene oxide) (PEO) block have been used in order to build micellar drug delivery systems. Such azido groups being able to react by alkyne-azide 1,3 Huisgens cycloaddition (a click reaction) have been used further in order to cross-link the micelles via redox-sensitive disulfide bridges. This reversible cross-linking allows to prevent micelle dissociation at high dilution upon injection and to trigger their dissociation in more reductive environment, such as the cytosol. Copolymers having three different architectures, i.e. able to cross-link either the core or the shell of core–shell–corona system have been used to investigate their micellization, cross-linking and cross-linking reversibility. The stealthiness of these micelles cross-linked in the hydrophobic segment has also been studied in vitro.

Kinetic Analysis of Nanocomposites Prepared in situ Consisting of an Aliphatic Biodegradable Polyester and Fumed Silica Nanoparticles

AbstractPPSu/fumed silica nanocomposites are prepared by in situ polymerization using 0.25, 0.5, 1, and 2.5 wt.‐% SiO2. The SiO2 content affects both esterification and polycondensation reactions directly. By increasing the SiO2 content in esterification, the rate of water production decreases. The reaction between PPSu and silanol groups of SiO2 is confirmed by XPS analysis. A quantitative model is developed to describe the influence of the SiO2 particles on the water production rate during esterification. The main reason for this is the adsorption of the produced water on the particles. The rate of adsorption/desorption processes is assumed to be comparable to the water evaporation rate in order to reproduce the experimental water production curves. magnified image

EFFECT OF INTERMOLECULAR HYDROGENBONDING ON CRYSTALLIZATION, MELTING AND DYNAMIC MECHANICAL BEHAVIOR OF POLY(BUTYLENE SUCCINATE) IN POLY(BUTYLENE SUCCINATE)/BISPHENOL A BLENDS

In order to investigate the effects of low molecular weight organic additives containing phenol hydroxyl group on the crystallization,melting and mechanical properties of biodegradable aliphatic polyester,poly(butylene succinate)(PBS) and bisphenol A(BAP) were selected to blend via solution mixing method.Then 13C-NMR spectroscopy was used to probe the interaction between PBS and BPA,and the effects of BPA on the crystallization,melting,glassy transition temperature(Tg) and dynamic mechanical properties were investigated using DSC(differential scanning calorimetry) and DMTA(dynamic mechanical thermal nalysis).The results indicate that hydrogen-bonding was formed between phenol hydroxyls in BPA and ester groups in PBS chain,leading to the decrease of crystallization ability and melting point for PBS,which is attributed to the formation of PBS-BPA complexes via intermolecular hydrogen-bonding that disrupts the regularity of the PBS chain structure.The storage modulus of PBS-BPA complexes decreases with the increase of BPA content above the glassy transition temperature due the decreasing of crystallization ability for PBS,while the maximun position of the loss factor shifts to high temperature.

In vitro and in vivo degradation profile of aliphatic polyesters subjected to electron beam sterilization

Degradation characteristics in response to electron beam sterilization of designed and biodegradable aliphatic polyester scaffolds are relevant for clinically successful synthetic graft tissue regeneration. Scaffold degradation in vitro and in vivo were documented and correlated to the macroscopic structure and chemical design of the original polymer. The materials tested were of inherently diverse hydrophobicity and crystallinity: poly( l-lactide) (poly(LLA)) and random copolymers from l-lactide and ε-caprolactone or 1,5-dioxepan-2-one, fabricated into porous and non-porous scaffolds. After sterilization, the samples underwent hydrolysis in vitro for up to a year. In vivo, scaffolds were surgically implanted into rat calvarial defects and retrieved for analysis after 28 and 91 days. In vitro, poly( l-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) samples degraded most rapidly during hydrolysis, due to the pronounced chain-shortening reaction caused by the sterilization. This was indicated by the rapid decrease in both mass and molecular weight of poly(LLA-co-DXO). Poly( l-lactide-co-ε-caprolactone) (poly(LLA-co-CL)) samples were also strongly affected by sterilization, but mass loss was more gradual; molecular weight decreased rapidly during hydrolysis. Least affected by sterilization were the poly(LLA) samples, which subsequently showed low mass loss rate and molecular weight decrease during hydrolysis. Mechanical stability varied greatly: poly(LLA-co-CL) withstood mechanical testing for up to 182 days, while poly(LLA) and poly(LLA-co-DXO) samples quickly became too brittle. Poly(LLA-co-DXO) samples unexpectedly degraded more rapidly in vitro than in vivo. After sterilization by electron beam irradiation, the three biodegradable polymers present widely diverse degradation profiles, both in vitro and in vivo. Each exhibits the potential to be tailored to meet diverse clinical tissue engineering requirements.

Enhanced gentamicin loading and release of PLGA and PLHMGA microspheres by varying the formulation parameters

The purpose of this study was to develop a suitable formulation for gentamicin sulfate (GS) that gives a sustained release of the drug. Therefore this drug was loaded into poly(D,L-lactide-co-glycolide) (PLGA) and poly(lactic-co-hydroxymethyl glycolic acid) (PLHMGA) microspheres. The effects of various formulation parameters (ethanol, surfactant, osmotic value of the external phase, polymer type and concentration) on particle characteristics (size, loading and release) were investigated. The GS loaded microspheres were prepared using a double emulsion evaporation technique. The results demonstrate that neither ethanol nor surfactants had beneficial effects on the drug loading efficiency (around 4-10%). However, an increase in buffer concentration (and thus osmotic pressure) of the external phase resulted in a substantial increase of GS-loading (from 10 to 28%). Further, an increase of concentration of PLGA in DCM from 10% to 15/20% caused a 4-time increase of the drug loading. The best formulation identified in this study had a loading efficiency of around 70% resulting in PLGA microspheres with a 6% (w/w) loading. The particles showed a burst release of the drug depending on their porosity, followed by a phase of 35 days where hardly any release occurred. The drug was then slowly released for around 25 days likely due to degradation of the microspheres. The drug loading efficiency of GS in PLHMGA was not significantly different from PLGA microspheres (64%). The release of GS from PLHMGA microspheres was faster than that of PLGA because the degradation rate of PLHMGA is more rapid than PLGA. This study shows that prolonged release of gentamicin can be obtained by loading this drug into microspheres made of biodegradable aliphatic polyesters.

Polylactides—Chemistry, Properties and Green Packaging Technology: A Review

Polylactide (PLA), a biodegradable aliphatic polyester, has been studied extensively for its wide applications in various fields from food packaging to interior materials for automobiles. One of PLA's advantages is that the raw material, lactic acid can be derived from renewable resources, which makes PLA very attractive for the packaging and considered as green packaging. Although, the cost of PLA is relatively higher compared to petroleum based packaging materials and it is predicted that the price will go down after commercial success of the process. This paper presents a review on polylactide with focus on its chemistry, synthesis, properties, and applications. Plasticization effect on PLA, sorption isotherm and mechanical properties of PLA based packaging materials have been discussed. PLA/layered organo nanocomposites exhibit significant improvement in mechanical, thermal, optical, and physicochemical properties over pure PLA. This review includes brief overview of PLA based nanocomposite, their mechanical properties, potential as packaging materials for industrial usage and their environmental implications.

Assessment of PHB with varying hydroxyvalerate content for potential packaging applications

Poly-(hydroxybutyrate) (PHB) is biodegradable aliphatic polyester that is produced by a wide range of microorganisms. Basic PHB has relatively high glass transition and melting temperatures. To improve flexibility for potential packaging applications, PHB is synthesized with various co-polymers such as poly-(3-hydroxyvalerate) (HV) leading to a decrease of the glass transitions and melting temperatures. In addition, the HV broadens the processing window since there is improved melt stability at lower processing temperatures. In this study, PHB synthesized with different valerate contents (5%, 12%, and 20%) and varying in molecular weights were characterized. All PHBV materials displayed a glass transition between −10 and 20 °C. The two melting transitions found for Aldrich 5%, 12%, and Tianan 20%, resulted from crystals formed during cooling of the samples. The complex viscosity decreased with increasing temperature due to a decrease in molecular weights of the samples. These results suggest that processing the co-polymer below 160 °C would be beneficial with low screw speed. The mechanical results indicate all PHBV materials had high elastic modulus and flexural strength with low tensile strength and elongation at break. The WVTR results indicated the polymer to be very hydrophilic, resulting in higher water transmission rates.

Surface modification of spruce wood flour and effects on the dynamic fragility of PLA/wood composites

AbstractPoly (lactic acid) (PLA), a biodegradable aliphatic semicrystalline polyester was filled with 40 wt% spruce wood flour (WF), to produce composite materials. Hydrothermal treatment, as well as maleic anhydride, vinyltrimethoxysilane, and stearic acid surface treatments were applied. The influence of surface modifications for WF was tested in terms of thermal, mechanical, and viscoelastic properties. The recorded results show that in both, the untreated and treated PLA/WF composites, the rigid amorphous phase content has been enhanced. The presence of WF causes a stiffness increase of the PLA/WF composites, while damping factor was decreased. The effect of wood surface modifications on interfacial compatibility with PLA was estimated by dynamic fragility parameter m calculated according the Williams‐Landel‐Ferry equation. The incorporation of untreated WF increased dynamic fragility of PLA/WF composites markedly, whereas used silane, maleic anhydride and hydrothermal treatments lead to lower values of parameter m. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers