Poly Ester Urethane Research Articles

Biodegradation of Polyester Urethane in Simulated Body Fluid

Biodegradation of the polyester urethane (PEU) has been performed in simulated body fluid (SBF) at 37°C for an extended period of time. Changes in physicochemical properties and toxic effects of polymer matrix as a result of degradation have been evaluated. Effect of soft segment to hard segment ratio on the degradation rate of PEU matrix has also been assessed. Biocompatibility testing of the degradation medium has been performed. This biodegradable coating may be used as coating on biomaterials, including implants as a matrix for entrapping antibiotics. Entrapped antibiotics would release in a control manner to prevent infection in biomaterials.

Fourier Transform Infrared Imaging to Elucidate Failures in Polyurethanes

ABSTRACTPolyurethanes are widely used, from medical devices to electrical materials to consumer goods. These materials have chemical stability issues which impact the mechanical stability. Infrared micro spectroscopy has been used to study polyurethane degradation, but due to experimental limitations, samples examined were no smaller than approximately 15 microns on a side. Because of the complex chemistry of urethanes, chemical examination of the material on a much higher spatial resolution scale would be valuable.A relatively new technique, Attenuated Total Reflection Fourier Transform Infrared Spectrochemical MicroImaging has been used to examine degraded polyester urethanes. Rather than using a single-element detector, a two dimensional array detector generates thousands of spectra simultaneously. In addition, a germanium prism generates a magnification effect; resulting in a significantly higher spatial resolution. The net output of the analysis is a hypercube of high resolution infrared spectra showing urethane degradation progression on a much smaller spatial scale than was previously possible.

Influence of silica nanofiller on the isothermal crystallization and melting of polyurethane elastomer

AbstractIn this article, isothermal crystallization kinetic of the linear hydroxyl polyester urethane (PUR), as well as influence of amorphous silica nanofiller, was investigated. With the aim to investigate the influence of filler surface modification on the crystallization process of polyurethane matrix, nonmodified silica, as well as silica modified with methacrylsilane and octylsilane, were used as fillers for PUR composite preparation. The crystallization kinetics depending on temperature of the isothermal crystallization and volume fraction of filler by using differential scanning calorimetry (DSC) were investigated. The measurements at temperatures 7, 12, and 17°C for PUR and composites with 0.5, 1, 2, and 4 vol % of filler were done. Kinetic parameters of the isothermal crystallization n and K were determined according to Avrami model. Melting of the isothermally crystallized samples was also investigated. Results of the research indicate that by increasing the isothermal crystallization temperature, the crystallization rate of the PUR soft phase decreases and that the perfection of the crystallites is improved. By addition of all fillers up to ≈1 vol %, the crystallization rate increases; however, addition of a higher amount of the filler significantly decreases the crystallization rate. It was found that surface modification can significantly affect crystallization rate and that the nucleation efficiency of silica increases in the following order: methacrylsilane‐modified silica < nonmodified silica < octylsilane‐modified silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Therapeutic nanoparticles from novel multiblock engineered polyesterurethanes

A novel biodegradable material belonging to the class of polyester-urethanes (PURs), based on poly(e-caprolactone) (PCL) blocks, was proposed as matrix-forming material for the preparation of nanoparticles by the solvent displacement method. This method has been widely applied to prepare nanoparticles with reproducible, small size with commercially available polyesters or polyester–polyether copolymers. These carriers often displayed fast and poorly controllable release rates. In response to these problems we proposed the insertion of polyesters into a more complex microstructure, such as that of polyurethanes, characterized by the alternation of hard and soft segments, in order to modulate and control the degradation rate and release profiles. PCL-based PUR (C-BC2000) was synthesized according to a two step synthesis procedure. Commercial PCL and poly(d, l lactide) (PLA) were used as controls; and paclitaxel, a potent anti-neoplastic drug, was encapsulated inside all carriers. Carriers prepared with the new material showed no intrinsic cytotoxicity (A-431 cells), with similar size in the range 211–226 nm and surface charge as the commercial controls. Moreover, C-BC2000 nanoparticles exhibited a slightly faster degradation rate, a much higher encapsulation efficiency (89 % against 24 % and 18 % for PLA and PCL, respectively) and a longer and more controlled release profile. This study highlighted the possibility to successfully employ biodegradable polyurethanes to prepare particles for controlled drug delivery, suggesting further and extensive investigation on the introduction of different PUR formulations in this field.

Synthesis, characterization and histomorphometric analysis of cellular response to a new elastic DegraPol® polymer for rabbit Achilles tendon rupture repair

Tendon rupture repair is a surgical field where improvements are still required due to problems such as repeat ruptures, adhesion formation and joint stiffness. In the current study, a reversibly expandable and contractible electrospun tube based on a biocompatible and biodegradable polymer was implanted around a transected and conventionally sutured rabbit Achilles tendon. The material used was DegraPol® (DP), a polyester urethane. To make DP softer, more elastic and surgeon-friendly, the synthesis protocol was slightly modified. Material properties of conventional and new DP film electrospun meshes are presented. At 12 weeks post-surgery, tenocyte and tenoblast density, nuclei and width, collagen fibre structure and inflammation levels were analyzed histomorphometrically. Additionally, a comprehensive histological scoring system by Stoll et al. (2011) was used to compare healing outcomes. Results showed that there were no adverse reactions of the tendon tissue following the implant. No differences were found whether the DP tube was applied or not for both traditional and new DP materials. As a result, the new DP material was shown to be an excellent carrier for delivery of growth factors, stem cells and other agents responsible for tendon healing.

A study of radiation effects on polyester urethane using two-dimensional correlation analysis based on thermogravimetric data

Polyester-urethane adhesive was irradiated by gamma rays at various radiation doses. Thermogravimetric analysis (TGA) and infrared attenuated total reflection (ATR) spectroscopy were used to study the radiation effects. Particularly, 2D correlation techniques were employed to study the derivative thermogravimetry (DTG) data. The results of the synchronous and asynchronous 2D correlation spectra are analyzed and discussed. Three decomposition pathways in the urethane linkages, and two decomposition mechanisms of the polyester in soft segments were proved. Besides, we obtained the sequential order of several polyester-urethane adhesive decomposition ranges along the perturbation variable (radiation dose), which showed the soft segments in polyester-urethane were affected by gamma radiation first, whilst the hard segments latest. These results could not be obtained only from the DTG data. In addition, we summarized the gamma radiation effects on polyester-urethane adhesive based on the results we observed.

Synthesis of urethane acrylate from PENTA based polyol and EB curing with varying ratio of TMTPA

PurposeUrethane Acrylate Oligomer with 100% solids was synthesised and characterised in order to study the application in electron beam curing with varying ratio of Trimethylol propane triacrylate (TMPTA). The purpose of this paper is to study effect of TMPTA addition on the crosslink density and different coating properties.Design/methodology/approachPolyester polyol was synthesised by reacting single diacid, adipic acid (AA), with Pentaerythritol (PENTA) and 1,6‐hexanediol (HD). Further, Urethane acrylate resin was synthesised by using Isophorone diisocyanate (IPDI), hydroxy ethyl acrylate (HEA) and Polyester polyol. The polyester polyol and urethane acrylate oligomer were characterised by 1H NMR, 13C NMR, FTIR and GPC. Further, TMPTA was added as a crosslinker to the urethane acrylate oligomer and cured by electron beam radiation. The cured UA films having varying concentration of TMPTA were employed to evaluate thermal property, contact angle analysis, mechanical and chemical properties.FindingsThe obtained results showed improvement in their chemical properties, mechanical properties, thermal properties and water contact angle at 20% of TMPTA iconcentration. The TMPTA also reduced the dose required for the curing.Research limitations/implicationsThe resin can be synthesised from different isocyanates as TDI, MDI and HMDI, etc. The study can also be done with different multi or mono functional monomers such as methacrylate, hexanediol diacrylate, ethylene glycol diacrylate, etc.Practical implicationsThe paper provides the better solution to reduce the cost of the electron beam radiation required for the curing.Social implicationsThe method presented in the paper could be very useful for controlling environmental pollution; as the conventional method of curing releases volatile organic compounds (VOC).Originality/valueIn this paper, urethane acrylate and TMTPA cured with electron beam are shown to offer good coating properties. A high‐solid urethane acrylate coating would find numerous industrial applications in surface coatings.

Reinforcement properties of 3-aminopropylmethyldiethoxysilane and N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane on polyurethane ester foam

Museum artifacts made of polyurethane foam are frequently affected by conservation issues mainly related to the loss of their mechanical properties. While effective polyurethane ether foam treatments already exist, no convenient consolidation treatment exists for polyurethane ester foams. The possibility of a reinforcement effect expected to prevent the mechanical properties loss has been evaluated. Two aminoalkylalcoxysilanes (AAAS), the 3-Aminopropylmethyldiethoxysilane and the N-(2-Aminoethyl)-3-aminopropylmethyldimethoxysilane, which gave promising results for consolidation of paper, have been tested on modern industrial flexible polyurethane ester foam samples. AAAS solutions at different concentrations have been applied, by immersion, on polyurethane ester foam samples. Mechanical properties have been studied by Compression Force Deflection Test, which shows that after AAAS treatment the resistance of the foam to compression improves. The color of the samples before and after consolidation has been monitored to assess the impact of the treatment on the visual aspect of the foam. The AAAS distribution in the thickness of the samples has been investigated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Magic angle spinning nuclear magnetic resonance (MAS NMR) has been used to confirm AAAS polymerization and to evaluate its average polymer chain length. The promising results obtained suggest that AAAS could be an efficient solution for the consolidation of polyurethane ester foams.

Effects of guar gum content on structure and properties of multi-crosslinked polyurethane composite films

Films from multi-crosslinked polyurethane with different contents of guar gum (1–10wt%) were prepared through a solution-casting method, followed by a thermal treatment or natural light exposure crosslinking procedure. Acrylic terminated prepolymers were prepared by capping the NCO groups of polyurethane prepolymers with pentaerythritol triacrylate. The effect of the guar gum content on the miscibility, morphology and physical properties of the blend films was investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, surface properties and tensile tests. The results reveal that small guar gum content is well embedded in the crosslinked polyurethane network and forms films with good mechanical properties, thermal behavior and hydrophilic properties. These results prove guar gum to be eco-friendly filler for multi-crosslinked polyurethane network. In the case of polyether urethanes, incorporating up to 3wt% guar gum leads to a slight enhancement of the elongation at break, while for polyester urethanes incorporation up to 3wt% guar gum slight increases stress at break values. Incorporating guar gum into the polyurethane networks leads to an increase in the hydrophilic nature of the polymer blends and improved surface structure. The properties of guar gum – which can be abundantly found in nature – make it desirable for polymer blends for biomedical applications.

Effect of the solubility of antibiotics on their release from degradable polyurethane

Application of biodegradable polyester urethane, as a drug loading matrix in the form of a coating on implant devices was investigated. Polyester urethane films were loaded with model antibiotics, like rifampicin, gentamicin and ciprofloxacin and their release characteristics were evaluated in simulated body fluid. Effect of solubility of antibiotics and degradation of matrix on the drug release behavior of biodegradable polyester urethane coating was also studied. It was observed that antibiotics having hydrophilicity or lipophilicity same as that of polymer matrix provide an extended release with relatively less initial burst release. Effect of degradation of polymer matrix has a dual significance in this case and the drug release rate increases with the increase in degradation rate. A high initial burst release was observed for antibiotics having hydrophilicity or lipophilicity opposite to that of polyurethane matrix and hence in this case antibiotic release was not significantly controlled by degradation of matrix.

Placement of an Elastic Biodegradable Cardiac Patch on a Subacute Infarcted Heart Leads to Cellularization With Early Developmental Cardiomyocyte Characteristics

BackgroundPlacement of an elastic biodegradable patch onto a subacute myocardial infarct (MI) provides temporary elastic support that may act to effectively alter adverse left ventricular (LV) remodeling processes. MethodsTwo weeks after permanent left coronary ligation in Lewis rats, the infarcted anterior wall was covered with polyester urethane urea (MI + PEUU; n = 15) or expanded polytetrafluoroethylene (MI + ePTFE; n = 15) patches, or had no implantation (MI + sham; n = 12). Eight weeks after surgery, cardiac function and histology were assessed. ResultsThe ventricular wall in the MI + ePTFE and MI + sham groups was composed of fibrous tissue, whereas PEUU implantation induced α-smooth muscle actin–positive muscle bundles coexpressing sarcomeric α-actinin and cardiac-specific troponin-T. This pattern of colocalization was also found in developing embryonic myocardium. Cardiac transcription factors Nkx-2.5 and GATA-4 were strongly expressed in the muscle bundles. In the MI + sham group, end-diastolic LV cavity area (EDA) increased and the percentage of fractional area change (%FAC) decreased. For ePTFE patched animals, both EDA and %FAC decreased. In contrast, with MI + PEUU patching, %FAC increased and EDA was maintained. With dobutamine-stress echocardiography, MI + PEUU patched LVs possessed contractile reserve significantly larger than the MI + sham group. ConclusionsMI + PEUU patch implantation onto subacute infarcted myocardium induced muscle cellularization with characteristics of early developmental cardiomyocytes as well as providing a functional reserve.

Antimicrobial electrospun nanofibers of cellulose acetate and polyester urethane composite for wound dressing

In this study, a series of nanofibrous membranes were prepared from cellulose acetate (CA) and polyester urethane (PEU) using coelectrospinning or blend-electrospinning. The drug release, in vitro antimicrobial activity and in vivo wound healing performance of the nanofiber membranes were evaluated for use as wound dressings. To prevent common clinical infections, an antimicrobial agent, polyhexamethylene biguanide (PHMB) was incorporated into the electrospun fibers. The presence of CA in the nanofiber membrane improved its hydrophilicity and permeability to air and moisture. CA fibers became slightly swollen upon contacting with liquid phase. CA not only increased the liquid uptake but also created a moist environment for the wound, which accelerated wound recovery. PHMB release dynamics of the membranes was controlled by the structure and component ratios of the membranes. The lower ratio of CA: PEU helped to preserve the physical and thermal properties of the membranes, and also reduced the burst release effectively and slowed down diffusion of PHMB during in vitro tests. The controlled-diffusion membranes exerted long-term antimicrobial effect for wound healing.

Enhancing the biological performance of synthetic polymeric materials by decoration with engineered, decellularized extracellular matrix

Materials based on synthetic polymers can be extensively tailored in their physical properties but often suffer from limited biological functionality. Here we tested the hypothesis that the biological performance of 3D synthetic polymer-based scaffolds can be enhanced by extracellular matrix (ECM) deposited by cells in vitro and subsequently decellularized. The hypothesis was tested in the context of bone graft substitutes, using polyesterurethane (PEU) foams and mineralized ECM laid by human mesenchymal stromal cells (hMSC). A perfusion-based bioreactor system was critically employed to uniformly seed and culture hMSC in the scaffolds and to efficiently decellularize (94% DNA reduction) the resulting ECM while preserving its main organic and inorganic components. As compared to plain PEU, the decellularized ECM-polymer hybrids supported the osteoblastic differentiation of newly seeded hMSC by up-regulating the mRNA expression of typical osteoblastic genes (6-fold higher bone sialoprotein; 4-fold higher osteocalcin and osteopontin) and increasing calcium deposition (6-fold higher), approaching the performance of ceramic-based materials. After ectopic implantation in nude mice, the decellularized hybrids induced the formation of a mineralized matrix positively immunostained for bone sialoprotein and resembling an immature osteoid tissue. Our findings consolidate the perspective of bioreactor-based production of ECM-decorated polymeric scaffolds as off-the-shelf materials combining tunable physical properties with the physiological presentation of instructive biological signals.

Stereocomplexes from Biosourced Lactide/Butylene Succinate‐Based Copolymers and Their Role as Crystallization Accelerating Agent

AbstractBiosourced co(polyester urethane)s containing different ratios of enantiomeric oligo(L‐ or D‐ lactide) (OLLA/ODLA) sequences and oligo(butylene succinate) (OBS) blocks (P(OD(L)LA‐b‐OBS)) are synthesized. Their stereocomplexation is confirmed by differential scanning calorimetry and X‐ray diffraction. The process is efficient independently on the OLA/OBS ratio and for OLLA/ODLA ratios from 2:3 to 3:2. The preformed stereocomplexes show remarkable crystallization accelerating efficiency when melt‐blended with a commercial PLLA in amounts from 2.5 to 10 wt%. Spectacular increase in the polyester matrix crystallinity (from 2 up to 42%) and crystallization rate (half‐time of ca. 3 min compared to ca. 30 min for the neat PLLA) is observed.

Effect of external influences on the structural and dynamic parameters of polyhydroxybutyrate-hydroxyvalerate-based biocomposites

The EPR probe, DSC, and WARDX methods are applied to study the molecular dynamics and structure of 3-hydroxybutyrate-3-hydroxyvalerate copolymer (PHBHV, 5 mol %) and its mixtures with segmented polyester urethane (SPEU) upon ozone oxidation and hydrothermal treatment. It is shown that time-limited (3 and 5 h) treatment of the mixed compositions with water at 40°C has no noticeable effect on the dynamics of rotation of the probe (EPR) and the crystallinity of PHBHV (DSC). However, hydrothermal treatment at 70°C causes an increase in the molecular mobility of the probe in the system, accompanied, according to XRD and DSC analyses, by increases in the degree of crystallinity and density of PHBHV crystallites. The temperature of fusion of mixed compositions also increases. During ozonation, the mobility of the probe slows gradually in PHBHV all the time, whereas in mixed compositions, a slowdown is observed only up to 3 h of oxidation time, after which, up to 5 h of ozonation, the mobility increases, along with decreases in the fraction of the amorphous phase and in the density of the crystallites.

Polyacylurethanes as Novel Degradable Cell Carrier Materials for Tissue Engineering.

Polycaprolactone (PCL) polyester and segmented aliphatic polyester urethanes based on PCL soft segment have been thoroughly investigated as biodegradable scaffolds for tissue engineering. Although proven beneficial as long term implants, these materials degrade very slowly and are therefore not suitable in applications in which scaffold support is needed for a shorter time. A recently developed class of polyacylurethanes (PAUs) is expected to fulfill such requirements. Our aim was to assess in vitro the degradation of PAUs and evaluate their suitability as temporary scaffold materials to support soft tissue repair. With both a mass loss of 2.5–3.0% and a decrease in molar mass of approx. 35% over a period of 80 days, PAUs were shown to degrade via both bulk and surface erosion mechanisms. Fourier Transform Infra Red (FTIR) spectroscopy was successfully applied to study the extent of PAUs microphase separation during in vitro degradation. The microphase separated morphology of PAU1000 (molar mass of the oligocaprolactone soft segment = 1000 g/mol) provided this polymer with mechano-physical characteristics that would render it a suitable material for constructs and devices. PAU1000 exhibited excellent haemocompatibility in vitro. In addition, PAU1000 supported both adhesion and proliferation of vascular endothelial cells and this could be further enhanced by pre-coating of PAU1000 with fibronectin (Fn). The contact angle of PAU1000 decreased both with in vitro degradation and by incubation in biological fluids. In endothelial cell culture medium the contact angle reached 60°, which is optimal for cell adhesion. Taken together, these results support the application of PAU1000 in the field of soft tissue repair as a temporary degradable scaffold.

Molecular Dynamics of Linear and Crosslinked Polyester Urethanes Studied by Dielectric Spectroscopy

The molecular dynamics of crosslinked polyurethanes have been studied by dielectric spectroscopy and compared with the dynamics of linear polyurethanes. Two local relaxations, γ and β, and a primary relaxation, α, were observed for all the samples, appearing in relation with the increase in temperature. The conductivity was studied at temperatures higher than the glass transition temperature and it was found to decrease with the increasing content of crosslinker. The presence of crosslinks strongly influences their dielectric properties, especially in the elastic state. The linear polyurethane exhibits the lowest α-relaxation temperature. For the crosslinked samples, α-relaxation temperature increases with increase in the amount of crosslinkers; β- and γ-relaxations are less affected by chemical crosslinking and their activation energies are in the ranges 40–55 and 34–37 kJ/mol, respectively. For the linear polyurethane, there is an exception in the case of the γ-relaxation, which has a higher activation energy determined by its physical crosslinks. Conductivity analysis reveals a high mobility of charge carriers and low barriers for the transport of the charged particles. Also, the conductivity process is dependent on the segmental mobility of polymers.

Patterning human stem cells and endothelial cells with laser printing for cardiac regeneration

Recent study showed that mesenchymal stem cells (MSC) could inhibit apoptosis of endothelial cells in hypoxic condition, increase their survival, and stimulate the angiogenesis process. In this project we applied Laser-Induced-Forward-Transfer (LIFT) cell printing technique and prepared a cardiac patch seeded with human umbilical vein endothelial cells (HUVEC) and human MSC (hMSC) in a defined pattern for cardiac regeneration. We seeded HUVEC and hMSC in a defined pattern on a Polyester urethane urea (PEUU) cardiac patch. On control patches an equal amount of cells was randomly seeded without LIFT. Patches were cultivated in vitro or transplanted in vivo to the infarcted zone of rat hearts after LAD-ligation. Cardiac performance was measured by left ventricular catheterization 8 weeks post infarction. Thereafter hearts were perfused with fluorescein tomato lectin for the assessment of functional blood vessels and stored for histology analyses. We demonstrated that LIFT-derived cell seeding pattern definitely modified growth characteristics of co-cultured HUVEC and hMSC leading to increased vessel formation and found significant functional improvement of infarcted hearts following transplantation of a LIFT-tissue engineered cardiac patch. Further, we could show enhanced capillary density and integration of human cells into the functionally connected vessels of murine vascular system. LIFT-based Tissue Engineering of cardiac patches for the treatment of myocardial infarction might improve wound healing and functional preservation.

Parameters affecting transition temperatures of poly(lactic acid‐co‐polydiols) copolymer‐based polyester urethanes and their shape memory behavior

A series of polyester urethanes (PEUs) comprising poly(lactic acid‐co‐polydiol) copolymers as a soft segment, 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (BDO) as a hard segment were systematically synthesized. Soft segments, which were block copolymers of L‐lactide (LA) and polydiols such as poly(ethylene glycol) and poly(trimethylene ether glycol), were prepared via ring opening polymerization. Glass transition temperatures (Tg) of the obtained PEUs were found strongly dependent on properties of copolymer soft segments. By simply changing composition ratio, type and molecular weight of polydiols in the soft segment preparation step, Tg of PEU can be varied in the broad range of 0–57°C. The synthesized PEUs exhibited shape memory behavior at their transition temperatures. PEUs with hard segment ratio higher than 65 mole percent showed good shape recovery. These findings suggested that it is important to manipulate molecular structure of the copolymer soft segment for a desirable transition temperature and design optimal soft to hard segment ratio in PEU for good shape recovery. Copyright © 2011 John Wiley & Sons, Ltd.

Design of Cross‐Linked Semicrystalline Poly(ε‐caprolactone)‐Based Networks with One‐Way and Two‐Way Shape‐Memory Properties through Diels–Alder Reactions

Cross-linked poly(ε-caprolactone) (PCL)-based polyesterurethane (PUR) systems have been synthesized through Diels-Alder reactions by reactive extrusion. The Diels-Alder and retro-Diels-Alder reactions proved to be useful for enhancing the molecular motion of PCL-based systems, and therefore their crystallization ability, in the design of cross-linked semicrystalline polymers with one-way and two-way shape-memory properties. Successive reactions between α,ω-diol PCL (PCL(2) ), furfuryl alcohol, and methylene diphenyl 4,4'-diisocyanate straightforwardly afforded the α,ω-furfuryl PCL-based PUR systems, and subsequent Diels-Alder reactions with N,N-phenylenedimaleimide afforded the thermoreversible cycloadducts. The cross-linking density could be modulated by partially replacing PCL-diol with PCL-tetraol. Interestingly, the resulting PUR systems proved to be semicrystalline cross-linked polymers, the melting temperature of which (close to 45 °C) represented the switching temperature for their shape-memory properties. Qualitative and quantitative measurements demonstrated that these PUR systems exhibited one-way and two-way shape-memory properties depending on their cross-linking density.