Poly Ether Urethane Research Articles

Oxidative degradation of Biomer fractions prepared by using preparative-scale gel permeation chromatography.

The possibility that some macromolecular chains within a chemically heterogeneous polyether-urethane (PEU) may be more susceptible to degradation than others has been investigated. Preparative scale gel permeation chromatography has been used to separate chemically different fractions of a sample of the commercial PEU, Biomer. The fractions were characterized and then tested for susceptibility to oxidative degradation by exposing them to hydrogen peroxide. After exposure to hydrogen peroxide, the samples were analyzed using high pressure gel permeation chromatography (HPGPC), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). By using these methods, we were able to identify chemical changes in some of the Biomer fractions but not in others. Clear differences in the chemistry and reactivity of the fractions were observed. Changes in the weight average molecular weight varied from a decrease of 55.8% to an increase of 3.9%. A decrease in hard segment content at the surface and in the bulk was observed in some samples, but opposite trends were observed in others. The evidence suggests that there may be a number of mechanisms by which hydrogen peroxide can react with PEUs. Some fractions separated from the Biomer were not significantly affected by concentrated hydrogen peroxide solutions. This suggests an intrinsic stability in some PEUs and points the way to the development of more degradation-resistant PEUs.

Studies on the tumor-promoting activity of biomaterials: inhibition of metabolic cooperation by polyetherurethane and silicone.

When V79 metabolic cooperation (MC) assay was performed to detect tumor-promoting activities, inhibitory activities on the gap-junctional intercellular communication were first detected in both extracts prepared from polyetherurethane (PEU) and silicone. The former inhibited more strongly than the latter. Furthermore, the lowest effective concentrations in MC assay correlated well with the values of the total active incidences obtained by histologic evaluation of the 2-year implantation test in rats. Poly(tetramethylene oxide) (PTMO) showed the highest inhibitory activities among the constituents of PU. Thus, the shorter the chain length of PTMO, the stronger the inhibitory activities of PTMO in MC assay. PTMO moiety may play an important role in the tumor-promotion stage during tumorigenesis induced by PU.

Synthesis and properties of unsaturated polyester diol–polyurethane hybrid polymer network

AbstractThis article deals with the synthesis and properties of poly[(propylene glycol maleate)‐co‐(propylene glycol phthalate)] diol (PGMPD)/polyester–urethane or polyether–urethane hybrid polymer networks (HPNs). The polyurethane type and the molar ratio of NCO/OH have an effect on their properties. The structure–property relationship is discussed as well. © 1994 John Wiley & Sons, Inc.

Studies on the causes of tumorigenesis induced by the biomaterials

V79 metabolic cooperation (MC) assay was performed to detect the tumor-promoting activities of polyetherurethane (PEU), silicone and the additives of antioxidants. The inhibitory activities on the MC were first detected in both extracts prepared from PEU and silicone. PEU inhibited stronger than silicone, and furthermore the monomer of the soft segment of PEU showed the highest inhibitory activities among the constituents. As for the additives, three chemicals among eight antioxidants showed stronger inhibitory activities than BHT, a tumor promoter. Therefore, we propose that there is a possibility of tumor-promotion caused by these chemicals as well as soft segment rich oligomers extractable from the PEU.

Ionic Conductivity and 7Li NMR Study of Solid Polymer Electrolytes Based on Polyetherurethane Copolymer Networks

Crosslinked polyetherurethane (PEU) copolymer networks consisting of the low molecular weight poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) segments with an aliphatic diisocyanate were synthesized and complexed with a LiClO 4 salt to form solid polymer electrolytes. The ionic conductivities of these samples were measured as a function of PEO composition at various temperatures and a solid 7 Li NMR relaxation technique was used as a means of understanding the local environments and dynamics of the lithium ions in the polymer electrolytes. The difference in spin-spin relaxation times (T 2 ) between two spectral components enabled to their separation, and thus we could monitor the mobile Li + ion concentration and its motion as a function of PEO composition and temperature

New fluorinated oxazoline block copolymer lowers the adhesion of platelets on polyurethane surfaces

AbstractWe have prepared an amphiphilic oxazoline block copolymer of hydrophilic poly(2‐methyl‐2‐oxazoline) and hydrophobic poly[2‐(2‐perfluorooctyl)ethyl‐2‐oxazoline] chains. By controlling the length and composition of polymer chains, we found that this fluorinated block copolymer can be readily dissolved in water. Furthermore, we can achieve a stable surface coating of the fluorinated block copolymer by dissolving the copolymer in water, then coating the aqueous copolymer solution onto surfaces of nonwater‐soluble polymers. This is a simple and useful method of modifying the surface character of polymer substrates. We have found that the polyether urethane (PEU) coated by block copolymer has a different surface chemistry and biological reactivity than the uncoated PEU. From XPS analysis, we found the fluorinated copolymer was coated on PEU (atomic % of F: 31.3 on coated PEU, 0.3 on uncoated). The two surfaces have different affinities for biological molecules. Specifically, the fibrinogen adsorption on the fluorinated copolymer‐coated PEU was 62 ± 39 ng/cm2, compared to a value of 156 ± 99 ng/cm2 for uncoated PEU. In an ex vivo evaluation of platelet adhesion, the surface of coated PEU attached a few white cells while uncoated PEU was covered with activated platelets. © 1994 John Wiley & Sons, Inc.

Activation of human neutrophils by organic polymer surfaces

By means of lucigenin-dependent chemiluminescence it has been demonstrated that films of organic polymers activate human neutrophils. The strongest response was always induced by polyvinyl chloride-D and the smallest by polyethylene. No significant differences were found between the number of adherent cells on the surfaces of the investigated materials. The stimulatory capacity of the organic polymers were changed after adsorption of some plasma proteins. These effects were not connected with similar alterations of cell attachment. A second stimulation by opsonized zymosan was only possible for neutrophils adherent to polyether urethane and polyvinyl chloride-D.

Synthesis of new siloxane urethane block copolymers and their properties

AbstractSiloxane urethane block copolymers were prepared with siloxanes as the soft segment. Films were cast from a variety of solvents. Solvent has an effect on the segregation of soft and hard segments. Surface studies, including ESCA, EDS, and FT‐IR, show well segregated block copolymers with enhanced siloxane on the surface. DSC studies show a low mp (‐44°C) for the soft segment and a Tg for the hard segment above room temperature. These materials show higher thermal stability compared to polyether urethane block copolymers. These copolymers also show relatively good resistance to exposure to oxygen plasma and show improved flame retardancy compared to nonsiliconated, polyether polyurethane block copolymers. © 1994 John Wiley & Sons, Inc.

Degradation of polyetherurethane by subcutaneous implantation into rats. I. Molecular weight change and surface morphology

Two kinds of polyetherurethane (PEU), U-3 and U-8, were coated in thin layers on an ethylene-vinylalcohol copolymer (EVAL) film 0.1 mm thick. U-3 is a nonsegmented PEU prepared from 4,4'-diisocyanatodiphenylmethane (MDI) and poly(tetramethylene oxide) of Mn = 1,000 (PTMO 1000), and U-8 is a segmented PEU prepared from MDI, PTMO 1000, and 1,4-butanediol. The coating thicknesses were 0.0068 and 0.022 mm for U-3 and U-8, respectively. These coated films were implanted subcutaneously into rats and retrieved after various weeks. The coatings on the retrieved samples were dissolved in tetrahydrofuran (THF), and the average molecular weight (MW) was determined by injecting the THF solution into a gel permeation chromatograph. In the case of U-3, MW increased after 2 weeks, then decreased over the implantation period. After 10 weeks, U-3 almost disappeared from the base film. In the case of U-8, MW reached the maximum at 4 weeks postimplantation then decreased gradually over the implantation period. The rate and degree of MW change were greater in U-3 than in U-8. Here, we argue that, in the early stage, low molecular weight PTMO/MDI oligomers leached out from the PEUs to the inflammatory exudate to increase MW, and in the later stage macrophage attachment/activation had a role in the degradation of PEUs. The surface morphologic changes observed by scanning electron microscopy are also discussed.

Phosphonated polyurethanes that resist calcification.

Cardiovascular implant mineralization involving bioprosthetic materials, such as glutaraldehyde cross linked porcine aortic valves or synthetic materials such as polyurethanes, is an important problem that frequently leads to clinical failure of bioprosthetic heart valves, and complicates long-term experimental artificial heart device implants. Novel, proprietary, calcification resistant polyetherurethanes (PEU) as an alternative to bioprosthetic materials were the subject of these investigations. A series of PEU was derivatized through a proprietary reaction mechanism to achieve covalent binding of 100 to 500 nM/mg of bisphosphonate (2-hydroxyethane bisphosphonic acid, HEBP). The stability of HEBP (physically dispersed or covalently bound) verified by studying the release kinetics in physiological buffer (pH 7.4) at 37 degrees C, demonstrated the covalent binding reaction to be stable, efficient, and permanent. Surface (FTIR-ATR, ESCA, SEM/EDX) and bulk (solubility, GPC) properties demonstrated that the covalent binding of HEBP occurs in the soft segment of the PEU, reduces surface degradation, and does not affect the original material properties of the PEU (prior to derivatization). In vitro calcium diffusion of the derivatized PEU showed a decrease in calcium permeation as the concentration of HEBP covalent binding was increased. In vivo properties of underivatized and derivatized PEU (containing 100 nM of covalently bound HEBP) were studied with rat subdermal implants for 60 days. Explants demonstrated calcification resistance due to the covalently bound HEBP without any side effects. It is concluded that a PEU containing HEBP might serve as a calcification resistant candidate material for the fabrication of a heart valve prosthesis and other implantable devices.

Materials chemistry communications. 13C Nuclear magnetic resonance spectroscopic study of plasticization in solid polymer electrolytes

Preliminary results are presented on the correlation between enhanced solvent mobility and ionic conductivity in plasticized polyether–urethane solid polymer electrolytes using 13C nuclear magnetic resonance spectroscopic spin–lattice relaxation time measurements to probe polymer mobility.

Protein adsorption and platelet adhesion onto polyurethane grafted with methoxy-poly(ethylene glycol) methacrylate by plasma technique.

Graft polymerization of methoxy-poly(ethylene glycol) methacrylate, an ester of methacrylic acid and monomethoxy-poly(ethylene glycol) (PEO), was performed onto a polyetherurethane (PU) film and tube under different polymerization conditions by a plasma treatment technique. The surface of grafted PU film was characterized by staining with dye, x-ray photoelectron spectroscopy, contact angle, and zeta potential. All these measurements indicated that water-soluble chains were immobilized on the PU surface, their location being restricted to the film surface region. The PU surface showed reduced protein adsorption in vitro and reduced platelet adhesion in vitro and ex vivo. The optimum graft density suppressing the protein adsorption was as low as 5 micrograms cm(-2). When a small amount of dimethacrylate was added to the monomer solution for graft polymerization to introduce crosslinking in the grafted layer, protein adsorption was further slightly reduced. The extent of reduction in serum albumin adsorption was always less than that of gamma-globulin. Although platelet adhesion was largely reduced by the surface graft polymerization, a definite amount of protein was always adsorbed to the grafted surface.

Degradation of polyurethanes in vitro and in vitro: comparison of different models

This study compares and contrasts mechanisms of polyetherurethane (PEU) degradation in vitro and in vivo. Models comprising incubation with hydrogen peroxide in vitro (H 2O 2), in vivo subcutaneous rat implant (SUBQ), and subcutaneous rat cage implant (CAGE) are described and compared with in vivo degradation of the pacemaker lead device retrieved after human implant (PACE). Experimental results support the hypothesis that stress accelerates PEU degradation. Scanning electron microscopy (SEM), gel permeation chromatography (GPC), and Fourier transform IR spectroscopy/attenuated total reflectance (FT-1R/ATR) evaluation of tested PEU samples suggests, for all models, decreased soft segment and increased ester functionality at the polymer surface. These observations are consistent with a single, metal ion catalyzed, polyester intermediate, oxidative degradation mechanism common to all models, and with device performance in vivo. Model comparison suggests that in vitro H 2O 2 and in vivo SUBQ and CAGE models accurately mimic in vivo degradation of the pacemaker lead device (PACE).

Effect of polyol type on the physical properties and thrombogenicity of sulfonate‐containing polyurethanes

Polyetherurethanes (PEUs) based on polytetramethylene oxide (PTMO) as the polyol, and derivatized with propyl sulfonate functionality, have previously been shown to possess antithrombotic properties. In this article, the bulk physical properties of sulfonated and nonsulfonated polyurethanes containing either polyethylene oxide (PEO) or PTMO as the soft segment are studied. The in vitro shape-change of platelets in contact with these surfaces, and their ex vivo blood-contacting response are also investigated. It was found that PEO-base was physically weaker than PTMO-base, which is attributed to a lower degree or phase separation in the former. In the dry state, sulfonation enhanced the physical properties for PTMO-containing polyurethane (PTMO-SO3-0.20), but weakened the PEO-containing polyurethane (PEO-SO3-0.15). In vitro platelet spreading studies showed the lowest degree of platelet spreading and also the lowest platelet density on PEO-base, while platelet spreading and density on the other three materials and polyethylene (PE) was greater. The thromboresistance of these materials was evaluated using a canine arteriovenous series shunt ex vivo. It was determined that PTMO-SO3-0.20 was the least thrombogenic, followed by both PEO-base and PEO-SO3-0.15, and that PTMO-base was the most thrombogenic.

Studies on the dynamic mechanical and vibration damping properties of polyether urethane and epoxy composites

AbstractThe dynamic mechanical and vibration damping properties of polyether urethane and epoxy composites have been studied. The experiment results show: the crosslink density is an important factor that influences the loss factor of polyether urethane damping materials; increasing the amount of pendant methyl of the backbone contributes to raising the value of the loss factor (tan δ) and broadens the damping temperature range; adding the planar filler can increase the shear motion and the internal dissipation in polyurethane materials. As the thickness ratio and the Young's modulus of the constraining layer increase, the composite loss factor (η) increases significantly. © 1993 John Wiley & Sons, Inc.

Dynamic-mechanical properties and cross-polarized, proton-enhanced, magic angle spinning 13C-NMR time constants of urethane acrylates—1. Homopolymer networks

Dynamic-mechanical properties have been measured for a series of urethane acrylates containing polyether and polyester soft segments. Polymer glass transition temperatures predicted from a crosslinking relation showed better agreement with experimental T g values than those obtained from applying the Fox equation to hard and soft segments in the polymer. Proton-enhanced, magic angle spinning 13C-NMR time constants were obtained for a polyether soft segment urethane acrylate series. Increasing soft segment molecular weight resulted in a release of both near static and high frequency (mid-kHz) components of motion in the soft segment.

Amide I absorption band: description of the urethane group association scheme in polyether urethane elastomers

On the strength of analysis of the amide I absorption band contour of the i.r. spectra of polyether urethane elastomers based on poly(tetramethylene oxide), poly(propylene oxide) and 4,4′-diphenylmethane diisocyanate, a scheme of association of urethane groups has been suggested. The amide I band has been shown to include five individual components at 1740, 1730, 1725, 1713 and 1702 cm −1. The isolated bands are considered to be characteristic for urethane groups forming part of various associations.

光重合型軟質裏装材の変色について

Soft linings to dentures are sometimes considered advantageous for patients who are capable of delivering a relatively heavy occlusal load to unfavourable denture-bearing tissues. The color change of heat and room temperature vulcanized soft lining materials have been discussed. The purpose of this study is to compare the color changes of two visible light curing soft lining materials. Tests were made on samples that were stored in four aqueous solutions and one oleaginous solution for 1, 2, 3, 4, 8 and 12 weeks. The aqueous solutions included saline, turmeric, instant coffee and red color No.102. The oleaginous solutions consisted of olive oil plus β-Caro-tene.The results were obtained as follows:1. Color difference of both visible light curing soft lining materials were larger than conven-tional soft lining materials such as silicone, fluoride and polyorefin.2. Two examined materials had almost the same color differences in both saline and red color No.102.3. Extreme color differences were observed in instant coffee, especially in the “Lite Line”.4. In the comparison of the “Lite Line”, which composed of a polyether urethane dimethacrylate resin material and the “Astron LC”, the former had a greater color difference than the latter in oleaginous solutions.

The formation, structure and properties of urethane-diacetylene copolymers as optical strain-sensitive surface coatings

Segmented copolyurethanes comprising ductile polyether-urethane (PE-U) and rigid diacetylene-urethane (DA-U) phases, have been prepared via a one-shot, bulk polymerisation process. Subsequent thermal treatment (100 °C/40 h) of the as-prepared linear copolymers effected solid-state topochemical reactions within the DA-U phase, producing crosslinked and intensely coloured materials. The cross-polymerised copolymers had values of T g between −32°C and 70°C depending on composition, and were elastically isotropic with tensile moduli and strengths ranging, respectively, from 20–1800 MPa, and 8–67 MPa. The copolymers exhibited optical properties similar to those of polydiacetylene single crystals, and produced intense resonance Raman spectra. In particular, the CC triple bond stretching Raman band at ~ 2080 cm −1 was well defined and shifted to lower frequency under the application of tensile stress/strain. The copolyurethanes may be readily applied as surface coatings to various substrates, and their use as optically stress/strain-sensitive materials (optical strain sensors) is demonstrated.

Albumin-binding surfaces for implantable devices.

Surfaces of implantable and blood contact-devices accumulate adsorbed and denatured proteins. This anomalous layer of proteins may help trigger unwanted events such as activation of coagulation systems and, perhaps, chronic inflammation. Because, in many experimental systems, the purposeful coating of surfaces with albumin will biologically "passivate" materials, we have attempted to develop polymers which, when exposed to blood or body fluids, will spontaneously, selectively, and reversibly adsorb host albumin. We report here a novel derivatization technique for increasing the albumin affinity of implantable polyetherurethane (PU). The technique is based on the incorporation of high-molecular-weight dextran to which the albumin-binding dye Cibacron Blue is covalently attached. Somewhat surprisingly, the amounts of human albumin adsorbed by Blue Dextran-modified and unmodified PU are quite similar. There are, however, important differences. First, the binding of albumin to derivatized PU is specific and not readily blocked by proteins in albumin-depleted human serum. Second, the majority of albumin associated with derivatized PU appears to be reversibly bound. Third, the binding of albumin to derivatized PU evidently is mediated primarily through ligand-specific binding of the protein to the albumin-binding dextran-dye conjugate. We conclude that it is possible to produce implantable polymers having surfaces which display albumin-binding dyes that selectively and reversibly bind albumin. Materials with this property, when implanted or exposed to blood, should form an infinitely renewable coating of albumin derived from physiologic fluids. This surface modification strategy may spawn a new generation of implantable materials with improved biologic compatibility.