Poly Ether Urethane Research Articles

Preparation of UV curing crosslinked polyviologen film and its photochromic and electrochromic performances

Polyether urethane diacrylate matrix (PEUDA) and acrylate-functional viologen (ACV2+) were successfully synthesized and characterized in detail by FTIR and 1H NMR spectra, respectively. Subsequently, they were used to prepare UV curing crosslinked polyviologen film in combination with 2-hydroxyethyl methacrylate (HEMA), trimethylolpropane ethoxylate triacrylate (TMPTA) and diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO). UV curing approach confined the polyviologen film on ITO electrode, which imparted the film excellent adhesion ability to ITO glass, good solvent resistance, excellent chemical stability, excellent optical and electrochemical properties. The crosslinked PACV2+ film exhibited excellent photochromic and electrochromic performances. After UV illumination for 60s, the crosslinked PACV2+ film can swiftly change its color from pale yellow to deep blue, while the optical transmission of crosslinked PACV2+ film at 610nm did not change significantly and still retained about 63.6% after 30 cycles. Simultaneously, the cyclic voltammetry experiment showed the PACV2+ film can undergo repeatable electrochemical redox reactions with good reversibility beyond the 10th scan. Furthermore, the electrochromic device composed of the PACV2+ film and gel electrolyte film can undergo reversible color change in response to the external voltages of −2.0V and 2.0V, respectively, while the contrast of EC device at 610nm did not change significantly and still retained about 39.5% after 10 cycles. This UV curing approach to preparing viologen-functional film offers a method to preparing large-scale photo- and electrochromic device, which is relatively simple, high productivity, energy saving, and environmental protection.

Behaviour of Segmented Polyether Urethane Urea in a Humid Atmosphere after Mechanical Loading

The laws governing the mechanical behaviour of plasticised polyurethane ureas in a wide range of air relative humidity are studied. It is shown that, in the presence of a plasticiser lowering the solubility of the rigid blocks in the flexible phase of the polymer, there is an increase in the stability of the mechanical characteristics of polyurethane urea on exposure to a humid atmosphere.

Synthesis and properties of poly(acrylates-co-urethane) adhesives for low surface energy materials

The series of poly(acrylates-co-urethane) were synthesized based on the copolymerization between 2-hydroxyethyl acrylate terminated polyether (or polyester) urethane and acrylate monomers initiated by tri-n-butylborane (TBB). The effects of the soft segment of polyether (or polyester) urethane diacrylate on the copolymer properties were mainly discussed. Polyether (or polyester) urethane was relatively well dispersed in polyacrylate continuous phase, and was intended to aggregate with the increase of soft segment polarity and content. The adhesion to low surface energy materials and loss factor (tan δ) of copolymers were almost not influenced by the soft segment content, but decreased with the increase of soft segment polarity within the scope of the study. On the other hand, the working life of copolymers as adhesives was shortened with the increase of soft segment polarity, but prolonged with the increase of soft segment content. The copolymers with different structures of polyether (or polyester) urethane diacrylate were also shown to be good candidates as adhesives at room temperature.

Biodegradation of Polyethylene Glycol-Based Polyether Urethanes

The biodegradation of polyethylene glycol (PEG of different molecular weights) based polyether urethanes were studied under soil burial condition for 180 days under indoor normal hydrothermal conditions and by cultured bacteria (Pseudomonas aeruginosa) for 30 days at 37°C. The biodegradation was estimated from the weight loss, tensile strength, ultimate elongation and also by FTIR spectroscopy, optical, scanning electron microscopy. The weight loss and losses in tensile strength, elongation at break of the polymer is maximum in case of PUPEG4000 and minimum in case of PUPEG200 (both in case of soil burial condition and in cultured bacteria).

New sensitive layers for surface acoustic wave gas sensors based on polymer and carbon nanotube composites

Surface acoustic wave (SAW) gas sensors based on carbon nanotube polymer composites as sensitive layers were investigated for the detection of low concentrations of volatile organic compounds as octane and toluene. Several nanocomposites based on polyepichlorohydrin (PECH) and polyetherurethane (PEUT) with different percentage of multiwalled carbon nanotubes (MWCNT) were tested to study the effect of MWCNTs in the response of sensors.

Mechanically active scaffolds from radio‐opaque shape‐memory polymer‐based composites

AbstractThe formation of functional tissue is strongly dependent on biochemical as well as physical signals. A common approach in tissue engineering is the application of passive scaffold systems with fixed morphology and stiffness. In this paper, we explored whether mechanically active scaffolds, exhibiting self‐sufficient shape changes under physiological conditions, can be prepared from radio‐opaque shape‐memory polymer composites (SMPCs). The influence of different thermomechanical treatments on the kinetics of the shape change was studied. Radio‐opaque SMPCs were obtained by incorporation of barium sulfate (BaSO4) microparticles (up to 40 wt%) into an amorphous polyether urethane (PEU) via co‐extrusion technique. The shape‐memory properties of the composites were investigated by cyclic, thermomechanical tensile tests consisting of a specific shape‐memory creation procedure (SMCP), in which the programming temperature (Tprog) was varied, followed by recovery under stress‐free condition, enabling the determination of the switching temperature (Tsw). An almost complete recovery with shape recovery rate (Rr) values ranging from 88% to 98% was realized within a small temperature interval of ΔTrec ≈ 30°C for all composites, while Tsw was found to be close to the applied Tprog. The feasibility of actively moving scaffolds was demonstrated using model scaffolds, where originally square‐shaped pores were temporarily fixed in an expanded circular shape at different Tprog. We found that the kinetics of the shape change obtained under physiological conditions could be adjusted by variation of Tprog between 1 and 6 hr. Such radio‐opaque scaffolds could serve as model scaffolds for investigating the active mechanical stimulation of cells in vitro or in vivo. Copyright © 2010 John Wiley & Sons, Ltd.

Synthesis, Characterization, and Cytotoxicity Analysis of Polyethylene Glycol-Based Polyether Urethanes

Different polyether urethanes (PUPEG200, PUPEG400, PUPEG600, PUPEG1000, PUPEG4000) were synthesized from five different polyethylene glycols (PEG 200, PEG 400, PEG 600, PEG 1000, PEG 4000). The polymers were characterized by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) and their mechanical properties were evaluated. Polyether urethanes synthesized from higher-molecular-weight PEG (PEG 4000) show comparatively maximum hydrophilicity, minimum tensile strength, and maximum elongation at break (%). Hydrolytic degradation of synthesized polyether urethanes was studied in alkali solutions of different concentrations (0.5, 1, 3% NaOH), different mineral acids (5 and 10% HCl, H2SO4, HNO3), phosphate buffer saline (PBS), and saline water (10% NaCl solution). Swelling behavior of the polyether urethanes was measured in water and in PBS solution. In order to assess the cellular responses of these polyether urethanes, cytotoxicity analysis was carried out against the human skin cell line.

Surface grafting thermoresponsive PEO-PPO-PEO chains

The objective of this study was to engineer surfaces comprising covalently bound polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) chains, able to coil and uncoil in aqueous media, as a function of temperature. Thermoresponsive surfaces can be used in diverse areas, such as tissue engineering and 'on-command' drug delivery. The grafting scheme was exemplified using a poly(ethylene terephthalate) (PET) film and started with the exposure of the substrate to plasma of ammonia, whereby amine groups were formed on the film. In the next stage, the amine moieties reacted with the hydroxyterminated thermoresponsive PEO-PPO-PEO triblocks via the hexamethylene diisocyanate (HDI) coupling agent. XPS analysis of the PET film after being exposed to plasma of ammonia revealed substantial amounts of nitrogen, as revealed by the sizeable N1s peak observed at 400.2 eV. A large increase in the C1s ether peak at 286.5 eV was apparent after binding the PEO-PPO-PEO triblocks to the substrate. These findings were confirmed by FTIR spectroscopy and supported by water contact angle measurements. PEO-PPO-PEO triblocks were chain extended by reacting them with HDI, whereby longer polyether urethane chains were formed. The long thermoresponsive chains produced (P-F127) were then tethered to the PET surface, following the procedure used to graft the shorter F127 triblocks. The thermoresponsiveness of the surface was demonstrated by measuring the water contact angle of the P-F127-containing surfaces as a function of temperature.

Coordination and morphology of metal/polyetherurethane complexes

Based on infrared spectra, differential scanning calorimetry, and quantum chemical calculations, this study investigated the effects of the species of metal (MnCl 2, FeCl 3, CoCl 2, CuCl 2, GaCl 3), their interaction sites and binding strength on the morphologies of polyetherurethane (PU). The calculated frequency and binding energy were consistent with the experimental results, suggesting that most of the binding strength (95%) is associated with the charge transfer from the lone pairs (on the nitrogen in NH and the oxygen in CO and COC) in the PU ligand to the metal. MnCl 2, CoCl 2, and CuCl 2 are more soluble in soft segments of PU than GaCl 3 and FeCl 3 via coordination with one or two polyether ligands and can significantly raise the glass transition temperature of PU. Conversely, GaCl 3 and FeCl 3 interact more strongly with hard-segment NH of PU than MnCl 2, CoCl 2, and CuCl 2 and markedly reduce the melting temperature of PU.

Two stages in three-dimensional in vitro growth of tissue generated by osteoblastlike cells

Bone regeneration is controlled by a variety of biochemical, biomechanical, cellular, and hormonal mechanisms. In particular, physical properties of the substrate such as stiffness and architecture highly influence the proliferation and differentiation of cells. The aim of this work is to understand the influence of scaffold stiffness and cell seeding densities on the formation of tissue by osteoblast cells within polyether urethane scaffolds containing pores of different sizes. MC3T3-E1 preosteoblast cells were seeded on the scaffold, and the amount of tissue formed within the pores was analyzed for culture times up to 49 days by phase contrast microscopy. The authors show that the kinetics of three-dimensional tissue growth in these scaffolds follows two stages and can be described by a universal growth law. The first stage is dominated by cell-material interactions with cell adherence and differentiation being strongly dependent on the polymer material. After a delay time of a few weeks, cells begin to grow within their own matrix, the delay being strongly dependent on substrate stiffness and seeding protocols. In this later stage of growth, three-dimensional tissue amplification is controlled rather by the pore geometry than the scaffold material properties. This emphasizes how geometric constraints may guide tissue formation in vitro and shows that optimizing scaffold architectures may improve tissue formation independent of the scaffold material used.

Adjusting shape-memory properties of amorphous polyether urethanes and radio-opaquecomposites thereof by variation of physical parameters during programming

Various composites have been prepared to improve the mechanical properties of shape-memorypolymers (SMPs) or to incorporate new functionalities (e.g. magneto-sensitivity) in polymer matrices.In this paper, we systematically investigated the influence of the programming temperatureTprog and theapplied strain εm as parameters of the shape-memory creation procedure (SMCP) on the shape-memoryproperties of an amorphous polyether urethane and radio-opaque composites thereof.Recovery under stress-free conditions was quantified by the shape recovery rateRr and the switchingtemperature Tsw, while themaximum recovery stress σmax was determined at the characteristic temperatureTσ, max underconstant strain conditions. Excellent shape-memory properties were achieved in all experiments withRr values in between 80 and98%. σmax could be tailoredfrom 0.4 to 3.7 MPa. Tsw andTσ, max could be systematicallyadjusted from 33 to 71 °C byvariation of Tprog for each investigated sample. The investigated radio-opaque shape-memory composites willform the material basis for mechanically active scaffolds, which could serve as an intelligentsubstitute for the extracellular matrix to study the influence of mechanical stimulation oftissue development.

Synthesis, extrusion and rheological behaviour of PU/HA composites for biomedical applications

Biostable polyurethane/hydroxyapatite (PU/HA) composites with potential application as bone replacement materials were synthesized in bulk and processed in a screw extruder. The polyurethanes (PU) were prepared by reacting an aliphatic diisocyanate, 4-methylene-bis-diisocyanate (MDI), with poly-(epsilon-caprolactone) (PCL) diols and polytetramethylene oxide (PTMO) of different molecular weights, extended with 1, 4-butanediol (BDO). Glass-transition temperatures were measured by differential scanning calorimetry (DSC). The specific PU groups were assessed by total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The effects of polymer chemistry and filler content on the rheological behaviour were studied by oscillatory rheometry. Polymers with larger chain lengths showed higher viscosity and, for identical chain lengths, polyether urethanes seem to have higher viscosities than polyester based urethanes. A lubricating effect was found for composites containing 50% weight of filler, whereas at higher filler contents a solid-like behaviour was measured. Polymer chemistry seems to be affected by ageing but not so by the presence of filler. Ageing is characterized by a decrease in the concentration of hydrogen bonds involving between urethane linkages.

Static and dynamic behavior of disk bearings for OSPG railway bridges under railway vehicle loading

The aim of the present study is to investigate the static and dynamic behavior of disk bearings under railway vehicle loadings. A disk bearing is operated as an elastic bearing in the vertical direction and is composed of a Polyether Urethane (Polyurethane) disk for elastic support and Polytetrafluoroethylene (PTFE) to accommodate lateral movements. Static tests are conducted in a laboratory to determine the static behavior of a Polyurethane disk. Finite Element (FE) analysis is also performed to assess the friction and the role of the pin inside a disk bearing. For dynamic behavior, four disk bearings having the identical Polyurethane disk, which are used in the static tests, are installed in a real railway bridge and tested under a running locomotive. From the test results, the static and dynamic stiffness of disk bearings are estimated and compared with each other. The estimated static stiffness of the disk bearing is almost half of that under dynamic loading. In addition, under relatively light loads the dynamic stiffness of a fixed disk bearing is approximately 80% greater than that of an expansion disk bearing since the PTFE deflects and the gap is closed in the expansion bearing. Deformation of the disk bearings in the real bridge is measured with varying locomotive speeds. The deformation of the disk bearings does not vary significantly with changes in the locomotive’s speed.

Antibacterial properties of silver nanoparticles in three different sizes and their nanocomposites with a new waterborne polyurethane

Silver nanoparticles (AgNPs) are strong bactericidal agents but they are also cytotoxic. Embedding them in a polymer matrix may reduce their cytotoxic effect. In the present study, AgNPs in three average sizes were tested for their antibacterial activities and cytotoxicity. Nanocomposites from a new waterborne polyetherurethane (PEU) ionomer and AgNPs were prepared without the use of any crosslinker. It was observed that the antibacterial activity of AgNPs against Escherichia coli started at the effective concentration of 0.1–1 ppm, while that against Staphylococcus aureus started at higher concentrations of 1–10 ppm. Cytotoxicity of AgNPs was observed at the concentration of 10 ppm. AgNPs with smaller average size showed greater antibacterial activity as well as cytotoxicity. The PEU synthesized in this study showed high tensile strength, and the addition of AgNPs at all sizes further increased its thermal stability. The delicate surface features of nanophases, however, were only observed in nanocomposites with either small-or medium-sized AgNPs. PEU-Ag nanocomposites had a strong bacteriostatic effect on the growth of E. coli and S. aureus. The proliferation of endothelial cells on PEU-Ag nanocomposites was enhanced, whereas the platelet adhesion was reduced. The expression of endothelial nitric oxide synthase gene was upregulated on PEU-Ag containing small-sized AgNPs (30 ppm) or medium-sized AgNPs (60 ppm). This effect was not as remarkable in nanocomposites from large-sized AgNPs. Overall, nanocomposites from the PEU and 60 ppm of the medium-sized (5 nm) AgNPs showed the best biocompatibility and antibacterial activity. Addition of smaller or larger AgNPs did not produce as substantial an effect in PEU, especially for the larger AgNPs.

Synthesis of Polyether Urethanes with a Pyrimidine Ring in the Main Chain

A series of polyetherurethanes containing a 2,4-dihydroxy-6-methylpyrimidine structure in the main chain was obtained in two steps: first, the synthesis of polyurethane pre-polymer, followed by a second step of chain extension with 2,4-dihydroxy-6-methylpyrimidine. Another series of polyurethanes was cross-linked with glycerine. The effect of 2,4-dihydroxy-6-methylpyrimidine content on the physical properties and thermal stability of the products were determined. Polyurethanes obtained with aromatic diisocyanate have better properties than those produced with aliphatic diisocyanate. The 5% weight losses, observed by thermogravimetric analysis, occurred in the temperature range of 250 to 340°C. This indicates an improvement in the thermal properties for these polymers, compared with similar polyurethanes.

Thermal, mechanical and wettability properties of some branched polyetherurethane elastomers

AbstractIn this study three series of polyetherurethanes (PEU) based on Terathane ® (polytetramethyleneetherglycol - PTMEG, Mn 1400) as polyol; isophorone diisocyanate (IPDI), 4,4’-methylene-bis-(cyclohexyl-isocyanate) (HMDI) and hexamethylene diisocyanate (HDI) as aliphatic diisocyanate components; 1,4- butanediol (BD) and glycerin (Gly) as chain extenders were synthesized. The glycerin as triol is responsible for the crosslinking structures. All polyether urethanes were synthesized by prepolymer method. The PTMEG was reacted with diisocyanate to realize a diisocyanate-terminated prepolymer, which in next step was extended with blend of the 1,4-butanediol (BD) and glycerin (Gly) in different proportion. The influence of the diisocyanate structure and chain extender functionality on the thermal, mechanical and wettability properties were the aim of this study. The physical, mechanical and wettability properties of these polymers were measured according to standard methods. All polymers were characterized by conventional characterization methods. Different methods of thermal analysis (TGA and DSC) were used for characterization. Wettability was estimated by determination of the dynamic contact angle. The structures were confirmed by FTIR and H-NMR analysis. The results show that the thermal stability, mechanical and wettability properties of the final products are influenced by the diisocyanate and chain extenders nature.

The effect of gamma irradiation on physical–mechanical properties and cytotoxicity of polyurethane–polydimethylsiloxane microfibrillar vascular grafts

Poly(ether) urethane (PEtU)-polydimethylsiloxane (PDMS) based materials have been processed by a spray, phase-inversion technique to produce microfibrillar small-diameter vascular grafts; however the effect of sterilization upon these grafts is still unknown. This study investigated the effect of gamma irradiation on grafts made of PEtU-PDMS materials containing different PDMS concentrations. Sterilisation-induced changes in surface chemical structure and morphology were assessed by infrared spectroscopy, light and scanning electron microscopy. Tensile tests were used to examine changes in mechanical properties and the cytotoxicity evaluation was performed on L929 fibroblasts. The study demonstrated that physical-chemical and mechanical properties of PEtU-PDMS grafts, at each PDMS concentration, were not significantly affected by the exposure to gamma irradiation, moreover no sign of cytotoxicity was observed after sterilisation. Although in vitro experiments have been promising, further in vivo studies are necessary to evaluate the biodegradation behaviour of PEtU-PDMS graft after gamma irradiation, before any clinical application.

In vitro evaluation of the PEtU-PDMS material immunocompatibility: the influence of surface topography and PDMS content

The aim of the present work is to evaluate the in vitro immunocompatibility of an elastomeric material with feasible applications in the cardiovascular field. In particular, since it is well known that surface chemistry and topography play a key role in the foreign body response, their influence on human monocytes was evaluated. The material, constituted by a poly(ether)urethane (PEtU) and a polydimethylsiloxane (PDMS), was synthesized to manufacture films and small-diameter vascular grafts with three different surface topographical features, smooth, rough and porous, and siloxane rates, 10, 30 and 40. Human THP-1 monocytes have been cultured for 72 h on the films and human blood has been circulating for 2 h into the grafts to assess leukocyte adhesion and cytokine releases. Materials extracts were utilized to evaluate monocyte apoptosis. Smooth films showed lower cell adhesion degrees than rough and porous ones. All the PEtU-PDMS (poly(ether)urethane-polydimethylsiloxane) films and vascular grafts induced a narrow inflammatory response, as demonstrated by slight cytokine secretion levels, in particular samples with the highest PDMS contents (30 and 40%) induced the lowest IL-1b secretion. Moreover, an absence of monocyte apoptosis advises that the negligible release values have not to be ascribed to material toxicity. In the end, surface topography showed to affect only monocyte adhesion while siloxane content the cytokine release. Therefore, the possibility to modify the above tested parameters during material synthesis and manufacture could allow to bound the inflammatory potency of the PEtU-PDMS devices and render them excellent candidates for cardiovascular reconstruction.

Thermo-optical study of UV cured polyether urethane diacrylate films with dispersed octadecanol

Thermally reversible light scattering (TRLS) films are prepared from ultraviolet (UV) curing of polyether urethane diacrylate (PEUDA) with dispersed low molecular weight 1-octadecanol (OD). Depending on the temperature, the OD domains are crystalline or amorphous and this produce opaque or transparent films in a reversible way. Stable optically transparent and light scattering states are obtained after 100 successive heating–cooling cycles. Moreover, morphologies of the OD domains could be varied significantly with the cure temperature and this led to notable discrepancy in optical properties. By using an UV-mask and curing in two steps at different temperatures, complex patterns could be recorded in the film that were encoded at high temperatures (60 °C) and revealed at low temperatures (i.e., at room temperature), which makes the film a candidate for thermo-optical recording medium.

Synthesis and characterisation of enhanced barrier polyurethane for encapsulation of implantable medical devices

Polymeric membranes have been used as interfaces between implantable devices and biological tissues to operate as a protective barrier from water exchanging and to enhance biocompatibility. Polyurethanes have been used as biocompatible membranes for decades. In this study, copolymers of polyether urethane (PEU) with polydimethylsiloxane (PDMS) were synthesised with the goal of creating materials with low water permeability and high elasticity. PDMS was incorporated into polymer backbone as a part of the soft segment during polyurethane synthesis and physical properties as well as water permeability of resulting copolymer were studied in regard to PDMS content. Increase in PDMS content led to increase of microphase separation of the copolymer and corresponding increase in elastic modulus. Surface energy of the polymer was decreased by incorporating PDMS compared to unmodified PEU. PDMS in copolymer formed a hydrophobic surface which caused reduction in water permeability and water uptake of the membranes. Thus, PDMS containing polyurethane with its potent water resistant properties demonstrated a great promise for use as an implantable encapsulation material.