On co-adsorption on passive iron from aqueous 1,2,3-benzotriazole and sodium phenylundecanoate

Passivation of iron and low-carbon steel in borate buffer solution (pH 7.40) was studied in the presence of 1,2,3-benzotriazole (BTA) and its equimolar mixture with sodium phenylundecanoate (SPU). As was shown BTA is an ineffective stabilizer of the passive state, while SPU has a better efficiency in this function. However, the stabilizing effect of BTA can be improved by forming its adsorption layer on the electrode surface pre-modified with SPU anions at anodic potential E = 0.2 V or by its co-adsorption with SPU. The analysis of attraction between the adsorbed particles of these inhibitors enabled to suggest that their co-adsorption on oxidized iron (E = 0.2 V) yields associates of SPU and BTA anions.     

聚醚氨酯薄膜表面性质的反相色谱法研究

本文报道了用反相色谱法研究多嵌段聚醚氨酯与几种低分子化合物的相互作用,测定了表征相互作用的热力学参数。结果表明,由ESCA证明表面软段富集的聚醚氨酯的反相色谱行为主要决定于富集层与探针分子的相互作用;苯及几种烷烃和聚醚氨酯的偏摩尔混合热和它的溶度参数与软段组分的溶度参数差值有关。     

Hydrogel‐like elastic membrane consisting of semi‐interpenetrating polymer networks based on a phosphorylcholine polymer and a segmented polyurethane

To obtain a hydrogel‐like elastic membrane, we prepared semi‐interpenetrating polymer networks (IPNs) by the radical polymerization of methacrylates such as 2‐methacryloyloxyethyl phosphorylcholine (MPC), 2‐hydroxyethylmethacrylate, and triethyleneglycol dimethacrylate diffused into segmented polyurethane (SPU) membranes swollen with a monomer mixture. The values of Young's modulus for the hydrated semi‐IPN membranes were less than that for an SPU membrane because of higher hydration, but they were much higher than that for a hydrated MPC polymer gel (non‐SPU). According to a thermal analysis, the MPC polymer influenced the segment association of SPU. The diffusion coefficient of 8‐anilino‐1‐naphthalenesulfonic acid sodium salt from the semi‐IPN membrane could be controlled with different MPC unit concentrations in the membrane, and it was about 7 × 10² times higher than that of the SPU membrane. Fibroblast cell adhesion on the semi‐IPN membrane was effectively reduced by the MPC units. We concluded that semi‐IPNs composed of the MPC polymer and SPU may be novel polymer materials possessing attractive mechanical, diffusive‐release, and nonbiofouling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 68–75, 2003     

Proliferation of endothelial cells on the plasma-treated segmented-polyurethane surface: attempt of construction of a small caliber hybrid vascular graft and antithrombogenicity

To prepare a porous segmented-polyurethane (SPU) tube, a solution of SPU containing different concentrations of NaCl was coated on a glass rod and the coated SPU was immediately immersed in water. When the surface of the porous SPU, where bovine aortic endothelial cells are not normally capable of adhering and proliferating, was modified by plasma treatment, the proliferation of endothelial cells could be drastically improved. The cells proliferated confluently on the porous SPU surface prepared at low concentrations of NaCl below 10 g per 100 ml, but poorly on the porous surface prepared at high concentrations of NaCl. The construction of a hybrid vascular graft consisting of a porous SPU tube (2 mm in inner diameter, 5 cm in length) and endothelial cells was attempted. The cells cultured on the inner surface of the tube proliferated to confluency everywhere. From an in vitro antithrombogenic evaluation test, which involved the use of human blood, the present hybrid graft can be considered to provide an inert surface against thrombus formation and blood coagulation. Negligible changes in shape of human leukocytes in contact with bovine aortic endothelial cell surface occurred, suggesting that the bovine aortic endothelial cells used are immunologically less active against human blood.     

STRUCTURE-PROPERTY RELATIONSHIP OF POLYELECTROLYTES AND ITS APPLICATION IN STABILIZING DRILLING-MUD IN PRESENCE OF SALTS

A new polyelectrolyte (SPU) has been prepared. It can depress the water-loss of drilling-mud much more effective than the commonly used acrylic polyelectrolytes even in 30% NaCl solution. SPU has phenyl group in the backbone with -SO_3~- in the side chain while the acrylic polyelectrolytes have C—C and -COO~- respectively, there exists an intrinsic relationship between the structure of polymer and its tolerance to salts, it has been found: 1) The adsorption amount of polymer on clay is related closely to the flexibility of polymer chain. 2) The salt-tolerance of -SO_3~- is superior to -COO-. 3) Both SPU-mud and HPAN-mud are plastic fluids. The dependence of yield point on salts relates to the molecular weight of polymer and hydration of ionogenic group, which is quite different for SPU-mud and HPAN-mud. 4 ) The extent of raising zeta-potential of base-mud by SPU is greater than by HPAN, but the extent of dropping zeta-potential of SPU-mud by NaCI is smaller than HPAN-mud. According to these results we suppose the salt-tolerance of SPU-mud is attributed mainly to hydration of -SO_3~- and that of HPAN-mud mainly to network structure formed in the drilling-mud.     

Free volume and water vapor permeability of dense segmented polyurethane membrane

This paper presented micro-structure, free volume and water vapor permeability of dense segmented polyurethane (SPU) membrane. Wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) techniques were employed to investigate the micro-structure. Free volume was measured by positron annihilation life spectroscopy (PALS). WAXD and DSC results indicated microcrystalline structure presents in the polymer membrane. Percent crystallinity of SPU would depend on the types of polyol used. The microphase-separated structure of copolymers was observed by transmission electron microscopy. Extent of phase separation was depended on the type and composition of polyol used. Free volume hole sizes are different for SPU samples due to the interaction between the polymer chains and packing of polymer chains due to the different compositions. The influences of temperature and chemical compositions on the free volume and water vapor permeability have been discussed. Experimental results revealed that the water vapor permeability can be controlled by free volume, which would depend on the chemical composition of SPU, and hydrophilicity of membranes.     

Synthesis of bis‐triethoxysilane endcapped polyurethane/urea and its self‐assembly morphologies with the assistance of hydrogen ion

A type of bi‐triethoxysilane endcapped polyurethane/urea (SPU) with well‐defined structure was synthesized through the reaction of polyethylene glycol (PEG), 2, 4‐toluene diisocyanate (TDI) and bis‐[trimethoxysiylpropyl]amine (DB‐520). The structure of the resultant product was confirmed by Fourier transform infrared (FT‐IR) and Nuclear magnetic resonance (¹HNMR). Different SPU nanoparticles were obtained with the assistance of hydrogen ion, and their morphologies were characterized by combination of transmission microscopy (TEM) and FT‐IR. The results showed that with increasing the concentration of hydrogen ions, the ratio of condensation accordingly increased, accompanying with the nanoparticle's morphology change from sphere to rod. Furthermore, the dispersion mechanism of SPU chains in protonic solution and the arrangement of molecular chains in hybrid particles were proposed. Copyright © 2011 John Wiley & Sons, Ltd.     

TGA/FTIR studies of segmented aliphatic polyurethanes and their nanocomposites prepared with commercial montmorillonites

Nanocomposites prepared with segmented polyurethane (SPU) and commercially available nanoclays (Cloisite™ Na⁺, Cloisite™ 15A, Cloisite™ 30B) were studied using thermogravimetric analysis coupled with Fourier Transform Infrared Spectroscopy (TGA/FTIR). The results showed that the thermal degradation of unfilled SPU and the 4, 6 and 10 wt% hand mixed nanocomposites occurred in two stages being the first due to degradation of hard segments and the second due to the degradation of soft segments. It was also found that the thermal stability of these nanocomposites was not improved by increasing nanoclay concentration except for SPU/Cloisite™ 15A nanocomposites were a 40 °C increase was observed. In a similar manner, FTIR spectra of the evolved gases obtained after the thermal degradation of these nanocomposites were qualitatively similar to the unfilled polymer except in those containing Cloisite™ 30B where isocyanate absorptions were detected. In contrast, SPU/Cloisite™ 30B nanocomposites prepared by in-situ polymerization, exhibited higher thermal stability than the corresponding hand mixed nanocomposites. In addition, these nanocomposites exhibited the presence of carbon dioxide in the evolved gases during its second degradation stage which was not observed in the hand mixed nanocomposites. In this case, it can be said that the presence of clays in the nanocomposites has a significant effect on the thermal degradation pathways.     

13C-NMR Study of Anomalous Linkages in Polyurethane

Several kinds of model compounds for anomalous linkages in polyurethanes (branching or crosslinking; allophanate and biuret) were prepared. The phenylisocyanate (PHI) based models were identified by IR and NMR. The ¹³C-NMR chemical shifts effects due to the anomalous linkages were determined. The 4,4′-diphenylmethane diisocyanate (MDI) based models were purified incompletely but the characteristic signals of the aromatic carbons were nevertheless found in their spectra. Two types of segmented polyurethane (SPU) were prepared and the anomalous linkages were investigated by ¹³C-NMR. The signals due to the allophanate (Al) and the triphenylbiuret (TB) linkages were observed in the spectra of the SPU prepared at high temperature (>80°C) or prepolymer gels yielded by abnormal reaction. A small signal due to a phenyl carbon of biuret (Bi) linkage was observed even in a normally prepared SPU (polyetherurethane-urea). Employing the phenyl carbon signals was advantageous for the determination of anomalous linkages because of their larger intensities.     

SYNTHETIC STUDIES ON BLOOD COMPATIBLE BIOMATERIALS 13:A NOVEL SEGMENTED POLYURETHANE CONTAINING PHOSPHORYLCHOLINE STRUCTURE:SYNTHESIS,CHARACTERIZATION AND BLOOD COMPATIBILITY EVALUATION

A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contactangle measurements. The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-richplasma (PRP) adhesion experiment, which was viewed by scanning electron microscopy (SEM) with polyurethane as areference. The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility.     

GRAFTING OF HYDROPHILIC MONOMERS ONTO POLYURETHANE MEMBRANES BY SOLUTION OR PRE-ABSORBING METHODS FOR ACCELERATION OF CELL COMPATIBILITY*

Two grafting methods, i.e. solution grafting and pre-adsorbing, are introduced to covalently immobilizehydrophilic polymers on segmented polyurethane (SPU) to modify its hydrophilicity and to improve its cell compatibility.Solution grafting results in higher degree of grafting and rougher surface morphology. Cell culture evaluation demonstratesthat the modified membranes thus obtained are disadvantageous to the endothelial cell (ECs) growth probably because thehydrophilic groups on the surface are over-crowded. However, pre-absorbing grafting generates lower degree of grafting,which is detected and confirmed by ATR-FTIR spectra and water conted angle. Scanning electron microscopic (SEM)measurement shows that the latter method produces a plane and smooth morphology, which is similar to the SPU controlsample controlled. When grafting with lower monomer concentration, ECs could grow on SPU-g-PHEA [poly(2-hydroxyethyl acrylate)], SPU-g-PAAm (polyacrylamide), SPU-g-PDMA [poly(2-(dimethylamino)ethyl methacrylate)] orquatemized SPU-g-PDMA surface with elongated cell shapes. Hence, the cell compatibility of SPU is improved and a usefulmethod to construct a cell compatible layer on the polymer surface has been developed.     

Pressure-induced change in permeation of insulin through a polymer alloy membrane for an implantable insulin pump

Pressure-induced change in insulin permeability through a polymer alloy membrane for an implantable insulin pump was investigated. The polymer alloy membrane was composed of a segmented polyurethane (SPU) and poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-2-ethylhexyl methacrylate) (PMEH). The polymer alloy membrane had a pathway for insulin permeation because the hydrophilic PMEH became the domain structure in the polymer alloy. The functions of the SPU/PMEH alloy membrane were characterized in terms of insulin permeability and water permeability with an applied pressure, mechanical properties, and strain and volume changes under the pressured condition. The insulin permeability synchronized with the applied pressure, that is, the insulin permeability increased 3.4 times with the applied pressure (pressure-on state) of 18 kPa in comparison with no applied pressure (pressure-off state). The permeability changed reversibly without lag time between the pressure-on and -off states. The phenomenon was caused by an increase in water permeation with the applied pressure. From the observation of volume change in the insulin reservoir in the pressure-on state, the effective pressure advancing water permeation was produced by the elasticity of the polymer alloy membrane. The polymer alloy membrane had excellent mechanical properties resisting the applied pressure, as was indicated by stress–strain measurements. It was concluded that the SPU/PMEH alloy membrane had a useful function for an implantable insulin pump.     

动态渗透压法测定水溶性聚电解质的分子量

用动态渗透压法,在适量含盐的水溶液中测量聚电解质——尿素改性磺化酚醛(SPU)的分子量。选取预计平衡点附近所作H-dv/dt的上升线为基准来测定溶液的平衡渗透压。从陶南渗透压求得SPU和第二维利系数A_2,比一般统计线团的A_2大,由A_2算得的Z~2/C'_s值,表征聚离子上有效荷电情况,其大小次序与样品处理钻井泥浆的降失水性能相一致,即Z~2/C'_s数值大则泥浆失水量小。因此, Z~2/C'_s值是聚电解质特性的一个有意义的量。     

Influence of solvents properties on morphology of electrospun polyurethane nanofiber mats

Segmented polyurethane (SPU) nanofiber mats were prepared by electrospinning technique using the combination of four different solvents viz. tetrahydrofuran, N,N′‐dimethyl formamide, N,N′‐dimethyl acetamide, and dimethyl sulfoxide. Morphology of the electrospun nanofibers was examined by field emission scanning electron microscope. Experimental results revealed that the morphologies of polyurethane nanofiber mats have been changed significantly with the solvent selection for the electrospinning. It was observed that the diameters and morphology of the SPU nanofibers were influenced greatly by the use of combination of solvents. The uniform polyurethane nanofibers without beads or curls could be prepared by electrospinning through the selection of combination of good conductive and good volatile solvent viz. 7.5 wt/v% of SPU in N,N′‐dimethyl formamide/tetrahydrofuran (30 : 70 v/v) solutions at 20 kV applied voltages and volume flow rate of 1 ml/min. On the basis of the results obtained from this investigation, it has been established that solvent selection is one of the driving factors for controlling the morphology of the polyurethane electrospun nanofiber mats. The well‐controlled morphology of electrospun polyurethane nanofiber mats could be useful for many potential industrial applications such as in biomedical, smart textiles, nanofiltration, and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and properties of room temperature curable trimethoxysilane‐terminated polyurethane and their dispersions

The purpose of this research is to study the synthesis and characterization of stable aqueous dispersions of externally chain extended polyurethane/urea compositions terminated by hydrolyzable or hydrolyzed trialkoxysilane groups incorporated through secondary amino groups. These dispersions with excellent storage stability are substantially free from organic solvents which cure to water and solvent resistant, tough, scratch resistant, preferably light stable (non‐yellowing) silylated polyurethane (SPU) films. The films were characterized by FT‐IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and water contact angle measurements, nanoindentation, gel content, water and xylene swellability tests. The properties of the films were discussed and correlated in detail by changing length of soft segment, diisocyanates, NCO/OH ratio and chain extender, ethylenediamine (EDA). From the results, it was found that the particle size and viscosity are lower whereas the gel content and thermal stability are higher for SPUs. Modulus, hardness and tensile properties of SPU films are superior compared to EDA‐PU film. Higher water contact angle and residual weight percentage of SPU films confirm silylation of PU by [3‐(phenylamino)propyl]trimethoxysilane (PAPTMS). Increase in NCO/OH ratios consumes more quantity of PAPTMS which makes PU with superior mechanical properties. Higher PAPTMS content in SPU results in effective crosslinking of the functional silanol groups formed by hydrolysis reaction of trimethoxysilane groups. Overall, SPUs synthesized at 1.4 NCO/OH ratio using Poly‐(oxytetramethylene)glycol (PTMG)‐2000 and isophorone diisocyanate (or) toluene‐2,4‐diisocyanate have excellent properties compared to SPUs prepared using PTMG‐1000 and at 1.2 and 1.6 NCO/OH ratios. SPUs prepared at 1.6 NCO/OH ratio are brittle due to higher crosslinking density. In addition, the crosslinking density of the films can be modified through silane end‐group modification to produce SPUs with a wide range of physical properties. Copyright © 2007 John Wiley & Sons, Ltd.     

多嵌段聚氨酯表面组成的ESCA研究

多嵌段聚氨酯(SPU)是一种重要的医用高分子材料,其表面化学组成、表面结构,对血液相容性有直接关系。本文用电子能谱(ESCA)研究了两种链结构SPU的表面化学组成,其目的是了解表面组成与其本体结构及性能的关系,并将SPU表面组成与本体的相分离程度联系起来。实验结果表明:(1)在SPU-空气界面上O/N原子比大于其本体O/N原子比,即软段富集于表面;(2)分相程度高的SPU试样较分相程度低的试样其软段在表面富集得更多;(3)在50左右深度的表面层内相分离程度高的试样其O/N组成变化的梯度较大。     

ESCA STUDIES ON SURFACE COMPOSITION OF SEGMENTED POLYURETHANE

Segmented polyurethanes (SPU) have been used as an important biomedical material, of which the hemocompatibility is determined mainly by the surface properties of the polymer. ESCA has. been used in the present study to characterize the surface composition of SPU samples with different degree of phase segregation. Our experimental results show that (1) the ratio of O/N on polymer-air interface is greater than that in the bulk, i. e., more soft segment is found on the surface than in the bulk average; (2) the soft segment is more abundant on the surface for the sample with better phase segregation; (3) within about 50A thickness of the air facing side the composition variation of the sample with better phase segregation is greater than the sample with poor phase segregation.     

Synthesis and surface properties of environmentally responsive segmented polyurethanes

Polyurethanes, containing well-defined assemblies of perfluoro-polyether (PFPE or hexafluoropropene oxide oligomer), polydimethylsiloxane (PDMS), and polyethylene glycol (PEG) segments, exhibit oleophobic, hydrophobic, and hydrophilic properties in response to the polarity of the contacting medium. These polymers were prepared by reacting hydroxy(polyethyleneoxy)-propylether-terminated PDMS block copolymer (HO-PEG-PDMS-PEG-OH) with 4,4'-methylene-bis(phenylene isocyanate) (MDI) in the presence of dibutyltin dilaurate catalyst, followed by reaction with 1,2-diol functional PFPE and chain extension with 2,2,3,3-tetrafluoro-1,4-butanediol (FB). The oleophobic and hydrophobic properties of the segmented polyurethanes (SPU) are due to the segregation of PFPE segments at the polymer-air interface. Wettability studies revealed that the same surface becomes hydrophilic, presumably due to the segregation of the PEG segments at the polymer-water interface. This hydrophobic-to-hydrophilic transformation of the surface prevails not only when the polymer is in contact with liquid water but with water vapor as well. The understanding of the reconstruction mechanism of this novel family of SPU surfaces would furnish valuable information for various applications where dynamic transformation of surface activity is desired.     

Esca studies of polyurethanes: blood platelet activation in relation to surface composition

Segmented polyurethanes (SPU) were synthesized with polyethylene oxide (PEO), polypropylene oxide, or polytetramethylene oxide as the “soft segment,” from the respective polyether diols, of which molecular weight varied from 600 to 2000. The “hard segment” was created from ethylene diamine and tolylene diisocyanate or 4,4′-diphenylmethane diisocyanate. Platelet activation was assessed using columns packed with beads coated with each of the SPU by solutions from which the solvent was subsequently evaporated. Citrated whole human blood was passed through the columns and the platelet count in aliquots leaving the columns was compared with the platelet count in blood that had not contacted the column surface. By this method the fraction of platelets retained in the column averaged for several donors, ρ, was determined. In parallel experiments, SPU surfaces formed under identical conditions by evaporation of solvent were examined by X-ray electron spectroscopy for carbon, oxygen, and nitrogen content of the surface. The carbon C_1s spectra proved to be particularly useful, when analyzed for the components with peaks respectively at 286 eV (carbon not bonded to an ether oxygen) and at 288 eV (carbon bonded to an ether oxygen). The platelet retention index ρ was found to increase nearly linearly with the ratio of the 286-eV intensity to the 288-eV intensity, and extrapolated to nearly zero for zero value of the intensity ratio, which would correspond to amorphous PEO, suggesting that if a surface were only amorphous PEO it would be remarkably inactive toward platelets. In contrast, nitrogen spectra show no systematic relationship with ρ.     

Waterborne trifunctionalsilane‐terminated polyurethane nanocomposite with silane‐modified clay

Trifunctional organosilane‐modified clay was synthesized and used to prepare waterborne trifunctionalsilane‐terminated polyurethane (WSPU)/clay nanocomposite dispersions in this study. Qualitative evidence of the presence of chemically attached silane molecules on clay were confirmed by Fourier transform infrared spectroscopy. The grafted amount and the grafting yield were determined by thermogravimetric analysis and the obtained results were in good agreement with the cation exchange capacity of pristine clay. X‐ray diffraction and transmission electron microscopy examinations indicated that the clay platelets are mostly intercalated or partially exfoliated in the SPU matrix with a d‐spacing of ～2.50 nm. Clay does not influence the location and peak broadness of the glass transition temperature of soft segment as well as hard segment domains in the WSPU/clay films. WSPU/clay dispersion with higher clay content exhibits a marginal increase in the average particle size, but silane modified clay has a pronounced effect compared with Cloisite 20A‐based nanocomposites. In addition, the incorporation of organophilic clay can also enhance the thermal resistance and tensile properties of WSPUs dramatically through the reinforcing effect. The improvement in water and xylene resistance of the silane modified clay nanocomposites proved that trifunctional organosilane can be used as effective modifiers for clays. Storage stability results confirmed that the prepared nanocomposite dispersions were stable. This method provides an efficient way to incorporate silane modified clay in SPU matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2747–2761, 2007