Segmented Polyurethane Membrane Research Articles

Methylsilicone-functionalized superhydrophobic polyurethane porous membranes as antifouling oil absorbents

The purpose of this study is to fabricate porous polyurethane membranes that maintain oil absorption performance even when the surface is contaminated. The segmented polyurethane (SPU) films were prepared by the solvent casting method and the porous SPU membranes were prepared by electrospinning. A superhydrophobic methylsilicone network was formed both on the hydroxylated SPU (SPU−OH) film and membrane surfaces by condensation with methyltrichlorosilane. The morphological changes to the methylsilicone-network-coated SPU (SPU−OH−Si) were observed by field emission scanning electron microscopy. The changes in the chemical components on the surface by the introduction of the methylsilicone network were confirmed by attenuated total reflection Fourier transform infrared spectroscopy, and the type of wettability of the surface was confirmed to be superhydrophobicity and superoleophilicity on the SPU−OH−Si film or membrane by contact angle measurements. The self-cleaning performances of the prepared surfaces were confirmed using methylene blue, Oil Red O, and SiC adsorption tests. As a result, the SPU−OH−Si surface displayed excellent self-cleaning properties, as well as oil removal performance, in contaminated water. Furthermore, the oil absorption property was preserved even when the membrane was pre-contaminated with SiC particles.

Abstract WMP35: A Novel Microporous Covered Stent NCVC-CS1 for the Treatment of Intracranial Aneurysms: Its Functional Features and Preliminary Results of Clinical Trial

Background and Purpose: The treatment for large and giant intracranial aneurysms remains unsatisfactory even after the introduction of flow diverters, especially in those located in posterior circulation. This study was aimed to assess the novel covered stent graft named NCVC-CS1 for the treatment of such complex aneurysms. Materials and Methods: NCVC-CS1 is a balloon-expandable stent covered with a thin, microporous segmented polyurethane membrane. After the confirmation of its function on navigability, aneurysm occlusion, and patency of branching vessels using animal models, an investor-initiated, first-in human clinical trial to evaluate the safety and efficacy of NCVC-CS1 was conducted. The inclusion criteria for the targeted aneurysm were unruptured, wide-necked aneurysms more than 7 mm, located in petrous/cavernous portion of ICA, intradural VA, or BA proximal to the orifice of superior cerebellar artery. The primary effectiveness endpoint was angiographic evaluation that demonstrated complete aneurysm occlusion and patency of target vessel (less than 50% stenosis) at 180 days. The primary safety endpoint was occurrence of any stroke or death related to the procedure. Results: A total of 10 patients were enrolled in the trial. Among them, nine aneurysms were large (more than 10mm) including one giant aneurysm (more than 25mm). Mean aneurysm size was 14.3mm. Five aneurysms (50%) were located in VA. NCVC-CS1 placement was technically successful in all cases. No coils were used. The instant cessation of inflow to the targeted aneurysm at the time of the procedure (so-called eclipse sign) was observed in nine cases (90%). Among the nine cases whose follow-up data at 180 days were obtained, five (55%) met the study’s primary effectiveness endpoint whereas the other four showed near complete occlusion without stenosis of the parent artery. As to the safety endpoint, one patient experienced a non-disabling infarction. No subsequent rupture of the aneurysm was observed during the follow-up period. Conclusion: NCVC-CS1 showed the safety and efficacy on its first-in-human clinical trial. This device can offer another therapeutic choice for wide-necked and large intracranial aneurysms.

Water vapor transmission and water resistant: opposite but may coexist

Abstract Water vapor transmission (WVT) and water resistance (WR) are two important properties of functional textile for thermo-physiological comfort to the human body. Water vapor transmitting ability will maximize the comfort level of the human body when the body is in active mode, and water resistant textile will protect our body from rain. In this study, we propose a laminated fabric with both water resistant and water vapor transmission property. As we found that, this kind of laminated fabric have good mechanical property. Our synthesized segmented polyurethane membrane and its laminated fabric has low water vapor transmitting ability at low temperature or low relative humidity and high water vapor transmitting ability at high temperature or high relative humidity.

Durable modification of segmented polyurethane for elastic blood-contacting devices by graft-type 2-methacryloyloxyethyl phosphorylcholine copolymer

We propose a novel application of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers for enhancing the performance of modified segmented polyurethane (SPU) surfaces for the development of a small-diameter vascular prosthesis. The SPU membranes were modified by random-type, block-type, and graft-type MPC polymers that were prepared using a double-solution casting procedure on stainless steel substrates. Among these MPC polymers, the graft-type poly(MPC-graft-2-ethylhexyl methacrylate [EHMA]), which is composed of a poly(MPC) segment as the main chain and poly(EHMA) segments as side chains, indicated a higher stability on the SPU membrane after being peeled off from the stainless steel substrate, as well as after immersion in an aqueous medium. This stability was caused by the intermiscibility in the domain of the poly(EHMA) segments and the soft segments of the SPU membrane. Each SPU/MPC polymer membrane exhibited a dramatic suppression of protein adsorption from human plasma and endothelium cell adhesion. Based on these results, the performance of SPU/poly(MPC-graft-EHMA) tubings 2 mm in diameter as vascular prostheses was investigated. Even after blood was passed through the tubings for 2 min, the graft-type MPC polymers effectively protected the blood-contacting surfaces from thrombus formation. In summary, SPU modified by graft-type MPC polymers has the potential for practical application in the form of a non-endothelium, small-diameter vascular prosthesis.

Occlusion of canine aneurysms using microporous self-expanding stent grafts: Long-term follow-up

PurposeThe treatment of large or giant cerebral aneurysms by surgical and/or endovascular techniques is difficult and poses relatively high risks. Therefore, a microporous self-expanding (hybrid) stent graft composed of a thin, expandable, segmented polyurethane (SPU) membrane with micropores and a drug-delivery system was developed. Materials and methodsA commercially available, self-expanding carotid stent was covered with a thin microporous SPU membrane fabricated by the dip-coating method and the excimer laser ablation technique, with an intraluminal coating of argatroban. Experimentally fabricated lateral-wall aneurysms in canine carotid arteries using venous pouches were occluded with the hybrid stent graft (bale-shaped pore density of 23.6%) on one side and a bare-metal stent on the other side without systemic antiplatelet therapy. ResultsAngiography at 1, 6, and 12 months of stenting revealed that all arteries were patent without marked stenosis without systemic antiplatelet therapy. All aneurysms treated with hybrid stent grafts remained occluded throughout the 12-month period, while among those treated by bare-metal stents, 2 of 3 aneurysms were occluded at 6 months (67%) and only 1 of 3 aneurysms were occluded at 12 months (33%). Histology revealed that the novel hybrid stent graft had less intimal hyperplasia than the bare-metal stent. The hybrid stent graft was useful for the successful occlusion of these canine carotid aneurysms, even at 12 months. ConclusionsThe novel hybrid stent grafts are expected to overcome the disadvantages of fully covered stent grafts and simple bare-metal stents, while combining both their merits, and appear to be useful in the treatment of large or giant cerebral aneurysms.

Effects of molecular architecture of phospholipid polymers on surface modification of segmented polyurethanes

To modify the surface properties of segmented polyurethane (SPU), effects of the molecular architecture of the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymers on the performance of the SPU/MPC polymer membrane were investigated. We combined the random-type, block-type, and graft-type of the MPC polymers with a typical SPU, Tecoflex® using double solution casting procedure. The graft-type MPC polymers composed of a poly(MPC) main chain and poly(2-ethylhexyl methacrylate (EHMA)) side chains were synthesized through the combination of two different living radical polymerization techniques to regulate the density and chain length of the side chains. The SPU membranes modified with the MPC polymers were characterized using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results revealed that the MPC units were located on the SPU surface. Although the breaking strength of the SPU membranes modified with block-type poly(MPC-block-EHMA) and graft-type poly(MPC-graft-EHMA) was lower than that of SPU membranes modified with random-type poly(MPC-random-EHMA), their breaking strengths were adequate for manufacturing medical devices. On the other hand, better stability was observed in the MPC polymer layer on the SPU membrane after immersion in an aqueous medium, wherein the SPU membrane had been modified with the poly(MPC-graft-EHMA). This was because of the intermixing of the hydrophobic poly(EHMA) segments in the domain of the hard segments in the SPU membrane. After this modification, each SPU/MPC polymer membrane showed hydrophilic nature based on the MPC polymers and a dramatic suppression of protein adsorption. From these results, we concluded that the SPU membrane modified with the poly(MPC-graft-EHMA) was one of the promising polymeric biomaterials for making blood-contacting medical devices.

Development of microporous self-expanding stent grafts for treating cerebral aneurysms: designing micropores to control intimal hyperplasia

Treatment of large (diameter 12-25 mm) or giant (diameter >25 mm) cerebral aneurysms with a broad neck in the cranio-cervical area is difficult and carries relatively high risks, even with surgical and/or endovascular methods. To this end, we have been developing a high-performance, self-expanding stent graft which consists of a commercially available NiTi stent (diameter 5 mm, length 20 mm) initially covered with a thin microporous segmented polyurethane membrane fabricated by the dip-coating method. Micropores are then created by the excimer laser ablation technique, and the outer surface is coated with argatroban. There are 2 types of micropore patterns: circular-shaped pore type (pore: diameter 100 μm, opening ratio 12.6%) and the bale-shaped pore type (pore: size 100 × 268 μm, opening ratio 23.6%). This self-expanding stent graft was tested on side-wall aneurysms of both canine carotid arteries that were experimentally induced using the venous pouches from the external jugular veins, with the self-expanding stent graft on one side and a bare self-expanding stent on the other side. All carotid arteries were patent and free of marked stenosis after 1 month. All aneurysms were occluded by stent grafts, while patent in those treated with bare stents. Histologically, the stent grafts with bale-shaped micropores and a high opening ratio were associated with less intimal hyperplasia (187 ± 98 μm) than the bare stents (341 ± 146 μm) or the stent grafts with circular micropores and a low opening ratio (441 ± 129 μm). A pore ratio of 23.6% was found to control intimal growth.

High-performance self-expanding stent graft: development and application to experimental aneurysms

Large or giant aneurysms in the craniocervical area with broad necks are of concern and are treated surgically, endovascularly, or in both ways. Surgically, their treatment is difficult, with relatively high risks. For their embolization, we have been developing a high-performance stent graft that has three characteristics: a thin and expandable segmented polyurethane (SPU) membrane, micropores formed by the excimer laser ablation technique, and a drug delivery system at the membrane. Stent grafts were fabricated using commercially available self-expanding stents. These stents were covered with a thin SPU membrane by the dip-coating method. Micropores were then formed by the excimer laser ablation technique and an argatroban coating was added. We tested the effectiveness of this new stent graft by treating experimental canine aneurysms. Experimental aneurysms were made in the bilateral carotid arteries of four female beagles by end-to-side anastomosis using an autologous venous pouch. One month after aneurysm formation, the experimental aneurysm in one of the carotid arteries was covered with our self-expanding stent graft and the aneurysm in the other artery was covered with a bare self-expanding stent. On angiograms 1 month after stenting, the aneurysms treated with our stent graft were completely occluded without significant parent artery stenosis, but the aneurysms treated with the original bare stent were still open. Our high-performance self-expanding stent graft was easily applied to the experimental aneurysms and accomplished complete occlusion of aneurysms in beagles. Further study should be performed for the goal of clinical use.

Structural characterization and mass transfer properties of dense segmented polyurethane membrane: Influence of hard segment and soft segment crystal melting temperature

AbstractAn attempt has been taken to investigate the microstructure and mass transfer properties of polycaprolactone diol (Mn = 2000 g mol–1, PCL 2000)‐based dense segmented polyurethane (SPU) membrane as a function of hard segment (HS) content. Structure of SPUs were investigated by Fourier transform infrared analysis, wide angle X‐ray diffraction, differential scanning calorimetry, dynamic mechanical thermal analysis, and scanning electron microscopy (SEM). On the other hand, mass transfer properties were measured by equilibrium sorption, dynamic sorption, and water vapor permeability measurements. From the experimental results, it was observed that with the increasing HS content in SPU the percentage crystallinity decreases, whereas the glassy state storage modulus increases. α transition temperature of polyurethane copolymers also increases with increasing HS content. SEM micrograph shows the dense surface structure of SPU films. Mass transfer rate of dense polyurethane membranes decreases with increasing HS content. In contrast, hydrophilic segment and soft segment crystal melting could enhance the mass transfer properties. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers

Thermal Degradation Study of Functionalized MWNT Reinforced Segmented Polyurethane Membrane

The thermal degradation of polytetramethylene glycol (PTMG, Mn 1/42900) based polyurethane (PU), along with four different weight contents (such as 0.25, 0.50, 1.0, and 2.5 wt%) of functionalized multiwalled nanotube (MWNT) reinforced PUs are studied in air as well as in nitrogen atmosphere. The degradation results are reported in 10 and 50% weight loss and derivative of thermogravimetry (DTG). As expected, PUs are thermally more stable in nitrogen than in air. However, the influence of MWNT content on thermal stability is unclear. At 0.25 and 0.50 wt% of MWNT content, thermal stability declined and a further increase of MWNT improved the thermal stability of PU. Fourier-transform infrared (FTIR) analysis is also performed for untreated and heat treated films in order to understand the degradation at different temperatures. Free C1/4O stretching neck dimension increases with increasing temperature which signifies breaking of H-bonding detected by FTIR measure ments.

Structural characterization and mass transfer properties of nonporous segmented polyurethane membrane: Influence of hydrophilic and carboxylic group

An attempt has been made to investigate the influence of hydrophilic and carboxylic groups on structure and mass transfer properties of polypropylene glycol (number average molecular weight of 1000 g mol −1, PPG 1000) based segmented polyurethane (SPU). Polyethylene glycol (number average molecular weight of 3400 g mol −1, PEG 3400) (hydrophilic segment) or dimethylol propionic acid (DMPA) (carboxylic group) or combination of PEG 3400 and DMPA were used to modify the SPU. For comparison, SPU without hydrophilic/carboxylic group was also synthesized. Structures were investigated by Fourier-transform infrared (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and tensile tester. Mass transfer properties were investigated by equilibrium sorption and water vapor permeability measurements. FT-IR spectra of C O stretching was indicated that with the introduction of hydrophilic or acid groups in the polymer backbone, the hydrogen bonding of urethane groups were became weaker or stronger respectively. Nearly amorphous structures of all SPU samples were evidenced by WAXD and DSC results. The presence of DMPA increases the interaction between the polymer chains, which increases the glass transition temperature ( T g) and make the polymer tough. In contrast flexible PEG 3400 segment decreases the T g and increases the percent strain at maximum load. Experimental results revealed that the mass transfer properties not only influenced by amorphous region but also on the interaction between the polymer chains. Presence of hydrophilic group enhances the sorption as well as water vapor permeability (WVP). Abrupt changes of mass transfer properties were observed for SPU with PEG 3400 due the presence of more polar group and longer flexible chains of PEG 3400 which will originates holes in the polymer membranes. The membrane with DMPA content, lowest permeabilities was characterized by a higher degree of physical cross-linking imposed by carboxylic functionality.

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

AbstractTo 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

Biocompatible elastomers composed of segmented polyurethane and 2-methacryloyloxyethyl phosphorylcholine polymer

To improve the biocompatibility of a segmented polyurethane (SPU), 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymer was blended in the SPUs, such as Pellethane® and TM-3®, by a solvent evaporation method from a homogeneous solution containing both SPU and MPC copolymer. X-ray electron spectra indicated that the MPC moieties were located at the surface of the SPU membrane blended with the MPC copolymer even when the composition of the MPC copolymer was only 7.5 w/w % against the matrix SPU. The mechanical property of the SPU membranes, as determined by tensile stress-strain measurements, changed very little by addition of the MPC copolymer. Biocompatibility of the MPC copolymer blended membrane was evaluated by plasma protein adsorption and blood cell adhesion on the surface. The amount of fibrinogen adsorbed on the SPU membrane significantly decreased by addition of the MPC copolymers. Moreover, addition of MPC copolymer in the SPU membrane suppressed platelet adhesion and activation. It is concluded that the blending of the MPC copolymer in the SPU membrane is an effective method to improve biocompatibility of the SPU membrane. Copyright © 2000 John Wiley & Sons, Ltd.

Assessing the resistance to calcification of polyurethane membranes used in the manufacture of ventricles for a totally implantable artificial heart.

Ventricles made from segmented polyurethane membranes and used in the fabrication of a totally implantable artificial heart are known to undergo biomaterial-associated calcification. As there is no effective method currently available to prevent such biomaterials from calcifying, a practical solution is to use only materials with a relatively high resistance to calcification, to extend ventricular durability and ensure a longer functional life for the manufactured device. In the present study, an in vitro calcification protocol was used to determine the relative resistance to calcification of six different polyurethanes, namely, Carbothane PC3570A, Chronoflex AR, Corethane 80A, Corethane 55D, Tecoflex EG80A, and Tecothane TT1074A. The results demonstrated that all six polyurethanes did become calcified during the 60-day incubation period in the calcification solution. The degree of calcification was found to be associated with the surface chemistry of the particular polyurethane, with the Tecothane TT1074A exhibiting the highest level. The Corethane 80A and 55D polymers showed a relatively low propensity to calcify. These two membranes can, therefore, be considered as the most appropriate materials for the fabrication of ventricles for a totally implantable artificial heart. In addition, since the calcification occurred primarily at the surface of the membranes, without affecting the bulk microphase structure, the issue of modifying the surface chemistry to reduce the incidence of calcification is discussed.

Improved blood compatibility of segmented polyurethanes by polymeric additives having phospholipid polar groups. I. Molecular design of polymeric additives and their functions.

To improve the blood compatibility of a segmented polyurethane (SPU), 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was blended with the SPU. The MPC was copolymerized with cyclohexyl methacrylate (CHMA) or 2-ethylhexyl methacrylate (EHMA), and the MPC polymers obtained could be dissolved in the same solvent as the SPU (Tecoflex 60). The blended membranes composed of SPU and MPC polymers were prepared by a solvent evaporation method. A small amount of MPC polymer in the blended membrane leached out after immersion in water for 10 days. The X-ray photo electron spectra indicated that the MPC moieties were located at the surface of the SPU membrane blended with poly(MPC-co-CHMA). On the other hand, the poly-(MPC-co-EHMA) was located homogeneously in the SPU membrane. The mechanical properties of the SPU membrane, as determined by tensile stress-strain measurements, changed very little even after addition of the MPC polymers. Blood compatibility of the blended membrane was evaluated by blood-cell adhesion on the surface when the membranes were placed in contact with rabbit whole blood or platelet-rich plasma. The addition of MPC polymer in the SPU membrane dramatically reduced cell adhesion. It is concluded that the blending of the MPC polymer in the SPU membrane is an effective method for imparting nonthrombogenicity.

Improved blood compatibility of segmented polyurethane by polymeric additives having phospholipid polar group. II. Dispersion state of the polymeric additive and protein adsorption on the surface.

To improve the blood compatibility of a segmented polyurethane (SPU), phospholipid polymer, i.e., 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymerized with cyclohexyl methacrylate or 2-ethylhexyl methacrylate, was blended into SPU as a polymeric additive. The blending was achieved by a solvent-evaporation technique from a homogeneous solution containing both the SPU and the MPC polymer. Surface analysis of the SPU membrane blended with the MPC polymer (SPU/MPC polymer membrane) revealed that the MPC polymer was concentrated at the surface of the SPU membrane which contacted the substrate, Teflon, compared with that which contacted air during the membrane-formation period. The dispersion state of the MPC polymer in the SPU membrane was evaluated in detail by staining the MPC unit with osmium tetraoxide. When sonication was applied during preparation of the mixed solution containing SPU and the MPC polymer, the dispersion of the MPC polymer in the SPU membrane was different from that without sonication. That is, the size of the domains of the MPC polymer became smaller but the number of the domains increased. The amount of the MPC polymer mixed with SPU affected the dispersion state. Plasma proteins adsorbed on the SPU/MPC polymer membrane surface after contact with human plasma were detected by gold-colloid-labeled immunoassay. Both albumin and fibrinogen were observed on the SPU membrane; however, the amount of these proteins was reduced on the SPU/MPC polymer membrane. Thus it was concluded that the blood compatibility of the SPU was effectively improved by the blending of the MPC polymer.