Surface Of Polyurethane Films Research Articles

Coating of silver nanoparticles on polyurethane film surface by green chemistry approach and investigation of antibacterial activity against S. epidermidis

Silver nanoparticles with potential antibacterial properties are included in biomaterials for the production of medical devices, which are used for diagnoses or treatment purposes. The aim of the current study was coating the polyurethane (PU) films with silver nanoparticles (AgNPs) due to their antibacterial efficacy. PU films were first modified by chitosan (CH), treated with AgNO3 to let CH chelate with silver ions, and then treated with vitamin-C (vit C) or glucose (Glu) to reduce the adsorbed ions to atomic silver to form AgNPs. The surfaces of the films were examined by ATR-FTIR, XPS, XRD, and SEM. Chemical bond formation between CH and Ag ions and AgNPs were determined by ATR-FTIR. Meanwhile, XPS and SEM analyses proved the presence of reduced metallic silver and nanoparticles on the film surfaces, respectively. According to the SEM analyses, a homogeneous distribution of AgNPs, with sizes 99–214 nm and 37–54 nm, on the film surfaces were obtained depending on Glu or vit C reduction, respectively. The films presented excellent antibacterial performance against Gram positive Staphylococcus epidermidis ( S. epidermidis). These results suggested that the mentioned green technology can be easily applied to obtain AgNP coated polymeric surfaces with very high antibacterial efficacy. Although there are some studies dealing with AgNP formation on PU sponges or fibers, to the best of our knowledge, this is the first study showing AgNP formation on the CH conjugated PU films.

Submicron topography design for controlling staphylococcal bacterial adhesion and biofilm formation.

Surface topography modification with nano- or micro-textured structures has been an efficient approach to inhibit microbial adhesion and biofilm formation and thereby to prevent biomaterial-associated infection without modification of surface chemistry/bulk properties of materials and without causing antibiotic resistance. This manuscript focuses on submicron-textured patterns with ordered arrays of pillars on polyurethane (PU) biomaterial surfaces in an effort to understand the effects of surface pillar features and surface properties on adhesion and colonization responses of two staphylococcal strains. Five submicron patterns with a variety of pillar dimensions were designed and fabricated on PU film surfaces and bacterial adhesion and biofilm formation of Staphylococcal strains (Staphylococcus epidermidis RP62A and Staphylococcus aureus Newman D2C) were characterized. Results show that all submicron textured surface significantly reduced bacterial adhesion and inhibited biofilm formation, and bacterial adhesion linearly decreased with the reduction in top surface area fraction. Surface wettability did not show a linear correlation with bacterial adhesion, suggesting that surface contact area dominates bacterial adhesion. From this, it appears that the design of textured patterns should minimize surface area fraction to reduce the bacterial interaction with surfaces but in a way that ensures the mechanical strength of pillars in order to avoid collapse. These findings may provide a rationale for design of polymer surfaces for antifouling medical devices.

Single-step fabrication of microsphere arrays on the surface of flexible materials by direct solidification

The formation of microarrays on the surface of flexible materials has great potential value in fabrication of functional devices such as various kinds of flexible electronic sensors. To fabricate microarrays on the surface of flexible materials, many methods have been proposed, such as nanoimprint lithography technique, single-pulse laser interference and colloidal self-assembly. In our study, we present a simple method to fabricate silica microsphere arrays embedded on the surface of polyurethane film in a single-step. We directly solidified self-assembled microspheres at the air-liquid interface, and obtained polyurethane film embedded with silica microarrays on its surface. Compared with other methods, precise operation and complicated equipment are not required. In addition, we also utilized the fabricated microarrays as a template to fabricate concave microarrays on the surface of other flexible materials.

Transparent and stretchable capacitive pressure sensor using selective plasmonic heating-based patterning of silver nanowires

This study utilizes the characteristics of an Ag nanowire (AgNW) that can rapidly generate heat under high energy pulsed light (HEPL) incidence. Upon HEPL irradiation, the AgNWs melted the polymer in contact with them owing to the instantaneous heat generation, thereby inducing wetting and adhesion properties; the areas unaffected by the HEPL irradiation could be easily peeled, as they were directly placed on the surface of the film without any physicochemical reactions. Thus, we easily fabricated a sensor comprising of tandem compound patterns of AgNWs on the polyurethane film surface, without employing photolithography, etching, lamination, or any additional materials. The capacitance formed in the electrode sensitively varied with the applied pressure, implying that it could be used as a stretchable and transparent pressure sensor.

Anchored quaternary ammonium salts adsorbed on polyurethane film surfaces

A flexible, thermoset and transparent polyurethane (PUR) film with high glass transition temperature, has been deployed as a substrate for anchoring anti-bacterial molecular layers. These layers are formed by adsorbing, from an aqueous solution, a silyl anchoring quaternary ammonium salt (AQAS) with a long alkyl chain (C18) onto the PUR film surface, followed by thermal curing at 160 °C. The presence of AQAS adsorbed on the PUR film surface is confirmed by the appearance of a distinctive N1 s level XPS peak at 402 eV, attributed to quaternary nitrogen (N+). The carbonyl groups on the PUR surface appear to be the main surface binding sites for the adsorbed AQAS molecules. This interpretation is validated by the relative decrease in the intensities observed for the ν (CO) at 1700 cm−1 in the infrared spectra, and decreases in the intensity of the C1 s binding energy peak for CO at 289 eV in the XPS spectra of the PUR following AQAS adsorption. Leaching studies suggest a chemisorbed first layer and several leachable higher layers of oligomeric forms of AQAS. A PUR surface incorporating a blended polydimethylsiloxane additive exhibits similar adsorptive capacity to pristine PUR. However exposing the PUR films to oxygen plasma treatment prior to AQAS adsorption leads to a higher coverage of the adsorbate on the PUR surface. The anchoring quaternary ammonium salt (AQAS) in this current work has established potencies against a wide range of critical organisms. Antibacterial assays adapted from the JIS 2801 wet fomite method confirm the potency (3-log reduction) of these PUR-AQAS films against Staphylococcus aureus and Escherichia coli.

A Facile Activation Method for Improving the Wettability of Polyurethane Surfaces

This work reports the activation of polyurethane film surfaces in order to enrich them with polar groups such as -NH2, -OH, -COOH or radicals, which further allows immobilization of several bioactive compounds. UV-activation was used to introduce new groups on the polymer surface without affecting the bulk properties. The current arising species improve the wettability of the PU surfaces as it was observed from the static contact angle measurements. The structure and composition of the new PU surfaces were analyzed by using ATR-FTIR spectroscopy. The results suggested the possibility of modifying the PU surfaces in a shorter time periods, in order to provide many sites to attach other biomacromolecules by polar interaction or hydrogen bonding.

Modification of polymer surfaces based on polyurethanes with photochromic compounds

The possibility of covalent fixing of hydroxyl-containing photochromic compounds on the surface of polyurethane films containing excess isocyanate groups was studied. By comparing the spectral-kinetic characteristics of polyurethane films treated with solutions and films with chromene or spirooxazine derivatives introduced into the bulk polymer, it was concluded that in the first case the polymer swells and the photochromic compound becomes distributed predominantly in the bulk polymer rather than on the surface.

Surface hydrophobic modification of polyurethanes by diaryl carbene chemistry: Synthesis and characterization

Dodecyl diaryl diazomethane was firstly synthesized from 4,4-dihydroxybenzophenone and 1-bromododecane by a series of reaction steps. Then water-borne polyurethane films with different amount of DMPA were prepared, as well as a type of solvent-borne polyurethane film for comparison. Finally, all these polyurethane films were modified by dodecyl diaryl diazomethane. The dodecyl diaryl carbene was generated from dodecyl diaryl diazomethane by strong solar light, which was very convenient to insert into the XH bonds (X = C, N) on the surface of polyurethane films. The contact angle test was used to characterize these films and depict the surface property. DSC analysis and tensile test were used to investigate the physical properties of polyurethane films before and after modification. It was suggested that the hydrophobic modification protocol with carbene insertion was very useful and convenient to prepare water-proof coatings outdoors under direct solar-light exposure.

Various nanoparticle morphologies and surface properties of waterborne polyurethane controlled by water.

Water plays important roles in organic reactions such as polyurethane synthesis, and the aqueous solution environment affects polymer morphology and other properties. This paper focuses on the morphology and surface properties of waterborne polyurethane resulting from the organic reaction in water involving different forms (solid and liquid), temperatures and aqueous solutions. We provide evidence from TEM observations that the appearance of polyurethane nanoparticles in aqueous solutions presents diverse forms, including imperfect spheres, perfect spheres, perfect and homogenous spheres and tubes. Based on the results on FTIR, GPC, AFM and XRD experiments, we suggest that the shape of the nanoparticles may be decided by the crimp degree (i.e., the degree of polyurethane chains intertangling in the water environment) and order degree, which are determined by the molecular weight (Mn) and hydrogen bonds. Meanwhile, solid water and high-temperature water can both reduce hard segments that gather on the polyurethane film surface to reduce hydrophilic groups and produce a soft surface. Our findings show that water may play key roles in aqueous polymer formation and bring order to molecular chains.

Preparation of hydrocarbon/fluorocarbon double-chain phospholipid polymer brusheson polyurethane films by ATRP

To fabricate artificial biomembrane mimicking cell surfaces, hydrocarbon/fluorocarbon double-chain phospholipid macromonomer was grafted on polyurethane (PU) film surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). The surface structures of modified PU film surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. The results indicate that initiator densities on these polymer film surfaces have a significant impact on graft polymerization of this fluorocarbon phospholipid macromonomer. The phospholipid polymer brushes grafted on PU film surfaces could self-assemble into biomimetic membranes under water environment, as demonstrated by liquid/liquid static contact angle measurement, atomic force spectroscopy (AFM), and attenuated total reflectance Fourier transform infrared (ATR-FTIR). These biomimetic membranes could maintain water within them as the “surrounding” water. Such would be favorable condition for the preservation of native conformational state of proteins and cell membranes. This work provides a new approach to fabricate biomimetic membranes on biomaterials surfaces.

Layer-by-layer assembly of epidermal growth factors on polyurethane films for wound closure

To facilitate the healing of chronic wounds, growth factors such as epidermal growth factor need to be safely encapsulated for their sustained and effective delivery to the wound bed. Using a layer-by-layer assembly technique, epidermal growth factor is successfully encapsulated on the surface of poly(acrylic acid)-modified polyurethane film. The amount of encapsulated epidermal growth factor is controlled by adjusting the number of chitosan/epidermal growth factor bilayers. A controlled release of epidermal growth factor from the surface of polyurethane film for a period of five days is achieved with well-retained bioactivity (over 90%) as evidenced by a cell proliferation assay. In an invitro cellular wounding assay, the cell gap covered with the epidermal growth factor-loaded polyurethane film closes at a rate more than twice as fast as that covered with a control polyurethane film. Fluorescent staining of F-actin reveals that the released epidermal growth factor induces differences in cytoskeletal organization, suggesting that stimulated cell migration also contributes to the close of the cell gap.

Surface Modification of Castor Oil‐Based Polyurethane by Polyacrylic Acid Graft using a Two‐Step Plasma Treatment for Biomedical Applications

ABSTRACTThe aim of this study is design and prepare medical grade polyurethane (PU) film based on castor oil without any additives. Acrylic acid (AAc) was grafted onto the surface of PU films using a two‐step oxygen plasma treatment. The first step of this method includes oxygen plasma pretreatment of the PU films, immersion in AAc monomeric solution, removal from the solution, and drying. The second step was carried out by plasma polymerization of preadsorbed reactive monomers on the surfaces of dried pretreated films. The effects of pretreatment time length and monomer concentration were studied on AAc graft amount. The surface of the modified PU films were characterized using attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy, scanning electron microscopy (SEM), and water drop contact angle measurements. The ATR‐FTIR results proved that the carbonyl (CO) and hydroxyl groups (OH) of AAc give rise to an absorption peak at 1698 cm–1, which was observed in the spectra of the modified PU. The SEM micrographs showed that poly(acrylic Acid) (PAAc)–grafted PU films have a different pattern compared with nonmodified PU films. Moreover, it was found that a decrease in contact angle indicated to a higher grafting amount of polymer. Finally, L929 fibroblast cell culture was done onto the PAAc–PU films. It was observed that cells are spherical and not uniformly distributed on the modified polymer surface.

Chitosan/heparin surface modified polyacrylic acid grafted polyurethane film by two step plasma treatment

The aim of this study is to design an artificial skin dress. A multilayer skin dressing included synthesised castor oil based polyurethane (PU) as the outer layer and two biopolymeric layers of heparin and chitosan as the inner layers were prepared. The surface of PU film was activated using two steps oxygen radio frequency plasma treatment. The surface of the modified PU films characterised by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy and water drop contact angle measurements. Scanning electron microscopy observations confirmed the presence of grafted poly acrylic acid on the surface of PU films. Also, heparin and chitosan were immobilised on PU films. In vitro cell culture showed that the samples have an excellent biocompatibility with L929 fibroblast cells. Cell adhesion and proliferation of cells on the chitosan/heparin immobilised surfaces showed better behaviours compared with poly (acrylic acid) grafted PU film.

Degradation of Polyurethane by Aspergillus flavus (ITCC 6051) Isolated from Soil

The present study deals with the isolation of fungi from soil with the ability to degrade polyurethane (PU). A pure fungal isolate was analyzed for its ability to utilize PU as a sole carbon source in shaking culture for 30 days. Incubation of PU with Aspergillus flavus resulted in 60.6% reduction in weight of PU. The scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) results showed certain changes on the surface of PU film and formation of some new intermediate products after polymer breakdown. Thermogravimetric curves showed changes between the thermal behavior of the samples that were inoculated with A. flavus and control. FTIR spectra showed detectable changes in control and incubated samples, suggesting that degradation occurs, with the decreased intensity of band at 1,715 cm(-1), corresponding to ester linkages. We have identified an extracellular esterase activity which might be responsible for the polyurethanolytic activity.

Chemically induced graft copolymerization of 2-hydroxyethyl methacrylate onto polyurethane surface for improving blood compatibility

To improve hydrophilicity and blood compatibility properties of polyurethane (PU) film, we chemically induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto the surface of polyurethane film using benzoyl peroxide as an initiator. The effects of grafting temperature, grafting time, monomer and initiator concentrations on the grafting yields were studied. The maximum grafting yield value was obtained 0.0275g/cm2 for HEMA. Characterization of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurements. ATR-FTIR data showed that HEMA was successfully grafted onto the PU films surface. Water contact angle measurement demonstrated the grafted films possessed a relatively hydrophilic surface. The blood compatibility of the grafted films was preliminarily evaluated by a platelet-rich plasma adhesion test and hemolysis test. The results of platelet adhesion experiment showed that polyurethane grafted polymerization with monomer of 2-hydroxyethyl methacrylate had good blood compatibility featured by the low platelet adhesion. Hemolysis rate of the PU-g-PHEMA films was dramatically decreased than the ungrafted PU films. This kind of new biomaterials grafted with HEMA monomers might have a potential usage for biomedical applications.

Study on surface hydrolytic kinetics of poly(vinyl acetate) grafted onto polyurethane film

Alkali catalytic hydrolysis of poly(vinyl acetate) (PVAc) grafting onto polyurethane film surface was a heterogeneous reaction. The hydrolysis was carried on the PVAc particle surface, and the concentration of the alkali in the system was tested by titration method. The kinetics of PVAc surface hydrolytic reaction was studied by simple second-order reaction model. From linear regression analysis of experimental data, we inferred that the activation energy (E a ) and pre-exponential factor (A) of PVAc surface hydrolytic reaction were 70.7 ± 0.2 kJ mol−1 and (5.7 ± 0.5) × 1012 kg mol−1 s−1, respectively. The results of transmission electron microscopy stated that the apparent hydrolytic degree was 2.1% when the surface of PVAc particle hydrolyzed absolutely.

ATR—FTIR Studies of the Temperature Effects on Polyurethane Doped with Silver Nanoparticles

We investigated by attenuated total reflection Fourier infrared spectroscopy the chemical behavior of macromolecules on the surface of polyurethane microporous film doped with silver nanoparticles at temperatures between 25 and 200°C. Silver nanoparticles interact with the urethane group and form a urethane-silver-urethane structure with a specific surface configuration and a higher resistance to temperature. Chemical transformations of the macromolecules on the surface of polyurethane film depend on both the silver nanoparticles concentration and temperature.

Study on Preparation and Properties of Nitric Oxide Releasing Polyurethane

In this study, a novel nitric oxide (NO) endogenously releasing polyurethane (PU) material, i.e. PU-g-L-cysteine(PU-Cys), was synthesized by grafting L-cysteine on the film surface. Fluorescence analysis and a BCA method were used to characterize qualitatively and quantitatively the grafted L-cysteine. The results showed that L-cysteine was successfully immobilized on the PU film surface and the density of L-cysteine grafted was calculated to be 15.3nmol/cm2. The NO releasing behavior study of PU-Cys film demonstrated that endogenous NO could be continuously released from PU-Cys film and the accumulated releasing amount within 3h added up to 1.06nmol/cm2. The releasing rate of NO was well matchable to the self-releasing rate of resting platelets in human body. The results of dynamic blood clotting test and hemolysis ratio measurement showed that PU-Cys film had a better haemocompatibility than PU film, which might be the result of endogenously released NO inhibiting platelet adhesion and thrombus formation. Therefore, PU-Cys with the property of endogenous NO releasing is expected to be an ideal blood compatibility material in clinical application.

Structure and Drug Release in a Crosslinked Poly(Ethylene Oxide) Hydrogel

Hydrogels are a continuously expanding class of pharmaceutical polymers designed for sustained or controlled drug release. The structure and intermolecular interactions in such systems define their macroscopic properties. The aim of this study was to investigate the mechanism of swelling, drug impregnation, and drug release from poly(ethylene oxide) (PEO) gel crosslinked by urethane bonds. A combination of SAXS/WAXS/SANS techniques enabled us to determine the phase transition between lamellar and extended gel network, and to apply different descriptions of crystallinity, based on lamellar and crystal lattice structures. It is shown that even low (1-7% w/w) loading of model drugs acetaminophen and caffeine, produced significant disorder in the polymer matrix. This effect was particularly pronounced for acetaminophen due to its specific ability to form complexes with PEO. The drug-release profiles were analyzed using a general cubic equation, proposed for this work, which allowed us to determine the gel hydration velocity. The results indicate that the release profiles correlate inversely with the polymer crystallinity.

PDMS‐Modified Polyurethane Films with Low Water Contact Angle Hysteresis

AbstractSummary: Polyurethane (PU) films with low water contact angle hysteresis (CAH) were prepared by employing less than 0.2 wt.‐% of mono‐ or bihydroxyl‐functionalized polydimethylsiloxane (PDMS) of 60–70 DMS repeat units. A Si content of as low as 0.03 wt.‐% was sufficient to lead to a CAH of 20°. The curing temperature demonstrated strong effects on the wetting behavior of the PDMS‐modified PU films: a relatively low curing temperature (40 °C) resulted in stronger surface segregation of PDMS than higher curing temperatures, giving rise to high water receding CAs and thus low CAH. It was found from angle‐resolved X‐ray photoelectron spectroscopy analysis that the surface silicon content was greater when cured at a lower temperature. The surface of PDMS‐modified PU films was very smooth from AFM observations, but the Si content had strong effects on the surface phase contrast. The chain length of 60–70 DMS repeating units for both mono‐ and bifunctional PDMS appeared to be long enough to prevent the surface reorganization during the CA measurements.Schematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.magnified imageSchematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.