Electrospinning of waterborne polyurethanes

Polyurethane (PU) fibers were obtained by electrospinning of waterborne PU dispersions. As dispersion cannot be electrospun, a water‐soluble polymer (poly (ethylene oxide) (PEO)) was dissolved in the PU dispersion and fibers were obtained from electrospinning the resulting mixture. Pure PU fibers were obtained after removing PEO with water extraction. Continuous PU fibers were obtained using a PU/PEO weight ratio higher than 2.5. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Blends of novel L‐tyrosine‐based polyurethanes and polyphosphate for potential biomedical applications

Elastomeric biodegradable polyurethanes and polyphosphate have been developed using an L ‐ tyrosine‐based diphenolic monomer desaminotyrosine‐tyrosine hexyl ester (DTH). Soft segments, which are polycaproloctone diol (PCL) and polyethylene glycol (PEG) have been used for the synthesis of two biodegradable L ‐tyrosine polyurethanes (LTUs), which are PEG‐C‐DTH and PCL‐C‐DTH. An investigation of the physico‐chemical properties shows that these polymers have dramatically different properties. By blending LTUs with L ‐tyrosine polyphosphate (LTP), we hope to produce a family of materials with a wide range of thermal, morphological, surface, and degradative properties. Examination of the blends shows a smooth surface morphology with a partially phase‐separated structure. These findings are consistent with the results obtained from thermal analysis of the blends. Hydrophilic nature of PEG imparts the PEG‐based blends (PEG‐C‐DTH/LTP) with a significantly higher surface and bulk hydrophilicity compared with the PCL‐based blends (PCL‐C‐DTH/LTP). Finally, the blends demonstrate a rapid initial hydrolytic degradation in phosphate buffered saline (PBS) followed by a significantly slower, prolonged degradation. The observed trend may occur due to the rapid hydrolytic degradation rate of the polyphosphate polymer followed by the degradation of the polyurethane component. Thus, tuning the physical properties by blending LTUs with LTP may be useful for drug delivery device and soft tissue engineering scaffold applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flurbiprofen axetil loaded coaxial electrospun poly(vinyl pyrrolidone)–nanopoly(lactic‐co‐glycolic acid) core–shell composite nanofibers: Preparation,characterization, and anti‐adhesion activity

Flurbiprofen axetil (FA)‐loaded coaxial electrospun poly(vinyl pyrrolidone) (PVP)–nanopoly(lactic‐co‐glycolic acid) core–shell composite nanofibers were successfully fabricated by a facile coaxial electrospinning, and an electrospun drug‐loaded system was formed for anti‐adhesion applications. The FA, which is a kind of lipid microsphere nonsteroidal anti‐inflammatory drug, was shown to be successfully adsorbed in the PVP, and the formed poly(lactic‐co‐glycolic acid) (PLGA)/PVP/FA composite nanofibers exhibited a uniform and smooth morphology. The cell viability assay and cell morphology observation revealed that the formed PLGA/PVP/FA composite nanofibers were cytocompatible. Importantly, the loaded FA within the PLGA/PVP coaxial nanofibers showed a sustained‐release profile and anti‐adhesion activity to inhibit the growth of the IEC‐6 and NIH3T3 model cells. With the significantly reduced burst‐release profile, good cytocompatibility, and anti‐adhesion activity, the developed PLGA/PVP/FA composite nanofibers were proposed to be a promising material in the fields of tissue engineering and pharmaceutical science. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41982.     

Tung oil‐based thermosetting polymers for self‐healing applications

Several bio‐renewable thermosetting polymers were successfully prepared from tung oil through cationic polymerization for the use as the healing agent in self‐healing microencapsulated applications. The tung oil triglyceride was blended with its methyl ester, which was produced by saponification followed by esterification. The changes in storage modulus, loss modulus, and glass transition temperature as functions of the methyl ester content were measured using dynamic mechanical analysis. In addition, the fraction of cross‐linked material in the polymer was calculated by Soxhlet extraction, while proton nuclear magnetic resonance, Fourier transform infrared spectroscopy and TEM were used to investigate the structure of the copolymer networks. The thermal stability of the thermosets as a function of their methyl ester blend contents was determined by thermogravimetric analysis. Finally, the adhesive properties of the thermosets were studied using compressive lap shear and the fracture surfaces were analyzed using SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40406.     

Electrospun gelatin/nylon‐6 composite nanofibers for biomedical applications

We describe the preparation and characterization of gelatin‐containing nylon‐6 electrospun fibers and their potential use as a bioactive scaffold for tissue engineering. The physicochemical properties of gelatin/nylon‐6 composite nanofibers were analyzed using field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, TGA and contact angle and tensile measurements. FE‐SEM and TEM images revealed that the nanofibers were well oriented and showed a good incorporation of gelatin. FTIR spectroscopy and TGA also revealed that there was good interaction between the two polymers at the molecular level. The adhesion, viability and proliferation properties of osteoblast cells on the gelatin/nylon‐6 composite nanofibers were analyzed by an in vitro cell compatibility test. Our results suggest that the incorporation of gelatin can increase the cell compatibility of nylon‐6 and therefore the composite mat obtained has great potential in hard tissue engineering. © 2012 Society of Chemical Industry     

Polyethylene glycol-containing polyurethanes for biomedical applications

The synthesis and characterization of some new polyethylene glycol (PEG)-containing polyurethane elastomers are described. These materials were evaluated with respect to their potential use as biomaterials, more specifically for their use as blood- or urine-contacting materials. The stability of the materials towards heat, hydrolysis and γ-irradiation was examined. Before biological testing, material purity was investigated using X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) revealed smooth, continuous films with a stability towards imaging depending on the chain extender used. Surface plasmon resonance (SPR) experiments indicated a strongly reduced adsorption of human serum albumin (HSA) on these PEG-containing polymers. Atomic absorption spectroscopy (AAS) was used to quantify in vitro calcium deposition after incubation in urine. Bacterial adhesion was strongly reduced and cytocompatibility experiments using fibroblast cultures showed the importance of catalyst residues in the materials. © 1998 SCI.     

Development of transdermal drug‐delivery films with castor‐oil‐based polyurethanes

Two different types of polyurethanes (PUs) were prepared with castor oil, ethylene glycol, isophorene diisocyanate and castor oil, and isophoren diisocyanate and poly‐(ethylene glycol) (400 or 600). PU films were prepared and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and gel permeation chromatography. We prepared transdermal patches by loading different amounts of drug, plasticizer, and penetration enhancer. In vitro drug permeability through the castor‐oil‐based aliphatic PU patches was examined with a Keshary–Chien diffusion cell. The effect of castor oil on the film‐forming properties and the effect of penetration enhancers on diffusion characteristics of indomethacin (IDM) drug through the castor‐oil‐based PU were investigated. Prolonged release of IDM was observed from the prepared PU patches. In vitro drug diffusion revealed that slow and prolonged release of IDM was achieved in the absence of penetration enhancers. The use of penetration enhancers showed a significant effect on drug diffusion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 779–788, 2007     

Antibacterial oil‐based polyurethane films for wound dressing applications

As an alternative to petroleum‐based polyol, hydroxyl containing material was prepared from linseed oil for polyurethane synthesis. Hexamethylene di‐isocyanate (HMDI) and/or 4, 4′‐methylene diphenyl di‐isocyanate (MDI) were used as isocyanate source. The polymerization reaction was carried out without catalyst. Polymer films were prepared by casting‐evaporation technique. The MDI/HMDI‐based polyurethane and its films had higher T_g and better thermal property than that of the HMDI‐based one because of the existence of benzene ring in the polymer chain. Static water contact angle was determined to be 74° and 77.5° for HMDI and MDI/HMDI‐based films, respectively. Water adsorption was found to be around 2.6–3.6% for both films. In vitro degradation of polyurethanes in phosphate buffered saline at 37°C was investigated by gravimetric method. Fourier transform infrared spectroscopy and scanning electron microscopy were used for confirmation of degradation on the polymer surface. The degradation rate of the HMDI‐based polyurethane film was found higher than that of the MDI/HMDI‐based film. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films, and the polyurethane films investigated here was not cytotoxic. Silver‐containing films were prepared using Biocera A® as filler and were screened for their antibacterial performance against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and/or Bacillus subtilis. The films prepared with and without Biocera A® exhibited antibacterial activity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Polypropylene fibers fabricated via a needleless melt‐electrospinning device for marine oil‐spill cleanup

Ultrafine polypropylene (PP) fibers as oil sorbents were fabricated via a needleless melt‐electrospinning device and were characterized by scanning electron microscopy and contact‐angle analysis. PP fibers of various diameters and porosities were obtained by the manipulation of the applied electrical field. The effects of the fiber diameter and porosity on the oil‐sorption capacity and oil‐retention behavior were investigated. The experimental results demonstrate that for fiber diameter on the microscale, the porosity played a paramount role in determining the oil‐sorption capacities. The maximum oil‐sorption capacity of the resulting PP fibers with regard to motor oil and peanut oil were 129 and 80 g/g, respectively; these values were approximately six to seven times that of commercial PP nonwoven fabricated through the melt‐blown method. In addition, even after seven sorption/desorption cycles, the oil‐sorption capacity of the chosen sample was still maintained around 80 g/g, and above 97%, oil could be recovered. This indicated excellent reusability and recoverability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40080.     

Electrospinning of gelatin fibers using solutions with low acetic acid concentration: Effect of solvent composition on both diameter of electrospun fibers and cytotoxicity

Gelatin fibers were prepared by electrospinning of gelatin/acetic acid/water ternary mixtures with the aim of studying the feasibility of fabricating gelatin nanofiber mats at room temperature using an alternative benign solvent by significantly reducing the acetic acid concentration. The results showed that gelatin nanofibers can be optimally electrospun with low acetic acid concentration (25%, v/v) combined with gelatin concentrations higher than 300 mg/mL. Both gelatin solutions and electrospun gelatin mats (prepared with different acetic acid aqueous solutions) were analyzed by Fourier transform infrared spectroscopy and differential scanning calorimetry techniques to determine the chemical and structural changes of the polymer. The electrospun gelatin mats fabricated from solutions with low acetic acid content showed some advantages as the maintenance of the decomposition temperature of the pure gelatin (～ 230°C) and the reduction of the acid content on electrospun mats, which allowed to reach a cell viability upper than 90% (analyzed by cell viability test using human dermal fibroblast and embryonic kidney cells). This study has also analyzed the influence of gelatin and acetic acid concentration both on the solution viscosity and the electrospun fiber diameter, obtaining a clear relationship between these parameters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42115.     

Preparation and characterization of castor oil‐based waterborne polyurethane crosslinked with 2‐amino‐2‐(hydroxymethyl)‐1,3‐propanediol

Crosslinked castor oil (CO)‐based waterborne polyurethane was synthesized from CO, polycarbonate diol, isophorone diisocyanate, 2,2‐dimethylol propionic acid, and 2‐amino‐2‐(hydroxymethyl)‐1,3‐propanediol (THAM) using pre‐polymer process. Fourier transform infrared spectroscopy, X‐ray diffraction, and transmission electron microscopy were utilized to characterize the above‐synthesized polyurethane. The effect of THAM content was studied on particle size, zeta potential, thermogravimetric analysis, differential scanning calorimetry, tensile tests, and contact angle measurement. Results showed that, with the increase of THAM content, the particle size increases and the thermal stability increases. Furthermore, as the THAM content increased from 0% to 1.5%, tensile strength increased from 9.5 to 16.3 MPa, contact angle increased from 67.8° to 87.4°, and bibulous rate decreased from 13.4% to 6.1%, the elongation at break dropped from 154.8% to 37.9%, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45532.     

Vapor‐based polymer coatings for potential biomedical applications

Over the last decade, biology and biotechnology have witnessed an extraordinary development spanning genomics, proteomics, and metabolics. This progress was so rapid and definite that it not only changed the face of modern biology, but indeed altered the way day‐to‐day business is done in biology and related fields. This scientific advancement came with a need for concurrent technological advances. In this context, the ability to interface sophisticated devices with relevant biological microenvironments has emerged as a critical challenge. Already, novel biomaterials are on the horizon that promise to fulfill the rigid criteria of being both biocompatible under the conditions of a versatile range of biological applications and compatible with the increasing demands for miniaturization, integration, and throughput of future device architectures. As currently employed solvent‐based polymer coatings are increasingly reaching their limits, a range of unconventional materials, such as vapor‐based polymer coatings, are discussed as attractive alternatives. One of the main features of vapor‐based polyreactions is their versatility in synthesizing both simple and complex polymers with relative ease and at generally low temperatures. The advantages of the chemical vapor deposition (CVD) technique also include control of the composition and architecture of the resulting materials, high accuracy, solvent‐free environments, excellent adhesion, and the ability to accommodate custom‐tailored surface modifications. For further illustration, selected examples of polymer‐based surface engineering approaches using vapor‐based polyreactions are discussed in this review. For instance, reactive coating technology uses CVD polymerization to deposit a wide range of chemically functionalized polymer coatings on various substrate materials. Its simplicity in providing chemically reactive groups and its applicability to three‐dimensional geometries (e.g. for microfluidics) enables exact tailoring of surface properties and the preparation of biologically relevant microenvironments. CVD‐based reactive coatings are compatible with soft lithographic processes allowing for patterning of proteins, DNA, cytokines, and mammalian cells. Copyright © 2006 Society of Chemical Industry     

Structure‐property relationship of L‐tyrosine‐based polyurethanes for biomaterial applications

The structure‐property relationship of L ‐tyrosine‐based polyurethanes was demonstrated by using different polyols and diisocyanates. L ‐tyrosine‐based chain extender, desaminotyrosyl tyrosine hexyl ester (DTH), was used to synthesize a series of polyurethanes. Polyethylene glycol (PEG) or poly caprolactone diol (PCL) was used as the soft segment and hexamethylene diisocyanate (HDI) or dicyclohexylmethane 4,4′‐diisocyanate (HMDI) was used with DTH as the hard segment. The polyurethanes were characterized to investigate the effect of structure on different polyurethane properties. From FTIR and DSC, these polyurethanes exhibit a wide range of morphology from phase‐mixed to phase‐separated structure. The decreasing molecular weight of the PEG soft segment leads to relatively more phase mixed morphology whereas for PCL‐based polyurethanes the extent of phase mixing is less with decreasing PCL molecular weight. Results show that PCL‐based polyurethanes are mechanically stronger than PEG‐based polyurethanes but PCL‐based polyurethanes degrade slower and absorb less water compared with PEG‐based polyurethanes. The HMDI‐based polyurethanes are less crystalline and comparatively more hydrophobic than HDI‐based polyurethanes. The characterization results show that the polyurethane properties are directly related to the structure and can be varied easily for a different set of properties that are pertinent for biomaterial applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Organic–inorganic hybrid linseed oil‐based urethane oil wood coatings

To prepare alkoxysilane‐functionalized urethane oil (AFUO) using linseed oil, 3‐aminopropyltriethoxysilane (APTES) was first reacted with diisocyanate to obtain an NCO‐terminating oligomer. The reaction was continued by adding linseed oil glyceride to form an AFUO prepolymer. The auto‐oxidative drying coating was obtained after adding a metal dryer to the AFUO prepolymer. Urethane oil (UO) coating, as a control, was obtained by the same procedure as that for AFUO, but without containing alkoxysilane‐functional groups in the formation. Siloxane hybrid urethane oil (SHUO) wood coatings were prepared by mixing tetraethyl orthosilicate (TEOS) solutions, as an external crosslinking agent by sol–gel process, with the AFUO and UO coatings. We found that introducing of APTES into the molecular chains of the UO coating resulted in a film with superior impact and abrasion resistance, and it is the most efficient process to enhance the UO films. The addition of TEOS into AFUO coatings shortened the curing time and further improved the crosslinking density of the AFUO films; however, the physical properties like impact resistance, bending resistance, and gloss were even worse than AFUO films. Mixing of TEOS and UO coating also shorten the curing time and improved the heat resistance, lightfastness, and hardness of the UO coating. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44562.     

A Novel Approach to Prepare Uniaxially Aligned Nanofibers and Longitudinally Aligned Seamless Tubes Through Electrospinning

A novel method to produce uniaxially aligned nanofibers is described, in which a pair of parallel auxiliary electrodes at a positive potential is placed between the needle and the collector electrodes. Charged nanofibers ejecting from the polymer solution are pre‐aligned by the electrostatic repulsion originating from the auxiliary electrodes and deposited on the collector electrodes, forming a narrow mat with the fiber segments strongly curved. By adjusting the conductivity and shape profile of the collector, the curved segments can be straightened longitudinally. A seamless tube composed of longitudinally aligned nanofibers can be obtained. Such seamless tubes may be useful as biomaterials in tissue engineering.

     

Electrospinning polycaprolactone dissolved in glacial acetic acid: Fiber production,nonwoven characterization,and In Vitro evaluation

The electrospinning of polycaprolactone (PCL) dissolved in glacial acetic acid and the characterization of the resultant nonwoven fiber mats is reported in this work. For comparison purposes, PCL fiber mats were also obtained by electrospinning the polymer dissolved in chloroform. Given the processing parameters chosen, results show that 14 and 17 wt % PCL solutions are not viscous enough and yield beaded fibers, 20 and 23 wt % solutions give rise to high quality fibers and 26 wt % solutions yield mostly irregular and fused fibers. The nonwoven mats are highly porous, retain the high tensile strain of PCL, and the fibers are semicrystalline. Cells adhere and proliferate equally well on all mats, irrespective of the solvent used in their production. In conclusion, mats obtained by electrospinning PCL dissolved in acetic acid are also a good option to consider when producing scaffolds for tissue engineering. Moreover, acetic acid is miscible with polar solvents, which may allow easier blending of PCL with hydrophilic polymers and therefore achieve the production of electrospun nanofibers with improved properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41068.     

Electrospinning core‐shell nanofibers for interfacial toughening and self‐healing of carbon‐fiber/epoxy composites

This article reports a novel hybrid multiscale carbon‐fiber/epoxy composite reinforced with self‐healing core‐shell nanofibers at interfaces. The ultrathin self‐healing fibers were fabricated by means of coelectrospinning, in which liquid dicyclopentadiene (DCPD) as the healing agent was enwrapped into polyacrylonitrile (PAN) to form core‐shell DCPD/PAN nanofibers. These core‐shell nanofibers were incorporated at interfaces of neighboring carbon‐fiber fabrics prior to resin infusion and formed into ultrathin self‐healing interlayers after resin infusion and curing. The core‐shell DCPD/PAN fibers are expected to function to self‐repair the interfacial damages in composite laminates, e.g., delamination. Wet layup, followed by vacuum‐assisted resin transfer molding (VARTM) technique, was used to process the proof‐of‐concept hybrid multiscale self‐healing composite. Three‐point bending test was utilized to evaluate the self‐healing effect of the core‐shell nanofibers on the flexural stiffness of the composite laminate after predamage failure. Experimental results indicate that the flexural stiffness of such novel self‐healing composite after predamage failure can be completely recovered by the self‐healing nanofiber interlayers. Scanning electron microscope (SEM) was utilized for fractographical analysis of the failed samples. SEM micrographs clearly evidenced the release of healing agent at laminate interfaces and the toughening and self‐healing mechanisms of the core‐shell nanofibers. This study expects a family of novel high‐strength, lightweight structural polymer composites with self‐healing function for potential use in aerospace and aeronautical structures, sports utilities, etc. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Castor oil and PEG‐based shape memory polyurethane films for biomedical applications

A series of polyurethane film were prepared from poly(ethylene glycol) with different molecular weight (PEG 1500, 3000, and 8000) and castor oil by one‐shot bulk polymerization method. Hexamethylene diisocyanate and 1,4‐buthane diol were used as diisocyanate and chain extender, respectively. In order to characterize the samples, their density, swelling ratio, water contact angle, surface free energy, gel content, thermal, and viscoelastic properties were determined. The effect of the soft segment length (SSL) and hard segment content (HSC) of all polyurethane films on their shape memory behavior such as shape fixity (R_f) and shape recovery (R_r) rates were investigated by bending test. Direct contact and MTT tests were used for assessment of cell adhesion and proliferation. The relatively high R_f and R_r values were obtained for the samples programmed at high temperature difference. R_f increased with decreasing HSC. On the other hand, R_r tended to decrease with increasing SSL. After evaluating experimental data by a nonlinear equation, it was found that HSC is more effective parameter on shape memory property than SSL. The gel content, swelling ratio, and water contact angle of the samples were dependent on both SSL and HSC in their structures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40590.     

Castor oil‐based polyurethanes containing cellulose nanocrystals

Partially foamed and nanocellulose‐reinforced polyurethanes (PU) based on castor oil (CO) were prepared and their different properties were measured and related to their structures. A castor oil‐based polyol (COPO) was obtained by alcoholysis of CO with triethanolamine. The COPO was used in the preparation of partially foamed and solid PU. Cellulose nanofibrils (NC) in the range of the rheological percolation content were incorporated to the materials and the final mechanical properties of these nanocomposites were analyzed. The incorporated NC considerably affected the rheology of the suspensions, which presented solid‐like behavior under frequency sweep tests with the addition of only 0.5 wt% of NC. By increasing the NC concentration the dispersion becomes increasingly difficult. The properties of the solid PU were also affected by the incorporation of NC and a significant increase of the tensile modulus was observed for the 0.5 wt% NC composite, compared to the unfilled solid PU. This behavior was associated to the incorporation of the rigid particle reinforcement and the interfacial bonding. As expected, the partially foamed PU showed lower modulus than the corresponding solid PU. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers