Electrospun zein fibers using glyoxal as the crosslinking reagent

After reaction of zein with glyoxal the resulting electrospun fibers have improved resistance to known zein solvents. Durable fibers with diameters of 0.6 μm could be produced. The reaction between zein and glyoxal was carried out in acetic acid (AcOH) at temperatures between 25 and 60°C at various lengths of time. Gelation would occur after higher extents of reaction. During the course of reaction, solution viscosity increased which increased the diameter of the electrospun fibers produced from these solutions. Gel electrophoresis showed increased molecular weight as the reaction progressed. When 6% glyoxal was allowed to react with zein at 25°C for 6 h, the resulting fibers were durable to AcOH as spun. Other formulations required a second thermal treatment to provide solvent durable fabrics. Fibers displayed different secondary structure utilizing far‐UV circular dichroism spectroscopy. The infrared spectra displayed peaks in the C? O region supporting the reaction of glyoxal with hydroxyl groups present on zein. Zein fabrics incorporating glyoxal had modestly improved tensile strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrospinning and crosslinking of zein nanofiber mats

Electrospinning processing can be applied to fabricate fibrous polymer mats composed of fibers whose diameters range from several microns down to 100 nm or less. In this article, we describe how electrospinning was used to produce zein nanofiber mats and combined with crosslinking to improve the mechanical properties of the as‐spun mats. Aqueous ethanol solutions of zein were electrospun, and nanoparticles, nanofiber mats, or ribbonlike nanofiber mats were obtained. The effects of the electrospinning solvent and zein concentration on the morphology of the as‐spun nanofiber mats were investigated by scanning electron microscopy. The results showed that the morphologies of the electrospun products exhibited a zein‐dependent concentration. Optimizing conditions for zein produced nanofibers with a diameter of about 500 nm with fewer beads or ribbonlike nanofibers with a diameter of approximately 1–6 μm. Zein nanofiber mats were crosslinked by hexamethylene diisocyanate (HDI). The tensile strength of the crosslinked electrospun zein nanofiber mats was increased significantly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:380–385, 2007     

Fabrication of antibacterial silver nanoparticle‐modified chitosan fibers using Eucalyptus extract as a reducing agent

Green chemical method could be a promising route to achieve large scale synthesis of nanostructures for biomedical applications. Here, we describe a green chemical synthesis of silver nanoparticles (Ag NPs) on chitosan‐based electrospun nanofibers using Eucalyptus leaf extract. A series of silver salt (AgNO₃) amounts were added to a certain composition of chitosan/polyethylene oxide aqueous acetic acid solution. The solutions were then electrospun to obtain nanofibrous mats and then, morphology and size of nanofibers were analyzed by scanning electron microscopy (SEM). Incubation of AgNO₃‐containing mats into Eucalyptus leaf extract led to the formation of Ag NP clusters with average diameter of 91 ± 24 nm, depicted by SEM and transmission electron microscopy. Surface enhanced Raman spectroscopy also confirmed formation of Ag NPs on the nanofibers. The mats also showed antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria with bigger inhibition zone for extract‐exposed mats against S. aureus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42133.     

Effect of crosslinking procedure on structural,thermal, and functional performances of cellulosic nanofibers: A comparison between chemical and photochemical crosslinking

In the current study, hydroxyethyl cellulose (HEC) based nanofibers were fabricated through electrospinning and then made water insoluble by chemical and photochemical crosslinking. Structural, thermal, and functional performances of electrospun fibers before and after crosslinking were fully assessed by a numerous techniques including microscopy, porosimetry, mechanical analysis, and cell culture study. Both crosslinking procures were found to able to preserve fibrous structure in an aqueous environment for short times, however; chemical process conferred better long‐term morphological stability and cell compatibility. These findings suggest that chemically crosslinked HEC mats may perform as a promising electrospun tissue engineering scaffold. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43832.     

Fabrication of electrospun fibers from a waterborne soy-based polyurethane employing polyethylene oxide as a coformer

The fabrication of electrospun fibers made from aqueous dispersions of polyurethane obtained from renewable sources is an eco-friendly method to produce porous membranes for different applications. Polyethylene oxide (PEO) has been already employed in formulations for allowing fiber formation, but its role was not yet completely understood. In this work the fabrication of electrospun fibers made from biobased polyurethane aqueous dispersion with PEO in order to obtain regular fibers is performed. The role of PEO was studied by thermal analysis, infrared and Raman spectroscopy, rheology, and fiber morphology. Polyurethane fibers were obtained only when PEO was added, otherwise the dispersion is electrosprayed and particles are formed. It was observed that PEO modifies the rheology of dispersion and assists coalescence of polyurethane particles. On the other hand, polyurethane fibers conserved their diameter and their homogeneous structure after removal of PEO by immersion in water, which indicates that the distribution of both polymers was even within the fibers. This work provides both an insight on the role of PEO and a route for the fabrication of eco-friendly biobased polyurethane microfibers from aqueous dispersions.     

Preparation and characterization of ultrafine electrospun polyacrylonitrile fibers and their subsequent pyrolysis to carbon fibers

The present contribution reports the fabrication and characterization of ultrafine polyacrylonitrile (PAN) fibers by electrospinning and further development of the as‐spun PAN fibers into ultrafine carbon fibers. The effects of solution conditions (i.e., solution concentration, viscosity, conductivity, and surface tension) and process parameters (i.e., applied electrostatic field strength, emitting electrode polarity, nozzle diameter, and take‐up speed of a rotating‐drum collector) on morphological appearance and average diameter of the as‐spun PAN fibers were investigated by optical scanning (OS) and scanning electron microscopy (SEM). The concentration, and hence the viscosity, of the spinning solutions significantly affected the morphology and diameters of the as‐spun PAN fibers. The applied electrostatic field strength and nozzle diameter slightly affected the diameters of the as‐spun fibers, while the emitting electrode polarity did not show any influence over the morphology and size of the as‐spun fibers. Utilization of the rotating‐drum collector enhanced the alignment of the as‐spun fibers. Within the investigated concentration range, the average diameter of the fibers ranged between 80 and 725 nm. Finally, heat treatment of the as‐spun fibers with their average diameter of about 450 nm was carried out at 230 and 1000 °C, respectively. Various characterization techniques revealed successful conversion into carbon fibers with an average diameter of about 250 nm. Copyright © 2006 Society of Chemical Industry     

Directional self‐assembly by electrospun wet fibers

In this study, we examined directional self‐assembly by electrospun wet fibers. The landing point of the wet fibers was controllable as its trajectory was strictly limited by the adjustment of the parameters of electrospinning. The wet fibers would not stack on the grounded plate in an irregular pattern but in the direction of an electric field in sequence. The preliminary wet fibers deposited and erected on the ground plate to form a controllable circle. The subsequent wet fibers traveled to the top of the circle directionally to organize a mesh tube. The apical circle of the mesh tube was the precise landing point of the subsequent wet fibers. With the wet fibers landing continuously, the mesh tube grew longer and longer. Finally, the controllable circle grew to be the growing mesh tube step by step. We discovered that the mesh tube was assembled by fibers spontaneously in the electrostatic field. In this article, we also try to explain the mechanism of self‐assembly and the formation of wet fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43003.     

Sulfonated and cross-linked polystyrene ultrafine fibers for the esterification of palmitic acid for biodiesel production

For the need of green and sustainable development, a fibrous solid acid catalyst was developed for the transformation of low cost oils to biodiesel in an efficient and green manner. Polystyrene was electrospun into ultrafine fibers with mean diameter of ~1.34 μm, and then simultaneously cross-linked and sulfonated in sulfuric acid/acetic acid mixed solvent with paraformaldehyde as the external cross-linker. The cross-linking and sulfonation degrees were controllable by changing the ratio of sulfuric acid/acetic acid. After sulfonation and cross-linking, the solvent resistance, chemical structure, and composition of these fibers were separately characterized by scanning electron microscopy, infrared spectroscopy, and elemental analysis. At last, this novel fibrous solid acid catalyst was used to catalyze the esterification reaction of palmitic acid and methanol for biodiesel production. After optimizing the reaction conditions, this fibrous solid acid catalyst can catalyze the esterification of palmitic acid and methanol with the conversion up to 92% under mild reaction conditions. Moreover, due to the fibrous structure, this fibrous solid acid catalyst could be readily separated and reused.     

Palladium complex embedded crosslinked polystyrene nanofibers as a green and efficient heterogeneous catalyst for coupling reactions

A simple and green chemical modification coupled with electrospinning technique has been developed to incorporate tetrakis(triphenylphosphine)palladium [Pd(PPh₃)₄] inside crosslinked polystyrene nanofibers (Pd@CPS) as an efficient and stable heterogeneous palladium catalyst. The catalytic activities and recyclabilities of the prepared Pd@CPS catalyst have been evaluated by using Suzuki and Heck reactions of various aromatic halides separately with phenylboronic acid and alkenes. The Pd@CPS exhibited high-catalytic activities for the Suzuki and Heck reactions of aromatic iodides to afford the products in excellent yields (coupling yields >88%). The catalytic activities and the nanofiber structure remained essentially unchanged even after recycling for five times. The high activities and stabilities of the prepared Pd@CPS catalyst can be attributed to the ultrafine fiber and embedment of palladium active species inside the nanofibers.     

Durable adhesives based on electrospun poly(vinylidene fluoride) fibers

Herein, the fabrication of poly(vinylidene fluoride) (PVDF) fibrous membrane using electrospinning is reported and its use for dry‐adhesive applications is demonstrated. The shear and normal adhesion performance of the samples was investigated using an Instron tensile tester and an atomic force microscope (AFM) respectively. For shear adhesion measurements, the electrospun membrane was finger pressed on to a glass slide and pulled in shear mode using a tensile tester. The thickness of the electrospun membrane was varied and the effect of thickness on shear adhesion was investigated. The shear adhesion strength increased when the thickness of the samples was reduced. Shear adhesion strength of a 200 µm thick sample was determined to be approximately 0.165 N/cm. For normal adhesion measurements, a flat tipless cantilever was used to indent the sample and then retract back to measure the pull‐off force. High shear adhesion strength and normal pull‐off force recorded are attributed to the fine size of the fibers that conform to the asperities present on the surfaces of the glass slide and the AFM cantilever. The durability of the adhesive was also verified by repeating the AFM adhesion measurements over 1000 consecutive attachment–detachment cycles. The pull‐off force was seen to be constant over 1000 attachment–detachment cycles. Our results indicate that these electrospun fibrous membranes can potentially be used as reusable dry‐adhesives. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44393.     

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.     

Effects of solvents on electrospun polymeric fibers: preliminary study on polystyrene

Six solvents [acetic acid, acetonitrile, m‐cresol, toluene, tetrahydrofuran (THF) and dimethylformamide (DMF)] with different properties (eg density, boiling point, solubility parameter, dipole moment and dielectric constant) were used to prepare electrospun polystyrene (PS) fibers. Fiber diameters were found to decrease with increasing density and boiling point of the solvents. A large difference between the solubility parameters of PS and the solvent was responsible for the bead‐on‐string morphology observed. Productivity of the fibers (the numbers of fiber webs per unit area per unit time) increased with increasing dielectric constant and dipole moment of the solvents. Among the solvents studied, DMF was the best solvent that provided PS fibers with highest productivity and optimal morphological characteristics. The beadless, well‐aligned PS fibers with a diameter of ca 0.7 µm were produced from the solution of 10 % (w/v) of PS in DMF at an applied electrostatic field of 15 kV/10 cm, a nitrogen flow rate of 101 ml min^?1 and a rotational speed of the collector of 1500 rev min^?1. Copyright © 2004 Society of Chemical Industry     

基于均匀设计优化制备静电纺丝相变储湿纤维

以醋酸纤维素为包裹材料、聚乙二醇800为相变材料、N,N-二甲基乙酰胺和丙酮为溶剂,采用静电纺丝法制备相变储湿纤维。基于均匀设计和多元非线性回归法研究了各因素对静电纺丝相变储湿纤维综合热-湿性能的影响。结果表明,各因素对性能影响的主次顺序为：聚乙二醇800用量＞N,N-二甲基乙酰胺用量＞醋酸纤维素用量＞反应温度＞干燥温度;优化制备方案：N,N-二甲基乙酰胺用量为11.3 g、醋酸纤维素用量为6.96 g、聚乙二醇800用量为8.12 g、反应温度为37.8 ℃、干燥温度为60.4 ℃.     

Study on the preparation of hyperbranched polyethylene fibers and hyperbranched polyethylene composite fibers via electrospinning

This contribution mainly studied the preparation of hyperbranched polyethylene (HBPE) fibers and HBPE/multiwalled carbon nanotube (MWCNT) composite fibers via electrospinning for the first time. Firstly, the effects of solvents, solution concentration, voltage, and rotating speed of collector on the morphology of HBPE fibers were studied. Among the factors, solvent type, concentration, and voltage showed notable influence on the morphology of HBPE fibers. HBPE has an excellent dispersion effect on CNT in organic solvents. Through ultrasonic dispersion, the HBPE solutions with dispersed MWCNT were obtained. Then HBPE/MWCNT composite fibers were obtained with different contents of MWCNT via electrospinning. The effects of voltage and working distance on the morphology of HBPE/MWCNT composite fibers were investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42517.     

电纺法制备TPU微/纳米纤维的研究进展

本文介绍了电纺热塑性聚氨酯(TPU)制备中所涉及熔融电纺法和溶液电纺法的研究现状,并综述了电纺TPU在医用支架材料、伤口敷料、锂电池电解质、形状记忆材料、吸声材料、压阻敏感性材料方面的应用研究进展。     

Experimental design to evaluate properties of electrospun fibers of zein/poly (ethylene oxide) for biomaterial applications

The production of polymer fibers from the combination of zein and PEO might have great potential in the field of biomaterial. Zein/PEO fibers were obtained in this work through solution electrospinning. An experimental design, 2^4-1, was used for evaluating the influences of PEO content in the blend, distance from the needle tip to the collector, applied electric voltage and solution flow for average fiber diameter and relative-yield process. Beyond this, the relationship between PEO content in the blend and the fiber properties were evaluated through FTIR, DSC, TG, tensile tests, and cytotoxic tests. The factor that exerts the greatest effect on the average fiber diameter response was the electrical voltage. The increase in PEO content in the blend decreased the thermal stability and increased the degree of the fibers' crystallinity. The mechanical tests showed that fibers with higher elongation were obtained at richer PEO blends. The fibers presented cytocompatible characteristics.     

Nanoporous hollow fibers as a phantom material for the validation of diffusion magnetic resonance imaging

Diffusion-weighted magnetic resonance imaging (MRI) is an emerging noninvasive imaging modality. In this study, highly aligned, uniform, nanoporous, hollow polycaprolactone fibers were successfully synthesized in a single step to mimic the axon bundle structure in human white matter. Their porous nature, morphology, and physicochemical properties were carefully studied with respect to their suitability as a phantom material for brain imaging. The aligned fibrous bundles were then arranged into specific angles (30 and 90°), scanned, and evaluated with high-resolution MRI fiber tractography. Diffusion tensor imaging and the tractography of fibers of five different structures at three temperatures were acquired and compared. Furthermore, an integrated brain phantom created from a combination of agar gel and aligned fibrous bundles was also fabricated and analyzed. The results demonstrate the excellent ability of the fibers to mimic the axonal bundles of brain white matter. The fibrous bundles were well mixed in the common agar phantom while retaining their fibrous configuration; this demonstrated their potential as brain white matter phantoms. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47617.     

Chemical treatments for improving adhesion between electrospun nanofibers and fabrics

Nanofiber‐coated fabrics have potential uses in filters and protective clothing. One major challenge is to ensure good adhesion of nanofibers to the fabrics achieving satisfactory durability against abrasion for practical use. This work is aimed to study adhesion mechanisms and their improvement between nanofibers and textile substrates; to achieve this goal cotton fabrics were treated with an alkali solution, while nylon fabrics were treated with ethanol. Adhesion of polyamide‐6 electrospun nanofiber layer to fabrics was evaluated by means of a peeling test. Treated fabrics showed improved bonding towards nanofibers: adhesion energy was ～0.58 J m^?2 for both untreated fabrics, and after treatments increased to 0.93 and 0.86 J m^?2 for cotton and nylon ones, respectively. Optical observations revealed that nanofibers deposited on fabrics are mainly linked to external protruding fibers (i.e., fabric hairiness). Therefore, surface hairiness seems to be the critical factor limiting adhesion. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39766.     

Novel zein‐based electrospun fibers with the water stability and strength necessary for various applications

BACKGROUND: Some of the problems with electrospun zein fiber are that it has very low tenacities in the dry and wet states and that mats of the fiber become films when immersed in water. The fibers are therefore unusable for various applications despite their good biocompatibility and biodegradability. This research was conducted to overcome these problems by electrospinning novel fibers containing various concentrations of zein, citric acid (CA) and sodium hypophosphite monohydrate (SHP) and by crosslinking the zein with CA and with SHP serving as a catalyst. RESULTS: The CA‐crosslinked electrospun zein fiber has as much as 10‐fold greater wet tenacity and 15‐fold greater dry tenacity than regular electrospun zein fiber. The average diameter of these fibers is 451 nm, which is the smallest diameter ever reported for zein‐based electrospun fiber. A mat of this fiber retains its fibrous structure when immersed in water, and the fiber retains about 70% of its tenacity after 16 days at 50 °C and 90% relative humidity. CONCLUSION: The high dry and wet tenacities, good water stability and small diameter of the novel CA‐crosslinked electrospun zein fiber make it attractive for biomedical and other applications that expose zein to water or that require high surface area. Copyright © 2008 Society of Chemical Industry     

Morphologies of electrospun fibers of lignin in poly(ethylene oxide)/N,N‐dimethylformamide

The effects of polyethylene oxide (PEO) molecular weight (Mv), and volume fraction ( ) on the morphology of electrospun sulfur free softwood lignin nanofibers were investigated. Small amounts of PEO were used during preparations of the solutions to aid the electrospinning process. It was found that tripling the PEO volume fraction resulted in a transition from semi‐dilute un‐entangled to semi‐dilute entangled solutions. Conversely, the solution remained in the semi‐dilute un‐entangled regime as the molecular weight was increased by five times. The effects of molecular weight and volume fraction of PEO both on entanglement density and fiber morphology were unified by scaling PEO viscosities as a function of . We investigated and discussed conditions that would produce smooth fibers and conditions that would produce fibers with beads. In the case of beads‐on‐a‐string formation, bead widths remained constant regardless of the molecular weight and concentration of PEO, but the bead length changed. Additionally, we observed a decrease in the diameter of the fibers and the dimension of beads (length and width of beads) with an increase in the electric field used for electrospinning. The aspect ratio of beads increased with increases to both the electric field and the PEO molecular weight or concentration. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44172.