Plasma-Assisted Preparation of High-Performance Chitosan Nanofibers/Gauze Composite Bandages

In this work, novel composite bandages were prepared by electrospinning chitosan nanofibers on 100% cotton substrate fabric. In the composite bandages, chitosan nanofiber web serves as a primary wound dressing whereas cotton substrate as a backing material. Cotton substrate was given plasma pretreatment and composite bandages were given plasma posttreatment to improve the durability of composite bandages and adhesion between nanofiber and cotton substrate layers. The adhesion of the nanofibers to the substrates was assessed by qualitative and quantitative techniques. Plasma pretreatment of the substrate with 100% helium and 99% helium/1% oxygen plasmas showed up to four times increase in force required to peel off the nanofiber layer. Even more increase in adhesion was obtained when composite bandages were given plasma pretreatment to substrate as well as posttreatment to composite bandages. Storage modulus, glass transition temperature, and crystallinity of untreated He and He/O₂-plasma treated chitosan nanofiber web were studied to observe the effect of plasma treatment on the chitosan nanofibers using dynamic mechanical analysis, differential scanning calorimetry, and wide angle X-ray diffraction, respectively. To understand the mechanism of improved adhesion, surface elemental analysis of plasma treated chitosan nanofibers and cotton substrate was carried out using X-ray photoelectron spectroscopy.     

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     

Improvement in nanofiber filtration by multiple thin layers of nanofiber mats

Nanofiber filtration is drawing great interest nowadays because of its large surface collection area as well as low air resistance. In this study, electrospun nanofiber mats of different thicknesses were evaluated for their filter quality factors. Shorter-term electrospun fiber mats exhibited a better quality factor than those longer-term electrospun ones. Multiple thin layers of nanofiber mats to improve the filter quality of the nanofiber filters were then evaluated. Filtration test results showed that the filter made up of multiple thin layers of nanofiber mats had a filter quality factor much higher than the single thick layer nanofiber mat. Better thickness uniformity in the multi-layer structure due to stacking compensation and smaller fiber diameters in nanofibers of short-term deposition time are two possible reasons for the improvement of the filter quality.     

Preparation and antibacterial activity of PET/chitosan nanofibrous mats using an electrospinning technique

The nanofiber deposition method, by electrospinning, was employed to introduce antibacterial activity and biocompatibility to the surface of poly (ethylene terephthalate) (PET) textiles. The polymer blends of PET and chitosan were electrospun on to the PET micro‐nonwoven mats for biomedical applications. The PET/chitosan nanofibers were evenly deposited on to the surface, and the diameter of the nanofibers was in the range between 500 and 800 nm. The surface of the nanofibers was characterized using SEM, ESCA, AFM, and ATR‐FTIR. The wettability of the PET nanofibers was significantly enhanced by the incorporation of chitosan. The antibacterial activity of the samples was evaluated utilizing the colony counting method against Staphylococcus aureus and Klebsiella pneumoniae. The results indicated that the PET/chitosan nanofiber mats showed a significantly higher growth inhibition rate compared with the PET nanofiber control. In addition, the fibroblast cells adhered better to the PET/chitosan nanofibers than to the PET nanofibers mats, suggesting better tissue compatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polymeric nanofibers containing solid nanoparticles prepared by electrospinning and their applications

Generally, polymer solution or sol–gel is used to produce electrospun nanofibers via the electrospinning technique. In the utilized sol–gel, the metallic precursor should be soluble in a proper solvent since it has to hydrolyze and polycondensate in the final solution; this strategy straitens the applications of the electrospinning process and limits the category of the electrospinnable materials. In this study, we are discussing electrospinning of a colloidal solution process as an alternative strategy. We have utilized many solid nanopowders and different polymers as well. All the examined colloids have been successfully electrospun. According to the SEM and FE SEM analyses for the obtained nanofiber mats, the polymeric nanofibers could imprison the small nanoparticles; however, the big size ones were observed attaching the nanofiber mats. Successfully, the proposed strategy could be exploited to prepare polymeric nanofibers incorporating metal nanoparticles which might have interesting properties compared with the pristine. For instance, PCL/Ti nanofiber mats exhibited good bioactivity compared with pristine PCL. The proposed strategy can be considered as an innovated methodology to prepare a new class of the electrospun nanofiber mats which cannot be obtained by the conventional electrospinning technique.     

Oxidative solution polymerization of aniline hydrochloride onto electrospun nanofibers mats of polylactic acid: Preparation method and characterization

In this work, we present the preparation of polylactic acid (PLLA)/polyaniline (PANI) conductive composite nanofibers mats. They are prepared by bulk oxidative solution polymerization of PANI onto electrospun non‐woven fibers mats of PLLA. The PANI ratio in the composite is about 70%w/w. Scanning electron microscopy (SEM) shows that PLLA nanofibers are randomly oriented, beads free with diameters of 186 ± 85 nm, The PLLA/PANI composite nanofibers diameter values are 518 ± 128 nm with a good adherence between PANI and PLLA nanofibers. DSC and XRD measurements reveal an amorphous structure of the electrospun PLLA fibers due to the rapid evaporization of the solvent. FTIR and UV–vis spectra reflect good mutual interactions between PANI and PLLA chains. The DC‐conductivities ( ) far better than other published ones for similar composites prepared by bulk oxidative solution polymerization of PANI onto other electrospun nanofiber mats or with electrospun nanofibers from a solution mixture of PLLA and PANI. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41618.     

Toughened electrospun nanofibers from crosslinked elastomer‐thermoplastic blends

A crosslink‐able elastomeric polyester urethane (PEU) was blended with a thermoplastic, polyacrylonitrile (PAN), and electrospun into nanofibers. The effects of the PEU/PAN ratio and the crosslinking reaction on the morphology and the tensile properties of the as‐spun fiber mats were investigated. With the same overall polymer concentration (9 wt %), the nanofiber containing higher composition of PEU shows a slight decrease in the average fiber diameter, but the tensile strength, the elongation at break and tensile modulus of the nanofiber mats are all improved. These tensile properties are further enhanced by slight crosslinking of the PEU component within the nanofibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Coating of polyelectrolyte multilayer thin films on nanofibrous scaffolds to improve cell adhesion

The adhesion of L929 cells to poly(?‐caprolactone) (PCL) nanofibers was successfully improved via coating with polyelectrolyte multilayer thin films (PEMs), which enhanced the potential of this material as a scaffold in tissue engineering applications. With the electrostatic self‐assembly technique, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4‐styrene sulfonate) (PSS) were formed as four‐bilayer PEMs on electrospun PCL nanofiber mats. Because PDADMAC and PSS are strong polyelectrolytes, they provided stable films with good adhesion on the fibers within a wide pH range suitable for the subsequent processes and conditions. PDADMAC and gelatin were also constructed as four‐bilayer PEMs on top of the PDADMAC‐ and PSS‐coated nanofibers with the expectation that the gelatin would improve the cell adhesion. L929 cells from mouse fibroblasts were then seeded on both uncoated and coated scaffolds to study the cytocompatibility and in vitro cell behavior. It was revealed by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay that both the uncoated and coated nanofiber mats were nontoxic as the cell viability was comparable to that of those cultured in the serum‐free medium that was used as a control. The MTT assay also demonstrated that cells proliferated more efficiently on the coated nanofibers than those on the uncoated ones during the 48‐h culture period. As observed by scanning electron microscopy, the cells spread well on the coated nanofibers, especially when gelatin was incorporated. The surface modification of PCL nanofiber mats described in this research is therefore an effective technique for improving cell adhesion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

ITO electrode modified by self-assembling multilayer film of polyoxometallate on poly(vinyl alcohol) nanofibers and its electrocatalytic behavior

Poly(vinyl alcohol) (PVA) nanofiber mats were collected on indium tin oxide (ITO) substrate by electrospinning method. A multilayer film composed of α-[P₂W₁₈O₆₂]⁶⁻ (abbr. P₂W₁₈), a polyoxometallate (POM) anion, and poly(diallymethylammonium chloride) (abbr. PDDA) was fabricated by layer-by-layer (LBL) self-assembly technique on the PVA/ITO electrode. The PDDA/P₂W₁₈ multilayer film could be unselectively or selectively deposited on the PVA/ITO electrode via changing the amount of PVA nanofibers on the ITO substrate. The scanning electron microscope (SEM) images showed that when the electrospun time was short the PDDA/P₂W₁₈ multilayer film was unselectively deposited on PVA nanofiber mats because the amount of PVA nanofibers was too little to cover most of the ITO substrate. However, when the electrospun time was long enough, the PDDA/P₂W₁₈ multilayer film was selectively deposited on PVA nanofiber mats because of the larger surface area and higher surface energy of PVA nanofibers in comparison with the flat ITO substrate. Growth process of the multilayer film was determined by cyclic voltammetry (CV). Electrocatalytic effects of the PDDA/P₂W₁₈ multilayer film unselectively and selectively deposited on the PVA/ITO electrode on NO₂⁻ were observed.     

Comparisons between silk fibroin nonwoven electrospun fabrics using aqueous and formic acid solutions

The objective of this study is to compare the spinnability, morphology, structure, mechanical properties, and cell compatibility of the silk fibroin nanofiber nonwoven electrospun fabrics using aqueous (AQ) solution and formic acid (FA) solution. The lower limit concentration was 5?wt% and 3?wt% of AQ solution and FA solution for electrospinning, respectively. The fiber diameter of electrospun fabric using FA solution was larger than that using aqueous solution at the same concentration. The secondary structure contents of silk fabrics were same between AQ and FA solutions. FA was remained in silk nanofibers, and the remained FA could be neutralized. Young’s modulus and cell adhesion on electrospun fabric using FA was lower than that using AQ solution. On the contrary, lower cell proliferation rate on electrospun fabric using FA was kept even after neutralization.     

Spider-net within the N6, PVA and PU electrospun nanofiber mats using salt addition: Novel strategy in the electrospinning process

Electrospun nanofibers are promising candidates in the nanotechnological applications due to the advantages of the nanofibrous morphology. Therefore, many attempts were reported to modify the electrospun mats to gain more beneficial properties. In the present study, we are introducing a strategy to synthesize electrospun polymeric nanofiber mats containing spider-net binding the main nanofibers. Addition with long stirring time of a metallic salt having tendency to ionize rather than formation of sol–gel in the host polymer solution reveals to synthesize a spider-net within the electrospun nanofibers of the utilized polymer. Nylon6, polyurethane and poly(vinyl alcohol) have been utilized; NaCl, KBr, CaCl₂ and H₂PtCl₆ have been added to the polymeric solutions. In the case of nylon6 and poly(vinyl alcohol), addition of the inorganic salts resulted in the formation of multi-layers spider-network within the electrospun nanofibers mats. The synthesized spider-nets were almost independent on the nature of the salt; the optimum salt concentration was 1.5 wt%. The metallic acid led to form trivial spider-nets within both of nylon6 and poly(vinyl alcohol) nanofibers. In a case of polyurethane, few spider-nets were formed after salt addition due to the low polarity of the utilized solvents. According to TEM analysis, the synthesized spider-net consisted of joints; the later issued from the main nanofibers at Taylor's cone zone. The spider-net improved the mechanical properties and the wetability of the nylon6 nanofiber mats, accordingly a mat having amphiphilic feature has been prepared.     

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.     

Enhancement of heavy metal ion adsorption using electrospun polyacrylonitrile nanofibers loaded with ZnO nanoparticles

This article describes the adsorption and tensile behavior of electrospun polyacrylonitrile (PAN) nanofiber mats loaded with different amounts of ZnO [0.5, 1.0, 2.0, and 5.0 wt%] nanoparticles. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforminfrared (FTIR) spectroscopy, and thermal gravimetric analysis (TGA) were utilized to characterize the resulting composite nanofibers. Microscopic investigations revealed that the increase in surface roughness and diameter of the electrospun PAN nanofibers was due to the addition of ZnO nanoparticles. Adsorption results indicated that the fabricated PAN/ZnO (2.0 wt%) composite nanofiber mats showed the best adsorption performance with 261% and 167% increase in adsorption capacities for Pb(II) and Cd(II) from aqueous solutions, respectively, compared to pristine PAN nanofibers. The adsorption equilibrium was reached within 60 min, and the process could be described using the nonlinear pseudo-second-order kinetic model. The adsorption isotherm study was better represented by the Langmuir model, which suggested a homogeneous distribution of the monolayer adsorptive sites on the surface of the composite nanofibers. Mechanical testing revealed that the decrease in tensile strength and elongation at breakof the PAN/ZnO composite nanofiber mats was due to the formation of some bead defects and agglomerates within the structure of the PAN nanofibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47209.     

Effect of organic solvent on morphology and mechanical properties of electrospun syndiotactic polypropylene nanofibers

We study the stress–strain behaviors of the electrospun sPP single nanofibers as well as nonwoven mats, which were electrospun from sPP solutions using two different solvents (decalin and cyclohexane) by electrospinning. The effects of organic solvents were explored on the morphologies and the mechanical properties of the corresponding electrospun sPP single nanofibers and nonwoven mats. It was found that the nature of organic solvents dramatically affected the surface morphologies, the circular and looping deposition of the electrospun sPP fibers, and the mechanical properties. The tensile strength of both electrospun sPP single nanofibers and nonwoven mats prepared from decalin-base solution was stronger than that of cyclohexane-base solution.     

Anion conductive polymer nanofiber composite membrane: effects of nanofibers on polymer electrolyte characteristics

Polymer composite membranes composed of anion conductive polymer nanofiber mats and the corresponding polymer matrix were prepared and characterized for future alkaline fuel cells. In this paper, electrospinning was attempted to fabricate anion conductive nanofiber mats. The anion conductivity of the composite membrane was higher than the corresponding membrane without nanofibers under all conditions due to outstanding anion conductive characteristics of the nanofibers. In addition, because of the rigid and anisotropic structure of the nanofibers, membrane stabilities such as reductive degradation resistance and mechanical strength were very much improved. The gas permeability and excessive hydration swelling that will degrade fuel cells after long‐term operation were suppressed in the nanofiber composite membrane. These results indicated that excellent properties of the anion conductive nanofibers were demonstrated even in the composite membrane, leading to the potential application of anion conductive nanofibers in future fuel cells. © 2016 Society of Chemical Industry     

Enhanced Piezoelectric Performance of Electrospun Polyvinylidene Fluoride Doped with Inorganic Salts

A novel approach to preparing electrospun polyvinylidene fluoride (PVDF) nanofibers is proposed, with high piezoelectric performance. PVDF nanofibers are doped with inorganic salts without the use of any postpolarization treatment. Twenty‐six salts are doped into the nanofibers and their piezoelectric properties are studied. The salts are classified into three groups based on their differing piezoelectric enhancement effects. A piezoelectric nanogenerator fabricated with an optimized electrospun PVDF nanofiber mat shows a piezovoltage seven times greater than that of a device based on undoped nanofibers. The simple and low‐cost approach to fabricate these piezoelectric nanofiber mats may broaden the range of industrial applications of these materials in energy‐harvesting devices and portable sensors.     

Effects of Fe2+ ions on morphologies,microstructures and mechanical properties of electrospun nylon‐6 nanofibers

In this study, nylon‐6 nanofiber mats containing Fe²⁺ ions were fabricated via electrospinning. The resultant electrospun nylon‐6/FeCl₂ nanofiber mats were characterized by SEM, TEM, Fourier transform IR spectroscopy, wide angle XRD and DSC. Unique morphological features, such as spider's‐web‐like morphologies, were observed and became evident with increasing additive Fe²⁺ ions. The metastable γ form was predominant in the as‐spun nylon‐6 nanofibers. The relative intensity of such γ form gradually decreased with increasing additive Fe²⁺ ions, indicative of transformation of the crystalline structure in the electrospun nylon‐6/FeCl₂ nanofibers due to strong molecular interactions between the nylon‐6 backbone and the additive Fe²⁺ ions. The effects of additive Fe²⁺ ions on the mechanical properties of both nonwoven nanofiber mats and single nanofibers were investigated. In particular, Young's modulus of nylon‐6/FeCl₂ single nanofibers gradually increased from 1.46 to 5.26 GPa with increasing additive Fe²⁺ ions. © 2013 Society of Chemical Industry     

Effects of hard and soft components on the structure formation,crystallization behavior and mechanical properties of electrospun poly(l-lactic acid) nanofibers

The effects of multi-wall carbon nanotubes (MWCNTs) and poly(ethylene oxide) (PEO) on the structure formation, morphology, crystallization behavior and mechanical property of electrospun poly (l-lactic acid) (PLLA) nanofiber mats were investigated by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and mechanical test. If incorporate hard filler, MWCNTs into electrospun PLLA nanofiber, the crystallinity, chain orientation, and crystallization behaviors were almost not influenced by the MWCNTs content owing to the MWCNTs mainly acted as impeding the crystal growth and chain diffusion. If incorporate small content of soft and miscible component, PEO (10 wt%) into the electrospun PLLA and PLLA/MWCNTs nanofibers, the crystallinity and crystallization rate of PLLA in nanofibers were obviously enhanced. The synergistic effect of PEO and MWCNTs in PLLA nanofibers was observed during melt-crystallization behaviors of PLLA/MWCNTs fibers. Based on those results, we found that the chain mobility is an important factor to influence the structure formation and crystallization behaviors in the electrospun nanofibers. Our results indicated that the structure and properties of electrospun nanofibers could be optimized by compounding with hard inorganic filler and soft polymer components.     

Investigation of thermal comfort properties of electrospun thermoplastic polyurethane fiber coated knitted fabrics for wind-resistant clothing

The integration of nanofibers into conventional fabrics may open up new opportunities such as improving the comfort performance and thermal management properties of outdoor clothing. Nanofibers are able to form a highly porous mesh and their large surface-to-volume ratio improves performance for many applications. This study shows the possible utility of the nanofiber coating on conventional knitted fabrics for improving the wind-resistance and breathability properties. It was seen that nanofiber coating did not cause a significant effect on water vapor and thermal resistance of electrospun thermoplastic polyurethane nanofiber coated cotton (CO), modal (CMD), viscose (CV), and lyocell (CLY) single jersey fabrics, while resistance to air permeability was increased with the increased nanofiber coating. High level of air resistance was achieved with 30 min of coating. In terms of comfort properties, the nanofiber coating proved to be advantageous due to its lower air permeability with its water vapor permeable structure. However, thermal insulation level of these fabrics was still low and fragile nanofiber layer needed to be protected. Therefore, a multi-layered fabric form was derived from combination of cotton and lyocell fabrics with a nanofiber layer. The results showed that nanofibers could be used to improve the wind-resistance and comfort properties of multi-layered knitted structures.     

Polyamide 6 nanofibrous nonwovens via electrospinning

Electrospinning of Polyamide 6 (PA 6) in 2,2,2‐trifluoroethanol (TFE) was investigated for the fabrication of nanofibrous nonwoven membranes useful for separation systems. The effects of solution characteristics such as concentration and conductivity as well as the effects of processing conditions such as relative humidity and applied potential on the resultant nonwoven fibers were studied. By changing the relative humidity of the electrospinning chamber and the conductivity of the solvent, it is possible to modulate the fiber's size and consequently the porosity of the mats. The morphology of the electrospun PA 6 nanofibers was observed by scanning electron microscopy. The mechanical properties of the nanofibers were also studied. The results showed that PA 6 nanofibers having a diameter ranging from 100 to 600 nm, has been successfully prepared. The electrospun PA 6 nanofiber mats show good mechanical properties, such as a high‐tensile strength (12 ± 0.2 MPa) and elongation (300% ± 50%). The strength of the web was high enough to use as filter without the need of any supporting matrix and could be applicable in the field of self‐supporting membranes. The X‐ray and DSC analyses of the PA 6 electrospun fibers show the presence of the γ‐form of PA 6 crystallite that is usually obtained in the condition where a high stress of the fibers is applied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010