Investigating the thermal,mechanical, and electrochemical properties of PVdF/PVP nanofibrous membranes for supercapacitor applications

Polyvinylidene fluoride and polyvinylpyrrolidone polymers incorporated with carbon black nanoparticles (50 nm) were electrospun to fabricate nanofibrous membranes for supercapacitor separators. Different weight percentages (0, 0.25, 0.5, 1, 2, and 4 wt %) of carbon black nanoparticles were dispersed in N,N‐dimethylacetamide and acetone prior to the electrospinning processes at various voltage, pump speed, and tip‐to‐collector distances. The morphology, thermal, mechanical, hydrophobic, and electrochemical characterization of nanofibrous membrane were analyzed using different techniques, such as scanning electron microscopy, differential scanning calorimetry, capacitance bridge, thermogravimetric analysis, dynamic mechanical analyzer, and water contact angle. Effects of annealing and UV irradiation exposures on the nanofibrous membranes were investigated in detail. Test results revealed that the physical properties of the nanocomposite separators were significantly enhanced as a function of carbon black inclusions in the polymeric structures, which may be useful for the applications of supercapacitor separators and other energy storage devices. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43707.     

Facile preparation and separation performances of cellulose nanofibrous membranes

Ultrafiltration (UF) is a size selective pressure‐driven membrane separation process increasingly required for high efficient water treatment and suspended solids removal in many industrial applications. This study examined the morphology of as‐prepared cellulose nanofibers and then utilized the nanofibers dispersion to fabricate nanofibrous nanoporous membranes with potential wide applications in various fields including water treatment. The nanofibers were prepared using a simple and powerful mechanical high intensity ultrasonication following a pre‐chemical treatment of α‐cellulose. The cellulose nanofibers’ morphology, crystallinity, and yield were found to be influenced by pre‐chemical treatment. Cellulose nanofibrous membranes were fabricated from cellulose nanofibers dispersion on a porous support. A nanoporous structure with an extensive interconnected network of fine cellulose nanofibers was formed on the support substrate. The resulting membranes exhibited typical and high‐efficient UF performances with high water fluxes of up to 2.75 10³ L/m²/h/bar. The membranes also displayed high rejections for ferritin and 10 nm gold nanoparticles with a reactive surface area capable of rapidly decolorizing methylene blue from its aqueous solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43544.     

A waterproof and breathable nanofibrous membrane with thermal-regulated property for multifunctional textile application

In this work, a waterproof and breathable nanofibrous membrane with thermal-regulated performance and exhibits excellent mechanical property is fabricated by coaxial electrospinning. The fiber shell is consisted of polyvinylidene fluoride (PVDF) and polyvinyl butyral (PVB), and the core is octadecane. First, well-performed waterproof and breathable membranes are obtained by optimizing its morphology and pore structure. Then octadecane is loaded into the fibers in the form of core by coaxial electrospinning, though it gives the membranes a thermal regulating function, but the drawback is the sacrifice of overall properties. Thus, carbon nanotubes are loaded into the shell and studied, finally, the best membrane has a comprehensive performance with hydrostatic pressure of 59.2 kPa, water vapor transmission rate (WVTR) of 7.846 kg m⁻² d⁻¹, latent heat of 50.1 J g⁻¹, as well as excellent tensile strength of 20.2 MPa, which shows its certain reference significance to the synthesis of multifunctional membrane.     

Co-electrospun cellulose diacetate-graft-poly(ethylene terephthalate) and collagen composite nanofibrous mats for cells culture

In this study, a kind of novel composite nanofibrous mats with cellulose diacetate-graft-poly(ethylene terephthalate) (CDA-g-PET) and Type I collagen were obtained by electrospinning and five different ratios of CDA-g-PET/Type I collagen (1:0, 1:0.1, 1:0.2, 1:0.3, 1:0.4) were set to explore the effects of components on its properties. The scanning electron microscope images demonstrated that the formation of uniform and smooth nanofibers with free beads. Compared with pure CDA-g-PET mats, the composite materials transformed into hydrophilic ones with increasing the content of Type I collagen. Moreover, the tensile strength of the composite nanofibrous mats got higher, while its water vapor transmission rate got lower after blending with Type I collagen. In addition, the cell proliferation and adhesion on composite nanofibrous mats were improved according by the results of bone marrow mesenchymal stem cells (BMSCs) culturing experiments. Especially, the cells growth attained optimum when the CDA-g-PET/Type I collagen ratio reached 1:0.3 and 1:0.4, where showed no significant difference. In consequence, the above results indicated that the novel composite nanofibrous mats consisted of CDA-g-PET and Type I collagen obtained by electrospinning combined good mechanical strength of CDA-g-PET and excellent biological functions of Type I collagen. The nanoscale structure might mimic the nanofibrous extracellular matrix feature, which present the potential use in cells culture.     

Construction of lysozyme exfoliated rectorite‐based electrospun nanofibrous membranes for bacterial inhibition

Lysozyme (LY) exfoliated rectorite (REC) based electrospun nanofibrous membranes with enhanced bacterial inhibition ability and thermostability were fabricated via electrospinning. All the obtained membranes exhibited better fiber shape and three‐dimensional structure, which could be observed by scanning electron microscopy. Energy‐dispersive X‐ray analysis, X‐ray photoelectron spectroscopy, and Fourier transform infrared (FTIR) spectrum denoted the existence of LY and REC in the composite membranes. Besides, the FTIR results suggested that there were interactions between REC and polyvinyl alcohol (PVA)/LY chains. Small angle X‐ray diffraction indicated that REC was exfoliated by PVA and LY chains. In addition, the exfoliation of REC was directly confirmed by transmission electron microscopy. According to Brunauer‐Emmett‐Teller surface area test results, PVA/LY/REC membranes had higher surface area than that of PVA/LY membranes. The performance tests showed that both the thermal stability and antibacterial activity of the composite membranes were enhanced after adding REC. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41496.     

Air filtration performance of nanofiber membranes with different morphologies produced by green electrospinning

To further target product development with low environmental impact, an integral green electrospinning (G-ES) approach has been adopted through the simultaneous application of various strategies, such as the use of biopolymers, reduction of energy use to avoid melting temperatures, and selection of non-toxic solvents and surfactants. Green solubility spinnability maps for cellulose acetate (CA), poly ε-caprolactone (PCL), and polyvinyl alcohol (PVA) are presented. Green electrospinning (G-ES) allows the production of new morphologies for CA and PCL nanofiber membranes. In this work, CA exhibits a ribbon-like morphology, PCL shows a honeycomb-like morphology and PVA cylindrical fibers. Membrane morphologies are compared with filtration efficiency (FE) for particle size of 1.0 μm and quality factor (Q_F) at a volumetric flux of 27.63 cm⁻¹. For CA is between 83% and 96% and high Q_F = 0.31–0.38 Pa⁻¹, PCL is 92% and 99% and high Q_F = 0.28–0.21 Pa⁻¹ and for PVA between 96% and 99% and high Q_F = 0.14–0.08 Pa⁻¹. These results suggest that the hierarchical nanofiber structure improves filtration performance because of the reduction in pressure drop and increase in PM interception. CA ribbon-like fibers favored air filtration performance, followed by PCL honeycomb-like fibers.     

Shape‐memory behaviors of electrospun chitosan/poly(ethylene oxide) composite nanofibrous membranes

With aim of constructing a class of functional environmentally friendly materials, we electrospun chitosan (CS) blends with various contents of poly(ethylene oxide) (PEO) into a series of composite nanofibrous membranes exhibiting shape‐memory behaviors. In the present composite system, CS and PEO served as hard and soft domains, respectively. The CS, presenting no thermal transition, and the PEO, with apparent melting–crystallization, were demonstrated by differential scanning calorimetry testing. Characterizations also revealed that the morphologies of the CS/PEO membranes were controlled by the mass ratios of CS/PEO. The composite fibrous membranes showed great mechanical performances and thermal stabilities as well. Moreover, CS/PEO possessed excellent shape‐memory behaviors. Such fibrous membranes could complete their shape‐recovery processes within 20 s at the temperature of 20°C above the melting transition temperature (T_m). Both the shape fixity and shape‐recovery ratios were higher than 90%, even after five cycles. The CS/PEO fibrous membranes present significant potential applications in the field of biotechnology and tissue engineering, such as in scaffolds and smart tubes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42532.     

Surface modification of electrospun chitosan nanofibrous mats for antibacterial activity

Chitosan (CS) blended with poly(ethylene oxide) (PEO) was electrospun into nanofibrous mats. The spinning solution of 6.7 : 0.3 (% w/v) of CS : PEO was dissolved in a 70 : 30 (v/v) trifluoroacetic acid/dichloromethane solution. The obtained fibers were smooth without beads on their surfaces and average diameter of the fiber was 272 ± 56 nm. N‐(2‐hydroxyl) propyl‐3‐trimethyl ammonium chitosan chloride (HTACC) and N‐benzyl‐N,N‐dimethyl chitosan iodide (QBzCS) were each prepared from the CS/PEO mats. They were identified by Fourier‐transform infrared and X‐ray photoelectron spectroscopy and degree of swelling in water. Both quaternized electrospun chitosan mats exhibited superior antibacterial activity to the unmodified electrospun CS/PEO against Staphylococcus aureus and Escherichia coli at short contact times. After 4 h of contact, the reduction of both bacterial strains by CS/PEO, HTACC, and QBzCS was equal at about 99–100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40981.     

Polydimethylsiloxane‐modified polyurethane–poly(ɛ‐caprolactone) nanofibrous membranes for waterproof,breathable applications

In this study, we prepared polydimethylsiloxane (PDMS)‐modified polyurethane–poly(?‐caprolactone) nanofibrous membranes with excellent waterproof, breathable performances via an electrospinning technique. Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing were used to characterize the morphologies and properties of the composite nanofibers. The fiber diameter and porous structure of the membranes were regulated by the adjustment of the temperatures of thermal treatment and the PDMS concentrations. The fibrous membranes obtained at a typical temperature of 70 °C possessed an optimized fibrous structure with a diameter of 514 ± 2 nm, a pore size of 0.55–0.65 µm, and a porosity of 77.7%. The resulting nanofibrous membranes modified with 5 wt % PDMS were endowed with good waterproof properties (water contact angle = 141 ± 1°, hydrostatic pressure = 73.6 kPa) and a high breathability (air permeability rate = 6.57 L m^?2 s^?1, water vapor transmission rate = 9.03 kg m^?2 day^?1). Meanwhile, the membranes exhibited robust mechanical properties with a high strength (breakage stress = 11.7 MPa) and excellent thermal stability. This suggests that they would be promising candidates for waterproof, breathable applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46360.     

Superhydrophobic PES/PDA/ODTS fibrous mat prepared by electrospinning and silanization modification for oil/water separation

With polydopamine (PDA) acting as interlayer, combined with electrospinning technology and a silanization method, here a versatile method for fabricating a superhydrophobic PES/PDA/ODTS fibrous mat is reported. Scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and contact angle measurements were applied to characterize the morphologies and chemical composition changes of the prepared fibrous mats. Their separation ability for oil/water mixtures was measured by self‐made instruments. The results show that the fabricated PES/PDA/ODTS fibrous mat displays a water contact angle too large to be assessed by the ordinary amount of water applied in a conventional measurement. In other words, a water drop of less than 10 μL adheres to the syringe needle and leaves with it during the measurement. The prepared PES/PDA/ODTS fibrous mat also shows a threshold sliding angle no more than 2.5°. At the same time, this kind of material exhibits superoleophilicity for organic solvents, such as n‐hexane, gasoline, toluene, and chloroform. The experimental contact angles were also analyzed using the Cassie–Baxter model to gain insights into the fundamental microstructure–wetting property relationship. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45923.     

One-step fabrication of superhydrophobic P(VDF-co-HFP) nanofibre membranes using electrospinning technique

In this study, superhydrophobic electrospun P(VDF-co-HFP) membranes were fabricated in a one-step electrospinning process. The effects of the key parameters of electrospinning (solution concentration, electrical potential, flow rate, and solvent) on the surface roughness, fiber formation, and hydrophobicity of the membranes were evaluated using Taguchi method. A 4 × 3 orthogonal array was utilized, and the results indicated that the solvent played the critical role in producing the superhydrophobic nanofibre membranes. It was demonstrated that it is possible to produce superhydrophobic membranes with P(VDF-co-HFP) without additional functionalisation and fillers. The highest water contact angle and the lowest contact angle hysteresis obtained were 156° and 5°, respectively, and the roughness values varied from 0.15 to 5.74 μm for the produced P(VDF-co-HFP) nanofibre membranes. The surface superhydrophobicity of the membranes was attributed to the specific structures consisting of a combination of beads and nanofibres. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48817.     

Statistical analysis of nanofibers alignment in magnetic‐field‐assisted electrospinning including an alignment percentage formula

Magnetic‐field‐assisted electrospinning (MFAES) is a simple and effective method to align polymer nanofibers. In this method, further research is needed to identify alignment mechanism. Hence, this article includes statistical analysis of affecting factors to investigate alignment mechanism in MFAES. Tip to target distance, magnets distance, voltage, and collection time, which are recognized as the most effective factors on nanofibers alignment, were applied in design of experiments. Central composite method was applied to get required experiments with designed expert 8 software. A response surface was proposed with regression coefficient of 97%. Then, the common physics concepts and statistical results were used to discuss the affecting mechanism of the electric and magnetic fields on the electrospinnig jet and the nanofibers alignment. Field emission scanning electron microscopy images were used to characterize the nanofibers alignment and calculate overall alignment percentage using a proposed statistical combinatorial weighted percentage formula. MFAES method, used in this research, achieved 95.3% polyacrylonitrile‐aligned nanofibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41179.     

Terpinen-4-ol liposomes-incorporated chitosan/polyethylene oxide electrospun nanofibrous film ameliorates the external microenvironment of healing cutaneous wounds

Chronic wounds are susceptible to infection and difficult to heal due to the complex healing process and terrible microenvironment. In order to overcome this problem, TOLs-CS/PEO nanofibrous film was successfully electrospun. The 6%(v/v) TOLs incorporation into CS/PEO nanofibrous film could improve the morphology and structure of nanofibers, weaken the interactions among macromolecules and rebalance the relationship between hydrophilicity and hydrophobicity of pore surface. Water vapor transmission rate and simulated tissue fluid absorption of films were optimized to reach 2193 g m⁻² d⁻¹ and 1676% so that to obtain the excellent moisture retention. The Young's modulus and elongation at break of films in wet state were 114.69 kPa and 72.04%, respectively, causing the mechanical characteristics similar to human skin. The film could effectively block more than 98% of bacteria and inhibit bacteria growth besides possessing procoagulant property and suitable biodegradability. These findings demonstrate that TOLs-CS/PEO nanofibrous film can construct a microenvironment suitable for wound healing.     

Composite nanofibrous microfiltration water filter

A novel environmentally friendly co‐extrusion and multiplication technology in combination with a water jet procedure was utilized to produce dual‐component fibrous filters. Polyvinylidene fluoride (PVDF)/high‐density polyethylene (HDPE) systems were selected as the filter materials. The orientation procedure was shown to greatly enhance the mechanical properties of the fibers as well as the filters. These filters were found to have micron‐size pores, high porosity, and high surface areas. Various physical treatments were applied on these filters which decrease the filter pore size. It was found that filter pore size decreased to 0.2 μm and the mechanical properties were enhanced. Water flux tests and microparticle separation tests were performed on these filters to evaluate their microfiltration behavior. PVDF/HDPE filters exhibit high water flux with low pressure requirement, making them good candidates for microfiltration water filters. In addition, the PVDF/HDPE filters exhibit high separation efficiencies 90% on 1 μm particles, 96% on 2 μm particles, and 99% on 5 and 10 μm particles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45557.     

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     

Characteristics and 3D formation of PVA and PEO electrospun nanofibers with embedded urea

The behavior of electrospun polyvinyl alcohol (PVA) and polyethylene oxide (PEO) nanofibers embedded with urea is studied as a function of various process parameters. Our results show that three‐dimensional nanofiber networks can be obtained when high concentrations of urea in the solution are used during electrospinning. The nanofibers are characterized using both scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The stability of the nanofiber as a function of electric field has also been studied. The successful formation of three‐dimensional nanofiber networks can open new trends toward applications in fertilizers containing nanofibers in the nanoagricultural field. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39840.     

Effects of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):Poly(styrenesulfonate) nanofibers

In this study, the effect of solvents on the morphology and conductivity of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) nanofibers is investigated. Conductive PEDOT:PSS nanofibers are electrospun by dissolving a fiber‐forming polymer, polyvinyl alcohol, in an aqueous dispersion of PEDOT:PSS. The conductivity of PEDOT:PSS nanofibers is enhanced 15‐fold by addition of DMSO and almost 30‐fold by addition of ethylene glycol to the spinning dopes. This improvement is attributed to the change in the conformation of the PEDOT chains from the coiled benzoid to the extended coil quinoid structure as confirmed by Raman spectroscopy, X‐ray diffraction, and differential scanning calorimetry. Scanning electron microscopy images show that less beady and more uniform fiber morphology could be obtained by incorporation of ethylene glycol in the spinning dopes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40305.     

Novel core‐sheath antimicrobial nanofibrous mats

The poor mechanical properties of electrospun materials remain one of the major hindrances toward their practical application. In this study, we report the synthesis of core‐sheath nanofibrous mats to enhance the mechanical properties of an antimicrobial polymer nanofiber for application in filter media. This objective was achieved via coaxial electrospinning of poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] as the sheath which is an antimicrobial polymer and nylon 6 polymer for the core which is well reported for exceptional mechanical properties. Extensive characterization of these fibers was performed using scanning electron microscopy, scanning transmission electron microscopy, confocal fluorescence microscopy as well as attenuated total reflectance Fourier transform spectroscopy to provide evidence of the core‐sheath morphology. Antimicrobial evaluation was also carried out on the fabricated fibers via the live/dead fluorescence technique. This was done to determine if the poly[styrene‐co‐N‐(N′,N′‐dimethyl‐3‐aminopropyl)maleimide] retained its antimicrobial activity. The fibers were found to be effective against the Gram‐positive Staphylococcus aureus (ATCC25925) and Gram‐negative Pseudomonas aeruginosa (ATCC27853). Subsequent tensile testing and filtration experiments provided evidence that the incorporation of the nylon core improved mechanical properties of the nanofiber mats. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46303.     

Solution blown sulfonated poly(ether sulfone)/poly(ether sulfone) nanofiber‐Nafion composite membranes for proton exchange membrane fuel cells

A composite membrane of sulfonated poly(ether sulfone) (SPES)/poly(ether sulfone) (PES) nanofiber (NF) mat impregnated with Nafion was prepared and evaluated for its potential use as a proton conductor for proton exchange membrane (PEM) fuel cells. The supporting composite nanofibrous mat was prepared by solution blowing of a mixture of SPES/PES solution. The characteristics of the SPES/PES NF and the composite membrane, such as morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of composite membranes was compared with that of Nafion117. The introduction of solution blown NFs to composite membranes modestly improved proton conductivity, water swelling, and methanol permeability. Therefore, composite membrane containing SPES/PES NFs can be considered as a novel PEM for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42572.     

Morphology,physical, and mechanical properties of potentially applicable coelectrospun polysulfone/chitosan-polyvinyl alcohol fibrous membranes in water purification

Polysulfone (PSU) is a widely used polymer in water purification membranes. However, its hydrophobicity hinders its practical application. Herein, the wettability of PSU has been improved by producing a coelectrospun fibrous composite membrane using a hydrophilic component, chitosan-polyvinyl alcohol (CS-PVA). First, different proportions of PVA and CS solutions were mixed and electrospun to prepare CS-PVA blend fibers. Scanning electron microscope (SEM) observations revealed that CS-PVA blend fibers with maximum CS content can be obtained in 30:70 CS:PVA weight ratio. The optimum CS-PVA solution was subsequently used alongside PSU solution and were fed into two distinct syringes, which were then electrospun simultaneously at a constant voltage and distance of 15 kV and 15 cm, respectively. Different composite compositions of PSU/CS-PVA were achieved using different feeding rates for each solution. Based on SEM images, the prepared composite fibers were beadless. The ultimate strength of the composite mats decreased by increasing the amount of CS-PVA due to the significant difference in the fiber diameter of each component and the resulting stress concentration. However, the thermal stability of composite membranes remained almost the same as pure PSU fibers. Moreover, samples with higher CS-PVA content showed better wettability and higher water flux.