Preparation and hemocompatibility of electrospun O‐carboxymethyl chitosan/PVA nanofibers

Chitosan was deacetylated and carboxymethylated to prepare O‐carboxymethyl chitosan (CMC) for further electrospinning. CMC was characterized using FTIR, NMR, and chemical titration, indicating a degree of carboxymethylation of 51.4%. CMC was electrospun together with poly(vinyl alcohol) (PVA) to prepare membranes composed of nanofibers. The electrospinning conditions were optimized. The CMC/PVA membrane obtained at the conditions of 15.2 g/mL CMC 50 mL, 8 g/mL PVA 5 mL, 25 kV, and a distance of 23 cm, had nanofibers without beads, with diameters of 70–200 nm. The mats were crosslinked by glutaraldehyde before platelet adhesion measurement. The nanofibrous structure remained after crosslinking while the wettability decreased. CMC/PVA mats with higher CMC amount and fewer beads, had fewer adherent platelets and less platelets aggregation showing better hemocompatibility. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43565.     

Functionalization of electrospun nanofibers of natural cotton cellulose by cerium dioxide nanoparticles for ultraviolet protection

Nanofibers of natural cotton cellulose with a degree of polymerization above 10,000 were prepared by electrospinning; they were then functionalized with a rare‐earth nano‐oxide material of cerium dioxide (CeO₂) by means of the hydrothermal method to obtain the designated properties. The morphology, structure, and properties of the as‐obtained nanocomposite fibers were characterized by scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet (UV)–visible spectrophotometry. The results show that hydrothermally grown CeO₂ nanoparticles exhibited a polycrystalline cubic fluorite structure and could be dispersed uniformly on the surface of the cellulose nanofiber. The strong interface and electrostatic interactions between the nanoparticles and nanofibers effectively prevented nanoparticle fall‐off. The modified natural cotton cellulose nanofibers showed excellent protection against UV radiation because of the function of the CeO₂ particles. Such cellulose nanocomposite materials could have potential applications in UV protection for data‐storage or memory devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1524–1529, 2013     

A method for scale‐up of co‐electrospun nanofibers via flat core‐shell structure spinneret

An approach to the scale‐up of co‐electrospinning via a flat core‐shell structure spinneret has been developed in this study. The spinneret with a flat surface involves shell‐holes and core‐needles. Electric field simulation reveals that the flat core‐shell spinneret configuration creates a more uniform electric field gradient. Experimental study shows that in comparison with the conventional needle co‐electrospinning, core‐shell nanofibers produced by this new designed setup are finer and of better morphology. Composite nanofibers with special morphologies can be fabricated by modifying the structure of this spinneret. The production rate of the core‐shell nanofibers can be enhanced by increasing the hole and needle number of the spinneret. This novel design is expected to provide a promising method towards the massive production of core‐shell nanofibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41027.     

The incorporation and release of ungeremine,an antifungal Amaryllidaceae alkaloid,in poly(lactic acid)/poly(ethylene glycol) nanofibers

Ungeremine (UNG) is an alkaloid typically isolated from Pancratium maritimum or synthesized by the oxidation of lycorine. This antifungal alkaloid was incorporated into electrospun nanofibers based on blends of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG). The effect of the UNG on the structure, morphology, and thermal properties of the fibers was evaluated, and the release of the alkaloid from the fibers was quantified. Studies on the release of the UNG for the nanofibers show that the release rate is related to the amount and distribution of the PEG in the nanofiber matrix. Initial burst release of the antifungal alkaloid is related to the PEG in the nanofibers, where after a sustained release occurs indicating that the UNG is present in both the PLA and PEG domains in the nanofibers.     

Effects of surfactants on the microstructures of electrospun polyacrylonitrile nanofibers and their carbonized analogs

In this study, the influence of surfactants on the processability of electrospun polyacrylonitrile (PAN) nanofibers and their carbonized analogs was investigated. The surfactants employed in this effort are Triton X‐100 (nonionic surfactant, SF‐N), sodium dodecyl sulfate (SDS) (anionic surfactant, SF‐A), and hexadecyltrimethylammonium bromide (HDTMAB) (cationic surfactant, SF‐C). Interactions between electrospun PAN and the surfactants, reflected in effects on as‐spun and carbonized nanofiber morphologies and microstructures, were explored. The results show that uniform nanofibers are obtained when cationic and anionic surfactants (surfactant free and nonionic surfactants) are utilized in the preparation of electrospun PAN. In contrast, a bead‐on‐a‐string morphology results when the aniconic and cationic surfactants are present, and defect structure is enhanced with cationic surfactant addition. Moreover, fiber breakage is observed when the nonionic surfactant Triton X‐100 is employed for electrospinning. After carbonizaition, the PAN polymers were observed to have less ordered structures with addition of any type of surfactant used for electrospinning and the disorder becomes more pronounced when the anionic surfactant is utilized. Owing to the fact that microstructure defects create midband gap states that enable more electrons to be emitted from the fiber, an enhancement of electron emission is observed for PAN electrospun in the presence of the anionic surfactant. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3726–3735, 2013     

The optical properties of PVA/TiO2 composite nanofibers

The electrospun nanofibers emerge several advantages because of extremely high specific surface area and small pore size. This work studies the effect of PVA nanofibers diameter and nano‐sized TiO₂ on optical properties as reflectivity of light and color of a nanostructure assembly consisting polyvinyl alcohol and titanium dioxide (PVA/TiO₂) composite nanofibers prepared by electrospinning technique. The PVA/TiO₂ composite spinning solution was prepared through incorporation of TiO₂ nanoparticles as inorganic optical filler in polyvinyl alcohol (PVA) solution as an organic substrate using the ultrasonication method. The morphological and optical properties of collected composites nanofibers were highlighted using scanning electron microscopy (SEM) and reflective spectrophotometer (RS). The reflectance spectra indicated the less reflectance and lightness of composite with higher nanofiber diameter. Also, the reflectance and lightness of nanofibers decreased with increasing nano‐TiO₂ concentration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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.     

Reversibly thermochromic and high strength core-shell nanofibers fabricated by melt coaxial electrospinning

Recent years, phase change materials (PCMs) with potential to store and transform energy have attracted broad attention, especially in the field of thermal energy storage. However, the instability and leak proneness of PCMs limit their universal application. In this paper, core-shell fibers with 1-tetradecanol (TD) as core and poly(vinylidene fluoride) (PVDF) as shell were prepared via melt coaxial electrospinning method, and for improvement, the dye composed of crystal violet lactone (CVL) and bisphenol A (BPA) was added to the core to endow the fiber the function of reversible thermochromism. During the preparation process, it was found that the addition of NaCl could regulate the fiber morphology and strength its mechanical property. By adjusting the concentration of shell solution and the flow rate of core solution, the high-strength reversible thermochromic fibers were produced when polymer concentration was 24 wt% with a core feed rate of 0.4 ml/h. The latent heat of these fibers is up to 88.71 J/g. Besides, its color can change from blue to white when heated, and the transition temperature is around 38°C. And 100 thermal cycle tests of the fiber showed its strong thermal stability and thermochromic property.     

Determination of twisting angle of electrospun nanofiber bundle for continuous electrospinning system

Electrospinning continuously produced twisted nanofibers with a convergence coil and a rotating ring collector. The positively charged nozzle was used in the electrospinning process to deposit electrospun fibers of polyacrylonitrile onto a rotating ring collector. By withdrawing the electrospun fibers from the rotating ring collector, it was possible to spin the electrospun fibers yarn. In this study, theoretical approaches and numerical simulations were used to determine the twisting angle of the yarn. Using the equations developed in this study, we performed numerical simulations and compared the experimental results with the numerical simulation results. Mechanical properties of the fiber bundle were analyzed for twisting angle. It was confirmed the relationship among the winding drum, the ring collector, and flux of the fibers mass per time during electrospinning in the developed system. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45528.     

A comprehensive study on Plantago ovata/PVA biocompatible nanofibers: Fabrication,characterization, and biological assessment

In this study, a biocompatible nanofiber is fabricated using Plantago ovata mucilage (POM) combined with polyvinyl alcohol (PVA), which is considered as a non-toxic polymer. High quality nanofibers were produced by controlling the electrospinning parameters after selecting an appropriate solvent for the POM/PVA combination (12% PVA and 3% POM). Electrospinning parameters, including high voltage, distance from collector to tip, feed rate and POM to PVA proportion were optimized following preparation of an aqueous POM/PVA solution. Using the results of scanning electron microscopy, the optimized electrospinning conditions for producing POM/PVA nanofibers were determined (high voltage = 18 kV, distance = 15 cm, feed rate = 0.125 ml/hr, PMM/PVA = 50/50) and uniform nanofibers with an average diameter of 250 nm were produced. The POM/PVA nanofiber sample was evaluated by determining the mechanical strength, characterization of produced nanofiber morphology, and investigating the cell viability by applying MTT assay. The bands for both POM and PVA from FTIR results showed that the samples remained stable. The tensile strength results showed that blending POM with PVA solution enhanced the Young's modulus by factor of 3.2 (0.2 MPa to 0.64 MPa). The MTT analysis on POM/PVA cell lines proved that the produced nanofiber considerably enabled the cellular proliferation. Enhancement in these analysis indicated how POM-based nanofibers is a promising scaffold for cell culture, drug delivery systems and food additives.     

Densifying and strengthening of electrospun polyacrylonitrile‐based nanofibers by uniaxial two‐step stretching

The effects of alignment of polyacrylonitrile (PAN) nanofibers and a two‐step drawing process on the mechanical properties of the fibers were evaluated in the current study. The alignment was achieved using a high‐speed collector in electrospinning synthesis of the nanofibers. Under optimal two‐step drawing conditions (e.g., hot‐water and hot‐air stretching), the PAN nanofiber felts exhibited large improvements in both alignment and molecular chain‐orientation. Large increase in crystallinity, crystallite size, and molecular chain orientation were observed with increasing draw ratio. Optimally, stretched PAN‐based nanofibers exhibited 5.3 times higher tensile strength and 6.7 times higher tensile modulus than those of the pristine one. In addition, bulk density of the drawn PAN nanofibers increased from 0.19 to 0.33 g/cm³. Our results show that fully extended and oriented polymer chains are critical in achieving the highest mechanical properties of the electrospun PAN nanofibers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43945.     

Electrospun nylon 6,6 nanofibers functionalized with cyclodextrins for removal of toluene vapor

Functional nylon 6,6 nanofibers incorporating cyclodextrins (CD) were developed via electrospinning. Enhanced thermal stability of the nylon 6,6/CD nanofibers was observed due to interaction between CD and nylon 6,6. X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy studies indicated the existence of some CD molecules on the surface of the nanofibers. Electrospun nylon 6,6 nanofibers without having CD were ineffective for entrapment of toluene vapor from the environment, whereas nylon 6,6/CD nanofibrous membranes can effectively entrap toluene vapor from the surrounding by taking advantage of the high surface‐volume ratio of nanofibers with the added advantage of inclusion complexation capability of CD presenting on the nanofiber surface. The modeling studies for formation of inclusion complex between CD and toluene were also performed by using ab initio techniques. Our results suggest that nylon 6,6/CD nanofibrous membranes may have potential to be used as air filters for the removal of organic vapor waste from surroundings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41941.     

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.     

Simple preparation and characterization of molecularly imprinted nylon 6 nanofibers for the extraction of bisphenol A from wastewater

Nylon 6 nanofibers incorporated with molecularly imprinted polymers (MIPs) were successfully fabricated by electrospinning with fiber diameters in the range 80–145 nm. Then, they were used as a new material for the extraction of selected bisphenol A (BPA) in water samples. Field emission scanning electron microscopy images revealed that the nanofibers had a smooth morphology with a good incorporation of MIPs. The Fourier transform infrared and energy-dispersive X-ray spectroscopy results also confirmed the formation of the MIPs in the nanofibers. Furthermore, Raman spectroscopy showed that the crystalline structure of the pristine nylon 6 nanofiber was a kind of α form, and the incorporation of MIPs led to a γ-form structure in the nanofibers; this proved the interactions between nylon 6 and the MIPs. Adsorption studies also confirmed that the adsorption efficiency of BPA onto the molecularly imprinted polymer nanofibers (MIP-NFs; 83.5%) was much greater than that onto nonimprinted polymer nanofibers (NIP-NFs; 36.8%). Also, the imprinting factor was 3.4; this strongly implied the successful formation of molecularly imprinted cavities on the MIP-NFs with a strong affinity to BPA. The maximum adsorption capacity of the MIP-NFs was 103.8 mg/g. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47112.     

Electrospinnability of poly(butylene succinate): Effects of solvents and organic salt on the fiber size and morphology

Submicrosized and nanosized fibers of polymers can be formed easily by electrospinning techniques. However, bead formation can occur if inappropriate solvent systems are used. In this study, we focused on investigating the effects of solvents and organic salt on the electrospinnability of poly(butylene succinate) (PBS). Electrospun PBS fibers were obtained from single‐solvent systems, that is, systems with chloroform (CF) or dichloromethane, at various concentrations (8–30% w/v). Discrete beads and beaded fibers were still found at every PBS concentration. In this study, the electrospinnability of the PBS solutions in CF were improved by the addition of methanol (MeOH) as a cosolvent and an organic salt [alkyl ammonium ethyl sulfate (AAES)]. The obtained fibers were smooth without any beads, and the diameters were affected by the amount of MeOH and the PBS concentration. The electrospinnability of PBS could be enhanced by the addition of a cosolvent with a high dielectric constant or organic salt (AAES). Moreover, the diameters of the electrospun PBS fibers decreased with increasing AAES concentration. We found that the presence of MeOH (30 vol %) and the addition of AAES caused an increase in the crystallinity of the PBS fibers. Therefore, we concluded that bead‐free ultrafine PBS fibers could be obtained through the addition of the cosolvent and the organic salt. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42716.     

Recent progress in interfacial toughening and damage self‐healing of polymer composites based on electrospun and solution‐blown nanofibers: An overview

In this article, we provide an overview of recent progress in toughening and damage self‐healing of polymer–matrix composites (PMCs) reinforced with electrospun or solution‐blown nanofibers at interfaces with an emphasis on the innovative processing techniques and toughening and damage self‐healing characterization. Because of their in‐plane fiber architecture and layered structure, high‐performance laminated PMCs typically carry low interfacial strengths and interlaminar fracture toughnesses in contrast to their very high in‐plane mechanical properties. Delamination is commonly observed in these composite structures. Continuous polymer and polymer‐derived carbon nanofibers produced by electrospinning, solution blowing, and other recently developed techniques can be incorporated into the ultrathin resin‐rich interlayers (with thicknesses of a few to dozens of micrometers) of these high‐performance PMCs to form nanofiber‐reinforced interlayers with enhanced interlaminar fracture toughnesses. When incorporated with core–shell healing‐agent‐loaded nanofibers, these nanofiber‐richened interlayers can yield unique interfacial damage self‐healing. Recent experimental investigations in these topics are reviewed and compared, and recently developed techniques for the scalable, continuous fabrication of advanced nanofibers for interfacial toughening and damage self‐healing of PMCs are discussed. Developments in the near future in this field are foreseen. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2225–2237, 2013     

Nanoencapsulation of intercalated montmorillonite‐urea within PVA nanofibers: Hydrogel fertilizer nanocomposite

This study describes the preparation and characterization of nanofibers with poly(vinyl alcohol) (PVA) as the wall matrix to encapsulate montmorillonite (MMT) clay and intercalated MMT‐urea nanocomposite using an electrospinning technique. Nanofibers encapsulated with (1–5%, w/w) MMT clay were successfully produced and characterized in relation to morphological, spectroscopic, structural, surface, and thermal properties. The electrospinning conditions for voltage, flow‐rate, and emitter to collector distance were 20 kV, 0.5, and 0.25 mL/h, and 10 cm, respectively. The surface roughness increased from 43.5 (empty fibers) to 56 nm in the PVA/MMT‐3% and bead‐less nanofibers were formed with the maximum diameter distribution and mean diameter value of 45–80 and 62 nm, respectively. The d‐spacing was increased significantly from 1.004 in MMT to 1.684 nm in MMT‐urea, indicating the intercalation of urea occurred successfully. Furthermore, elemental analysis results showed that the intercalated MMT‐urea contained 30.4% nitrogen. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45957.     

Fabrication of ceramic nanofibers using polydimethylsiloxane and polyacrylonitrile polymer blends

Nanofibers with several hundred of nanometers were successfully fabricated using electrospinning process and a mixture of two types of polymers which are: polydimethylsiloxane and polyacrylonitrile as precursors. After stabilization and carbonization at 1000 °C, three phases which are: silicon carbide (SiC), carbon, and oxy‐SiC were presented. Spectroscopic and microscopic techniques had confirmed the presence of nanocrystalline SiC and turbostratic carbons. These phases formed an intertwined network at the nanometric scale. In addition, the resulted fibers showed a core‐skin effect with skin richer in carbon and a core mainly dominated by silicon‐based phases in the form SiC or Si? O? C ceramics. A significant improvement was observed in both tensile strength and elastic modulus in these hybrid fibers. In term of crystallography, these nanofibers seem to exhibit similar microstructure that was observed in Nicalon fiber. However, it was difficult to determine the ratio of these phases and their influence on the physical properties of these hybrid fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45967.     

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     

Increasing mechanical strength of electrospun gelatin nanofibers by the addition of aluminum potassium sulfate

Increasing mechanical strength of gelatin‐based materials is required to expand the range of their applications, which is desirable because of biocompatibility, biodegradability, and low cost of gelatin. The effect of aluminum potassium sulfate on preparation and properties of nanofibrous gelatin were investigated. Samples were electrospun from 10M aqueous acetic acid and analyzed by scanning electron microscopy (SEM), Fourier transform infrared microscopy (FTIR), energy‐dispersive x‐ray analysis (EDX), and tensile test. The addition of AlK(SO₄)₂ considerably increases the elastic modulus of the material up to about 10% salt content. The elastic modulus of electrospun gelatin meshes prepared as described in the present work increased from 20 MPa to 70 MPa and the elastic modulus of the fiber material increased from 150 MPa to 620 MPa as the salt content in the fibers increased from 0% to 9.6%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42431.