Solution Blowing of Poly（dimethylsiloxane）/Nylon 6 Nanofiber Mats for Protective Applications

A new strategy was developed to fabricate superhydrophobic nylon 6 nanofibers, in which the blend solutions of poly(dimethylsiloxane)(PDMS) prepolymer and nylon 6 was spun using an innovative solution blowing process, and then the PDMS prepolymer contianning nanofibers were cured to obtain PDMS/nylon 6 nanofiber mats. Morphology, surface composition, non-wetting property and protective performance were investigated. The results showed that the addition of PDMS prepolymer improved the spinnability of the spinning solutions, and the PDMS/nylon 6 nanofibers had smooth surfaces and diameters from 100 nm to 350 nm. The presence of PDMS effectively enhanced the hydrophobicity of the nanofiber mats, showing water contact angles of 132° to 161° for PDMS contents of 1 wt% to 3 wt%. The PDMS/nylon 6 mats also possessed excellent protective and transport properties. The results indicated the potential application of the novel nanofiber mats in protective clothing.     

Plasma-Electrospinning Hybrid Process and Plasma Pretreatment to Improve Adhesive Properties of Nanofibers on Fabric Surface

Electrospun nanofiber mats are inherently weak, and hence they are often deposited on mechanically-strong substrates such as porous woven fabrics that can provide good structural support without altering the nanofiber characteristics. One major challenge of this approach is to ensure good adhesion of nanofiber mats onto the substrates and to achieve satisfactory durability of nanofiber mats against flexion and abrasion during practical use. In this work, Nylon 6 nanofibers were deposited on plasma-pretreated woven fabric substrates through a new plasma-electrospinning hybrid process with the objective of improving adhesion between nanofibers and fabric substrates. The as-prepared Nylon 6 nanofiber-deposited woven fabrics were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength and flex resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates. The nanofiber-deposited woven fabrics also exhibited good resistance to damage under repetitive flexion. X-Ray photoelectron spectroscopy and water contact angle analyses were conducted to study the plasma effect on the nanofibers and substrate fabric, and the results suggested that both the plasma pretreatment and plasma-electrospinning hybrid process introduced radicals, increased oxygen contents, and led to the formation of active chemical sites on the nanofiber and substrate surfaces. These active sites helped in creating crosslinking bonds between substrate fabric and electrospun nanofibers, which in turn increased the adhesion properties. The work demonstrates that the plasma-electrospinning hybrid process of nanofiber mats is a promising method to prepare durable functional materials.     

A novel method for a high‐strength electrospun meta‐aramid nanofiber by microwave treatment

Electrospun nanofibers have attracted great attention as potential reinforcements in composite application due to their high specific surface area, high porosity, and versatility. Because the electrospun nanofibers exhibit relatively low mechanical strength due to low crystallinity and random alignment, many researchers have tried to enhance the mechanical strength through various approaches, such as heat treatment and fiber orientation control. These methods, however, are difficult to control and require the use of high temperatures and sophisticated apparatuses, and high costs. In this study, we investigate a novel microwave technique to fabricate high‐strength electrospun meta‐aramid nanofiber mats. To optimize the microwave irradiation conditions, the electrospun nanofiber was treated at varying levels of moisture and for different irradiation times. Field emission scanning electron microscopy was used to observe the surface morphology of the electrospun nanofiber mats at the different irradiation times. The changes in the crystallinity and thermal properties were investigated using X‐ray diffraction and thermogravimetric analysis measurements. Tensile tests were performed to measure the mechanical strength of the meta‐aramid nanofiber mats with respect to each parameter. As a result, any residual solvents and salts were removed, and the degree of crystallization was dramatically increased by microwave irradiation under wet conditions. These effects led to a 2.8‐fold increase in the tensile strength of the nanofiber mats compared with an untreated mat. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 807–814     

The tensile properties of electrospun nylon 6 single nanofibers

In this article, we have aimed to mechanically characterize the nylon 6 single nanofiber and nanofiber mats. We have started by providing a critical review of the developed mechanical characterization testing methods of single nanofiber. It has been found that the tensile test method provides information about the mechanical properties of the nanofiber such as tensile strength, elastic modulus and strain at break. We have carried out a tensile test for nanofiber/composite MWCNTs nanofiber mats to further characterize the effect of the MWCNTs filling fiber architecture. In addition, we have designed and implemented a novel simple laboratory set‐up for performing tensile test of single nanofibers. As a result, we have established the stress–strain curve for single nylon 6 nanofibers allowing us to define the tensile strength, axial tensile modulus and ultimate strain of this nanofiber. The compared values of the tensile strength, axial modulus and ultimate strain for nylon 6 nanofiber with those of conventional nylon 6 microfiber have indicated that some of the nylon 6 nanofiber molecule chains have not been oriented well along the nanofiber axis during electrospinning and through the alignment mechanism. Finally, we have explained how we can improve the mechanical properties of nylon 6 nanofibers and discussed how to overcome the tensile testing challenges of single nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1719–1731, 2010     

Conducting core‐sheath nanofibers for electroactive shape‐memory applications

Conducting nanofibers coated with polypyrrole (PPy) and poly(3‐hexylthiophene) (P3HT) exhibiting core‐sheath structures were prepared by vapor‐phase polymerization of the conducting polymers on electrospun polyurethane nanofibers. The synthesis of the conducting polymers was confirmed by Fourier transform infrared spectroscopy and energy‐disperse X‐ray spectroscopy. The surfaces of the PPy‐coated nanofibers were slightly rough, while very smooth and regular surfaces were observed in the case of the P3HT‐coated nanofibers. The initial polymerization rate of PPy was higher than that of P3HT. In addition, the electrical conductivities of the core‐sheath structured nanofiber webs of both types increased with polymerization time. The maximum sheet conductivity of the PPy and P3HT‐coated nanofiber webs was 5 × 10^?3 S/cm and 1 × 10^?2 S/cm, respectively. The webs of the conducting core‐sheath structured nanofibers were effective in generating sufficient electrical heating necessary for harnessing these materials for electroactive shape‐memory‐based applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Carbon nanofibers decorated with poly(furfuryl alcohol)-derived carbon nanoparticles and tetraethylorthosilicate-derived silica nanoparticles

The present paper introduces a novel method to functionalize nanofiber surfaces with carbon or silica nanoparticles by dip coating. This novel approach holds promise of significant benefits because dip coating of electrospun and carbonized nanofiber mats in poly(furfuryl alcohol) (abbreviated as PFA) is used to increase surface roughness by means of PFA-derived carbon nanoparticles produced at the fiber surface. Also, dip coating in tetraethylorthosilicate (abbreviated as TEOS) is shown to be an effective method for decorating carbon nanofibers with TEOS-derived silica nanoparticles at their surface. Furthermore, dip coating is an inexpensive technique which is easier to implement than the existing methods of nanofiber decoration with silica nanoparticles and results in a higher loading capacity. Carbon nanofiber mats with PFA- or TEOS-decorated surfaces hold promise of becoming the effective electrodes in fuel cells, Li-ion batteries and storage devices.     

An optimistic approach “from hydrophobic to super hydrophilic nanofibers” for enhanced absorption properties

Water holding capacity becomes essential for hygiene applications including baby diapers. Microfibers of hydrophilic polymers have been useful source for such applications. While, super hydrophilic and stable nanofibers incorporation with functional antibacterial agent are essential to get higher absorption of water along with antimicrobial activity against harmful bacteria. In current work, hydrophobic polymeric nanofibers are transformed to super hydrophilic nanofibers by addition of copper (II) oxide (CuO hereafter) nanoparticles. CuO nanoparticles provided two distinctive properties to existing nanofibers. Firstly, nanofibers surface area was significantly increased, and secondly copper (II) oxide itself is hydrophilic material which imparted hydrophilicity to base polymer. Polyacrylonitrile, crosslinked Polyvinyl Alcohol, and PICT were selected as super hydrophobic polymeric nanofibers. Copper II oxide nanoparticles (same concentration) were added in all polymer solution and electrospun. Surface, morphological, and hydrophilic properties were characterized and it was concluded that copper II oxide is suitable for transforming hydrophobic nanofibers to super hydrophilic nanofibers. Water holding capacity (WHC) was also improved for all prepared nanofiber mats. WHC for PVA/CuO, PAN/CuO, and PICT/CuO were recorded an average of 23 g/g, 21 g/g, and 18 g/g respectively. Combining all useful results from possible characterization of nanofiber mats, it is expected that CuO nanoparticles loaded nanofibers will have potential application as antibacterial, sustainable, and stable replacement of hygiene products.     

Modified electrospun polymer nanofibers as affinity membranes: The effect of pre-spinning modification versus post-spinning modification

This paper presents a comparison between the effectivity of 2 different polymer nanofiber modification methods. Poly(styrene-co-maleic anhydride) (SMA) was bulk-modified before electrospinning and SMA nanofibers were surface-modified after electrospinning with identical chemical moieties. These nanofibrous mats, prepared using different synthetic routes, were compared in their use as affinity membranes for micro-organisms, specifically BCG. Characterization of the modified poly(styrene-co-maleimide) (SMI) and its modified nanofibers were done using ATR-FTIR, SEM, ¹H NMR and ¹³C NMR, and fluorescence microscopy was used to measure the interaction between the micro-organisms (BCG) and the surfaces of the modified polymer nanofibers. The results indicated that the modification method used to prepare the modified polymer nanofibers did not influence the outcome of the affinity studies with regard to the effectivity of the modified nanofibers as a BCG-capturing platform. The modification agent used for the modification of the polymer nanofibers played the most important role and not the method used for the modification.     

Enhancing the effect of the nanofiber network structure on thermoresponsive wettability switching

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.     

Fabrication and electrochemical instrumentation of redox‐active nanofiber mat for polyaniline incorporated with poly(imide sulfonate)

In this study, we demonstrate the fabrication of an electrochemically active nanofiber mat that is a composite of high‐performance poly(imide sulfonate) (PIS) and polyaniline (PANI). First, a nonconductive nanofiber mat comprising nanofibers having diameters of ca. 300 nm was fabricated by the electrospinning of ionomeric PIS in N,N‐dimethylformamide (DMF). Then, the nanofibers were modified using PANI, which was synthesized by the oxidative polymerization of aniline, yielding an electrochemically active nanofiber mat having a diameter of ca. 350 nm. It was confirmed that PANI was successfully incorporated onto the PIS nanofiber mats by X‐ray photoelectron spectroscopy. Subsequently, we conducted electrochemical measurements of the PANI‐modified nanofiber mats using a tailor‐made attachment in which the working electrode gently comes in contact with the nanofiber mat surface. This attachment was observed to be widely useful in the cyclic voltammetry measurements related to redox‐active nanofibers. These observations are expected to contribute to the advancements in application development of the electrochemically active nanofiber mats.     

Characterization of poly(methyl methacrylate) nanofiber mats by electrospinning process

In this study, the aim is to describe the influence of electrospinning parameters on the morphology, the water wetting property and dye adsorption property of poly(methyl methacrylate) nanofiber mats. Specifically, the effects of solution concentration, solvent type, applied voltage, distance between the electrodes and particulate reinforcement on the diameter and shape of the nanofibers were investigated. All poly(methyl methacrylate) nanofiber mats contained beaded nanofiber structures. With increasing the polymer solution concentration, the average fiber diameter also increased. Poly(methyl methacrylate) nanofiber mat electrospun from dimethylformamide solution resulted in thicker fibers when compared with the mat electrospun from acetone solution. Increasing the electric potential difference between the collector and the syringe tip did not increase the average fiber diameter. Besides increasing the distance between the electrodes resulted in a decrease in the average fiber diameter. When compared with PMMA nanofiber mat, thicker fibers were obtained with silica nanoparticles reinforced nanofiber mat. According to the water contact angle measurements, all poly(methyl methacrylate) nanofiber mats revealed hydrophobic surface property. PMMA nanofiber mat with the highest water contact angle gave rise to the highest dye adsorption capacity.     

In situ synthesis of ZnO nanocrystal/PET hybrid nanofibers via electrospinning

Hybrid nanofibers of ZnO precursors/PET were fabricated by electrospinning a nonaqueous poly(ethylene terephthalate) (PET) solution containing zinc acetate dihydrate. Scanning electron microscopy images showed that the as prepared nanofibers had smooth and uniform surfaces, and the diameter was decreased with increasing zinc acetate dihydrate content and reducing PET concentration. After the treatment by a mild process of immersing the fibers in ammonia‐ethanol mixtures (pH ≈ 9–11), the surface of the nanofibers became rough during the formation of ZnO nanocrystals in the fibers. High resolution transmission electron microscopy images showed that the mean particle size became smaller with increasing diameter of the polymer fibers and decreasing content of ZnO. Fourier transform infrared spectra confirmed the ZnO formation in the hybrid nanofibers. X‐ray diffractometry patterns indicated that ZnO had the Wurtzite structure. The formation and growth of ZnO nanocrystals in the nanofiber matrices was also influenced by the various other parameters, that is, the pH value of the reaction solution, the content of zinc acetate dihydrate within the fibers, the reaction time and temperature. Photoluminescence spectra under excitation at 300 nm revealed a broad and intense ultraviolet emission. The UV‐visible diffuse reflectance spectra demonstrated the blue shift in the absorbance curve, which was ascribed to the quantum confinement effects of ZnO nanoparticles in the hybrid materials. These hybrid nanofibers can potentially be used in light emitters, chemical sensors, photo‐catalysts and solar cells. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1360–1368, 2011     

Fabrication and Formation Mechanism of Ag Nanoplate‐Decorated Nanofiber Mats and Their Application in SERS

We report a new simple method to fabricate a highly active SERS substrate consisting of poly‐m‐phenylenediamine/polyacrylonitrile (PmPD/PAN) decorated with Ag nanoplates. The formation mechanism of Ag nanoplates is investigated. The synthetic process of the Ag nanoplate‐decorated PmPD/PAN (Ag nanoplates@PmPD/PAN) nanofiber mats consists of the assembly of Ag nanoparticles on the surface of PmPD/PAN nanofibers as crystal nuclei followed by in situ growth of Ag nanoparticles exclusively into nanoplates. Both the reducibility of the polymer and the concentration of AgNO₃ are found to play important roles in the formation and the density of Ag nanoplates. The optimized Ag nanoplates@PmPD/PAN nanofiber mats exhibit excellent activity and reproducibility in surface‐enhanced Raman scattering (SERS) detection of 4‐mercaptobenzoic acid (4‐MBA) with a detection limit of 10^?10 m , making the Ag nanoplates@PmPD/PAN nanofiber mats a promising substrate for SERS detection of chemical molecules. In addition, this work also provides a design and fabrication process for a 3D SERS substrate made of a reducible polymer with noble metals.     

Applications of polymer nanofibers in biomedicine and biotechnology

Recent advancements in the electrospinning method enable the production of ultrafine solid and continuous fibers with diameters ranging from a few nanometers to a few hundred nanometers with controlled surface and internal molecular structures. A wide range of biodegradable biopolymers can be electrospun into mats with specific fiber arrangement and structural integrity. Through secondary processing, the nanofiber surface can be functionalized to display specific biochemical characteristics. It is hypothesized that the large surface area of nanofibers with specific surface chemistry facilitates attachment of cells and control of their cellular functions. These features of nanofiber mats are morphologically and chemically similar to the extracellular matrix of natural tissue, which is characterized by a wide range of pore diameter distribution, high porosity, effective mechanical properties, and specific biochemical properties. The current emphasis of research is on exploiting such properties and focusing on determining appropriate conditions for electrospinning various polymers and biopolymers for eventual applications including multifunctional membranes, biomedical structural elements (scaffolds used in tissue engineering, wound dressing, drug delivery, artificial organs, vascular grafts), protective shields in specialty fabrics, and filter media for submicron particles in the separation industry. This has resulted in the recent applications for polymer nanofibers in the field of biomedicine and biotechnology.     

Green synthesis of polymer nanofibers and their composites as flame‐retardant materials for polymer nanocomposites

Polyaniline nanofibers and their composites with carbon nanotubes were developed as an effective flame‐retardant material using a facile green method. Polyaniline nanofibers were used as a smart flame‐retardant for acrylonitrile–butadiene–styrene polymer. The polyaniline nanofibers were dispersed in polymer matrix forming well‐dispersed polymer nanocomposites. Effect of polyaniline nanofiber mass ratio on the polymer nanocomposite properties was studied. Polyaniline nanofiber composites with carbon nanotubes were also dispersed in polymer matrix. The thermal stability and flammability properties of the polymer nanocomposites were investigated. The rate of burning of polymer nanocomposites achieved 82.5% reduction (7.32 mm/min) compared with virgin polymer (42.5 mm/min). The reduction in peak heat release rate and total heat release of the polymer nanocomposites containing nanofibers achieved 74 and 34%, respectively. Interestingly, the average mass loss rate was significantly reduced by 58% and the emission of carbon monoxide and carbon dioxide gases were suppressed by 20 and 47%, respectively. The effect of polyaniline nanofibers composites on the flammability of polymer nanocomposites was also studied. Polyaniline nanofibers and their composites were characterized using Fourier transform infrared spectroscopy and transmission and scanning electron microscopy. The dispersion of polyaniline nanofibers in polymer nanocomposites was characterized using transmission electron microscopy. The different polymer nanocomposites were characterized using thermogravimetric analysis, UL94 flame chamber, and cone calorimeter tests. Copyright © 2016 John Wiley & Sons, Ltd.     

聚(丙交酯-co-乙交酯)/β-磷酸三钙复合物的电纺研究

对生物可吸收聚(丙交酯-co-乙交酯)(poly(lactide-co-glycolide),PLGA)与β-磷酸三钙(-βTCP)复合物体系进行了电纺.研究了PLGA的浓度,-βTCP与PLGA比例,加料速度,电压,喷头与接收体之间的距离等因素对电纺过程的影响,制备出纳米纤维膜,并用扫描电镜(SEM)等对纤维膜进行表征.结果表明,电纺溶液浓度越高,或者加料速度越快,纳米纤维的直径越粗.力学实验显示,复合物中-βTCP的含量增加使纳米纤维膜的拉伸强度和杨氏模量下降.     

Use of electrospinning to directly fabricate three-dimensional nanofiber stacks of cellulose acetate under high relative humidity condition

Unique structure-controllable three-dimensional (3D) nanofiber stacks of cellulose acetate (CA) were fabricated successfully by simply increasing relative humidity (RH) during the electrospinning process. It is found that once the RH exceeding 60 %, 3D flocculent nanofiber stacks would grow on the flat plate collector toward the needle tip without using special assisting apparatus or preparing special electrospinning solution. Compared with those obtained at low RH, the as-prepared nanofibers fabricated under high RH condition exhibited similar nanofiber diameter, density and porosity, and more importantly, 3D flocculent structures instead of typical two-dimensional (2D) electrospun non-woven mats, which would contribute to a significant improvement on the hydrophilicity. It is believed that rapid solidification of CA during the jet process and strong charge repulsion among CA nanofibers play important roles in the formation of 3D nanofibrous structure. Furthermore, these 3D flocculent nanofiber scaffolds exhibited better cytocompatibilities with human MG-63 cells than common 2D nanofibrous mats. Thus a facile and effective approach was presented to prepare 3D nanofiber stacks with tunable and reproducible properties for biodegradable scaffold applications.     

Influence of solvents properties on morphology of electrospun polyurethane nanofiber mats

Segmented polyurethane (SPU) nanofiber mats were prepared by electrospinning technique using the combination of four different solvents viz. tetrahydrofuran, N,N′‐dimethyl formamide, N,N′‐dimethyl acetamide, and dimethyl sulfoxide. Morphology of the electrospun nanofibers was examined by field emission scanning electron microscope. Experimental results revealed that the morphologies of polyurethane nanofiber mats have been changed significantly with the solvent selection for the electrospinning. It was observed that the diameters and morphology of the SPU nanofibers were influenced greatly by the use of combination of solvents. The uniform polyurethane nanofibers without beads or curls could be prepared by electrospinning through the selection of combination of good conductive and good volatile solvent viz. 7.5 wt/v% of SPU in N,N′‐dimethyl formamide/tetrahydrofuran (30 : 70 v/v) solutions at 20 kV applied voltages and volume flow rate of 1 ml/min. On the basis of the results obtained from this investigation, it has been established that solvent selection is one of the driving factors for controlling the morphology of the polyurethane electrospun nanofiber mats. The well‐controlled morphology of electrospun polyurethane nanofiber mats could be useful for many potential industrial applications such as in biomedical, smart textiles, nanofiltration, and sensors. Copyright © 2013 John Wiley & Sons, Ltd.     

Thin, bendable electrodes consisting of porous carbon nanofibers via the electrospinning of polyacrylonitrile containing tetraethoxy orthosilicate for supercapacitor

In the present study, electrically conducting carbon nanofiber (CNF) mats were produced by incorporating tetraethoxy orthosilicate (TEOS) into polyacrylonitrile (PAN) via electrospinning. A simple thermal treatment was applied to the electrospun nanofibers to create ultramicropores that could accommodate a large number of ions were formed on the surface of the CNFs, removing the need for a time-consuming activation step. The Si/CNF composites showed high capacitance and energy/power density values due to the formation of ultramicropores and the introduction of heteroatoms.     

Piezoelectric PVDF-TrFE nanocomposite mats filled with BaTiO3 nanofibers: The effect of poling conditions

BaTiO₃ nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF-TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β-crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two-step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d₃₃ (−31.7 pC N⁻¹), strongly dependent on the added BaTiO₃ nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices.