UV-protection and photocatalytic properties of electrospun polyacrylonitrile nanofibrous mats coated with TiO<Subscript>2</Subscript> nanofilm via sol–gel

UV radiation causes serious damage to skin, and a protective system capable of absorbing or reflecting UV radiation is required to protect skin. This paper describes the UV protection and photocatalytic properties of TiO₂ nanofilm coated electrospun polyacrylonitrile (PAN) nanofibrous mats with various nanofiber diameter and area density. The mats were coated by sol–gel process. The results of this research showed that sol–gel is capable of coating porous nanofibrous mats with a weight increase as low as 0.8%. The TiO₂ nanofilm coated on the nanofibrous mats has a considerable effect on its UV protection. The UV protection factor (UPF) of the mats increases with decreasing nanofiber diameter. In fact decreasing the diameter of nanofibers of the TiO₂ nanofilm coated PAN nanofibrous mats increases their photocatalytic activity. Moreover, this research showed that TiO₂ nanofilm produced through sol–gel process on the PAN nanofibers has a crystalline structure. The UPF of the nanofibrous mat coated with a TiO₂ nanofilm via sol–gel process can be classified as excellent.     

Thermoresponsive conductive polymer composite thin film and fiber mat: Crosslinked PEDOT:PSS and P(NIPAAm‐co‐NMA) composite

The thermoresponsive conductive composite (TCC) thin films and fiber mats, whose electrical property changed with temperature, were fabricated successfully. The thermocrosslinkable and thermoresponsive copolymer, poly(N‐isopropyl acrylamide‐co‐N‐methylolacrylamide) (PNN), was synthesized. The TCC thin film and fiber mat were fabricated by spin coating and electrospinning process of PEDOT:PSS/PNN solutions, respectively. After thermocrosslinking and doping by DMSO, the composite thin films and fiber mats were obtained. Fibrous structures of TCC fiber mats were observed by SEM. The surface resistance and conductivity of composites were measured. The thermoresponsivity and swelling ratio of TCCs were also studied. The thermoresponsive conductive property was analyzed by measuring the surface resistance of TCCs in water bath under various temperatures from 20 to 50 °C. With the increase of temperature, the TCCs shrank to be dense structure and showed lower surface resistance. The TCC fibers mat exhibited greater sensitivity to temperature than thin film owing to its fibrous structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1078–1087     

Polyacrylonitrile fiber mat‐supported palladium catalyst for Mizoroki–Heck reaction in aqueous solution

A novel palladium catalyst immobilized on polyacrylonitrile fiber mats (Pd/PAN) was prepared by electrospinning. The catalytic activity and recyclability of the microwave‐assisted Pd/PAN fiber mats were examined for the Mizoroki–Heck cross‐coupling of aryl iodides with three different acrylates in aqueous solution. The morphology of the prepared Pd/PAN fiber mats was characterized by scanning electron microscopy. The large size of the PAN fiber mat‐supported palladium catalyst enables much easier separation from the reaction mixture by simple filtration. Density functional theory calculation indicates that the chelation energy of palladium chloride (PdCl₂) with propionitrile (model of PAN) is considerable smaller than that of PdCl₂ with water, suggesting that the stability and reactivity of the Pd/PAN fiber mats catalyst could be improved through the surface derivatization with polar functional groups. Copyright © 2011 John Wiley & Sons, Ltd.     

Fibroin nanofibers production by electrospinning method

Silk fibroin, which has many characteristic properties such as low inflammation reaction, biodegradation, suppleness, good antithrombogenic details, biocompatibility and high tensile strength is a very good candidate for biomedical applications. Electrospinning procures high surface area, porous, nanofiber dimension fiber generation, which is a plain method. An experimental study was carried out to produce nanofiber structure from silk fibroin by electrospinning and the electrospinning parameters for the spinning of uniform, continuous and silk fibroin fibers were optimized. As a result, the effect of variables of concentration, distance and applied voltage on the strength, thickness, surface structure, fiber diameter of nanomaterial was investigated. Then, in vitro cell viability of the silk fibroin mat was analyzed. It was seen that the strength, mat thickness, and fiber diameter increased with solution concentration rise. It was found that the values of the fiber diameter and tensile strength decreased with increasing distance. It was determined that the effect of distance varies depending on the concentration in the mat thicknesses. The tensile strength was affected inversely proportional the applied voltage rises and distance. It was found that the fiber diameter values decreased together with increasing applied voltage. At cell viability of silk fibroin mat was occurred high cell viability after 24 h, but it was obtained low cell viability at the 48th h.     

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.     

The morphology and crystalline region distribution of polyacrylonitrile nanofibers prepared by electrospinning

The effects of electrospinning parameters in a wider range on the morphology and diameters of polyacrylonitrile (PAN) fibers are studied in detail. The fibers’ diameter increases from 288 to 3469 nm swiftly with the increasing PAN concentration. With the increasing voltage or prolonging gap distance, the diameter increases primarily and decreases later. The combined effects of surface tension, splitting and stretching, electric force, viscosity, and solvent volatilization are the main reasons. Ultrasonic etching method, Atomic force microscope (AFM), Scanning electron microscope (SEM) and X-ray diffraction (XRD) technology have been utilized to verify the nature structure of electrospun PAN fibers. Combining all the results, it is deduced that there are many grooves arranging nearly perpendicular to the fiber axis on the surface of electrospun PAN fibers. The thickness of relative ordered region is 40 to 190 nm and the thickness of amorphous region is 20 to 35 nm.     

Application of surface wettability modified polypropylene nonwoven in Janus composite fibrous mats for the function of directional water transport

Textiles with the function of directional water (sweat) transport play a pivotal role in regulating human thermal and wet comfort. Polypropylene nonwoven (PPNW) fabric has an excellent moisture (sweat) conduction due to its inert water absorption, which makes moisture be difficult to adhere on the PP fiber surface. Nevertheless, excessive hydrophobicity also affects the comfort of clothing materials, and thus it is significant to improve wettability of PP fiber used in the field of textile. In this study, it was reported a kind of composite fibrous mats with the function of directional water transport. The polymerization of acrylic acid (AAc) was grafted on the surface of plasma‐treated PPNW (TPPNW) as the inner layer (TPPNW‐AAc), which was able to improve the wettability of the PPNW surface. Polyacrylonitrile containing alumina nano‐particles (PAN‐Al₂O₃) layer was deposited on the surface of TPPNW‐AAc by electrospinning technology as the outer layer. The wettability difference between the inner and outer layers of the material was utilized to induce the push‐pull effect to transport water from the TPPNW‐AAc layer to the PAN‐Al₂O₃ layer. The surface wettability of the TPPNW‐AAc layer and the performance of the directional water transport of composite fibrous mats were characterized systematically. Experimental results demonstrated that the composite fibrous mats showed the excellent accumulative one‐way transport index (AOTI, 870%), remarkable overall moisture management capacity (OMMC, 0.8) when the contact angle of the TPPNW‐AAc surface can be reduced from 119° to 30°, and decent wearability performance.     

Electrospun fiber mats of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and their blends

Electrospinning of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and their blends was first carried out in chloroform at 50 °C on a stationary collector. The average diameter of the as‐spun fiber from PHB and PHBV solutions decreased with increasing collection distance and increased with increasing solution concentration and applied electrical potential. In all of the spinning conditions investigated, the average diameter of the as‐spun pure fibers ranged between 1.6 and 8.8 μm. Electrospinning of PHB, PHBV, and their blends was carried out further at a fixed solution concentration of 14% w/v on a homemade rotating cylindrical collector. Well‐aligned, cross‐sectionally round fibers without beads were obtained. The average diameter of the as‐spun pure and blend fibers ranged between 2.3 and 4.0 μm. The as‐spun fiber mats appeared to be more hydrophobic than the corresponding films and much improvement in the tensile strength and the elongation at break was observed for the blend fiber mats over those of the pure fiber ones. Lastly, indirect cytotoxicity evaluation of the as‐spun pure and blend fiber mats with mouse fibroblasts (L929) indicated that these mats posed no threat to the cells. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2923–2933, 2006     

Encasement of metallic cardiovascular stents with endothelial cell‐selective copolyetheresterurethane microfibers

Cardiovascular metallic stents established in clinical application are typically coated by a thin polymeric layer on the stent struts to improve hemocompatibility, whereby often a drug is added to the coating to inhibit neointimal hyperplasia. Besides such thin film coatings recently nano/microfiber coated stents are investigated, whereby the fibrous coating was applied circumferential on stents. Here, we explored whether a thin fibrous encasement of metallic stents with preferentially longitudinal aligned fibers and different local fiber densities can be achieved by electrospinning. An elastic degradable copolyetheresterurethane, which is reported to selectively enhance the adhesion of endothelial cells, while simultaneously rejecting smooth muscle cells, was utilized for stent coating. The fibrous stent encasements were microscopically assessed regarding their single fiber diameters, fiber covered area and fiber alignment at three characteristic stent regions before and after stent expansion. Stent coatings with thicknesses in the range from 30 to 50 µm were achieved via electrospinning with 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFP)‐based polymer solution, while a mixture of HFP and formic acid as solvent resulted in encasements with a thickness below 5 µm comprising submicron sized single fibers. All polymeric encasements were mechanically stable during expansion, whereby the fibers deposited on the struts remained their position. The observed changes in fiber density and diameter indicated diverse local deformation mechanisms of the microfibers at the different regions between the struts. Based on these results it can be anticipated that the presented fibrous encasement of stents might be a promising alternative to stents with polymeric strut coatings releasing anti‐proliferative drugs. Copyright © 2015 John Wiley & Sons, Ltd.     

Ammonia Gas Sensor Using Polypyrrole‐Coated TiO2/ZnO Nanofibers

Highly porous polypyrrole (PPy)‐coated TiO₂/ZnO nanofibrous mat has been successfully synthesized. The core TiO₂/ZnO nanofibers have an average diameter of ca. 100 nm and the shell of ultrathin PPy layer has a thickness of ca. 7 nm. The NH₃ gas sensor using the as‐prepared material exhibited a fast response over a wide dynamic range and high sensitivity with a detection limit of 60 ppb (S/N=3). Compared to conventional pristine PPy film, the improved performance in NH₃ detection can be attributed to the free access of NH₃ to PPy and a minimized gas diffusion resistance through the ultrathin PPy layer.     

Electrospinning of cyclodextrin functionalized chitosan/PVA nanofibers as a drug delivery system

A new type of nanofibrous structure from chitosan bearing carboxymethyl-β-cyclodextrin (CS-g-β-CD) as a novel drug delivery system was synthesized by grafting carboxymethyl-β-cyclodextrin (CM β-CD) onto chitosan (CS) in the presence of water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as the condensing agent and N-hydroxysuccinimide (NHS). Defect free mats containing CS-g-β-CD have been fabricated using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)/CS-g-β-CD blends. The morphology and diameter of the electrospun nanofibers were examined by scanning electron microscopy (SEM). The average fiber diameter was in the range of 130–210 nm. SEM images showed that the morphology and diameter of the nanofibers were mainly affected by weight ratio of the blend at constant applied voltage. The results revealed that increasing CS-g-β-CD content in the blends decreases the average fiber diameter. It was observed that the PVA/CS-g-β-CD nanofibrous mat provided a slower release of the entrapped drug in compare to PVA/CS nanofibrous mat.     

Thermal shrinkage of electrospun PVP nanofibers

This paper outlines the shrinkage of electrospun polyvinylpyrrolidone (PVP) fiber mats during thermal treatment. The thermal behavior and phase changes within the fibers were investigated by DSC and TGA/DTA. Five precursors with different PVP loading in ethanol were electrospun. The mats shrinkage as function of temperature was measured in the RT–200 °C range. Shrinkage rate drastically increased above the polymer glass transition point, T_g (150–180 °C), due to increase in polymer chain mobility. Mats shrinkage at 200 °C as function of PVP concentration showed a minimum at ∼10%wt. Below 10% PVP the mats morphology is non‐uniform, consisting of beads and fibers. Above 10% PVP, only flat and uniform fibers were observed. This paper outlines the dominant mechanism governing the mats shrinkage during heating. In addition, the effect of PVP concentration on the expansion of fibers diameter was investigated and found to be consistent with the linear shrinkage observing a minimum at ∼10% PVP. The effect of applied voltage on mat shrinkage was investigated, and showed a minimum at 12 kV. Understanding the interplay between fibers morphology and thermal shrinkage allows precursor composition and system optimization needed for minimizing shrinkage negative effects on the structure and properties of electrospun fiber mats. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 248–254     

A composite polyaniline/graphene–coated polyamide6 nanofiber mat for electrochemical applications

In this study, polyamide6 (PA6) nanofiber mats were fabricated through the electrospinning process. The nanofibers were coated by polyaniline (PANI) using the in situ polymerization of aniline in the presence of graphene oxide. The composite of the PANI/graphene oxide–coated nanofiber mat was treated with hydrazine monohydrate to reduce graphene oxide to graphene, and this was followed by the reoxidation of PANI. Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), wide angle X‐ray diffraction (WAXD), thermal gravimetric analysis (TGA), tensile strength tests, electrical conductivity measurements, cyclic voltammetry (CV), and charge/discharge measurements were conducted on the composite PA6/graphene nanofiber mats. It was found that the surface of the PA6 nanofibers was coated uniformly with the granular PANI and graphene oxide. Besides, the composite nanofibers showed good tensile and thermal properties. Their electrical conductivity and specific capacitance, when used as a separator in the cell, were 1.02 × 10^?4 S/cm and 423.28 F/g, respectively. Therefore, the composite PANI/reduced graphene oxide–coated PA6 nanofiber mats could be regarded as suitable candidates for application in energy storage devices.     

功能化聚丙烯腈纳米纤维膜同时高效萃取莠去津及其毒性代谢物

研制了一种新型固相萃取(SPE)介质,用于同时高效萃取莠去津(ATZ)及其两种毒性代谢产物脱乙基莠去津(DEA)和脱异丙基莠去津(DIA),为全面客观地评价ATZ的水污染状况提供基础.以聚丙烯腈纳米纤维(PAN NFs)膜为基底膜,制备了3种功能化的NFs膜.吸附容量和吸附效率实验结果表明,羧基修饰的PAN NFs(COOH-PAN NFs)膜对3种目标物的静态和动态吸附容量分别为2.00和0.19 mg/g,动态吸附流出率低于30.0％,显著优于其它3种NFs膜,且对极性较大的目标物保留最强,表明其为同时高效吸附ATZ、 DIA和DEA的优势SPE介质,且主要通过羧基基团与目标物之间形成的氢键进行目标物吸附.采用基于COOH-PAN NFs膜的SPE,结合高效液相色谱-二极管阵列检测器(HPLC-DAD),建立了同时检测水样中ATZ、 DIA和DEA的方法,方法回收率为81.4％～120.3％, DIA检出限(LOD, S/N=3)为0.12 ng/mL,DEA和ATZ的检出限为0.09 ng/mL,可应用于实际水样监测.     

Controlling electrospun nanofiber morphology and mechanical properties using humidity

Electrospinning is a fiber spinning technique used to produce nanoscale polymeric fibers with superior interconnectivity and specific surface area. The fiber diameter, surface morphology, and mechanical strength are important properties of electrospun fibers that can be tuned for diverse applications. In this study, the authors investigate how the humidity during electrospinning influences these specific properties of the fiber mat. Using two previously uninvestigated polymers, poly(acrylonitrile) (PAN) and polysulfone (PSU) dissolved in N,N‐Dimethylformamide (DMF), experimental results show that increasing humidity during spinning causes an increase in fiber diameter and a decrease in mechanical strength. Moreover, surface features such as roughness or pores become evident when electrospinning in an atmosphere with high relative humidity (RH). However, PAN and PSU fibers are affected differently. PAN has a narrower distribution of fiber diameter regardless of the RH, whereas PSU has a wider and more bimodal distribution under high RH. In addition, PSU fibers spun at high humidity exhibit surface pores and higher specific surface area whereas PAN fibers exhibit an increased surface roughness but no visible pores. These fiber morphologies are caused by a complex interaction between the nonsolvent (water), the hygroscopic solvent (DMF), and the polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Development and characterization of electrospun cellulose acetate nanofibers modified by cationic surfactant

Polymeric electrospun nanofibers have been gaining notoriety in the same way as their industrial applications, since the manufacturing of this type of material is simple and low-costed. In order to obtain fibrous polymeric material with small diameters and with reduced beads formation, a 2⁴ factorial experiment with triplicate at center point was performed. Cellulose acetate (CA) and cationic cetylpyridinium bromide (CPB) surfactant nanofibers were made using a homemade electrospinning apparatus. The assessed inputs were as follows: CA%, CPB%, flow rate, and applied voltage. From the analysis of the response surface methodology and scanning electron microscope (SEM), the optimal concentrations of CA and CPB for producing nanofibers were 21 w/v-% and 0.5 w/v-%, respectively, using a flow rate of 0.7 mL h⁻¹ and applied voltage of 18 kV. Fibers mats morphology shows average diameter of 0.2 μm and 7 nm pore size, as well as it was found that the single fiber unit presented nanoheterogeneity. Mechanical resistance of 2.70 MPa was obtained in the tensile strength test. The modification of CA by the addition of surfactant attributed better thermal and mechanical resistances to the nanofibers without, however, affecting their biodegradability and water resistance properties. The morphological characteristics of the newly obtained CA/CPB nanofibers combined with mechanical resistance provided subsidies to suggest that the as-obtained material presents potential to be applied as an air filter.     

Fabrication of Electrically Conducting Polypyrrole‐Poly(ethylene oxide) Composite Nanofibers

Summary: Electrically conducting polypyrrole‐poly(ethylene oxide) (PPy‐PEO) composite nanofibers are fabricated via a two‐step process. First, FeCl₃‐containing PEO nanofibers are produced by electrospinning. Second, the PEO‐FeCl₃ electrospun fibers are exposed to pyrrole vapor for the synthesis of polypyrrole. The vapor phase polymerization occurs through the diffusion of pyrrole monomer into the nanofibers. The collected non‐woven fiber mat is composed of 96 ± 30 nm diameter PPy‐PEO nanofibers. FT‐IR, XPS, and conductivity measurements confirm polypyrrole synthesis in the nanofiber.

An SEM image of the PPy‐PEO composite nanofibers. The scale bar in the image is 500 nm.     

Local Release of VEGF Using Fiber Mats Enables Effective Transplantation of Layered Cardiomyocyte Sheets

Cell sheet transplantation is a key tissue engineering technology. A vascular endothelial growth factor (VEGF)‐releasing fiber mat is developed for the transplantation of multilayered cardiomyocyte sheets. Poly(vinyl alcohol) fiber mats bearing poly(lactic‐co‐glycolic acid) nanoparticles that incorporate VEGF are fabricated using electrospinning and electrospray methods. Six‐layered cardiomyocyte sheets are transplanted with a VEGF‐releasing mat into athymic rats. After two weeks, these sheets produce thicker cardiomyocyte layers compared with controls lacking a VEGF‐releasing mat, and incorporate larger‐diameter blood vessels containing erythrocytes. Thus, local VEGF release near the transplanted cardiomyocytes induces vascularization, which supplies sufficient oxygen and nutrients to prevent necrosis. In contrast, cardiomyocyte sheets without a VEGF‐releasing mat do not survive in vivo, probably undergo necrosis, and are reduced in thickness. Hence, these VEGF‐releasing mats enable the transplantation of multilayered cardiomyocyte sheets in a single procedure, and should expand the potential of cell sheet transplantation for therapeutic applications.

     

Electrospun EGNPs reinforced precursor carbon nanofibril composites by using RSM

Response surface methodology (RSM),based on five‐level, four variable Box‐Benkhen technique was investigated for modeling the average fiber diameter of electrospun polyacrylonitrile (PAN) nanofibers. The four important electrospinning parameters were studied including applied voltage (kV), Berry's number, deposition distance from nozzle to collector (cm), and spinning angle (? in degree). The measured fiber diameters were in a good agreement with the predicted results by using RSM technique. High‐regression coefficient between the variables and the response (R² = 87.74%) indicates excellent evaluation of experimental data by second‐order polynomial regression model. The optimum PAN average fiber diameters of 208 and 37‐nm standard deviation were collected at 19 kV, Berry's number = 10, 25^° spinning angle, and 16‐cm deposition distance. The PAN/N,N‐dimethylformamide (DMF) polymer solution with the optimum weight concentration (10 wt.%) was selected to study the effect of dispersing exfoliated graphite nanoplatelets (EGNPs) in PAN/DMF solution on the electrospun EGNP/PAN fibril composite diameter. Five different EGNPs weight concentrations (2, 4, 6, 8, and 10 wt.%) were dispersed in the optimized PAN/DMF polymer solution. Morphology of EGNPs/PAN fibril composites and its distribution were investigated by scanning electron microscopy (SEM) to show the minimum fiber diameter for the above‐mentioned 5 wt. % of EGNPs. A minimum fibril composite diameter of 182 nm was obtained at 10 wt.% of EGNPs. Morphological characteristics of electrospun fibers and their distribution were tested by Raman spectroscopy, SEM, differential light scattering, and high‐resolution transmission electron microscopy.     

Surface morphology and electrical properties of polyurethane nanofiber webs spray‐coated with carbon nanotubes

Multiwalled carbon nanotubes (MWNTs) were spray‐coated on electrospun polyurethane nanofiber webs for electrical conductive application. For the effective coating of MWNTs, hyperbranched polyurethane (HBPU) was used by blending with linear polyurethane, which was synthesized in the A₂ + B₃ approach using poly(ε‐caprolactone)diol, 4,4′‐methylene bis(phenylisocynate), and castor oil. SEM measurements showed that the MWNTs could be coated well along the surface of nanofibers when the HBPU was blended in the linear polyurethane nanofibers. Blending of HBPU in the nanofibers also affected the electrical conductivity of MWNT‐coated nanofiber webs. The low electrical resistance from 20 to 400 Ω/sq was obtained for MWNT‐coated nanofiber webs and their electrical resistance decreased with an increase of spraying frequency. As a potential application of MWNT‐coated nanofiber webs, the electrical heating effect because of applied voltage was demonstrated. Copyright © 2011 John Wiley & Sons, Ltd.