Hydrophilic non-wovens made of cross-linked fully-hydrolyzed poly(vinyl alcohol) electrospun nanofibers

Fully-hydrolyzed poly (vinyl alcohol) (PVA) nanofibers were successfully electrospun from aqueous solutions of PVA in the presence of acetic acid. A continuous spinning of uniform PVA nanofibers proceeded by the addition of acetic acid due to the changes of electronic conductivity and surface tension of aqueous solution of PVA. When cross-linking agent 1 was added to aqueous solution of PVA and subsequent thermal treatment of as-spun nanofibers, chemically cross-linked PVA nanofibers were achieved to resist disintegration in contact with hot water and the tensile mechanical property of nanofiber non-wovens was greatly improved by the formation of cross-linking points. Magnetite was deposited uniformly onto the hydrophilic surface of cross-linked PVA nanofibers and the resulted nanofibers decorated with magnetite showed a magnetic responsiveness. The deposition of magnetite on the PVA nanofibers can generate self-standing magnetic non-wovens.     

静电纺特殊结构纳米纤维的研究现状

纳米级纤维具有优良的机械性能和高比表面积等特性.以静电纺特殊结构纳米纤维为研究对象,根据其表观形态分别介绍了一维特殊结构纳米纤维、二维特殊结构纳米纤维膜、三维结构纳米纤维气凝胶等,并阐述了各种结构的形成机理.总结了近年来国内外采用静电纺丝技术制备特殊结构纳米纤维的调控方法,如改变溶液性质(溶液浓度、黏度、表面张力、电导...     

Carbonized electrospun polyvinylpyrrolidone/metal hybrid nanofiber composites for electrochemical applications

Electrospinning is a very versatile and efficient method of fabricating nanofibers with the desired properties. Polyvinylpyrrolidone (PVP) in ethanol solution was electrospun into nanofibers and used as a precursor for the preparation of carbon nanofibers. Cobalt chloride was also incorporated with PVP nanofibers to produce carbon nanofiber composites with enhanced electrical conductivity and electrochemical properties. The surface morphology and physical properties of the electrospun nanofibers, carbonized nanofibers, and their composites were observed by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The electrochemical behavior of the carbon nanofiber composites was studied by drop‐casting on a working surface of the screen‐printed carbon electrode and examined by cyclic voltammetry and electrochemical impedance spectroscopy. The results indicated that carbon nanofiber composites were decorated with cobalt nanoparticles and enhanced the charge‐transfer efficiency on the electrode surface. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45639.     

Preparation and surface-enhanced Raman performance of electrospun poly(vinyl alcohol)/ high-concentration-gold nanofibers

A facile approach to prepare electrospun poly(vinly alcohol) (PVA) nanofibers with high concentration of gold nanoparticles (Au NPs) on the fibers, had been developed. These PVA/Au nanofibers could be used as flexible surface-enhanced Raman scattering (SERS) substrates. Relatively high concentration of PVA aqueous solution (10 wt %) was used as the stabilizing agent for gold salt precursor, as well as the starting solution for electrospinning. This method was demonstrated to be effective to prepare high-concentration-gold nanoparticles without aggregation and precipitation by reducing high concentration of gold salt in the presence of PVA aqueous solution. SEM and TEM images showed that both the amount and the size of Au NPs which embedded in PVA nanofibers, increased with increasing the gold salt content, while the gap between the adjacent NPs decreased. Raman spectra showed an apparent enhancement in the signal of 4-mercaptobenzoic acid (4-MBA) molecules pre-absorbed from its ethanol solution onto the PVA/Au nanofibers. The high SERS activity to 4-MBA in solution with a relatively low concentration (10⁻⁶ M), could be mainly attributed to the reduced gap of Au NPs.     

海藻酸钠/聚乙烯醇溶液的性能及静电纺丝

将质量分数为2%的海藻酸钠(SA)与质量分数为8%的聚乙烯醇(PVA)按一定体积比混合后进 行静电纺丝,研究了SA与PVA溶液的相容性及SA/PVA共混溶液性能.结果表明:SA与PVA溶液相容;随着PVA含量的增加,SA/PVA共混溶液的粘度、表面张力、电导率则降低,共混溶液的可纺性提高;静电纺丝得到的SA/PVA超细...     

Study of electrospinning of sodium alginate,blended solutions of sodium alginate/poly(vinyl alcohol) and sodium alginate/poly(ethylene oxide)

Alginate is an interesting natural biopolymer for many of its merits and good biological properties. This paper investigates the electrospinning of sodium alginate (NaAlg), NaAlg/PVA‐ and NaAlg/PEO‐ blended systems. It was found in this research that although NaAlg can easily be dissolved in water, the aqueous NaAlg solution could not be electrospun into ultrafine nanofibers. To overcome the poor electrospinnability of NaAlg solution, synthetic polymers such as PEO and PVA solutions were blended with NaAlg solution to improve its spinnability. The SEM images of electrospun nanofibers showed that the alginate (2%, w/v)–PVA (8%, w/v) blended system in the volume ratio of 70 : 30 and the alginate (2%, w/v)–PEO (8% w/v) blended system in the volume ratio of 50 : 50 could be electrospun into finest and uniform nanofibers with average diameters of 118.3 nm (diameter distribution, 75.8–204 nm) and 99.1 nm (diameter distribution, 71–122 nm), respectively. Rheological studies showed a strong dependence of spinnability and fiber morphology on solution viscosity and thus on the alginate‐to‐synthetic polymer (PVA or PEO) blend ratios. FTIR studies indicate that there are the hydrogen bonding interactions due to the ether oxygen of PEO (or the hydroxyl groups of PVA) and the hydroxyl groups of NaAlg. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Alumina nanofibers obtained from poly(vinyl alcohol)/boehmite nanocomposites

Poly(vinyl alcohol) (PVA)/boehmite nanocomposite (precursor) nanofibers were formed by electrospinning using a PVA aqueous solution of dispersed boehmite nanoparticles as the spinning solution. The alumina nanofibers were obtained by calcination of the precursor nanofibers between 500 and 1200°C. The specific surface area of the precursor nanofibers was around 6 m²/g, and that of the γ‐alumina nanofibers calcined at 500°C was around 300 m²/g. The specific surface areas and the fiber diameters were not affected by the alumina contents in the precursors. Also, the diameter of the alumina nanofibers was not affected by the calcination temperature of the precursor nanofibers. The pore characteristics of the alumina nanofibers decreased with increased calcination temperature due to the sintering, and nonporous α‐alumina nanofibers were obtained by calcination of the precursor nanofibers at 1200°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fluorescent poly(p-phenylene vinylene)/poly(ethylene oxide) nanofibers obtained by electrospinning

Poly(p-phenylene vinylene) (PPV)/poly(ethylene oxide) (PEO) hybrid nanofibers were prepared by electrospinning a composite solution of PPV precursor/PEO in a mixture of ethanol and water, followed by thermal conversion. The precursor/PEO composite solutions were successfully electrospun into nanofibers with diverse helical, helical and linear, and helical bead-on-string morphologies by controlling the amount of aqueous PEO solution in a composite solution. Moreover, adding aqueous PEO solution to a precursor ethanol solution decreased the diameters of the fibers. The experimental data suggest that the viscosity, conductivity, and surface tension of the electrospinning solution are the main factors that influence the morphology of the fibers. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) investigations indicated that the PPV precursor reacts with PEO during thermal conversion. Ultraviolet–visible (UV-vis) and photoluminescence (PL) spectra of the PPV-PEO nanofibers exhibited appreciable blue shifts with the addition of PEO, which made it possible to fabricate nanofibers with fluorescence ranging from yellow-green to blue. These highly fluorescent PPV/PEO nanofibers with various morphologies are potentially interesting for many applications, such as micro- and nanooptoelectronic devices and systems.     

Fabrication and characterization of novel nanofibers from cress seed mucilage for food applications

Cress seed mucilage (CSM) as a new source of biomacromolecule has gained attraction in food science due to its biodegradability and biocompatibility. In this research CSM–poly(vinyl alcohol) (PVA) nanofibers were produced under different conditions by electrospinning technique. Viscosity and electrical conductivity of the produced biopolymers were analyzed. The effect of CSM to PVA volume ratio and applied electrical field were evaluated on nanofiber morphology by scanning electron spectroscopy. The optimum nanofibers showed smooth and uniform surfaces with diameter size range of 95–278 nm. The results of Fourier transform infrared spectroscopy of CSM–PVA nanofiber with volume ratio of 60:40 showed characteristic peaks of CSM and PVA. X‐ray diffractometer data clearly revealed the amorphous structure of the electrospun nanofibers. Thermogravimetric and derivative thermogravimetric analysis indicated that thermal stability of electrospun nanofibers increased in comparison to CSM and PVA. The results of this study indicated that CSM can be applied as a new source of biopolymer for production of nanofibers that could be used for different applications such as delivery systems and packaging film fabrication. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45811.     

Crystallinity study of electrospun poly (vinyl alcohol) nanofibers: effect of electrospinning,filler incorporation,and heat treatment

This study aims to explore crystallinity variations of polyvinyl alcohol (PVA) as a result of electrospinning, filler addition, and heat treatment. Pure PVA and PVA nanocomposite fibers containing only nanohydroxy apatite (nHAp) and together with cellulose nanofibers (CNF) were electrospun. Electrospun nanofibers were heat treated at 180 °C for 8 h. The morphology of electrospun fibers was evaluated by scanning electron microscopy (SEM) while Fourier transform infrared spectroscopy, differential scanning calorimetry, and wide angle X-ray scattering were used to analyze nanofibers crystallinity. Un-treated electrospun nanofibers were shrank and lost their porous structure in water, while heat treatment of nanofibers caused stabilization of fibrous mats in boiling water. It was concluded that the crystallinity of electrospun PVA were considerably reduced compared to PVA powder due to formation of metastable—small and/or defective crystals. Adding small content (1 wt%) of nHAp led to increase in electrospun nanofibers crystallinity. However, incorporation of higher content of nHAp and CNF caused reduction of crystallinity most probably due to possible interactions among components which interrupt the orientation of macromolecules. All analyzing methods proved the crystallinity enhancement of nanofibers upon heat treatment which can be attributed mostly to water evaporation from electrospun fibers structure.     

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     

Thermal and morphological properties of PVA/4‐vinylbenzene boronic acid hybrid nanofibrous

The aim of this study was to investigate the preparation and characterization of PVA and PVA/4‐VBBA (4‐Vinylbenzene boronic acid) hybrid electrospun nanofiber mat. PVA was mixed with cross‐linkable 4‐Vinylbenzene boronic acid (4‐VBBA), enabling the polymer to cross‐link upon UV irradiation. The photo‐cross‐linking reaction was characterized by a Fourier transform infrared spectroscopy. The structure and morphology of electrospun membranes were investigated by scanning electron microscopy (SEM). SEM images showed that the nanofiber diameter and the nanostructured morphology depended on solution viscosity, applied electric voltage(AV), tip to collector distance (TCD), and the amount of the 4‐VBBA. The thermal properties of PVA and PVA/4‐VBBA hybrid nanofibers were investigated by thermo gravimetric analysis. The photo‐crosslinked nanofibers were insoluble in water. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Dye-sensitized solar cells based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) nanofibers

Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers were prepared by the electrospinning method and used as polymer electrolytes in dye-sensitized solar cells (DSSCs). The electrolyte uptake and ionic conductivity of electrospun PVDF-HFP nanofibers with different diameters changed significantly, regardless of the nanofiber thickness. The PVDF-HFP nanofibers prepared from a 15 wt% spinning solution showed high ionic conductivity (1.295 S/cm) and electrolyte uptake (947 %). DSSCs based on the 15 wt% PVDF-HFP nanofiber electrolyte showed an electron transit time of 6.34 × 10^?3 s, electronic recombination time of 5.88 × 10^?2 s, and conversion efficiency of 3.13 %. Thus, we concluded that the electrospun PVDF-HFP nanofibers can be used as polymer electrolytes in flexible DSSCs as well.     

A cost effective and facile approach to prepare beadless polycarbonate nanofibers with ultrafine fiber morphology

Preparing defect free nanofibers with average diameter well below 100 nm is a challenge to researchers by electrospinning technology. In the present contribution, the electrospinning method was utilized to prepare beadless polycarbonate (PC) nanofibers with average diameter 90 nm using comparatively less toxic and suitable solvents in a convenient way. Spinning PC with pure dichloromethane (DCM) and also with 1:1 mixture of DCM and N,N dimethylformamide under the same spinning parameters with varying PC concentration has very much helped to establish the effect of solvents on fiber formation. This study also proved the impact of solution concentration, viscosity, and solution conductivity on the formation of beadless ultrafine PC fibers and subsequently on the bead density and average fiber diameter. The appropriate proportion of solvents under suitable spinning parameters has helped to minimize the quantity of PC during the formation of bead free nanofibers by electrospinning. The ultrafine, uniform, and beadless morphology of the electrospun PC fibers can be utilized for various nanotechnology advancements. POLYM. ENG. SCI., 59:1799–1809, 2019. © 2019 Society of Plastics Engineers     

Preparation and characterization of biomimetic tussah silk fibroin/chitosan composite nanofibers

Tussah silk fibroin (TSF)/chitosan (CS) composite nanofibers were prepared to mimic extracellular matrix by electrospinning with hexafluoroisopropanol (HFIP) as a solvent. The viscosity and conductivity of TSF/CS blend solution were analyzed and the morphology, secondary structure, and thermal property of TSF/CS composite fibers were investigated by SEM, ¹³C CP/MAS-NMR, X-ray diffraction, and DSC Techniques. The electrospinnability of TSF solution was improved significantly by adding 10 wt% CS, and morphology of electrospun TSF nanofibers changed from flat strip to cylindrical. At the same time, the average fiber diameters decreased from 542 to 312 nm, accompanying by an obvious improvement in fiber diameter uniformity. However, when the CS content in blend solution was more than 15 wt%, the diameter of electrospun TSF/CS nanofibers appeared to be polarized which can be attributed to phase separation of the two components in composite nanofibers. Blending 10 wt% CS did not change the conformation of TSF in TSF/CS composite nanofibers, and TSF in composite nanofibers at various composition ratios had mainly taken the α-helix structure. The thermal decomposition temperature of electrospun TSF/CS composite nanofibers decreased with the increase of CS content due to the lower decomposition temperature of CS. To study the cytocompatibility and cell behavior on the TSF/CS nanofibers, human renal mesangial cells were seeded onto electrospun TSF/CS composite nanofibers. Results indicated that the addition of CS promoted cell attachment and spreading on TSF nanofibers significantly, suggesting that electrospun TSF/CS composite nanofibers could be a candidate scaffold for tissue engineering.     

Green fabrication route of robust,biodegradable silk sericin and poly(vinyl alcohol) nanofibrous scaffolds

Silk sericin (SS) has been extensively used to fabricate scaffolds for tissue engineering. However, due to its inferior mechanical properties, it has been found to be a poor choice of material when being electrospun into nanofibrous scaffolds. Here, SS has been combined with poly(vinyl alcohol) (PVA) and electrospun to create scaffolds with enhanced physical properties. Crucially, these SS/PVA nanofibrous scaffolds were created using only distilled water as a solvent with no added crosslinker in an environmentally friendly process. Temperature has been shown to have a marked effect on the formation of the SS sol–gel transition and thus influence the final formation of fibers. Heating the spinning solutions to 70 °C delivered nanofibers with enhanced morphology, water stability and mechanical properties. This is due to the transition of SS from β‐sheets into random coils that enables enhanced molecular interactions between SS and PVA. The most applicable SS/PVA weight ratios for the formation of nanofibers with the desired properties were found to be 7.5/1.5 and 10.0/1.5. The fibers had diameters ranging from 60 to 500 nm, where higher PVA and SS concentrations promoted larger diameters. The crystallinity within the fibers could be controlled by manipulation of the balance between PVA and SS loadings. In vitro degradation (in phosphate buffer solution, pH 7.4 at 37 °C) was 30–50% within 42 days and fibers were shown to be nontoxic to skin fibroblast cells. This work demonstrates a new green route for incorporating SS into nanofibrous fabrics, with potential use in biomedical applications. © 2019 Society of Chemical Industry     

溶剂及溶液中无机盐对电纺纤维的影响

采用二甲基乙酰胺(DMAc)与丙酮的混合溶剂,对醋酸纤维素(SCA)电纺过程中溶液性质对纤维直径及形态的影响进行研究。不同的溶液性质具体表现为不同的溶度参数、黏度、表面张力、挥发度等,而纤维直径的细化是以上参数共同作用的结果。而本文中,由于丙酮对溶液的挥发度起了决定性作用,使电纺纤维的直径的改变受其影响最大。当DMAc∶丙酮的混合比为20∶80时,纤维表面会充满凹陷的小孔。另外,无机盐的加入也会导致溶液黏度、表面张力呈先下降后上升的趋势,电导率和电荷密度随之上升。在其他条件一定时,SCA/LiCl体系的纤维直径要小于SCA/CaCl2体系;无机盐含量超过2%时,纤维直径会有一定程度的增加。     

Microstructure and characterization of electrospun poly(vinyl alcohol) nanofiber scaffolds filled with graphene nanosheets

Graphene nanosheets (GNSs) have attracted significant scientific attention because of their remarkable features, including exceptional electron transport, excellent mechanical properties, high surface area, and antibacterial functions. Poly(vinyl alcohol) (PVA) solutions filled with GNSs were prepared for electrospinning, and their spinnability was correlated with their solution properties. The effects of GNS addition on solution rheology and conductivity were investigated. The as‐spun fibers were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC). The results revealed the effects of GNS on the microstructure, morphology, and crystallization properties of PVA/GNS composite nanofibers. The addition of GNSs in PVA solution increased the viscosity and conductivity of the solution. The electrospun fiber diameter of the PVA/GNS composite nanofiber was smaller than that of neat PVA nanofiber. GNSs were not only embedded at the fibers but also formed protrusions on the fibers. In addition, the crystallinity of PVA/GNS fiber decreased with higher GNS content. The possible application of PVA/GNS fibers in tissue engineering was also evaluated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41891.     

Controlling the Diameter of Electrospun Yttria‐Stabilized Zirconia Nanofibers

This work reports the precise diameter control of electrospun yttria‐stabilized zirconia (YSZ) nanofibers from 200 to 900 nm after calcination. Fabricated YSZ nanofibers showed porous nanocrystalline structures with high aspect ratios of more than 500:1 and high surface‐to‐volume ratios with a specific surface area of 43.32 m²/g. The diameter of the YSZ nanofibers increased with the viscosity of the precursor solution, which was controlled by the concentrations of either polymers (polyacrylonitrile) or ceramic precursors (YSZ). We present a modified correlation between the diameter of a nanofiber and the synthetic conditions, as the observed behavior for calcined ceramic nanofibers deviated from the expected behavior. Our results demonstrate a modified but simple approach to fabricate ceramic nanofibers with desired diameters, providing a new design guideline for many electrochemical applications.     

Fabrication and characterization of electrospun Plantago major seed mucilage/PVA nanofibers

Electrospinning is a well-known technique for producing nanofibers using synthetic and natural polymers like mucilage. In this study, Plantago major Mucilage (PMM) was blended with polyvinyl alcohol (PVA) as a nontoxic adding agent, in order to produce electrospun nanofiber. Electrospinning parameters (voltage, tip-to-collector distance, feed rate, and PMM/PVA ratio) were optimized and solution properties were analyzed. The morphology of nanofibers was investigated using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET). Mechanical strength of nanofibers was determined, and cell viability on nanofibers was discussed by MTT assay. The results of SEM indicated that the PMM/PVA (50/50) nanofibers obtained with average diameter of 250 nm. Viscosity, electrical conductivity, and surface tension of PMM/PVA solution were 550 Cp, 575 μS/cm, and 47.044 mN/m, respectively. FTIR and XRD results verified the exiting PMM in produced nanofibers and no chemical reaction between PMM and PVA. Improvement in mechanical strength and cell viability of nanofibers by adding PMM to PVA nanofibers indicated the potential application of PMM-based nanofibers for medical and food industries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47852.