Electrospinning and characterization of medium-molecular-weight poly(vinyl alcohol)/high-molecular-weight poly(vinyl alcohol)/montmorillonite nanofibers

Submicron fibers of medium-molecular-weight poly(vinyl alcohol) (MMW-PVA), high-molecular-weight poly(vinyl alcohol) (HMW-PVA), and montmorillonite clay (MMT) in aqueous solutions were prepared by electrospinning technique. The effect of HMW-PVA and MMT on the morphology and mechanical properties of the MMW-PVA/HMW-PVA/MMT nanofibers were investigated for the first time. Scanning electron microscopy, viscometer, tensile strength testing machine, thermal gravimetric analyzer (TGA), and transmission electron microscopy (TEM) were utilized to characterize the PVA/MMT nanofibers morphology and properties. The MMW-PVA/HMW-PVA ratios and MMT concentration played important roles in nanofiber's properties. TEM data demonstrated that exfoliated MMT layers were well distributed within nanofibers. It was also found that the mechanical property and thermal stability were increased with HMW-PVA and MMT contents.     

Efficient method for fabrication of fluorescein derivative/PDAC composite nanofibers and characteristics of their photoluminescent properties

Electrospinning is a simple and cost-effective approach for the production of nanofibers and assemblies with controllable structures. In this work, the pure poly (diallyldimethylammonium chloride) (PDAC) nanofibers with smooth surface and uniform morphology were successfully fabricated by electrospinning. On this basis, fluorescein/PDAC, dibromofluorescein/PDAC, diidofluorescein/PDAC and fluorescein sodium/PDAC composite nanofibers were also fabricated using the same method. The average diameters of the pure PDAC nanofibers increased with the applied field strength and the amount of PDAC in the solutions; and the average diameters ranged from 280 to 450 nm. The morphology of pure PDAC nanofibers has been observed by scanning electron microscopy (SEM) and the photoluminescent properties of fluorescein derivative/PDAC composite nanofibers have been characterized by fluorescence microscopy.     

Enhancement in the photocatalytic activity of TiO2 nanofibers hybridized with g-C3N4 via electrospinning

TiO₂/g-C₃N₄ nanofibers with diameter of 100–200 nm were prepared by electrospinning method after calcination at high temperature, using polyvinylpyrrolidone (PVP), Melamine (C₃H₆N₆), Ti(OC₄H₉)₄ as raw materials. The composite nanofibers were characterized by XRD, FT-IR, SEM, UV–vis and PL respectively. The effects of different g-C₃N₄ contents on structure and photocatalytic degradation of the composite nanofibers were investigated. The results indicated that with increasing g-C₃N₄ content, the diameter of the composite fibers increased and the morphology changed from uniform structure to a nonuniform one, containing beads. The composite nanofibers displayed the best photocatalytic degradation on RhB, when the g-C₃N₄ content was 0.8 wt%. The degree of degradation was up to 99% at the optimal conditions of 40 min. The degradation activity of the composite nanofibers on RhB, MB and MO was found to be higher than that of the TiO₂ nanofibers.     

硫化锌掺锰/聚乙烯醇复合纳米纤维的制备与表征

利用静电纺丝法与气固反应相结合, 成功地制备了硫化锌掺锰/聚乙烯醇复合纳米纤维, 并对所制备的复合物进行了表征, 探讨了复合物的结构及其性能.     

A nanofibrous composite membrane of PLGA-chitosan/PVA prepared by electrospinning

Tissue engineering scaffolds produced by electrospinning feature a structural similarity to the natural extracellular matrix. In this study, poly(lactide-co-glycolide) (PLGA) and chitosan/poly(vinyl alcohol) (PVA) were simultaneously electrospun from two different syringes and mixed on the rotating drum to prepare the nanofibrous composite membrane. The composite membrane was crosslinked by glutaraldehyde vapor to maintain its mechanical properties and fiber morphology in wet stage. Morphology, shrinkage, absorption in phosphate buffered solution (PBS) and mechanical properties of the electrospun membranes were characterized. Fibroblast viability on electrospun membranes was discussed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay and cell morphology after 7 days of culture. Results indicated that the PBS absorption of the composite membranes, no matter crosslinked or not, was higher than the electrospun PLGA membrane due to the introduction of hydrophilic components, chitosan and PVA. After crosslinking, the composite membrane had a little shrinkage after incubating in PBS. The crosslinked composite membrane also showed moderate tensile properties. Cell culture suggested that electrospun PLGA-chitosan/PVA membrane tended to promote fibroblast attachment and proliferation. It was assumed that the nanofibrous composite membrane of electrospun PLGA-chitosan/PVA could be potentially used for skin reconstruction.     

Preparation and characterization of porous TiO_2/ZnO composite nanofibers via electrospinning

<正>Porous TiO_2/ZnO composite nanofibers have been successfully prepared by electrospinning technique for the first time.It was generated by calcining TiO_2/ZnCl_2/PVP[PVP:polyvinyl pyrrolidone)]nanofibers,which were electrospun from a mixture solution of TiO_2,ZnCl_2 and PVP.Transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses were used to identify the morphology of the TiO_2/ZnO nanofibers and a formation of inorganic TiO_2/ZnO fibers.The porous structure of the TiO_2/ZnO fibers was characterized by N_2 adsoption/desorption isotherm.Surface photovoltage spectroscopy(SPS) and photocatalytic activity measurements revealed advance properties of the porous TiO_2/ZnO composite nanofibers and the results were compared with pure TiO_2 nanofibers,pure ZnO nanofibers and TiO_2/ZnO nanoparticles.     

INFLUENCE OF TRACES OF WATER ON THE SYNTHESIS AND ELECTROLUMINESCENCE PROPERTIES OF POLY(2-METHOXY, 5- (2'''' -ETHYLHEXYL OXY)- 1, 4-PHENYLENE VINYLENE)

It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease ofmolecular weight of the poly(2-methoxy, 5-(2'-ethylhexyloxy)-1, 4-phenylene vinylene) during the polymerization, whichultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPVprepared under dry conditions has an external quantum efficiency of above 2.0%.     

Synthesis and characterization of exfoliated MEH-PPV/clay nanocomposites by in situ polymerization

In this article, we demonstrate the synthesis of a conjugated polymer, poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) in the presence of organophilic montmorillonite (OMMT) and the properties of the MEH-PPV/OMMT composites produced herefrom. By controlling the reaction conditions, such as the ratio of monomeric precursors to montmorillonite, exfoliated MEH-PPV/OMMT nanocomposites were synthesized via in situ polymerization. These materials exhibit higher electroluminescent properties and enhanced performance of thermal stability than that of the pure polymer. Additionally, based on the solid-state ¹³C NMR measurement results, the possible origin of the optoelectronic property improvement is discussed from the point of view of segmental mobility.     

Immobilization of cellulase in nanofibrous PVA membranes by electrospinning

Electrospinning is a nanofiber-forming process by which either polymer solution or melt is charged to high voltages. With high specific surface area and porous structure, electrospun fibrous membranes are excellent candidates for immobilization of enzymes. In this paper, immobilization of cellulase in nanofibrous poly(vinyl alcohol) (PVA) membranes was studied by electrospinning. PVA and cellulase were dissolved together in an acetic acid buffer (pH 4.6) and electrospun into nanofibers with diameter of around 200 nm. The nanofibrous membranes were crosslinked by glutaraldehyde vapor and examined catalytic efficiency for biotransformations. The activity of immobilized cellulase in PVA nanofibers was over 65% of that of the free enzyme. Nanofibers were superior to casting films from the same solution for immobilization of cellulase. The activity of immobilized cellulase descended with ascending in enzyme loading efficiency and crosslinking time, which retained 36% its initial activity after six cycles of reuse.     

Selective fabrication of porous iron oxides hollow spheres and nanofibers by electrospinning for photocatalytic water purification

Porous hematite (α-Fe₂O₃) hollow spheres and nanofibers could be obtained via electrospinning and subsequent thermal decomposition in air. The precursor could be fabricated by electrospinning using Fe(NO₃)₃ as the iron source and Polyvinylpyrrolidone (PVP) as a complexing reagent. Upon calcination, pure porous α-Fe₂O₃ hollow spheres and nanofibers could be obtained at 650 °C for 3 h. The novel hollow spheres have an abundantly porous structure as well as large surface areas. Benefitting from the special porous structure, narrow bandgap, and higher surface area, porous α-Fe₂O₃ hollow materials are used as visible-light-responsive photocatalysts. So we have investigated the visible light photodegradation behavior of porous hematite (α-Fe₂O₃) hollow spheres and nanofibers towards organic dyes, as Rhodamine B (RhB). The synergetic effects of higher surface area, pore structures promoted the photocatalytic efficiency for RhB degradation under visible light and contributed to achieving the enhanced and stable photocatalytic activity.     

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers were prepared by atmospheric plasma treatment and electrospinning. Atmospheric helium plasma treatment was first used to reduce the AgNO₃ precursor in pre-electrospinning solutions into metallic silver nanoparticles, followed by electrospinning into continuous and smooth nanofibers with Ag nanoparticles embedded in the matrix. SEM, TEM, and EDX spectra were used to study the structure and surface elemental composition of the nanofibers. Silver nanoparticles, with diameters ranging between 3 and 6 nm, were found to be uniformly dispersed in the nanofiber matrix. The Ag/PAN nanofibers exhibited slow and long-lasting silver ion release, which provided robust antibacterial activity against both Gram-positive Bacillus cereus and Gram-negative Escherichia coli microorganisms.     

Control release of lactate dehydrogenase encapsulated in poly (vinyl alcohol) nanofibers via electrospinning

Sustained release of lactate dehydrogenase (LDH, EC 1.1.1.27) from electrospun poly (vinyl alcohol) (PVA) nanofibers was successfully achieved using the coaxial electrospinning technique. The presence of the encapsulated enzyme in the nanofibers was confirmed by infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was used to evaluate the morphology and diameter of the nanofibers. The conversion of lactate to pyruvate by LDH coupling with the reduction of the cofactor nicotinamide adenine dinucleotide (NAD⁺) to dihydronicotinamide adenine dinucleotide (NADH) produces an increment in the ultraviolet absorption (UV) at 340 nm. This change in the UV absorbance was used to follow the release kinetic of LDH from the PVA nanofibers and also as a measure to evaluate the residual enzymatic catalytic function. Most of the encapsulated LDH enzyme was released in a sustained manner from the PVA nanofibers within a period of 1 month.     

Electrospinning and characterization of poly(vinyl alcohol)/chitosan oligosaccharide/clay nanocomposite nanofibers in aqueous solutions

Submicron fibers of the composite of poly(vinyl alcohol) (PVA), chitosan oligosaccharide [COS, (1→4)2-amino-2-deoxy-β-d-glucose], and montmorillonite clay (MMT) were prepared using electrospinning method with aqueous solutions. Scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analyzer, and tensile strength testing machine (Zwick) were utilized to characterize the PVA/COS/MMT nanofiber mats morphology and properties. The PVA/COS ratio and MMT concentration play important roles in nanofiber mat properties. XRD and TEM data demonstrated that exfoliated MMT layers were well-distributed within nanofiber. It was also found that the mechanical property and thermal stability were increased with COS and MMT contents.     

Parameter study and characterization for polyacrylonitrile nanofibers fabricated via centrifugal spinning process

Electrospinning is currently the most popular method for producing polymer nanofibers. However, the low production rate and safety concern limit the practical use of electrospinning as a cost-effective nanofiber fabrication approach. Herein, we present a novel and simple centrifugal spinning technology that extrudes nanofibers from polymer solutions by using a high-speed rotary and perforated spinneret. Polyacrylonitrile (PAN) nanofibers were prepared by selectively varying parameters that can affect solution intrinsic properties and operational conditions. The resultant PAN nanofibers were characterized by SEM, and XRD. The correlation between fiber morphology and processing conditions was established. Results demonstrated that the fiber morphology can be easily manipulated by controlling the spinning parameters and the centrifugal spinning process is a facile approach for fabricating polymer nanofibers in a large-scale and low-cost fashion.     

Rose thorns-like polymer micro/nanofibers via electrospinning and controlled temperature-induced self-assembly

Novel rose thorns-like nanofibers, composed of polyarylene ether nitriles (PEN) “rose stems” and iron phthalocyanine (FePc) “thorns”, are prepared by combining electrospinning and controlled temperature-induced self-assembly. After removing solvent and subsequent temperature treatment, the FePc sheath structure changes from bead structure to rose thorns-like structure. The unique nanoscale architecture can be finely controlled by the processing time and temperature. The length of “thorns” on the “rose stems” can change from several nanometers to decade micrometers. The driving force for the morphology changes comes from self-assembly of FePc, including the π–π supramolecular interaction between aromatic cores and the cooperative complexation of metal ions between peripheral crown ether moieties. This novel structure, rendering a 3-D feature, can offer potential in a number of applications, including nanoelectronics.     

Living Polymerization via Anionic Initiation for the Synthesis of Well‐Defined PPV Materials

The anionic polymerization of PPV via the sulfinyl precursor route is further investigated. When LHMDS is employed as the base to form the actively propagating quinodimethane system and THF as the solvent, anionic polymerizations can be observed. With the use of tert‐ butyl‐substituted anionic initiators, specific functional groups can be built in the polymer chain and the chain length can be efficiently controlled, which is demonstrated here for the first time. With introduction of branched side chains on the aromatic core, soluble conjugated PPV material can be obtained with molecular weights in the range of 5000–16 000 g mol⁻¹.     

可溶性聚对苯乙炔衍生物的合成

聚对苯乙炔（ＰＰＶ）具有独特的光电性能,经强氧化剂掺杂后是一类重要的导电材料［１］,而且具有良好的非线性光学（ＮＬＯ）性质［２］,也是目前性能最好的高分子电致发光材料［３,４］．可溶性的ＰＰＶ衍生物有望在显示领域广泛应用,从而成为电致发光领域研究的新...     

聚[2-甲氧基-5-(4-溴-丁氧基)对苯乙炔]新型前聚物的合成及表征]

采用不同方法由三锍盐合成新型的聚电解质前聚物及可溶于有机溶剂的侧链溴代聚对苯乙炔前聚物,发现侧链烷氧取代基上的锍盐并不参与聚合,所得前聚物加热后都可转化为聚对苯乙炔.光物理初步研究表明,溴代侧链聚对苯乙炔与C₆₀掺杂后具有良好的光电特性.以IR、UV-Vis、¹H NMR、DSC对单体及前聚物进行了表征.     

Bicomponent aligned nanofibers of N-carboxyethylchitosan and poly(vinyl alcohol)

Bicomponent nanofibers of N-carboxyethylchitosan (CECh) and poly(vinyl alcohol) (PVA) were obtained by electrospinning of mixed aqueous solutions. The electrospinning of CECh-containing nanofibers was enabled by the ability of PVA to form an elastically deformable entanglement network based on hydrogen bonds. The average diameters of the bicomponent fibers were in the range 100-420 nm. Water-resistant nanofibrous mats were obtained by thermal crosslinking at 100 °C for 10 h. Nanofibrous materials with 1D-, 1D-transversery or 3D fiber alignment were obtained depending on the type of the collector used.     

Fabrication of Highly Photoluminescent TiO2/PPV Hybrid Nanoparticle‐Polymer Fibers by Electrospinning

In this study, we have synthesized highly photoluminescent TiO₂/poly (phenylene vinylene) (PPV) hybrid nanoparticle‐polymer fibers by electrospinning a PPV precursor added to a TiO₂ sol‐gel solution. The diameters of the hybrid fibers ranged from 100–300 nm and the average size of TiO₂ nanoparticles within the fibers was 10–60 nm. FT‐IR analysis indicated that a new band around 1 632 cm⁻¹ assigned to the Ti O C vibration appeared, which resulted in the stronger luminance of the fluorescence of the TiO₂/PPV hybrid fibers compared to free standing PPV nanofibers.