Preparation of poly(phenylene vinylene) nanofibers by electrospinning

PPV nanofibers were fabricated by electrospinning PPV precursor solution in solvent mixtures of ethanol/water. PPV nanofibers with smooth surface were obtained when the ethanol/water ratio was 70/30 (w/w) and the average diameter was 653 nm. The fluorescence peak positions of fibers were in 515 and 550 nm, which were the same as that of PPV film. The morphology of fibers has been characterized by scanning electron microscopy (SEM) and fluorescence microscopy.     

Preparation and photoluminescence properties of electrospun nanofibers containing PMO-PPV and Eu(ODBM)3phen

This communication explores a facile approach for fabricating nanofibers containing luminescent conjugated polymer, poly(2-methoxy-5-octoxy)-1,4-phenylene vinylene)-alt-1,4-(phenylene vinylene) (PMO-PPV), and rare earth complex, Eu(ODBM)₃phen (ODBM: 4-n-Octyloxydibenzoylmethanato; phen: 1,10-phenanthroline) via an electrospinning technique. The morphology and photoluminescent properties of the electrospun fibers were characterized by scanning electron microscopy, fluorescence spectrophotometer and UV optical microscopy. The electrospun fibers with diameters ranging from 70 nm to 200 nm as well as parallel orientation show strong green and red photoluminescence. This is the first but important approach towards novel applications of luminescent conjugated polymers and rare earth complex nanofibers. This kind of eletrospun nanofiber is a promising candidate for optical and electrical nanomaterials.     

Stacked-lamellar structure of electrospun poly(heptamethylene terephthalate) nanofibers

Poly(heptamethylene terephthalate) (poly(7GT)), which is an aromatic polyesters was synthesized, and nanofibers of poly(7GT) were prepared via electrospinning from its solution in 1,1,1,3,3,3-hexafluoro-2-propanol. Uniaxially oriented thin films were also prepared by applying shear strain to molten poly(7GT). Morphology of as-spun and annealed nanofibers and that of uniaxially oriented thin films were investigated by transmission electron microscopy. Selected-area electron diffraction (SAED) of bundles of the annealed nanofibers gave a highly oriented fiber pattern. In addition, dark-field images of the poly(7GT) nanofibers, which had been annealed at 85 °C for 48 h, were taken by using some of the reflections on/near the equator. The images showed a stacked-lamellar structure, in which crystalline lamellae appearing as bright striations oriented perpendicularly to the fiber axis were stacked in the direction of the fiber axis, and the corresponding average long period was estimated at about 19 nm. As for the uniaxially oriented thin films, SAED also gave an oriented fiber pattern. When the annealing of the films was performed similar to nanofibers, crystallization occurred and a stacked-lamellar structure was constructed parallel to the shearing direction. The corresponding average long period was estimated at about 27 nm. By comparing the fiber patterns between annealed nanofibers and thin films, it seems that electrospinning is more effective than uniaxial stretching in enhancing the molecular orientation in the case of poly(7GT).     

Release of lysozyme from electrospun PVA/lysozyme-gelatin scaffolds

This article describes an electrospinning process in fabricating ultra fine fibers with core-shell structure. A biodegradable polymer, poly(vinyl alcohol) (PVA), was used as the shell; lysozyme was a kind of antioxidant; and gelatin were used as the core.Morphology and microstructure of the ultra fine fibers were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. As a comparison, composite nanofiber PVA/lysozyme-gelatin blend was prepared by a normal electrospinning process. In vitro drug release behaviors of the nanofibrous membranes were determined in phosphatebuffered saline (PBS) solution. It was found that core-shell nanofibers PVA/lysozyme-gelatin obviously exhibit higher initial release rates compared to that of PVA/lysozymegelatin blend nanofibers. The current method may find wide application in controlled release of bioactive proteins and tissue engineering.     

Preparation and characterization of electrospun core sheath nanofibers from multi-walled carbon nanotubes and poly(vinyl pyrrolidone)

Electrospinning is a versatile technique to prepare polymer fibers in nano to micrometer size ranges using very high electrostatic fields. Electrospun nanofibers with tunable porosity and high specific surface area have various applications, including chromatographic supports for protein separation, biomedical devices, tissue engineering and drug delivery matrices, and as key components in solar cells and supercapacitors. Unspinnable materials such as nanoparticles, nanorods, nanotubes or rigid conducting polymers can also be electrospun into fibers through co-axial electrospinning. In this study, we have prepared core-sheath nanofibers utilizing co-axial electrospinning. The core portion of these electrospun fibers consists of multi-walled carbon nanotubes and the sheath portion is poly(vinyl pyrrolidone) (PVP). Various morphologies were obtained by changing both core and sheath solution concentrations. The core-sheath nanofibers were characterized by scanning electron microscopy and transmission electron microscopy, to confirm core-sheath morphology, thermogravimetric analysis, and mechanical strength testing. The electrical conductivity of the surfaces of poly(vinyl pyrrolidone) fibers and poly(vinyl pyrrolidone)-multi-walled nanotube fibers were both 10(-15) S/m. The highest bulk conductivity observed for the poly(vinyl pyrrolidone)-multi-walled nanotube fibers was 1.2 x 10(-3) S/m.     

静电纺丝复合纳米纤维研究进展

静电纺丝是一种利用聚合物溶液或熔体在强电场中进行喷射纺丝的加工技术,是获得纳米尺寸纤维的有效方法之一。然而单一组分的纳米纤维已经难以满足应用的需求,而采用两种或两种以上的聚合物(或聚合物/填料颗粒)进行静电纺丝得到的复合纳米纤维逐渐受到了人们的关注。文中总结了由静电纺丝技术制备的复合纳米纤维及其性能等方面的研究进展。主要包括复合物/碳复合纳米纤维、聚合物/金属复合纳米纤维、聚合物/粘土复合纳米纤维、共混物复合纳米纤维、装饰型复合纳米纤维等。     

Electrical properties of polyaniline and multi-walled carbon nanotube hybrid fibers

We have fabricated for the first time one-dimensional multiwalled carbon nanotube (MWNT) nanocomposite fibers with improved electrical properties using electrospinning. Polyaniline (PANi) and poly(ethylene oxide) (PEO) were used as a conducting and a nonconducting matrix, respectively, for hybrid nanofibers including MWNTs. The hybrid nanofibers fabricated by electrospinning had a length of several centimeters and a diameter ranging from approximately 100 nm to approximately 1 microm. Transmission electron microscopic analysis confirmed that the MWNTs were successfully oriented along the fiber axis without any severe aggregation during electrospinning. The hybrid nanofibers showed an enhanced electrical conductance with increasing MWNT content up to 0.5 wt%, and compared to PANi/PEO fibers, they also showed a stable linear ohmic behavior. These hybrid conducting nanofibers can be applied to chemical and biosensors that require a high sensitivity.     

A new nanofiber fabrication technique based on coaxial electrospinning

In tissue engineering, nanofibrous scaffolds can achieve better biological responses than microfibrous scaffolds and electrospinning is a common method for producing fibrous scaffolds. However, not all biopolymers can be made into nanofibers through conventional electrospinning. The current investigation developed an innovative nanofiber fabrication technique based on coaxial electrospinning and used poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) as an example for achieving nanofibers. For obtaining PHBV nanofibers, core-shell structured fibers were fabricated first via coaxial electrospinning, with PHBV being the core and chitosan being the shell. The chitosan shell was then removed by washing electrospun scaffolds with water, leading to the formation of nanofibrous PHBV scaffolds. The PHBV nanofiber diameter was affected by the inner polymer (i.e., PHBV) solution concentration during coaxial electrospinning, which can be explained in terms of the coaxial electrospinning process and polymer solution viscosity. Compared to the approach of using a conductivity-enhancing salt in polymer solution to produce polymer nanofibers, the new technique not only eliminates the biocompatibility concerns but also provides a more effective way of reducing fiber diameters to the nano-size range.     

Polyacrylonitrile nanofibers prepared using coaxial electrospinning with LiCl solution as sheath fluid

A modified coaxial electrospinning process including an electrolyte solution as sheath fluid was used for preparing high quality polymer nanofibers. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing a coaxial electrospinning containing LiCl in N, N-dimethylacetamide (DMAc) as the sheath fluid. FESEM results demonstrated that the sheath LiCl solutions have a significant influence on the quality of PAN nanofibers. Nanofibers with smaller diameters, smoother surfaces and uniform structures were successfully prepared. The diameters of nanofibers were controlled by adjusting the conductivity of the sheath fluid over a suitable range and this was determined by varying LiCl concentrations. The influence of the effect of LiCl on the formation of PAN fibers is discussed and it is concluded that coaxial electrospinning with electrolyte solutions is a convenient and facile process for achieving high quality polymer nanofibers.     

Lecithin blended polyamide-6 high aspect ratio nanofiber scaffolds via electrospinning for human osteoblast cell culture

In this study, we focused on the preparation and characterization of lecithin blended polyamide-6 nanofibers via an electrospinning process for human osteoblastic (HOB) cell culture applications. The morphological, structural characterizations and thermal properties of polyamide-6/lecithin nanofibers were determined by using scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). SEM images revealed that the nanofibers were well-oriented with good incorporation of lecithin. FT-IR results indicated the presence of amino groups of lecithin in the blended nanofibers. TGA analysis revealed that the onset degradation temperature decreased with increasing lecithin content in the blended nanofibers. The morphological features of cells attached on polyamide-6/lecithin nanofibers were confirmed by SEM. The adhesion, viability and proliferation properties of osteoblast cells on the polyamide-6/lecithin blended nanofibers were analyzed by in vitro cell compatibility test. This study demonstrated the non-cytotoxic behavior of electrospun polyamide-6/lecithin nanofibers for the osteoblast cell culture.     

SiC nanofibers by pyrolysis of electrospun preceramic polymers

Silicon carbide (SiC) nanofibers of diameters as low as 20 nm are reported. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fiber flowing during pyrolysis. Electrospun SiC fibers were characterized by Fourier transform infrared spectroscopy, thermo gravimetric analysis-differential thermal analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electron diffraction. Fibers were shown to be polycrystalline and nanograined with β-SiC 4H polytype being dominant, where commercial methods produce α-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced α-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core–shell structure of an oxide scale that was variable by pyrolysis conditions.     

PVP nanofibers prepared using co-axial electrospinning with salt solution as sheath fluid

A modified co-axial electrospinning process using salt solutions as sheath fluids for preparing polymer nanofibers was investigated. A series of polyvinylpyrrolidone (PVP) fibers were prepared with NaCl aqueous solutions at varying concentrations as sheath fluids. The sheath fluid had a significant influence on the formation of the compound Taylor cone. Scanning electron microscopy results demonstrated that the diameters of PVP nanofibers could be manipulated through the concentration of NaCl solutions within an appropriate range. With 2 mg ml^− 1 NaCl solution as sheath fluid, the smallest PVP nanofibers, with a diameter of 120 ± 40 nm, were obtained. Co-axial electrospinning with salt solutions as sheath fluids is a facile method for achieving finer, homogeneous polymer nanofibers.     

Control of self organization in conjugated polymer fibers

We propose new strategy to facilitate the fabrication of conjugated polymer fiber with higher oriented structures, which focused on electrospinning of a blend solution of regioregular poly(3-hexylthiophene) (rr-P3HT) and poly(vinyl pyrrolidone) (PVP). SEM observation revealed that the blend system forms homogeneous composite nanofibers. This system exhibits the specific feature of strong interchain contribution of P3HT from UV-vis absorption, fluorescence spectroscopic, XRD, and photoelectron spectrometric (for HOMO levels) investigations. We also demonstrate the removal of the PVP component from the P3HT/PVP composite fibers through the selective extraction and such strong interchain stacking of pristine P3HT fiber mat can be remarkably maintained.     

聚偏氟乙烯电纺纤维膜的制备及其热释电性能研究

β晶相的聚偏氟乙烯(PVDF)由于具有强压电和热释电特性,被广泛应用在能量收集、红外探测等领域。采用静电纺丝技术制备PVDF纤维,通过SEM以及XRD表征,研究了溶剂组成、溶液浓度和纺丝液供给速度等纺丝参数对PVDF纤维膜形貌和β晶相含量的影响,制备出连续、均匀、直径约600nm的PVDF纤维。另外,测试了PVDF纤维膜对不同调制频率的3.4μm波长红外光的热释电响应特性。     

Preparation of PVP/MEH-PPV composite polymer fibers by electrospinning and study of their photoelectronic character

Ultrafine polyvinylpyrrolidone (PVP)/poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) composite fibers were successfully prepared by electrospinning of PVP/MEH-PPV blend solutions in solvent mixtures of 1,2-dichloroethane/chlorobenzene. Composite polymer fibers with smooth surface were obtained using solutions in which MEH-PPV's concentration was 1.0 (wt.%). Compared with the MEH-PPV solution and bulk, PVP/MEH-PPV fibers show a significant blue shift, a stronger intensity of fluorescence and a higher surface photovoltage (SPV). The morphology of fibers has been characterized by scanning electron microscopy (SEM) and fluorescence microscopy.     

Preparation of the crosslinked poly(vinyl alcohol)/blocked isocyanate prepolymers nanofibers with hydrolyzed products of Scutellariae Radix

We report on the preparation and characterizations of Scutellariae Radix (SR) blended poly(vinyl alcohol) (PVA)/blocked isocyanate prepolymer (BIP) composite nanofibers via electrospinning process. In order to improve the biocompatibility properties, SR biological macromolecules were blended in PVA/BIP composite nanofibers. SEM images revealed that the composite nanofibers were well-oriented and had good incorporation of SR. Ultraviolet (UV) absorbance spectra revealed that the maximum measured absorbance intensities were linearly increased with increasing SR in the composite nanofibers. TEM images revealed a peculiar morphology by the additive SR. This additive SR possesses a lower molecular component which was exhibited at the outside of the nanofibers structure due to strong applied electric field during electrospinning process. These results indicated that the PVA/BIP blended SR composite nanofibers might be utilized for many biomedical applications including control release and wound dressing.     

High performance polyimide composite films prepared by homogeneity reinforcement of electrospun nanofibers

Highly aligned polyimide (PI) and PI nanocomposite fibers containing carbon nanotubes (CNTs) were produced by electrospinning. Scanning electron microscopy showed the electrospun nanofibers were uniform and almost free of defects. Transmission electron microscopy indicated that the CNTs were finely dispersed and highly oriented along the CNT/PI nanofiber axis at a relatively low concentration. The as-prepared well-aligned electrospun nanofibers were then directly used as homogeneity reinforcement to enhance the tensile strength and toughness of PI films. The neat PI nanofiber reinforced PI films showed good transparency, decreased bulk density and significantly improved mechanical properties. Compared with neat PI film prepared by solution casting, the tensile strength and elongation at break for the PI film reinforced with 2 wt.% CNT/PI nanofibers were remarkably increased by 138% and 104%, respectively. The significant increases in the overall mechanical properties of the nanofibers reinforced polyimide films can be ascribed to good compatibility between the electrospun nanofibers and the matrix as well as high nanofiber orientation in the matrix. Our study demonstrates a good example for fabricating high performance and high toughness polyimide nanocomposites by using this facile homogeneity self-reinforcement method.     

Release of lysozyme from electrospun PVA/lysozyme-gelatin scaffolds

This article describes an electrospinning process in fabricating ultra fine fibers with core-shell structure. A biodegradable polymer, poly(vinyl alcohol) (PVA), was used as the shell; lysozyme was a kind of antioxidant; and gelatin were used as the core. Morphology and microstructure of the ultra fine fibers were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis. As a comparison, composite nanofiber PVA/lysozyme-gelatin blend was prepared by a normal electrospinning process. In vitro drug release behaviors of the nanofibrous membranes were determined in phosphate-buffered saline (PBS) solution. It was found that core-shell nanofibers PVA/lysozyme-gelatin obviously exhibit higher initial release rates compared to that of PVA/lysozyme-gelatin blend nanofibers. The current method may find wide application in controlled release of bioactive proteins and tissue engineering.     

Preparation and electrical characterization of polyamide-6/chitosan composite nanofibers via electrospinning

We report on the preparation and electrical characterization of polyamide-6/chitosan composite nanofibers. These composite nanofibers were prepared using a single solvent system via electrospinning process. The resultant nanofibers were well-oriented and had good incorporation of chitosan. Current-voltage (I-V) measurements revealed interesting linear curve, including enhanced conductivities with respect to chitosan content. The electrical conductivity of the polyamide-6/chitosan composite nanofibers increased with increasing content of chitosan which was attributed to the formation of ultrafine nanofibers. In addition, the sheet resistance of composite nanofibers was decreased with increasing chitosan concentration.     

Synthesis of anatase-silver nanocomposite fibers via electrospinning

There has been growing interest in new ways to produce composite nanofibers. Continuous TiO2 (anatase phase) nanofibers with silver nanoparticles were prepared successfully via sol-gel and electrospinning. A sol containing poly(vinyl pyrrolidone), titanium tetraisopropoxide, and silver nitrate was injected through a conductive capillary where high voltage was applied. As a result of electrospinning, continuous composite nanofibers were collected and they were calcined in air at 500 degrees C in order to complete the crystallization of anatase phase. The anatase-silver nanocomposite fibers were characterized with X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy.