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Preparation of PVP/PLLA Ultrafine Blend Fibers by Electrospinning
Jia Xu,Jinxian Wang,Xiangting Dong,Guixia Liu
International Journal of Chemistry , 2011, DOI: 10.5539/ijc.v3n4p57
Abstract: The Polyvinylpyrrolidone (PVP) / Poly (L-lactic acid) (PLLA) ultrafine blend fibers have been prepared for the first time by electrospinning. Trichloromethane was found to be the co-solvent for electrospinning. The PVP/PLLA blend solutions in various ratios were studied for electrospinning into ultrafine fibers. The morphology of the fibers was shown by scanning electron microscope (SEM). It was found that the morphology of the fibers became finer with the content of PLLA increasing. To show the molecular interactions, PVP/PLLA fibers were characterized by Fourier transform infrared spectroscopy (FTIR). The spun ultrafine fibers are expected to be used in the native extracellular matrix for tissue engineering.
A Confirmed Model to Polymer Core-Shell Structured Nanofibers Deposited via Coaxial Electrospinning  [PDF]
K. Boubaker
ISRN Polymer Science , 2012, DOI: 10.5402/2012/603108
Abstract: A model to core-shell structured polymer nanofibers deposited via coaxial electrospinning is presented. Investigations are based on a modified Jacobi-Gauss collocation spectral method, proposed along with the Boubaker Polynomials Expansion Scheme (BPES), for providing solution to a nonlinear Lane-Emden-type equation. The spatial approximation has been based on shifted Jacobi polynomials with was n the polynomial degree. The Boubaker Polynomials Expansion Scheme (BPES) main features, concerning the embedded boundary conditions, have been outlined. The modified Jacobi-Gauss points are used as collocation nodes. Numerical examples are included to demonstrate the validity and applicability of the technique, and a comparison is made with existing results. It has been revealed that both methods are easy to implement and yield very accurate results. 1. Introduction Polymer nanofibers have gained much attention due to their great potential applications, such as filtration, catalysis, scaffolds for tissue engineering, protective clothing, sensors, electrodes electronics applications, reinforcement, and biomedical use [1–6]. Particularly, polymeric nanofibers with core-shell structure have been attractive in the past decades [4, 5]. Coaxial electrospinning, which has emerged as a method of choice due to the simplicity of the technology and its cost effectiveness, provides an effective and versatile way to fabricate such nanofibers [6–8]. This technique uses a high electric field to extract a liquid jet of polymer solution from the bot core and shell reservoirs. The yielded jet experiences stretching and bending effects due to charge repulsion and, in the process, can reach very small radii. Coaxial electrospinning cannot only be used to spin the unspinnable polymers (polyaramid, nylon, and polyaniline) into ultrafine fibers, but also ensures keeping functionalizing agents like antibacterial and biomolecules agents inside nanofibers [9–11]. In this paper, a mathematical model to coaxial electrospinning dynamics, in a particular setup, is presented. The model is based on solutions to the related Lane-Emden equation on semi-infinite domains as follows: Lane-Emden-type equations model many phenomena in mathematical physics and nanoapplications. They were first published by Lane in 1870 [12], and further explored in detail by Emden [13]. In the last decades, Lane-Emden has been used to model several phenomena such as the theory of stellar structure, quantum mechanics, astrophysics, and the theory of thermionic currents in the neighbourhood of a hot body in thermal
Coaxial electrospinning of liquid crystal-containing poly(vinylpyrrolidone) microfibres  [cached]
Eva Enz,Ute Baumeister,Jan Lagerwall
Beilstein Journal of Organic Chemistry , 2009, DOI: 10.3762/bjoc.5.58
Abstract: With the relatively new technique of coaxial electrospinning, composite fibres of poly(vinylpyrrolidone) with the liquid crystal 4-cyano-4′-octylbiphenyl in its smectic phase as core material could be produced. The encapsulation leads to remarkable confinement effects on the liquid crystal, inducing changes in its phase sequence. We conducted a series of experiments to determine the effect of varying the relative flow rates of inner and outer fluid as well as of the applied voltage during electrospinning on these composite fibres. From X-ray diffraction patterns of oriented fibres we could also establish the orientation of the liquid crystal molecules to be parallel to the fibre axis, a result unexpected when considering the viscosity anisotropy of the liquid crystal kept in its smectic phase during electrospinning.
Polyacrylonitrile nanofibers coated with silver nanoparticles using a modified coaxial electrospinning process
Yu DG, Zhou J, Chatterton NP, Li Y, Huang J, Wang X
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S37455
Abstract: lyacrylonitrile nanofibers coated with silver nanoparticles using a modified coaxial electrospinning process Original Research (1336) Total Article Views Authors: Yu DG, Zhou J, Chatterton NP, Li Y, Huang J, Wang X Published Date November 2012 Volume 2012:7 Pages 5725 - 5732 DOI: http://dx.doi.org/10.2147/IJN.S37455 Received: 28 August 2012 Accepted: 04 October 2012 Published: 12 November 2012 Deng-Guang Yu,1 Jie Zhou,2 Nicholas P Chatterton,3 Ying Li,1 Jing Huang,2 Xia Wang1 1School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai, People's Republic of China; 2School of Life Sciences, East China Normal University, Shanghai, People's Republic of China; 3Faculty of Life Sciences, London Metropolitan University, London, United Kingdom Background: The objective of this investigation was to develop a new class of antibacterial material in the form of nanofibers coated with silver nanoparticles (AgNPs) using a modified coaxial electrospinning approach. Through manipulation of the distribution on the surface of nanofibers, the antibacterial effect of Ag can be improved substantially. Methods: Using polyacrylonitrile (PAN) as the filament-forming polymer matrix, an electrospinnable PAN solution was prepared as the core fluid. A silver nitrate (AgNO3) solution was exploited as sheath fluid to carry out the modified coaxial electrospinning process under varied sheath-to-core flow rate ratios. Results: Scanning electron microscopy and transmission electron microscopy demonstrated that the sheath AgNO3 solution can take a role in reducing the nanofibers' diameters significantly, a sheath-to-core flow rate ratio of 0.1 and 0.2 resulting in PAN nanofibers with diameters of 380 ± 110 nm and 230 ± 70 nm respectively. AgNPs are well distributed on the surface of PAN nanofibers. The antibacterial experiments demonstrated that these nanofibers show strong antimicrobial activities against Bacillus subtilis Wb800, and Escherichia coli dh5α. Conclusion: Coaxial electrospinning with AgNO3 solution as sheath fluid not only facilitates the electrospinning process, providing nanofibers with reduced diameters, but also allows functionalization of the nanofibers through coating with functional ingredients, effectively ensuring that the active antibacterial component is on the surface of the material, which leads to enhanced activity. We report an example of the systematic design, preparation, and application of a novel type of antibacterial material coated with AgNPs via a modified coaxial electrospinning methodology.
A modified coaxial electrospinning for preparing fibers from a high concentration polymer solution
eXPRESS Polymer Letters , 2011, DOI: 10.3144/expresspolymlett.2011.71
Abstract: A new process technology modified from conventional coaxial electrospinning process has been developed to prepare polymer fibers from a high concentration solution. This process involves a pure solvent concentrically surrounding polymer fluid in the spinneret. The concentric spinneret was constructed simply by inserting a metal needle through a high elastic silica gel tube. Two syringe pumps were used to drive the core polymer solution and the sheath solvent. Using polyvinylpyrrolidone (PVP) as the polymer model, which normally has an electrospinnable concentration of 10% w/v in ethanol, it was possible to electrospin 35% w/v of PVP in the same solvent, when pure N, N-dimethylacetamide (DMAc) was used as sheath fluid. The resultant fibers have a smooth surface morphology and good structural uniformity. The diameter of the fibers was 2.0±0.25 μm when the DMAc-to-polymer-solution flow rate ratio was set as 0.1. The process technology reported here opens a new window to tune the polymer fibers obtained by the electrospinning, and is useful for improving productivity of the electrospinning process.
Triple-Component Drug-Loaded Nanocomposites Prepared Using a Modified Coaxial Electrospinning  [PDF]
Wei Qian,Deng-Guang Yu,Ying Li,Xiao-Yan Li,Yao-Zu Liao,Xia Wang
Journal of Nanomaterials , 2013, DOI: 10.1155/2013/826471
Abstract: Triple-component nanocomposites for improved sustained drug release profiles are successfully fabricated through a modified coaxial electrospinning process, in which only organic solvent N,N-dimethylacetamide was used as sheath fluid. Using polyacrylonitrile (PAN) as filament-forming matrix, ibuprofen (IBU) as functional ingredient, and polyvinylpyrrolidone (PVP) as the additional component, the IBU/PVP/PAN triple-component nanocomposites had uniform structure and an average diameter of ?nm and ?nm when the contents of PVP in the nanofibers were 10.5% and 22.7%, respectively. The optimal sheath-to-core flow rate ratio was 0.11 under a total sheath and core fluid flow rate of 1.0?mL/h. Compared with the IBU/PAN composite nanofibers, the triple-component composites could release 92.1% and 97.8% of the contained IBU, significantly larger than a value of 73.4% from the former. The inclusion of PVP in the IBU/PAN could effectively avoid the entrapment of IBU in the insoluble PAN molecules, facilitating the in vitro release of IBU. The modified coaxial process and the resulted multiple component nanocomposites would provide new way for developing novel drug sustained materials and transdermal drug delivery systems. 1. Introduction Electrospinning is a one-step straightforward nanofiber fabrication process, in which electrical energy is exploited to dry and solidify microfluid jets directly [1–4]. The processes produce nanosized fibers very rapidly, often at approximately 10?2?s. As a result, the physical state of the components in the liquid solutions is often propagated into the solid nanofibers to generate solid dispersions at a molecular scale or polymer-based composites, with few discerned nanoparticles resulted from phase separation [5, 6]. There exist numerous reports of electrospinning being used to produce polymer-based nanocomposite in the form of nanofibers. By virtue of the advantageous properties of nanofibers (e.g., high surface area, high porosity, and continuous web structure), these composites usually display improved functional performance [7–11]. Significant progress has been made in this process throughout the past few years and electrospinning has advanced its applications in many fields, including pharmaceutics. Electrospun nanofibers show great promise for developing many types of novel drug delivery systems (DDS) due to their special characteristics and the simple but useful and effective top-down fabricating process. For controlled release of active pharmaceutical ingredients, electrospun nanofibers are reported to provide a series of
Fabrication and formation mechanism of poly (L-lactic acid) ultrafine multi-porous hollow fiber by electrospinning
Q. Z. Yu,Y. M. Qin
eXPRESS Polymer Letters , 2013, DOI: 10.3144/expresspolymlett.2013.5
Abstract: Poly(L-lactic acid) (PLLA) ultrafine multi-porous hollow fibers are fabricated by electrospinning with methylene dichloride as solvent. The Kirkendall effect has been widely applied for the fabrication of hollow structure in metals and inorganic materials. In this study, a conceptual extension is proposed for the formation mechanism: the development of porous hollow fiber undergoes three stages. The initial stage is the generation of small voids or pits on the surface of the fiber via surface diffusion and phase separation; the second stage is the formation of multi-pores penetrating the core of the fiber through the interaction of Kirkendall effect, surface diffusion and phase separation; the third stage is dominated by surface diffusion of the core material along the pore surface. To explore the formation conditions, the factors including ambient temperature, relativity humidity (R. H.), molecular weight and fiber diameter are studied. The longitudinal and cross sectional morphologies of these fibers are examined by scanning electron micrograph (SEM). The results show that the prerequisite for the formation of uniform porous hollow PLLA fibers include moderate ambient temperature (10~20°C) and appropriate molecular weight for the PLLA, as well as the diameter of the fiber in the range of several micrometers to about 100 nanometers.
Electrochemical Performance of LiFePO4/C via Coaxial and Uniaxial Electrospinning Method  [PDF]
Yan Hu, Dawei Gu, Hongying Jiang, Lei Wang, Hongshun Sun, Jipeng Wang, Linjiang Shen
Advances in Chemical Engineering and Science (ACES) , 2016, DOI: 10.4236/aces.2016.62017
Abstract: In this work, LiFePO4/C (LFP/C) cathode materials with superior electrochemical performance have been prepared by coaxial and uniaxial electrospinning method. The electrode materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Also, cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) measurements were performed on these materials. The experimental results indicate that the electrochemical properties of LFP/C-C, such as specific capacity, coulombic efficiency, Li+ diffusion coefficient and overpotential are significantly improved. The enhanced electrical conductivity and polarization of the LFP/C-C electrode are mainly due to its porous morphology and amorphous carbon coating layer.
Study on the Morphologies and Formational Mechanism of Poly(hydroxybutyrate-co-hydroxyvalerate) Ultrafine Fibers by Dry-Jet-Wet-Electrospinning  [PDF]
Shuqi Zhu,Hao Yu,Yanmo Chen,Meifang Zhu
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/525419
Abstract: Dry-jet-wet-electrospinning (DJWE) was carried out to study the formational mechanism of poly(hydroxybutyrate-co-hydroxyvalerate) electrospun fibers. Morphological comparison between normal electrospinning (NE) and DJWE was investigated. The results showed that jet could solidify quickly in DJWE to avoid bead collapse or fiber coherence. Jet structures could be maintained at very low collection distance. Beanpod-like beads, which were named as primary beads, could be seen at the boundary of stability and instability section and divided into spindle-like beads with longer collection distance. Bead-free electrospun fibers from DJWE had few bonding points among each other, and fast solidification and double-diffusion led to rough and shriveled fiber surface. DJWE mats were higher hydrophobic than that from NE due to more loose structure and higher surface porosity. Higher bead ratio on the surface and rounder bead structure resulted in higher hydrophobicity. 1. Introduction Electrospinning was regarded as a very convenient and effective method for preparing nanofibers and ultrafine fibers, which could be used for filtration [1, 2], tissue engineering scaffolds [3–5], protective clothes [6, 7], carriers for enzymes [8, 9], sensors [10–12], and so forth. Many researchers focused on the theories and the phenomena of the electrospinning process [13–16]. However, there were some difficulties in studying the morphology at very low collection distance. For example, the transformation process of instability section, especially the deformation of beads, which was of great importance for understanding the formation of ultrafine fibers, could not be observed clearly by high-speed photography. Besides, as the solidification mechanism of the normal electrospun fibers was solvent volatilization, the jet near the needle contained a large amount of solvent and could not maintain the structures when collected on glass slides or aluminum foils. So the fiber collected at low distance always deformed or even collapsed on solid substrates and the exact morphology could not be observed. Dry-jet-wet-electrospinning (DJWE) was one electrospinning method for producing fibers from nonvolatile solvent, such as room temperature ionic liquids [17, 18]. It was also used for preparing aligned nanofiber yarns [19]. This method, though usually called wet electrospinning, actually had the similar fiber solidification mechanism with dry-jet-wet-spinning, only differed in driving force. Fibers were electrospun into the coagulation bath, with precipitant for polymers in it. In another word,
Fast Disintegrating Quercetin-Loaded Drug Delivery Systems Fabricated Using Coaxial Electrospinning  [PDF]
Xiao-Yan Li,Yan-Chun Li,Deng-Guang Yu,Yao-Zu Liao,Xia Wang
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms141121647
Abstract: The objective of this study is to develop a structural nanocomposite of multiple components in the form of core-sheath nanofibres using coaxial electrospinning for the fast dissolving of a poorly water-soluble drug quercetin. Under the selected conditions, core-sheath nanofibres with quercetin and sodium dodecyl sulphate (SDS) distributed in the core and sheath part of nanofibres, respectively, were successfully generated, and the drug content in the nanofibres was able to be controlled simply through manipulating the core fluid flow rates. Field emission scanning electron microscope (FESEM) images demonstrated that the nanofibres prepared from the single sheath fluid and double core/sheath fluids (with core-to-sheath flow rate ratios of 0.4 and 0.7) have linear morphology with a uniform structure and smooth surface. The TEM images clearly demonstrated the core-sheath structures of the produced nanocomposites. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results verified that quercetin and SDS were well distributed in the polyvinylpyrrolidone (PVP) matrix in an amorphous state, due to the favourite second-order interactions. In vitro dissolution studies showed that the core-sheath composite nanofibre mats could disintegrate rapidly to release quercetin within 1 min. The study reported here provides an example of the systematic design, preparation, characterization and application of a new type of structural nanocomposite as a fast-disintegrating drug delivery system.
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