Poly(methyl methacrylate)/silica nanocomposite fibers by electrospinning

Uniform poly(methyl methacrylate) (PMMA)/silica nanocomposite fibers containing up to 20 wt % silica were prepared by electrospinning. The electrospun solutions were prepared by mixing a solution of PMMA in dimethyl formamide (DMF) with colloidal silica in methyl ethyl ketone (MEK). The average fiber diameter decreases from 2.49 μm to 1.69 μm when 20 wt % silica is incorporated as a result of considerably increased solution conductivity, although the solution viscosity increases significantly, which should result in opposite effect. Thinner fibers (down to 350 nm) can be obtained by changing DMF/MEK proportion and by the addition of an ammonium salt. Nano‐sized silica particles (10–40 nm) distributes homogeneously in the fibers, as revealed by transmission electron microscopy. Furthermore, the incorporation of silica nanoparticles can change the thermal properties and surface wettability of the fiber mats. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1211–1218, 2009     

Electrospinning of poly(vinyl pyrrolidone)-iodine complex and poly(ethylene oxide)/poly(vinyl pyrrolidone)-iodine complex - a prospective route to antimicrobial wound dressing materials

New nanofibers containing poly(vinyl pyrrolidone)-iodine complex (PVP-iodine) were obtained by electrospinning in order to prepare materials suitable for wound dressings. Different approaches were used: a one-step method based on electrospinning of PVP-iodine or poly(ethylene oxide)/PVP-iodine solutions and a three-step method based on electrospinning of PVP or poly(ethylene oxide)/PVP mixed solutions followed by photo-mediated crosslinking of the obtained nanofibers and subsequent complexation with iodine. The average diameters of the fibers were in the range 150-470 nm depending on the composition and on the applied field strength (AFS) and increased with increasing the amount of PEO in the spinning solutions. Higher AFS resulted in greater fiber diameter and in size distribution broadening. Photo-mediated crosslinking in the presence of 4,4′-diazidostilbene-2,2′-disulfonic acid disodium salt successfully stabilized the electrospun PVP and PEO/PVP nanofibers against water and water vapor.     

Formation of Ultrafine Apatite Fibers by Sol-gel/Electrospinning

Ultrafine apatite fibers were prepared by electrospinning of sol-gel precursor/poly（ vinyl pyrrolidone） （PVP） solutions followed by subsequent calcination. The as-electrospun and calcinated fibers were observed under a scanning electron microscope and an optical polarizing microscope. Results show that the morphology and the diameter of as-electrospun fibers strongly depend on the viscosity and the surface tension of sol-gel precursor/PVP solutions. After calcination, the smooth as-electrospun fibers shrink and the fiber diameter decreases because of the removal of the polymer. The chemical evolution upon the transformation of the precursor from a gel to the final apatite fibers was investigated by thermogravimetric-differenfial thermal analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It is thus suggested that the crystalline structure of the calcined fibers is largely influenced by the calcination temperature. After being calcined at 600 ℃, the apatite fibers with a diameter of about 280 nm containing β-tricalcium phosphate were obtained.     

Melt-electrospinning of PMMA

<正>The melt electrospinning of PMMA was investigated.The averaged fiber diameter thus obtained was reduced from 34.0μm to 19.7μm by adding di-(2-ethylhexyl)phthalate to reduce viscosity of the molten PMMA,and it further lowered down to 4.0μm when a KCl/ice-water solution was used as collection media.A comparison study on the PMMA fibers made through melt electrospinning and done by solution electrospinning was made.It was found that solution electrospinning was capable of fabricating very thin fibers as small as to a nanometer size,but resulted in a much wider fiber diameter range than melt-electrospinning did.In general,within some extent an increase in applied voltage and amount of the additive or a decrease in collection distance can give rise to a decreased fiber diameter and improved mechanical performance for the PMMA fibers by melt electrospinning.It was also indicated that the mechanical properties of the PMMA fibers made through melt-electrospinning were superior to those by solution elctropspinning.     

Single particle analysis using fluidic, optical and electrophoretic force balance in a microfluidic system

A unique microfluidic system is developed which enables the interrogation of a single particle by using multiple force balances from a combination of optical force, hydrodynamic drag force, and electrophoretic force. Two types of polystyrene (PS) particles with almost identical size and refractive index (plain polystyrene (PS) particle - mean diameter: 2.06 μm, refractive index: 1.59; carboxylated polystyrene (PS-COOH) particles - mean diameter: 2.07 μm, refractive index: 1.60), which could not be distinguished by optical chromatography, reveal different electrokinetic behaviors resulting from the difference in their surface charge densities. The PS-COOH particles, despite their higher surface charge density when compared to the PS particles, experience a lower electrophoretic force, regardless of ionic strength. This phenomenon can be understood when the more prominent polarization of the counter ion cloud surrounding the PS-COOH particles is considered. The surface roughness of the carboxylated particles also plays an important role in the observed electrokinetic behavior.     

静电纺丝法制备超细聚苯乙烯纳米纤维

采用静电纺丝方法制备了超细聚苯乙烯纤维, 通过向溶液中添加有机胺盐并降低溶液浓度将纤维的平均直径降至100 nm, 并研究了盐的添加量对纤维直径的影响.     

Ultrafine Electrospun Conducting Polymer Blend Fibers and Their Photoluminescence Properties

Ultrafine poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene) (MEH-PPV)/polyvinylpyrrolidone (PVP) blend fibers with the average diameters ranging from 625 nm to 1.46 µm were prepared by electrospinning of polymer blend solutions in the mixed solvent of chlorobenzene and methanol. The average diameter of fibers was found to decrease with initial increase in the applied electrical potential and composition of MEH-PPV, reach a minimum value at an intermediate value, and increase with further increase in the applied electrical potential and composition of MEH-PPV, while it was found to decrease with increasing collection distance. PVP was easily removed from MEH-PPV/PVP fibers by the Soxhlet extraction, and after the removal of PVP at high composition of MEH-PPV, pure MEH-PPV fibers were obtained as a ribbon-like structure aligned with wrinkled surface in fiber direction. The increase in MEH-PPV composition and the removal of PVP from as-spun MEH-PPV/PVP fibers resulted in a significant blue-shift in UV-Vis absorption peak and red-shift in PL peak.     

Development of PEG-PLA/PLGA microparticles for pulmonary drug delivery prepared by a novel emulsification technique assisted with amphiphilic block copolymers

We developed a novel "spray dry-based" method for preparing surface-modified particle via "block copolymer-assisted" emulsification/evaporation for pulmonary drug delivery. The method included three steps: (1) o/w emulsion containing both hydrophobic polymers and amphiphilic block copolymers was obtained by emulsification of water and a polymer-containing organic solvent, (2) the o/w emulsion was misted with a nebulizer, and (3) the emulsion mists were dried by a heater. In this way, the hydrophobic polymers and the hydrophobic part of the amphiphilic block copolymers gradually tangled during the evaporation of organic solvents from the o/w emulsion. Consequently, the hydrophilic polymer chain was introduced on the particle surface. The particle surface can be easily modified although there are no reactive groups in the hydrophobic polymer molecules. We successfully obtained dry PEG-PLA/PLGA microparticles by controlling the weight ratio of the block copolymer and the hydrophobic polymer. The introduction of PEG to the particle surface involves an increase in the Zeta potential of the particles. Interestingly, the "dimpled" microparticles having a diameter of approximately 2 μm were obtained. The "dimpled" microparticles can serve as drug carriers for pulmonary drug delivery, because the particles have a large surface area. We expect that this novel surface-modification technique will enable efficient fabrication of particles in drug delivery systems.     

Polypyrrole-palladium nanocomposite coating of micrometer-sized polymer particles toward a recyclable catalyst

A range of near-monodisperse, multimicrometer-sized polymer particles has been coated with ultrathin overlayers of polypyrrole-palladium (PPy-Pd) nanocomposite by chemical oxidative polymerization of pyrrole using PdCl(2) as an oxidant in aqueous media. Good control over the targeted PPy-Pd nanocomposite loading is achieved for 5.2 μm diameter polystyrene (PS) particles, and PS particles of up to 84 μm diameter can also be efficiently coated with the PPy-Pd nanocomposite. The seed polymer particles and resulting composite particles were extensively characterized with respect to particle size and size distribution, morphology, surface/bulk chemical compositions, and conductivity. Laser diffraction studies of dilute aqueous suspensions indicate that the polymer particles disperse stably before and after nanocoating with the PPy-Pd nanocomposite. The Fourier transform infrared (FT-IR) spectrum of the PS particles coated with the PPy-Pd nanocomposite overlayer is dominated by the underlying particle, since this is the major component (>96% by mass). Thermogravimetric and elemental analysis indicated that PPy-Pd nanocomposite loadings were below 6 wt %. The conductivity of pressed pellets prepared with the nanocomposite-coated particles increased with a decrease of particle diameter because of higher PPy-Pd nanocomposite loading. "Flattened ball" morphologies were observed by scanning/transmission electron microscopy after extraction of the PS component from the composite particles, which confirmed a PS core and a PPy-Pd nanocomposite shell morphology. X-ray diffraction confirmed the production of elemental Pd and X-ray photoelectron spectroscopy studies indicated the existence of elemental Pd on the surface of the composite particles. Transmission electron microscopy confirmed that nanometer-sized Pd particles were distributed in the shell. Near-monodisperse poly(methyl methacrylate) particles with diameters ranging between 10 and 19 μm have been also successfully coated with PPy-Pd nanocomposite, and stable aqueous dispersions were obtained. The nanocomposite particles functioned as an efficient catalyst for the aerobic oxidative homocoupling reaction of 4-carboxyphenylboronic acid in aqueous media for the formation of carbon-carbon bonds. The composite particles sediment in a short time (相似文献   

A novel polystyrene/epoxy ultra‐fine hybrid fabric by electrospinning

In this work, electrospinning technique has been used to produce a new ultra‐fine hybrid fiber from a solution consists of polystyrene (PS) and epoxy polymers in dimethylformamide (DMF) solvent. Five ratios of different weight percentages of epoxy in PS/DMF solutions of 4 different concentrations; 15, 20, 25 and 30 wt.% were made to obtain the minimum diameter of the produced hybrid fiber. The minimum obtained hybrid fiber diameter was found to be 897 ± 239 nm at a PS/epoxy ratio of 5:1 and 13.33 Berry's number. Adding epoxy to PS has reduced the electrospun fiber diameter from 2.64 ± 0.49 μm for PS only to 1.52 ± 0.72 μm for PS/epoxy hybrid ultra‐fine fibers because of the reduction in Berry's number from 12.4 to 11.53, which gives an indication for the effect of adding epoxy on the PS molecular chain entanglement in DMF. Nuclear magnetic resonance spectroscopy results unambiguously reveal the coexistence of both epoxy and PS polymers in the hybrid fiber. We hypothesize that a hydrophopic (π‐π) interaction between the benzene rings of PS and epoxy polymers could contribute to the stability of the resulting hybrid fiber under electrospinning conditions. The fact that the lack of functional groups on both of PS and epoxy polymers that can results in covalent bonding or crosslinking between the 2 polymers supports the hypothesis of hydrophopic (π‐π) interaction in the stability of the hybrid fiber. Such (π‐π) interaction is well known to contribute to DNA single strand helical structure via intrastrand staking of the consecutive purine and pyrimidine nucleobases.     

Preparation of ultrafine fast-dissolving feruloyl-oleyl-glycerol-loaded polyvinylpyrrolidone fiber mats via electrospinning

Fast-dissolving drug delivery membranes for poorly water-soluble drugs were prepared by electrospinning using feruloyl-oleyl-glycerol (FOG) as a model drug and polyvinylpyrrolidone (PVP) K90 as a polymer matrix in a mixed solvent of chloroform/ethanol (4:1, v/v). Results from Fourier-transform infrared spectroscopy (FT-IR) illustrated good compatibility between FOG and PVP as well as a good distribution of FOG within the fibers. The morphology and diameter of the fibers were influenced by the concentration of PVP and the applied voltage. When the PVP concentration was 5% (w/v) and the applied voltage was 14 kV, uniform and smooth fibers were obtained, with diameter 700-800 nm. Wetting time assays confirmed fast-dissolving properties with the average dissolution time for FOG-loaded PVP fiber membranes being 2.0±1.5 s. These results demonstrate the potential of electrospinning solid dispersions to improve the dissolution profile of poorly water-soluble drugs.     

Study of superhydrophobic electrospun nanocomposite fibers for energy systems

Polystyrene (PS) and polyvinyl chloride (PVC) fibers incorporated into TiO(2) nanoparticles and graphene nanoflakes were fabricated by an electrospinning technique, and then the surface morphology and superhydrophobicity of these electrospun nanocomposite fibers were investigated. Results indicated that the water contact angle of the nanocomposite fiber surfaces increases to 178° on the basis of the fiber diameter, material type, nanoscale inclusion, heat treatment, and surface porosity/roughness. This is a result of the formation of the Cassie-Baxter state in the fibers via the nanoparticle decoration, bead formation, and surface energy of the nanofiber surface. Consequently, these superhydrophobic nanocomposite fibers can be utilized in designing photoelectrodes of dye-sensitized solar cells (DSSCs) as self-cleaning and anti-icing materials for the long-term efficiency of the cells.     

Novel antibacterial fibers of quaternized chitosan and poly(vinyl pyrrolidone) prepared by electrospinning

The preparation of continuous defect-free fibers from quaternized chitosan derivative (QCh) has been achieved by electrospinning of mixed aqueous solutions of QCh with poly(vinyl pyrrolidone) (PVP). The average fiber diameter significantly decreases from 2800 to 1500 nm on increasing the polyelectrolyte content. In order to impart to QCh/PVP electrospun fibers stability to water and water vapor, the fibers have been crosslinked by incorporation of photo-crosslinking additives into QCh/PVP spinning solutions and subsequent UV irradiation of the electrospun fibers. Photo-crosslinked QCh-containing electrospun mats show high antibacterial activity against the Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.     

Highly crosslinked micron-range polymer microspheres by dispersion polymerization of divinylbenzene

Narrow disperse microparticles are formed by dispersion polymerization of commercial divinylbenzene in acetonitrile or ethanol solution in the presence of 2,2′-azobis(2-methylpropionitrile) initiator and polyvinylpyrrolidone stabilizer. The particles have average diameters between 1 and 9 μm depending on monomer concentration, solvent, and temperature. While the smaller particles are relatively smooth, surface texture increases with diameter to give popcorn shapes at 9 μm diameter. High crosslinker concentration is shown to be essential for particle formation. © 1993 John Wiley & Sons, Inc.     

Model filled polymers. VIII. Synthesis of crosslinked polymeric beads by seed polymerization

Monodisperse crosslinked polystyrene (PS) and polymethacrylate (PMA) beads of sizes greater than 1 μm in diameter are prepared by particle nucleation onto pre-existing polymer seeds in a multistage emulsion polymerization, in the absence of emulsifier. An adequate seed number concentration, which decreases with increasing seed size, is necessary to achieve monodisperse beads. Monodisperse multicomposition beads are prepared by polymerizing styrene onto PMA seeds, but not by polymerizing methyl methacrylate onto PS seeds. Phase separation in growing seed particles or surface polymerization following free radical capture may lead to the formation of asymmetric shaped particles.     

Chromatography of Suspensions – An Experimental and Theoretical Investigation of Axial Dispersion Phenomena

Abstract

Herein is reported an experimental and theoretical investigation of axial dispersion phenomena in the chromatography of spherical suspensions in the submicron range. Peak separation and broadening were measured for a number of particle suspensions (polystyrene, polyvinylacetate, styrene-acrylic acid copolymer, butadiene-acrylonitrile copolymer latices and silica particles) using different column combinations containing porous inorganic packing materials (Fractosils, Bioglass, Corning Glass) and over a wide range of carrier fluid (water containing 1 g/l Aerosol O.T. and 1 g/l potassium nitrate) flowrates. Peak separation was virtually independent of carrier fluid flowrate while peak broadening increased significantly. Analytical solutions of the integral equation which describes axial dispersion in the chromatography of suspensions have been found for a general detector which includes light scattering, refractometer and viscosity-concentration detectors. These solutions were used to obtain dispersion corrections for various particle diameter averages (number, surface, weight and volume). Corrections to number and surface average particle diameters for axial dispersion are excessive with a light scattering detector. These large corrections are related to the fact that in the Rayleigh scattering regime, the extinction coefficient is proportional to diameter to the fourth power. The refractometer gives reasonable dispersion corrections for all particle diameter averages. The theoretical equations derived herein are equally applicable to hydrodynamic chromatography (HDC) and capillary particle chromatography (CPC).     

Spreading of a suspension drop on a horizontal surface

Experimental studies were performed on the contact line motion of a suspension of PS particles on a glass surface. The base liquids were silicone oil and glycerin. The particle size was in the range of 1-6 μm and the particle loading was 0.5-5 vol %. The drop shape was determined by using a drop image and its reflection and the drop outline was traced to the subpixel level. The Tanner-Voinov-Hoffman relation was valid for suspensions as well as for pure liquids. Silicone oil suspensions showed almost no noticeable change compared with the pure fluid. Glycerin suspensions showed an increase in contact line speed at low particle loading. The difference was due to the microstructure change at the contact line region, and the microstructure change was originated from the wetting characteristics of particles. Particle alignment occurred during the spreading stage for partially wetting particles. The contact line showed a stop-and-go fashioned motion due to surface irregularities. This result can be used as the boundary condition at the contact line in the numerical simulation of suspension spreading.     

同轴静电纺丝法在纳米中空Ti02纤维中填充Ag的应用

以聚乙烯吡咯烷酮(PVP)溶胶,钛酸四正丁酯和PVP溶胶,银颗粒为前驱体,以共轴静电纺丝法制备了银填充的TiO2中空纳米纤维.将双组分纤维在200℃下热处理去除乙醇与表面吸附水后,继而在空气气氛中焙烧至600℃.可以得到在内表面上沉积银颗粒的TiO2纳米管,银颗粒的直径为5-40 nm,TiO2纳米管的外径150-300 nm.管臂厚10-20 nm.用红外吸收光谱(IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等测试手段对超细纤维进行了表征.中空纤维的直径和管壁可以通过改变电纺参数来调节.与Ag-TiO2纳米纤维、TiO2纳米中空纤维、TiO2纳米纤维及TiO2纳米粉体相比较,Ag颗粒填充的TiO2纳米中空纤维在光分解亚甲基蓝上表现出了更好的光催化性能.     

同轴静电纺丝法在纳米中空TiO2纤维中填充Ag的应用

以聚乙烯吡咯烷酮(PVP)溶胶/钛酸四正丁酯和PVP溶胶/银颗粒为前驱体, 以共轴静电纺丝法制备了银填充的TiO2中空纳米纤维. 将双组分纤维在200 ℃下热处理去除乙醇与表面吸附水后, 继而在空气气氛中焙烧至600 ℃, 可以得到在内表面上沉积银颗粒的TiO2纳米管, 银颗粒的直径为5-40 nm, TiO2纳米管的外径150-300 nm, 管臂厚10-20 nm. 用红外吸收光谱(IR)、X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等测试手段对超细纤维进行了表征. 中空纤维的直径和管壁可以通过改变电纺参数来调节. 与Ag-TiO2纳米纤维、TiO2纳米中空纤维、TiO2纳米纤维及TiO2纳米粉体相比较, Ag颗粒填充的TiO2纳米中空纤维在光分解亚甲基蓝上表现出了更好的光催化性能.     

Influence of solvents on the formation of ultrathin uniform poly(vinyl pyrrolidone) nanofibers with electrospinning

Although there have been many reports on the preparation and applications of various polymer nanofibers with the electrospinning technique, the understanding of synthetic parameters in electrospinning remains limited. In this article, we investigate experimentally the influence of solvents on the morphology of the poly(vinyl pyrrolidone) (PVP) micro/nanofibers prepared by electrospinning PVP solution in different solvents, including ethanol, dichloromethane (MC) and N,N‐dimethylformamide (DMF). Using 4 wt % PVP solutions, the PVP fibers prepared from MC and DMF solvents had a shape like a bead‐on‐a‐string. In contrast, smooth PVP nanofibers were obtained with ethanol as a solvent although the size distribution of the fibers was somewhat broadened. In an effort to prepare PVP nanofibers with small diameters and narrow size distributions, we developed a strategy of using mixed solvents. The experimental results showed that when the ratio of DMF to ethanol was 50:50 (w/w), regular cylindrical PVP nanofibers with a diameter of 20 nm were successfully prepared. The formation of these thinnest nanofibers could be attributed to the combined effects of ethanol and DMF solvents that optimize the solution viscosity and charge density of the polymer jet. In addition, an interesting helical‐shaped fiber was obtained from 20 wt % PVP solution in a 50:50 (w/w) mixed ethanol/DMF solvent. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3721–3726, 2004