Synthesis and characterization of poly (linoleic acid)-g-poly(methyl methacrylate) graft copolymer with applying in Au/PLiMMA/n-Si diode

Poly (linoleic acid)-g-poly(methyl methacrylate) (PLiMMA) graft copolymer was synthesized and characterized. PLiMMA graft copolymer was synthesized from polymeric linoleic acid peroxide (PLina) possessing peroxide groups in the main chain by free radical polymerization of methyl methacrylate. Later, PLiMMA was characterized by proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. Furthermore, Au/PLiMMA/n-Si diode was fabricated for the purpose of investigating PLiMMA׳s conformity in diodes. The main electrical characteristics of this diode were investigated using experimental current–voltage (I–V) measurements in dark and at room temperature. Obtained results, such as sufficiently high rectifying ratio of 4.5×10⁴, indicate that PLiMMA is a promising organic material for electronic device applications.     

Formation of water-resistant hyaluronic acid nanofibers by blowing-assisted electro-spinning and non-toxic post treatments

A unique blowing-assisted electro-spinning process has been demonstrated recently to fabricate hyaluronic acid (HA) nanofibers. In this article, effects of various experimental parameters, such as air-blowing rate, HA concentration, feeding rate of HA solution, applied electric field, and type of collector on the performance of blowing-assisted electro-spinning of HA solution were investigated. With the assistance of air-blowing, the solution-feeding rate could be increased to 40 μl/min/spinneret and the applied electric field could be decreased to 2.5 kV/cm. The optimum conditions for consistent fabrication of HA (with a molecular weight of ∼3.5 million) nanofibers involved the use of an air-blowing rate of around 70 ft³/h and a concentration range between 2.5 and 2.7% (w/v) in aqueous solution. Two benign methods to fabricate water-resistant HA nanofibrous membranes without the use of reactive chemical agents were demonstrated: (a) the exposure of HA membranes in hydrochloric acid (HCl) vapor, followed by a freezing treatment at −20 °C for 20-40 days; and (b) the immersion of HA membranes in an acidic mixture of ethanol/HCl/H₂O at 4 °C for 1-2 days. Although both methods could produce hydrophilic, substantially water-resistant HA nanofibrous membranes (the treated membranes could keep their shape intact in neutral water at 25 °C for about 1 week), the immersion method (6) was shown to be more versatile and effective. IR spectroscopy was used to investigate this ‘cross-linking’ mechanism in the solid HA membrane. Viscosity studies of acidic HA solutions under varying freezing conditions were also carried out. It was found that when the freezing time exceeded 8 h, the HA solution became gel-like and exhibited a large increase in the hydrogen-bond concentration. Thus, the resistance to water solubility could be due to the high density of hydrogen bonds in the solid HA membranes that were treated by the ‘freezing’ approach.     

Phase morphology of nanofibre interlayers: Critical factor for toughening carbon/epoxy composites

Electrospun thermoplastic nanofibres were employed to toughen carbon/epoxy composites by direct deposition on carbon fibre fabrics, prior to resin impregnation and curing. The toughening mechanism was investigated with respect to the critical role of phase morphology on the toughening effect in carbon/epoxy composites. The influences of solubility in epoxy and melting characteristics of thermoplastics were studied towards their effects on phase structure and delamination resistance. For the three different thermoplastic nanofibre interlayers used in this work, i.e. poly(ε-caprolactone) (PCL), poly(vinylidene fluoride) (PVDF) and polyacrylonitrile (PAN) nanofibre interlayers, only PCL nanofibres produced toughening. Although cylinder-shaped fibrous macrophases existed in all three interlayer regions, only PCL nanofibres had polymerisation-induced phase separation with epoxy, forming ductile thermoplastic-rich particulate microphases on the delamination plane. These findings clearly show that the polymerisation-induced phase separation is critical to the interlayer toughening by thermoplastic nanofibres. An optimal concentration (15 wt.%) of PCL solution for electrospinning was found to produce composites with enhanced mode I interlaminar fracture toughness (G_IC), stable crack growth and maintained flexural strength and modulus.     

静电纺丝纳米纤维研究的最新动向

综述静电纺丝纳米纤维研究的最新动向,有关静电纺丝法制取导电性纳米纤维和聚合物合金型纳米纤维以及静电纺丝装置开发。     

静电纺丝素-明胶管状支架的结构与性能

为研制组织工程小口径血管,以良好生物相容性的丝素蛋白、明胶为原料,通过静电纺丝法,以高速旋转的滚轴为收集装置,构建了丝素-明胶管状支架(直径为4.5 mm).测定其形貌结构、孔隙率和溶失率,并在该支架上进行人脐静脉内皮细胞(HUVECs)培养实验.结果表明:在缝素-明胶质量比例为70:30、纺丝液质量分数为13%、滚轴转速为1 000 r/min的条件下静电纺丝,可获得纤维直径较细、纤维分布较均匀、具有较高孔隙率的丝素-明胶管状支架:随着纺丝液质量分数的提高,丝素-明胶管状史架的溶失率降低,乙醇处理后管状支架溶失率大大降低;MTT显示细胞可以在支架上生长、增殖.     

Nanofibres of CA/PAN with high amount of carbon nanotubes by core–shell electrospinning

We prepared polyacrylonitrile (PAN) and cellulose acetate (CA) based nanofibres with high amount of carbon nanotubes (CNTs) by core–shell electrospinning. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to evaluate the morphology and structure of the electrospun nanofibres. Raman spectroscopy (Raman) and TEM indicate alignment of CNTs in the polymer fibres. Core–shell electrospinning improved the distribution and uniformity of the fibres. The loading of carbon nanotubes showed better thermal stability.     

Design of a ductile carbon nanofiber/ZrB2 nanohybrid film with entanglement structure fabricated by electrostatic spinning

Polyacrylonitrile (PAN), a kind of multi-purpose man-made polymer material, has been widely used in various products, including carbon fiber precursor fiber manufacturing. Organic/inorganic nanocomposites can provide precursor material with unique properties due to optimal structural design. Herein, PAN based carbon nanofiber (CNF) coated zirconium borate (ZrB₂) particles fiber film was prepared via electrostatic spinning strategy. Crosslinking network between carbon atoms formed at 280 °C due to long chain PAN molecules, which underwent pyrolysis at 800–1200 °C. Scanning electron microscope analysis showed that ductile CNF/ZrB₂ hybrid material with entanglement structure was successfully fabricated. Phase composition of the materials was analyzed by X-ray diffractometer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, which confirmed the presence of carbon atoms in the materials. Entanglement structure between CNFs and ZrB₂ enhanced tensile performance of nanohybrid film, in which CNF film with 25% ZrB₂ content exhibited optimal mechanical properties. The design of nanohybrid structure provides facile and universal approach for exploration of organic/inorganic nanocomposites with controlled structures and excellent mechanical properties.     

Electrospinning of polymer nanofibers: Effects on oriented morphology,structures and tensile properties

The interest in fabrication of nanofibers using electrospinning method has attracted considerable attention due to its versatile maneuverability of producing controlled fiber structures, porosity, orientations and dimensions. Although the process appears to be simple and straightforward, an understanding of the technique and its influence on the morphology, structural and mechanical properties is still not completely clear. Recently, the size effect on the mechanical properties was reported for fibers across different length scales. Both modulus and strength of poly(ε-capro-lactone) (PCL) fibers were found to increase significantly when the diameter of the fibers was reduced to below ∼500 nm. In this article, for the first time, we critically review and evaluate the role of the microstructures on the fiber deformation behavior and present possible explanations for the enhanced properties of the nanofibers. Our discussions are focused on the techniques to obtain controlled structures and the mechanisms behind the size effect in electronspun fibers are given. In-depth understanding of these mechanisms can provide fruitful outcomes in the development of advanced nanomaterials for devices and miniaturized load-bearing applications.     

Lightweight nanofibrous EMI shielding nanowebs prepared by electrospinning and metallization

The metal-deposited poly(vinyl alcohol) (PVA) composite nanofibrous mats were fabricated by electrospinning and metal-deposition methods for electromagnetic interference (EMI) shielding applications. The metal-deposited nanofiber mats prepared with various metals (Cu, Ni, Ag), their different thicknesses, and different metal deposition systems composed of Cu and Ni were used for EMI shielding measurement. For the EMI SE measurement, a near-field antenna measurement system was used. The measurement of EMI SE was carried out at the frequency range from 0.5 to 18 GHz, and the electromagnetic parameters were measured. The experimental results showed that absorption was the major shielding mechanism and reflection was the secondary shielding mechanism. The effect of unique porous structure of the metal-deposited composite nanofibrous mats was also discussed.     

Electrospun aligned PLLA/PCL/functionalised multiwalled carbon nanotube composite fibrous membranes and their bio/mechanical properties

Aligned poly(L-lactide) (PLLA)/poly(ε-caprolactone) (PCL)/functionalized multiwalled carbon nanotube (F-MWNT) composite fibrous membranes were fabricated by electrospinning. Their morphology, mechanical properties, in vitro degradation and biocompatibility were studied. With a collector rotation speed of 3000 rpm, the electrospun fibers are highly aligned and the F-MWNTs are oriented along the fiber axis, reinforcing the electrospun fibrous membranes. When the F-MWNTs are incorporated, the PLLA/PCL/F-MWNT composite fibers become thinner due to the increased electrical conductivity. However, when the F-MWNTs are increased to 3.75 wt.%, the higher viscosity and aggregation of F-MWNTs have lead to the formation of beads and a wider diameter distribution in the electrospun fibers. Also, the electrospun fibers having smaller diameter, larger porosity and lower crystallinity induced by F-MWNTs have improved the bio-degradation of the PLLA/PCL/F-MWNT fibrous membranes, which have no toxic effects on the proliferation of adipose-derived stem cells.