Molecularly imprinted polyimide nanofibers prepared by electrospinning

An estrone imprinted polyimide nanofiber mat was prepared by using an electrospinning method. The diamine monomer-template complex was synthesized by the reaction of the diamine monomer having an isocyanate group and estrone (template) having a phenol moiety, in which the template was attached to the monomer via a thermally reversible urethane bond. A poly(amic acid) was synthesized by polymerization of the diamines (1:19 mole ratio of the diamine monomer-template complex to 4,4′-oxydianiline) and pyromellitic dianhydride in N,N-dimethylformamide and the reaction solution was used for electrospinning. The poly(amic acid) fibers were thermally imidized and then heated in 1,4-dioxane in the presence of water to remove the template molecules. The imprinted polyimide nanofibers showed the specific recognition ability and fast kinetic adsorption for estrone.     

Preparation of chitosan/PLA blend micro/nanofibers by electrospinning

The chitosan/PLA blend micro/nanofibers have been prepared for the first time by electrospinning. Trifluoroacetic acid (TFA) was found to be the co-solvent for electrospinning. The chitosan/PLA blend solutions in various ratios were studied for electrospinning into micro/nanofibers. The morphology of the fibers was shown by scanning electron microscope (SEM). It was found that the average diameter of the chitosan/PLA blend fibers became larger, and the morphology of the fibers became finer with the content of PLA increasing. To show the molecular interactions, chitosan/PLA fibers were characterized by Fourier transform infrared spectroscopy (FTIR). The spun micro/nanofibers are expected to be used in the native extracellular matrix for tissue engineering.     

Transient charge-masking effect of applied voltage on electrospinning of pure chitosan nanofibers from aqueous solutions

Abstract

The processing of a polyelectrolyte (whose functionality is derived from its ionized functional groups) into a nanofiber may improve its functionality and yield multiple functionalities. However, the electrospinning of nanofibers from polyelectrolytes is imperfect because polyelectrolytes differ considerably from neutral polymers in their rheological properties. In our study, we attempt to solve this problem by applying a voltage of opposite polarity to charges on a polyelectrolyte. The application of this ‘countervoltage’ can temporarily mask or screen a specific rheological property of the polyelectrolyte, making it behave as a neutral polymer. This approach can significantly contribute to the development of new functional nanofiber materials.     

Atomic force microscopy visualization of hard segment alignment in stretched polyurethane nanofibers prepared by electrospinning

Molecular-level orientation within nanofibers has been attracting attention as a tool for controlling and designing highly functional nanofibers. In this study, we used atomic force microscopy to visualize the phase separation between soft and hard segments on a polyurethane (PU) nanofiber surface prepared by electrospinning. Furthermore, the stretched nanofibers prepared with a high-speed rotating collector were found to have a different phase distribution in the phase-separated structure, with the hard segment domains aligned to the fiber axis. In contrast, unstretched PU nanofibers prepared without rotation were observed to have nonuniformly distributed segments. These results indicate that the application of an intense elongation force along the nanofiber axis with a rotating mandrel collector changed the distribution of segment alignments.     

Transient charge-masking effect of applied voltage on electrospinning of pure chitosan nanofibers from aqueous solutions

The processing of a polyelectrolyte (whose functionality is derived from its ionized functional groups) into a nanofiber may improve its functionality and yield multiple functionalities. However, the electrospinning of nanofibers from polyelectrolytes is imperfect because polyelectrolytes differ considerably from neutral polymers in their rheological properties. In our study, we attempt to solve this problem by applying a voltage of opposite polarity to charges on a polyelectrolyte. The application of this ‘countervoltage’ can temporarily mask or screen a specific rheological property of the polyelectrolyte, making it behave as a neutral polymer. This approach can significantly contribute to the development of new functional nanofiber materials.     

Mechanical properties of nylon-6/SiO2 nanofibers prepared by electrospinning

SiO₂ nanoparticles reinforced nylon-6 nanofibers were prepared by electrospinning of nylon-6/SiO₂ solution in formic acid. The effect of concentration and applied voltage on the diameter of the fibers was investigated. A nanoscale three-point bending test was used to evaluate the mechanical property of a single nylon-6/SiO₂ nanofiber. It was found that the elastic modulus of the nanofibers decreased with the increase in fiber diameter. This elastic modulus was in the range of 3.1-6.9GPa as the diameter ranged from 600 to 100nm.     

Titania nanofibers prepared by electrospinning

TiO₂ nanofibers with a diameter of 54-78 nm have been successfully prepared by electrospinning method using a solution that contained poly(vinyl pyrrolidone) (PVP) and Ti(IV)-isopropoxide. The effect of viscosity and applied electric field on the morphology of the electrospun titania fibers was investigated. It has been observed that the increase in electric field causes bead formation and discontinuity in nanofiber morphology.     

Fabrication of hydrophobic/super-hydrophobic nanofilms on magnesium alloys by polymer plating

Hydrophobic/super-hydrophobic nanofilms with improved corrosion resistance were fabricated on the surfaces of Mg-Mn-Ce magnesium alloy by a surface modification technique, named as polymer plating, which has been developed to modify superficial characteristics of magnesium alloys with polymeric nanofilms through synthesized organic compounds of triazine dithiol containing functional groups. The nanofilms were prepared by the electrochemical and polymerization reactions during polymer plating analyzed from characteristics of Fourier transform infrared spectrophotometer, X-ray photoelectron spectroscopy and scanning electron microscopy. The fabricated nanofilms changed the surface wettability of blank magnesium alloy from hydrophilic to hydrophobic with contact angle 119.0° of distilled water with lower surface free energy of 20.59 mJ/m² and even super-hydrophobic with contact angle 158.3° with lowest surface free energy of 4.68 mJ/m² by different functional nanofilms on their surfaces. Alteration of wettability from hydrophilic to hydrophobic and super-hydrophobic resulted from their low surface free energy and surface morphology with micro- and nano-rough structures. The corrosion behaviors from potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that the super-hydrophobic nanofilm has higher corrosion resistance and stability in 0.1 mol/L NaCl solution and lower corrosion current density (I_corr) with R_ct increasing two orders of magnitude of 16,500 Ω·cm² compared to that obtained for blank of 485 Ω·cm².     

静电纺丝制备PVDF多孔纳米纤维及其在吸油中的应用

采用静电纺丝和PEO模板相结合加工制备了具有超疏水性能的PVDF多孔纳米纤维.通过扫描电镜(SEM)观察所制备的PVDF纤维具有均匀微纳米二级孔道显微结构,测得该多孔纳米纤维表面接触角高达158°,呈现良好的超疏水特性.研究发现,将PVDF多孔纳米纤维作为溢油吸附材料具有良好的吸油效能,其对润滑油、柴油、植物油和汽油的...     

CO gas sensing of Pd-doped ZnO nanofibers synthesized by electrospinning method

Pure and Pd-doped ZnO nanofibers were synthesized by electrospinning method, and characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diameters of the fibers annealed at 600 °C range from 70 to 160 nm. Compared with pure ZnO nanofiber sensor, the Pd-doped ZnO nanofiber sensor exhibits improved sensing properties to CO at 220 °C. Moreover, this sensor processes considerable sensitivity to low concentration CO in the range of 1-20 ppm with good selectivity. The response and recovery times are in the range of 25-29 s and 12-17 s, respectively. The sensing mechanism is also discussed.