Needleless emulsion electrospinning for scalable fabrication of core–shell nanofibers

This article reports a new needleless emulsion electrospinning method for scale‐up fabrication of ultrathin core–shell polyacrylonitrile (PAN)/isophorone diisocyanate (IPDI) fibers. These core–shell fibers can be incorporated at the interfaces of polymer composites for interfacial toughening and self‐repairing due to polymerization of IPDI triggered by environmental moisture. The electrospinnable PAN/IPDI emulsion was prepared by blending PAN/N,N‐dimethylformamide and IPDI/N,N‐dimethylformamide solutions (with the solute mass fraction of 1 : 1). The electrospinning setup consisted of a pair of aligned metal wires as spinneret (positive electrode) to infuse the PAN/IPDI emulsion and a rotary metal disk as fiber collector (negative electrode). The formed ultrathin core–shell PAN/IPDI fibers were collected with the diameter in the range from 300 nm to 3 μm depending on the solution concentration and process parameters. Optical microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the core–shell nanostructures. Dependencies of the fiber diameter on the PAN/IPDI concentration, wire spacing, and wire diameter were examined. Results show that needleless emulsion electrospinning provides a feasible low‐cost manufacturing technique for scalable, continuous fabrication of core–shell nanofibers for potential applications in self‐repairing composites, drug delivery, etc. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40896.     

静电纺丝制备中空纳米纤维/纳米管研究进展

介绍了静电纺丝的制备原理和制备中空纳米纤维/纳米管的方法,简述了静电纺丝制备中空纳米纤维/纳米管的影响因素;对目前静电纺丝制备中空纳米纤维/纳米管的研究进展情况进行阐述,并对其在光催化、传感器和电池方面的应用加以介绍。     

Crosslinking assisted fabrication of ultrafine poly(vinyl alcohol)/functionalized graphene electrospun nanofibers for crystal violet adsorption

This article reports the fabrication of water‐stable electrospun mats made from water‐soluble poly(vinyl alcohol) and comprising ultrafine nanofibers for a high surface area to volume ratio as required for the adsorption of crystal violet. Acid‐catalyzed crosslinking is uniquely demonstrated as a facile strategy to improve water stability and, just as importantly, fine‐tune the nanofiber size of the electrospun mats. Amine‐functionalized graphene nanoplatelets are incorporated as an adsorption performance enhancer instead of the more widely reported graphene oxide. The functionalized graphene also facilitates fabrication of the composite electrospun mats by direct mixing of the water‐dispersible graphene with the aqueous polymer solution. The enhanced adsorption performance of the polymer nanocomposite mats is explained in detail at the molecular level, while the adsorption mechanism is supported by adsorption isotherm and related kinetic data. Moreover, the adsorbent mats can be removed from the water after use with the mat integrity still maintained. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46318.     

Controlled fabrication of drug-loaded protein nanoparticles via flash nanoprecipitation

Protein nanoparticles (NPs) are perspective vehicles for delivery of therapeutic agents. However, whether they will ever reach the stage of widespread application relies crucially on the development of reliable fabrication strategies and techniques. Herein, we report a continuous precipitation approach, namely flash nanoprecipitation (FNP) for efficient construction of drug-loaded protein NPs with regulated size and properties. Our design relies on rapid mixing of solvent streams containing drug and protein with anti-solvent streams which triggers co-precipitation of the solutes and creates NPs by controlled nucleation and growth. The established process is generally capable for controlled formulation of diverse drug-loaded protein NPs. Our results validate the distinctive advantages of FNP over conventional precipitation approaches, including fast process, continuous production and excellent control of product size and properties. FNP is therefore likely to be the method of choice for preparing nanosized dispersions of hydrophobic drugs or food additives on an industrial scale.     

Polymer nanofiber‐templated fabrication and characterization of gallium oxide nanofibers consisting of granular nanoparticles

Gallium oxide (β‐Ga₂O₃) is an interesting semiconductor that has a wide bandgap and can be used as an optoelectronic material in flat‐panel displays, solar energy conversion devices and optical limiters for UV light. However, it is difficult to fabricate and process Ga₂O₃ nanofibers for actual optoelectronic applications. When the excellent processability of polymeric materials is introduced into the inorganic nanofiber fabrication process, this limitation can be easily overcome. The aim of the research reported was to prepare granular Ga₂O₃ nanofibers utilizing an electrospun polyacrylonitrile nanofiber template combined with sol‐gel technology. Ga₂O₃ nanofibers were successfully fabricated by electrospinning a solution of polyacrylonitrile mixed with gallium nitrate and subsequent calcination. The surface and bulk morphologies of the calcined nanofibers investigated using field‐emission scanning electron microscopy and transmission electron microscopy (TEM) indicated that Ga₂O₃ nanofibers were constructed by the fusion of gallium oxide nanoparticles. TEM bright‐field images combined with selected‐area electron diffraction indicated that the average diameter of the Ga₂O₃ nanofibers produced was ca 55 nm and the crystalline structure was β‐Ga₂O₃ with a monoclinic unit cell. Furthermore, the photoluminescence spectrum of the Ga₂O₃ nanofibers exhibited two strong green emission peaks and one UV emission peak. Copyright © 2010 Society of Chemical Industry     

One-step fabrication of branched poly(vinyl alcohol) nanofibers by magnetic coaxial electrospinning

Branching has been emerging in 3-D interconnecting building blocks. Branched and hyperbranched poly(vinyl alcohol) (PVA) nanofibers were fabricated by coaxially electrospinning two-liquids under an alternating magnetic field in a facile manner. Both the PVA nanofiber trunks with diameter of 100–200 nm and the PVA nanofiber branches with diameter of 10–30 nm were formed in a single step. The length and the morphology of the branched PVA nanofibers could be controlled through a rational design of the magnetic field. The facile technique may readily be extended to prepare 3-D branched nanofibers from other materials such as various polymers and polymer–ceramic materials. Moreover, the multifunctional and multicomponent materials with branched nanostructure could be expected by using the magnetic coaxial electrospinning technique. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of polydimethylsiloxane concentration on properties of polyurethane/polydimethylsiloxane hybrid dispersions

A series of waterborne polyurethane (WPU) derived from isophorone isocyanate and poly(tetramethylene glycol) were modified by hydroxyl‐terminated polydimethylsiloxane (HPMS). The solutions were then cast into films named as PUHS. Rheological behavior of the emulsions were studied using Rheometer and morphology was studied with transmission electron microscope. Meanwhile, the casting films were prepared from the WPU/HPMS hybrid dispersions, and their glass transition behavior, miscibility, water resistance, and medium resistance were studied with differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and so on. The results revealed that the emulsions' particle size decreases with increasing HPMS content and the particles are more easily affixed to each other when the HPMS content is more than 15%, and emulsions are endowed with pseudoplasticity and thixotropy. WAXD and DSC figures manifested that the casting films all exhibited a certain degree of miscibility. The degrees of crystallinity (x_c) decreased with increasing HPMS content, and the PUHS films were almost amorphous. It is noticed that water and medium absorption increased in the HPMS/PU compared to pure PU, which demonstrate that the membrane surfaces have excellent water and chemical medium repellency. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5538–5544, 2006     

Characterization of siloxane residues from polydimethylsiloxane elastomers by MALDI-TOF-MS

The hydophobic recovery properties of polydimethylsiloxane (PDMS) elastomers after environmental degradation arises from the migration of low molecular weight siloxanes from the bulk to the surface. MALDI-TOF-MS analysis of the isotopic distribution of oligomers from the surface of vulcanized PDMS has enabled unambiguous assignment of these as predominantly cyclic siloxanes ranging from 13 to 47 repeat units with smaller proportions of methyl and hydroxyl terminated linear chains ranging from 12 to 24 repeat units. © 2000 Society of Chemical Industry.     

Controllable fabrication of cadmium phthalocyanine nanostructures immobilized on electrospun polyacrylonitrile nanofibers with high photocatalytic properties under visible light

A novel photocatalyst of nanostructured cadmium phthalocyanine (CdPc) immobilized on the surface of polyacrylonitrile (PAN) nanofibers had been successfully fabricated by a simple combination of electrospinning technique and the solvent-thermal process. FE-SEM micrographs indicated that the nanostructured CdPc uniformly immobilized on the surface of PAN nanofibers without agglomeration. And the obtained CdPc/PAN composite nanofibers exhibited high visible light photocatalytic activity for the degradation of rhodamine B. Moreover, this photocatalyst could be easily separated for reuse due to the one-dimensional nanostructural property of the CdPc/PAN composite nanofibers.     

Facile fabrication of polyaniline/polypyrrole copolymer nanofibers with a rough surface and their electrorheological activities

Hierarchical polyaniline/polypyrrole (PANI/PPy) copolymer nanofiber was prepared via a two‐step method and adopted as dispersing materials for electrorheological (ER) fluids. The first step was used to synthesize PANI nanofibers by a rapid mixing method. Subsequently, the PANI/PPy copolymer nanofibers with a rough surface were obtained using an in situ polymerization method continuously. The morphology of the resultant PANI/PPy copolymer nanofibers can be controlled by varying the amount of Py monomer in the secondary in situ polymerization method. The rough surface of PANI/PPy copolymer nanofibers were confirmed by scanning electron microscopy and transmission electron microscopy. The diameter of PANI/PPy nanofiber is within the range 100–200 nm. The obtained PANI/PPy copolymer particles all exhibit amorphous structure through X‐ray diffraction measurement. We also demonstrated that the hierarchical PANI/PPy copolymer nanofibers exhibited characteristic ER behaviors, which were investigated using a Haake rotational rheometer at various electric field strengths. The ER efficiency e for PANI‐1mLPPy and PANI‐2mLPPy ER fluids at shear rate 0.1 s⁻¹ is 36.6 and 28.5 under electric field strength E = 3 kV/mm, respectively. Low leaking current density is observed even at high electric field strength and wide plateau region appeared, which show a strong ER activity for the PANI/PPy composite nanofibers. The results also indicate that the PANI/PPy composite particles have distinctly enhanced ER effect compared with the pure PANI and PPy particles under electric stimuli. The significantly improved ER property of PANI/PPy‐based ER fluid is ascribed to the enhanced interfacial polarization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46289.     

聚二甲基硅氧烷涂层材料的研究

本论文采用一定黏度的聚二甲基硅氧烷为基体,加八适量的填料和助剂,成功制备了室温硫化硅橡胶涂层.研究了白炭黑和交联剂对涂层材料的影响,并进行了TG和SEM的测试.研究结果表明：填料的添加明显改善了涂层的力学性能和耐高温性能,拉伸强度达1.42 MPa,可耐温288℃;并且该涂层有较好的耐水和耐酸、盐性能.耐碱性能有待进一步改善.     

A novel and facile impregnation-combustion fabrication of spherical CoAl2O4 supported on sepiolite nanofibers

In this study, sepiolite nanofibers-supported spherical CoAl₂O₄ composites were prepared by a novel and facile impregnation-combustion method, using nitrates and sepiolite minerals as the raw materials. The results showed that the optimal process for the nanocomposites formation was an impregnation step facilitated by stirring for 24?h at room temperature coupled with a calcination step performed at 300?℃ for 6?h. The characterizations by XRD, SEM and BET revealed that the CoAl₂O₄ particles were dispersed evenly on the surface of the sepiolite nanofibers with a complete crystal shape and uniform particle size, and the specific surface area has been improved significantly by adopting the sepiolite nanofibers as the support. Therefore, the sepiolite nanofibers-supported spherical CoAl₂O₄ composites with a good dispersion and suspension performance are a promising candidate in the fields of water-based coatings, heterogeneous catalytic reactions, ceramic materials, and so on.     

Pervaporation performance of polydimethylsiloxane membranes for separation of benzene/cyclohexane mixtures

Crosslinked polydimethylsiloxane/polyetherimide (PDMS/PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat‐plate composite membrane. The different function composition of the PDMS/PEI composite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PEI composite membranes were investigated by scanning electron microscope (SEM). The composite membranes prepared in this work were employed in pervaporation separation of benzene/cyclohexane mixtures. Effects of feed temperature, feed composition, concentration of crosslinking agent on the separation efficiency of benzene/cyclohexane mixtures were investigated experimentally. In addition, the swelling rate and stableness of composite membrane during long time operation were studied, which should be significant for practical application. The results demonstrated that the pervaporation method could be very effective for separation of the benzene/cyclohexane mixtures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

羟基聚硅氧烷在单螺杆挤出机中的脱挥

研究了α,ω-二羟基聚二甲基硅氧烷在单螺杆挤出机中的脱挥,分析了影响脱挥效果的因素。结果表明,温度与真空度是影响脱挥效果的关键参数。温度升高,脱挥效果提高,最佳温度200～220℃;真空度升高,脱挥效果提高,但同时增加了冒料的可能性,适宜的真空度为24～28kPa。得出了实验范围内的挥发分最终质量分数与螺杆转速及进料流量的关联式。     

Microencapsulated amino-functional polydimethylsiloxane as autonomous external self-healing agent for epoxy systems

The self-healing material under investigation is a diglycidyl ether of bisphenol A (DGEBA) epoxy matrix, which incorporates microcapsules filled with amine-functionalized polydimethylsiloxane (PDMS-a), as a new healing agent, combined with microcapsules filled with triethylenetetramine (TETA). The fracture toughness (K_IC) and healing efficiency of these systems were measured using tapered double-cantilever beam specimens. Fractographic analysis shows the rupture of microcapsules and release of the healing agent, inducing a change in the mirror-like fracture plane morphology of neat epoxy and healing of cracks. It was also observed that PDMS-a reduces the stiffness of the epoxy matrix, resulting in greater energy release rate (U_IC) values. The values of self-healing efficiency for systems healed for 48 h at room temperature varied from 0.82 to 1.0 (η, from K_IC values) and from 1.0 to 1.4 (η’, considering U_IC values). Specimens healed at 80°C containing 2.5 wt% of microcapsules filled with PDMS-a and TETA achieved η = 1.1 and η’ = 2.0, indicating a highly efficient self-healing process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47627.     

Graphitic carbon nanofibers developed from bundles of aligned electrospun polyacrylonitrile nanofibers containing phosphoric acid

Graphitic carbon nanofibers (GCNFs) with diameters of approximately 300 nm were developed using bundles of aligned electrospun polyacrylonitrile (PAN) nanofibers containing phosphoric acid (PA) as the innovative precursors through thermal treatments of stabilization, carbonization, and graphitization. The morphological, structural, and mechanical properties of GCNFs were systematically characterized and/or evaluated. The GCNFs made from the electrospun PAN precursor nanofibers containing 1.5 wt.% of PA exhibited mechanical strength that was 62.3% higher than that of the GCNFs made from the precursor nanofibers without PA. The molecules of PA in the electrospun PAN precursor nanofibers initiated the cyclization and induced the aromatization during stabilization, as indicated by the FT-IR and TGA results. The stabilized PAN nanofibers possessed regularly oriented ladder structures, which facilitated the further formation of ordered graphitic structures in GCNFs during carbonization and graphitization, as indicated by the TEM, XRD, and Raman results.     

Mechanical and electrical properties of carbon nanotubes surface‐stamped on polydimethylsiloxane for microvalve actuation

We report a study of the electrical and mechanical effects of the inclusion of a thin layer of multiwalled carbon nanotubes (MWCNTs) into the surface of polydimethylsiloxane (PDMS) as a method of creating an electrically actuated, flexible microfluidic valve. Samples of PDMS with various surface loadings of MWCNTs were prepared and tested using a uniaxial tension tester, combined with a four‐point probe electrical test. In contrast to other works reporting the inclusion of MWCNTs in the bulk of the material, we have found that inclusion of the MWCNTs on the surface only has no discernible effect on the mechanical properties of the PDMS samples, but causes a significant and repeatable change in the electrical performance. We have found that a loading of 4.16 g m^?2 results in an electrical resistivity of 7.31 × 10^?4 Ω cm, which is 200% lower than that previously reported for bulk inclusion samples. The microstructure of the MWCNTs was found to consist of both individual fibers and spherical clumps of fibers. We suggest that, due to the microstructure of the MWCNTs used in this study, the mechanical properties can be modeled as a thin layer of particulates, while the electrical properties can be modeled as a thin bed of bulk MWCNTs. © 2012 Society of Chemical Industry     

Synthesis of polystyrene-carbon nanofibers nanocomposite foams

In this study, the use of carbon nanofibers (CNFs) as nucleating agents to produce polystyrene nanocomposite foams was demonstrated. With the addition of CNFs, microcellular foams with uniform cell size distributions were obtained. Compared to nanoclay and single-walled carbon nanotubes (SWCNTs), CNFs exhibit substantially higher nucleation efficiency in the foaming process. The underlying mechanism is semi-quantitatively explained by the classical nucleation theory. The homogeneous fiber distribution and favorable surface and geometrical characteristics of CNFs make them ideal nucleating agents.     

Electrospun polymeric nanofibers for dental applications

Electrospinning is an economical, efficient, and versatile process for the preparation of continuous nanofibers with desired patterns, tailored fiber diameters, and orientations. Since its invention, electrospinning has been utilized to prepare nanofibers from several natural polymers and synthetic polymers for use as scaffolds in tissue engineering, regeneration, and biomedical applications. Furthermore, complex scaffolds were prepared by electrospinning complex polymer solutions formulated by blending natural and synthetic organic polymers with bioceramics and other inorganic molecules. Lately, coaxial electrospinning has emerged as a promising technology in the preparation of drug-loaded biodegradable core-shell structured micro/nanofibers for sustained drug delivery applications. This paper will discuss the basic mechanism of electrospinning, parameters governing the electrospinning process, various materials investigated for use in the electrospinning process, and its recent advances.     

静电纺丝制备纳米级纤维的研究

介绍了静电纺丝制备纳米纤维的原理及其影响因素,归纳、总结了当前国内外静电纺丝制备纳米纤维的研究内容,并对今后的研究提出了建议.