Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers

Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp² bonding between carbon atoms.     

Processing of continuous poly(amide‐imide) nanofibers by electrospinning

Continuous poly(amide‐imide) nanofibers were fabricated using a novel electrospinning method with rotating and re‐collecting cylindrical collectors. The nanofilaments were modified using various post‐treatments, i.e. glycerol treatment and thermal imidization under tension, for possible application as high‐performance reinforcements. Morphological and mechanical properties of continuous poly(amide‐imide) nanofibers prepared by the electrospinning process and various post‐treatments were measured. Severe adhesion between individual nanofibers within fiber bundles was inhibited through surface treatment of the electrospun nanofiber bundles by spraying with glycerol. The morphological and mechanical properties of the continuous poly(amide‐imide) nanofibers and thermal stability were improved using thermal imidization at high temperature under tension. The morphological and mechanical properties of the continuous electrospun nanofibers were improved significantly by post‐treatments after electrospinning because uniform and complete thermal imidization occurred through the core region of the nanofibers. Copyright © 2009 Society of Chemical Industry     

Electrospun Nanofibers: Materials,Synthesis Parameters,and Their Role in Sensing Applications

Since the last decade, electrospinning is garnering more attention in the scientific research community, industries, applications like sensing (glucose, H₂O₂, dopamine, ascorbic acid, uric acid, neurotransmitter, etc.), biomedical applications (wound dressing, wound healing, skin, nerve, bone tissue engineering, and drug delivery systems), water treatment, energy harvesting, and storage applications. This review paper provides a brief overview of the electrospinning method, history of the electrospinning, factors affecting the electrospun nanofibers, and their morphology with different materials and composites (metals, metal oxides, 2D material, polymers and copolymers, carbon-based materials, etc.) used in the electrospinning technique with optical spinning parameters. Moreover, this paper deliberates the application of electrospun nanofibers and fibrous mats for sensing (electrochemical, optical, fluorescence, colorimetric, mechanical, photoelectric, mass sensitive change, resistive, ultrasensitive, etc.) in most illustrative representations. In the end, the challenges, opportunities of the electrospun nanofibers, and new direction for future progress are also discussed.     

Polymeric nanofibers containing solid nanoparticles prepared by electrospinning and their applications

Generally, polymer solution or sol–gel is used to produce electrospun nanofibers via the electrospinning technique. In the utilized sol–gel, the metallic precursor should be soluble in a proper solvent since it has to hydrolyze and polycondensate in the final solution; this strategy straitens the applications of the electrospinning process and limits the category of the electrospinnable materials. In this study, we are discussing electrospinning of a colloidal solution process as an alternative strategy. We have utilized many solid nanopowders and different polymers as well. All the examined colloids have been successfully electrospun. According to the SEM and FE SEM analyses for the obtained nanofiber mats, the polymeric nanofibers could imprison the small nanoparticles; however, the big size ones were observed attaching the nanofiber mats. Successfully, the proposed strategy could be exploited to prepare polymeric nanofibers incorporating metal nanoparticles which might have interesting properties compared with the pristine. For instance, PCL/Ti nanofiber mats exhibited good bioactivity compared with pristine PCL. The proposed strategy can be considered as an innovated methodology to prepare a new class of the electrospun nanofiber mats which cannot be obtained by the conventional electrospinning technique.     

Electrospinning of Polymers,Their Modeling and Applications

Although there are several methods for obtaining sub-micro or nanofibers, electrospinning is perhaps the most versatile process. Nanotechnology has been widely accepted as dealing with the science and technology where at least one dimension is of roughly 1 to 100 nm. Electrospinning has been recognized as a feasible technique for the fabrication of polymeric nanofiber yarns. Various materials including polymers, composites, ceramics and metals have been electrospun into nanofibers. The nanofibers thus produced exhibit novel and significantly improved physical, chemical and biological properties due to their nanolevel size. In this article, the electrospinning process, along with its modeling equations and applications have been discussed. Some typical case studies regarding electrospinning under various categories have also been discussed.     

Polymer-based composites by electrospinning: Preparation & functionalization with nanocarbons

Electrospinning is a straightforward yet versatile technique for the preparation of polymeric nanofibers with diameters in the range of nanometers to micrometers, and has been rapidly developed in the last two decades. Nanocarbon materials, usually referring to carbon nanotubes, graphene, and fullerenes with their derivatives including quantum dots, nanofibers, and nanoribbons, have received increasing attention due to their unique structural characteristics and outstanding physico-chemical properties. Incorporation of nanocarbons in electrospun polymeric fibers has been used to increase the functionality of fibers, for example, to improve the mechanical, electrical, and thermal properties, as well as confer biofunctionality as scaffolds in tissue engineering and sensors, when the advantageous properties given by the encapsulated materials are transferred to the fibers. In this review, we provide an overview of polymer-based composites reinforced with nanocarbons via the electrospinning technique. After a brief introduction of various types of nanocarbons, we summarize the latest progress of the design and fabrication of electrospun polymeric nanofibers with nanocarbon fillers. With regard to the preparation of composites, we focus on functionalization strategies of nanocarbons and the production of random & aligned polymeric nanocomposites. Then, the physical properties such as mechanical, electrical, and thermal properties are also reviewed for electrospun nanocomposite nanofibers reinforced with nanocarbons, especially carbon nanotubes. Benefiting from the exceptional properties including superior electric conductivity, high porosities, unique mat structure, etc. the polymeric composite nanofibers have demonstrated numerous advantages and promising properties in the fields of tissue engineering and sensors. In the application section, we will give state-of-the-art examples to demonstrate the advantages of electrospun polymer-based nanocomposites. Finally, the conclusion and challenge of the polymer-based nanocomposites are also presented. We believe the efforts made in this review would promote the understanding of the methods of preparation and unique physical and chemical properties of nanocarbon reinforced polymer-based nanocomposites.     

Electrospinning of nanofibers from non-polymeric systems: polymer-free nanofibers from cyclodextrin derivatives

High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.     

电纺纳米纤维取向对其特性的影响

传统静电纺丝技术制备的纳米纤维在收集装置中随机排列，取向度较低，性能较弱，限制了其应用。通过改进收集装置可获得有序排列的取向纳米纤维，取向纳米纤维在组织工程、传感器、增强材料和能源等领域具有极大地应用潜力，得到研究工作者们的广泛关注。制备高性能、低成本的纳米纤维材料已成为目前的研究目标和趋势。通过增加纤维取向度，纳米纤维分别在导电性能、压电性能、热稳定性、力学性能和光学性能上得到增强。指出借助纤维的取向，促使复合纳米纤维材料的性能改善及其在材料领域的应用。总结取向纳米纤维的特性优于随机排列纳米纤维的原理。     

Nanofibrous nonwovens based on dendritic‐linear‐dendritic poly(ethylene glycol) hybrids

Dendritic‐linear‐dendritic (DLD) hybrids are highly functional materials combining the properties of linear and dendritic polymers. Attempts to electrospin DLD polymers composed of hyperbranched dendritic blocks of 2,2‐bis(hydroxymethyl) propionic acid on a linear poly(ethylene glycol) core proved unsuccessful. Nevertheless, when these DLD hybrids were blended with an array of different biodegradable polymers as entanglement enhancers, nanofibrous nonwovens were successfully prepared by electrospinning. The pseudogeneration degree of the DLDs, the nature of the co‐electrospun polymer and the solvent systems used for the preparation of the electrospinning solutions exerted a significant effect on the diameter and morphology of the electrospun fibers. It is worth‐noting that aqueous solutions of the DLD polymers and only 1% (w/v) poly(ethylene oxide) resulted in the production of smoother and thinner nanofibers. Such dendritic nanofibrous scaffolds can be promising materials for biomedical applications due to their biocompatibility, biodegradability, multifunctionality, and advanced structural architecture. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45949.     

静电纺丝法制备碳纳米纤维及其应用

碳纳米纤维由于因其比表面积大、导电和导热性好,被广泛用于催化剂载体、吸附和储能材料。静电纺丝是制备一维纳米纤维直接、有效的方法,在介绍静电纺丝的基本原理和工艺影响因素的基础上,综述了电纺碳纳米纤维的特性及其应用。     

静电纺丝技术及其应用

静电纺丝是一种新技术,它可制备出直径为纳米级的丝,最小直径可至1纳米。介绍了电纺丝制备原理、设备、影响纤维性能的主要工艺参数,综述了静电纺丝技术应用的最新进展,如制备长度无限可控的微米／纳米管子、超净纳米过滤材料等。     

Avoiding fusion of electrospun 3,3′,4,4′-biphenyltetracarboxylic dianhydride-4,4′-oxydianiline copolymer nanofibers during conversion to polyimide

Man-made high-performance fibers produced a revolution in structural materials in the twentieth century. Fiber properties are known to increase with the decrease of their diameters. Ultrafine sub-micron and nanometer-sized fibers attract rapidly growing interest due to their unique advantages for diverse applications. Electrospinning is a straightforward low-cost top-down nanomanufacturing technique producing continuous nanofibers. Electrospinning allows direct fabrication of macroscopic nanofilamentary assemblies for structural and functional applications. Recently, high-performance polyimide nanofibers have been produced by electrospinning of polyamic acid precursors followed by thermal curing. However, curing resulted in fusion of nanofilaments at contacts. While fusion might be beneficial for some applications, it usually results in deterioration of the ordered molecular structure and mechanical properties of fibers in bundles and tows. In this report, we investigated the effect of residual solvent dimethylacetamide (DMAc) on the fusion of nanofibers in electrospun nanofiber bundles during thermal curing of polyimide. Feasibility of removal of the residual DMAc by aging in vacuum and by washing with other solvents was explored. The effect of an additive, dodecylethyldimethylammonium chloride (DEDAC) on fusion was investigated. It was found that the removal of residual DMAc by aging in vacuum reduced the nanofilament fusion during imidization. The presence of DEDAC in the absence of DMAc was shown to further reduce the fusion. DEDAC may represent a new class of additives with a potential to preserve nanostructure of polyamic acid precursors during thermal conversion to polyimides. The results of this report can be used in the development of ultrahigh-performance nanofilamentary fibers.     

Recent advances in mechanism,influencing parameters,and dopants of electrospun EMI shielding composites: A review

The rapid development and popularization of smart and portable electronic devices have led to increasingly related electromagnetic pollution affecting human health and equipment safety. Thus, designing high-performance electromagnetic interference (EMI) shielding materials with lightweight, flexible, and easy preparation is urgent. The intrinsic physiochemical properties of electrospun micro/nanofibers provide an attractive potential to ease and accelerate the next-generation EMI shielding materials. Here, a detailed review of the electrospun EMI shielding materials is established. First, this article outlines the shielding mechanism of EMI shielding materials obtained via electrospinning. Then, the affecting factors of electrospinning process conditions on the resulting EMI shielding micro/nanofibers are discussed. Next, diverse fillers that contribute to the EMI shielding efficiency of electrospun materials are demonstrated. Finally, the conclusion and prospects are introduced, hopefully contributing to assisting with more comprehensive and rational designs of high-performance electrospun fiber-based EMI shielding for various applications. Priority measures and future directions are suggested for the future development of electrospun EMI shielding materials.     

Effect of organic solvent on morphology and mechanical properties of electrospun syndiotactic polypropylene nanofibers

We study the stress–strain behaviors of the electrospun sPP single nanofibers as well as nonwoven mats, which were electrospun from sPP solutions using two different solvents (decalin and cyclohexane) by electrospinning. The effects of organic solvents were explored on the morphologies and the mechanical properties of the corresponding electrospun sPP single nanofibers and nonwoven mats. It was found that the nature of organic solvents dramatically affected the surface morphologies, the circular and looping deposition of the electrospun sPP fibers, and the mechanical properties. The tensile strength of both electrospun sPP single nanofibers and nonwoven mats prepared from decalin-base solution was stronger than that of cyclohexane-base solution.     

静电纺丝法制备醋酯纳米纤维的最新研究进展

采用静电纺丝法制备醋酯纳米纤维,既可以保留醋酯纤维的耐化学性和可生物降解性等优点,又具有纳米材料的高比表面积、高孔隙率和量子效应。综述了近几年国内外静电纺丝法制备纳米级醋酯纤维的最新研究进展,系统介绍了几种新型纳米纤维结构的制备方法、原理及影响因素,同时对醋酯纳米纤维在吸附过滤方面的应用研究状况进行了概述,最后对静电纺丝法制备醋酯纤维的发展前景进行了展望。     

Antibacterial ciprofloxacin HCl incorporated polyurethane composite nanofibers via electrospinning for biomedical applications

We report on the preparation and characterization of polyurethane (PU) composite nanofibers by electrospinning. Two different approaches were adopted to obtain the PU composite nanofibers. In the first approach, a homogeneous solution of 10 wt% PU containing ciprofloxacin HCl (CipHCl) drug was electrospun to obtain PU/Drug composite nanofibers. And in the second approach, the PU with ciprofloxacin HCl drug and ceramic hydroxyapatite (HA) particles were electrospun to obtain the PU/Drug and PU/Drug/HA composite nanofibers. The surface morphology, structure, bonding configuration, optical and thermal properties of the resultant products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The antibacterial activity was tested against common food borne pathogenic bacteria, namely, Staphylococcus aureus, Escherichia coli by the minimum inhibitory concentration (MIC) method. Our result results demonstrate that these composite nanofibers possess superior characteristics which can utilized for variety of applications.     

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.     

Poly(ε-caprolactone)/poly(m-anthranilic acid) and poly(ε-caprolactone)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) electrospun nanofibers: Characterization,antioxidant, and electrochemical properties

Conducting polymers are widely used in many biomedical applications, but their non-degradability and non-biocompatibility limit their widespread use in applications. For this reason, many studies have been carried out on the developing degradable, biocompatible, and electrically conductive polymers. In this study, mixtures of conductive polymers (poly(m-antranilic acid) (P3ANA) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)) with biocompatible and biodegradable poly(ε-caprolactone) (PCL) were prepared. Their nanofibers were obtained by electrospinning and their antioxidant properties were investigated by 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and copper ion reducing antioxidant capacity (CUPRAC) assays. Electrochemical properties were also investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The highest antioxidant activity was obtained from PCL/P3ANA3 electrospun nanofiber containing 10% (of PCL w/w) P3ANA with 93 and 614 μg TE/mg values for ABTS and CUPRAC assays, respectively. This nanofiber was found to be non-toxic according to 2,5-diphenyl-2H-tetrazolium bromide (MTT) analysis. PCL/PEDOT:PSS electrospun nanofiber has the highest maximum anodic current value of 0.08 mA. The maximum anodic current value of PCL/P3ANA3 nanofiber with the highest amount of P3ANA is also higher than other PCL/P3ANA nanofibers. These nanofibers were characterized by FT-IR, UV–vis., XRD and TGA and their surface morphologies were examined by scanning electron microscopy (SEM).     

Synthesis and morphology optimization of electrospun SiBNC nanofibers

SiBNC nanofibers were synthesized through the polymeric route by a one-pot synthesis approach. DMTA (dichloroboryl methyl trichlorosilyl amine) polymer was selected as pre-ceramic for SiBNC, which was shaped into nanofibers by electrospinning. Then, the nanofibers were cured in an inert atmosphere in order to obtain the final ceramic. By changing the curing atmosphere, the compound of final ceramic has been manipulated. In addition, the ceramic yield of DMTA as a preceramic was increased in the nitrogen atmosphere. The effects of applied voltage, solution concentration, and feeding rate on the morphology of final electrospun ceramic nanofibers were also investigated. Final ceramic remains amorphous up to elevated temperatures with outstanding mechanical and thermal properties.     

Synthesis of hydroxyapatite fibers using electrospinning: A study of phase evolution based on polymer matrix

Hydroxyapatite (HA) is considered as the most promising biomaterial candidate to replace and regenerate hard tissues. A small amount of β-tricalcium phosphate (β-TCP) phase is advantageous for rapid bonding of the artificial bones to natural ones due to its high solubility compared to hydroxyapatite. Synthesizing HA nanofibers from electrospinning of sol-gel is considered as a widely researched topic. Motivation of the current work was to investigate the influence of polymeric binder in the final phase evolution after heat treatment of electrospun nanofibers. Calcium phosphate nanofibers were fabricated by electrospinning sols using gelatine and polyvinylpyrrolidone as carrier polymers and subjected to heat treatment. It was realized that carrier polymers facilitate preferential calcium phosphate phase formation by forming hydroxyapatite as major phase while PVP was used and β-TCP with HA as secondary phase while gelatine was employed. XRD and thermal analyses were performed to ascertain the reason behind this interesting behaviour.