Preparation and characterization of electrospun polyurethane–polypyrrole nanofibers and films

Polyurethane (PU)–polypyrrole (PPy) composite films and nanofibers were successfully prepared for the purpose of combining the properties of PU and PPy. Pyrrole (Py) monomer was polymerized and dispersed uniformly throughout the PU matrix by means of oxidative polymerization with cerium(IV) [ceric ammonium nitrate Ce(IV)] in dimethylformamide. Films and nanofibers were prepared with this solution. The effects of the PPy content on the thermal, mechanical, dielectric, and morphological properties of the composites were investigated with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR)–attenuated total reflection (ATR) spectroscopy, dielectric spectrometry, and scanning electron microscopy. The Young's modulus and glass-transition temperatures of the composites exhibited an increasing trend with increases in the initially added amount of Py. The electrical conductivities of the composite films and nanofibers increased. The crystallinity of the composites were followed with DSC, the mechanical properties were followed with DMA, and the spectroscopic results were followed with FTIR–ATR spectroscopy. In the composite films, a new absorption band located at about 1650 cm⁻¹ appeared, and its intensity improved with the addition of Py. The studied composites show potential for promising applications in advanced electronic devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication and characterization of poly(ε-caprolactone)/gelatin nanofibrous scaffolds for retinal tissue engineering

Different ratios of poly(ε-caprolactone) (PCL) and gelatinwere used to fabricate scaffolds for regeneration of retinal pigment epithelium (RPE) layer. Physical and chemical characterizations were performed and the behavior of human RPE cells on the scaffolds was evaluated subsequently. An increase in gelatin content in the scaffold enhanced hydrophilicity, RPE cell attachment, proliferation, and spreading over PCL scaffolds. Granular and cytoplasmic expressions of RPE65 and Cytokeratin 8/18 markers confirmed the presence of RPE cells. It was believed that PCL/gelatin scaffolds could be used as substrates to replace RPE extracellular matrix to facilitate regeneration of RPE layer in retinal diseases.     

Superhydrophobic–superoleophilic electrospun nanofibrous membrane modified by the chemical vapor deposition of dimethyl dichlorosilane for efficient oil–water separation

Superhydrophobic and superoleophilic functionalized electrospun poly(vinylidene fluoride) (PVDF) membranes with water repellence, breathability, and oil-sorption and oil–water separation properties were achieved with a combination of an electrospinning technique and the chemical vapor deposition of dichlorodimethyl silane. The samples were laterally characterized by scanning electron microscopy, atomic force microscopy, water contact angle measurement, and Fourier transform infrared spectroscopy. The maximum water contact angle value was 152.0 ± 2.5° for the PVDF nanofibrous membranes with 500 μL of deposited silane (PMS2) obtained under certain conditions. The PMS2 membranes showed 100.0, 93.7, 23.3, 35.0, and 100.0% separation efficiencies for n-hexane, kerosene, crude oil, frying oil, and toluene, respectively. The understudy membrane exhibited reasonable waterproofness and remarkable breathability (water vapor transition rate = 215.21 g/m².h). Moreover, the superhydrophobic and superoleophilic nanofibrous membranes also showed good reusability, stability, moderate water-repellent properties, breathability, antifouling properties, and oil–water separation ability after several cycles. These properties confirmed potential in feasible applications, including protective cloths and in the purification of oil-polluted water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47621.     

Fabrication and characterization of biomorphic cellular C/SiC–ZrC composite ceramics from wood

Biomorphic cellular C/SiC–ZrC composite ceramics were fabricated from pine and oak wood precursors. Carbonaceous preforms were first prepared by wood pyrolysis and subsequently infiltrated with polyzirconobutanediol (PZC) and polycarbosilane (PCS) to form the composite ceramics. TGA/DTG and dilatometric analysis were used to study the pyrolysis of the wood precursor. XRD and SEM analyses were applied to characterize the microscopic properties of the resulting biomorphic cellular C/SiC–ZrC composite ceramics. Compared with oak, pine was preferable for preparation of cellular C/SiC–ZrC composite ceramics because of its unique microstructure. The SiC–ZrC phase distribution differed within the composite ceramics. In addition, the compression strengths of wood, charcoal, and cellular C/SiC–ZrC composite ceramics were measured in the axis direction. Results showed the improved compression strength of biomorphic cellular C/SiC–ZrC composite ceramics when the impregnation cycles were repeated.     

Preparation and characterization of Al2O3/TiC micro–nano-composite ceramic tool materials

An Al₂O₃-based composite ceramic tool material reinforced with micro-scale and nano-scale TiC particles was fabricated by a hot-pressing technology with cobalt additive in different sintering processes. The microstructure, indention cracks and phase composition of composites were characterized with scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The experimental results showed that Al₂O₃/TiC_μ/TiC_n micro–nano-composite containing 6 vol% nano-scale TiC and 35 vol% micro-scale TiC, which were sintered under a pressure of 32 MPa at a temperature of 1650 °C in vacuum for 20 min, had optimum mechanical properties. The addition of both nano-scale TiC and Co contributed to the microstructure evolution and the improvement of mechanical properties. Effects of nano-scale TiC on mechanical properties were investigated. The toughening and strengthening mechanisms of micro–nano-composites were discussed.     

Fabrication and characterization of anorthite–mullite–corundum porous ceramics from construction waste

In this work, anorthite–mullite–corundum porous ceramics were prepared from construction waste and Al₂O₃ powders by adding AlF₃ and MoO₃ as mineralizer and crystallization catalyst, respectively. The effects of the sintering temperature and time on open porosity, mechanical properties, pore size distribution, microstructure, and phase composition were characterized in detail. The results showed that the formation of the mullite whiskers and the properties of the anorthite–mullite–corundum porous ceramics depended more on the sintering temperature than the holding time. By co-adding 12 wt% AlF₃ and 4 wt% MoO₃, mullite whiskers were successfully obtained at sintering temperatures upon 1350 °C for 1 h. Furthermore, the resultant specimens exhibited excellent properties, including open porosity of 66.1±0.7%, biaxial flexural strength of 23.8±0.9 MPa, and average pore size of 1.32 µm (the corresponding cumulative volume percent was 37.29%).     

Fabrication and characterization of multiwalled carbon nanotube–loaded interconnected porous nanocomposite scaffolds

Novel nanocomposite porous scaffolds based on poly(?-caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were manufactured by a compression-molding/polymer-leaching approach utilizing cryomilling for homogeneous dispersion of nanotubes and blending of polymers. Addition of MWCNTs to PCL and PCL/polyglycolide (PGA) blends resulted in significant changes to scaffold morphology compared to control samples despite persistent interconnected porosity. Several structures exhibiting rough and nanotextured surfaces were observed. Mean pore sizes were in the range of ～3–5?µm. The nanocomposites presented good mechanical and water uptake properties. The results of this research provide significant insight into a strategy for producing nanocomposite scaffolds with interconnected porosity.     

Fabrication and characterization of poly(vinylidene fluoride)–polytetrafluoroethylene composite membrane for CO2 absorption in gas–liquid contacting process

The wetting resistance of poly(vinylidene fluoride) (PVDF) membrane is a critical factor which determines the carbon dioxide (CO₂) absorption performance of the gas–liquid membrane contactors. In this study, the composite PVDF–polytetrafluoroethylene (PTFE) hollow fiber membranes were fabricated through dry-jet wet phase-inversion method by dispersing PTFE nanoparticles into PVDF solution and adopting phosphoric acid as nonsolvent additive. Compared with the PVDF membrane, the composite membranes presented higher CO₂ absorption flux due to their higher effective surface porosity and surface hydrophobicity. The composite membrane with addition of 5 wt % PTFE in the dope gained the optimum CO₂ absorption flux of 9.84 × 10⁻⁴ and 2.02 × 10⁻³ mol m⁻² s⁻¹ at an inlet gas (CO₂/N₂ = 19/81, v/v) flow rate of 100 mL min⁻¹ by using distilled water and aqueous diethanolamine solution, respectively. Moreover, the 5% PTFE membrane showed better long-term stability than the PVDF membrane regardless of different types of absorbent, indicating that polymer blending demonstrates great potential for gas separation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47767.     

Fabrication of ultrafast temperature-responsive nanofibrous hydrogel with superelasticity and its 'on–off' switchable drug releasing capacity

The temperature-responsive bulky hydrogel with fast response rate and satisfactory mechanical property has fascinating application potential in many aspects, such as the implantable macroscale controlled drug release carrier for post-surgical therapy; however, creating such a smart hydrogel was proven extremely challenging. Here a novel type of temperature-responsive bulky hydrogel with ultrafast response rate and super compressible elasticity was fabricated by the fibrous freeze-shaping technique using shortened temperature-responsive polymer based electrospun hollow nanofibers as building blocks, followed by heat treatment for endowing the hydrogel with high stability in water. Because the hydrogel has hierarchical porous structure and its constituent nanofibers have hollow structure, which are beneficial to diffusion of its embodied water during temperature-induced volume phase transition, its temperature-response time is less than 30 s. In addition, the hierarchical porous structure benefits dissipation of the compression stress exerted on the hydrogel. Fluorescein isothiocyanate (FITC)-dextran as a model biomacromolecular drug, was loaded into the shells of the hollow nanofibers during coaxial electrospinning, and the ultimately obtained nanofibrous hydrogel can release its loaded FITC-dextran in a 'on–off' switchable fashion in response to temperature alternation between 15 and 47°C. Cell cytotoxicity test results demonstrate that the temperature-responsive nanofibrous hydrogel is biocompatible.     

Fabrication and characterization of nanoporous copper through chemical dealloying of cold-rolled and annealed Mn–Cu alloy

Journal of Porous Materials - This study investigated the effects of the manufacturing process on the microstructure of nanoporous copper (NPC) produced using cold-rolled Mn–30 at.% Cu and...     

Synthesis,characterization, and ionic conductivity of electrospun organic–inorganic hybrid gel electrolytes

In this work, we described the synthesis of organic–inorganic hybrid gel electrolytes combining electrospinning, sol–gel, and ultraviolet (UV) curing techniques in order to investigate their ionic conductivity properties. First, 3-glycidyloxypropyl trimethoxysilane modified polyamic acid and alkoxysilane functional poly(dimethyl siloxane) were electrospun together. Then, the following thermal imidization, the obtained fiber was cured in the UV curable gel formulation. To improve the interaction between fiber and gel matrix, 3-(trimethoxysilyl)propyl methacrylate was partly hydrolyzed and then used as a bifunctional crosslinker. Finally, the membrane was soaked into 0.5 M LiFP₆ salt solution to obtain organic–inorganic hybrid gel electrolytes. The chemical structure, ionic conductivity, and range of electrochemical stability window of the photocured nanocomposite electrolytes were investigated by using FTIR, thermogravimetric analysis, differential scanning calorimetry, electrochemical impedance spectroscopy, linear sweep voltammetry, and SEM analysis. The acquired results from experiments indicate that a convenient nanocomposite electrolyte for lithium-ion batteries with high electrolyte (Li salt) uptake, adequate conductivity (1.02 × 10⁻³ S cm⁻¹) at ambient temperature and electrochemically stable between 1 and 6 V had been prepared. POLYM. ENG. SCI., 60:619–629, 2020. © 2019 Society of Plastics Engineers     

Fabrication and characterization of sol–gel derived hydroxyapatite/zirconia composite nanopowders with various yttria contents

Homogeneous composite nanopowders of hydroxyapatite/30 wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8 mol% Y₂O₃ (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared nanopowders. Analyses of HA–YSZ composite nanopowders showed the successful formation of desirable phases. HA unit cell volume in the composites increased as a result of ion exchange of calcium and zirconium between HA and zirconia. Results revealed the formation of HA particles with irregular morphology (40–80 nm) and spherical yttria-stabilized zirconia particles (20–30 nm). Segregation of yttrium ions at the grain boundaries of ZrO₂ particles retarded the grain growth of zirconia particles and the presence of ZrO₂ nanoparticles among the hydroxyapatite particles resulted in grain growth inhibition of HA particles. This process can be used to synthesize HA–YSZ composite nanopowders with improved properties, which are much needed for hard tissue repair and biomedical applications.     

Preparation and characterization of polysulfone–cyclodextrin composite nanofiltration membrane: Solvent effect

α-Cyclodextrin membranes were prepared by the phase inversion method using four types of casting solvents such as N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc), and dimethyl formamide (DMF) herein-after termed as α-CD-NMP, α-CD-DMSO, α-CD-DMAc, and α-CD-DMF, respectively. The membranes were characterized by IR, XRD, TGA-DTA, DSC, and SEM analysis and show that solvents like NMP, DMA, DMF give good uniform morphological membranes and are better than that of DMSO. Thermal decompositions of the pure polymer and composite membranes indicate different range of thermal degradation of the membrane. This study reveals that the casting solvents NMP, DMF, DMAC have nearly same significant effect on morphology and other properties of the membranes. This is explained in terms of demixing behavior of the polymer and the combined effect of solvent volatility and polymer–solvent interactions as estimated from Hansen solubility parameter. Solvent hydrophobicity also affects the performance of the membrane and can be determined in terms of water permeability. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabrication of superhydrophobic electrospun polyimide nanofibers modified with polydopamine and polytetrafluoroethylene nanoparticles for oil–water separation

The oil–water separation technologies of removing oil pollutants from water in an efficient and economical way is a challenge. The current methods used for oil–water separation suffer many shortcomings, including a low separation efficiency, complex separation equipment, high operation costs, and secondary pollution. In this study, we fabricated a highly flexible, high-intensity, quite stable superhydrophobic and superoleophilic polyimide (PI) nanofibrous membranes, which are much more efficient and cost efficient for oil–water separation by modifying the membranes with a polydopamine (PDA) solution and polytetrafluoroethylene (PTFE) dispersion. The fabricated membrane (PDA–PTFE–PI) possesses both the high tensile stress of PI and the superhydrophobic and superlipophilic properties of the PDA–PTFE coating. The modified membrane could separate various oil–water mixtures efficiently at a high flux (6000 L·m⁻²·h⁻¹) and an extremely high efficiency (>99%). Furthermore, even when the membrane was under an extremely hostile environment (with an ultrahigh temperature, strong acidity, or strong basicity), it still remained quickly stable with a good separation efficiency and recyclability after 10 cycles. We anticipate that our study will provide a new technology for the highly efficient mass production of oil–water mixture management. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47638.     

Preparation and properties of core–shell silver/polyimide nanocomposites

A new series of core–shell structured silver/polyimide (PI) nanocomposites was prepared by in situ polymerization followed by the chemical imidization of poly(amic acid) (PAA, precursor of PI) at a low temperature. The TEM images showed that the silver cores of the nanocomposites were encapsulated with homogeneous shells with thickness of 4 and 8 nm at silver contents of 90 and 60 %, respectively. The shell thickness was controlled by varying the content of PAA. FTIR spectroscopic analysis indicated that the imide ring formation occurred after the chemical imidization. The Ag/PI nanocomposites showed excellent thermal stability and exhibited only 10 % weight loss at 300 °C in the air. Moreover, percolation was observed at silver weight fractions close to the critical value, and the maximum dielectric permittivity of the nanocomposites was 120, which is about 40 times higher than that of pristine PI.     

Fabrication of multifunctional TiO2–fly ash/polyurethane nanocomposite membrane via electrospinning

In this study, we demonstrate the fabrication of multifunctional composite polyurethane (PU) membrane from a sol gel system containing TiO₂ and fly ash (FA) nanoparticles (NPs). The adsorptive property of FA and photocatalytic property of TiO₂ can introduce different functionalities on PU mat for water purification. Different types of PU nanofiber mats were prepared by varying the composition of NPs in blend solution. FE-SEM, TEM, TGA, XRD, UV–visible spectra, and water contact angle measurement confirmed the incorporation of FA and TiO₂ NPs on/into PU nanofibrous mat. The influence of NPs on PU membrane was evaluated from the adsorption of heavy metals (Hg, Pb), removal of dyes (methylene blue), antibacterial activity, and water flux. The improvement of all these activities is attributed to the adsorptive property of FA and photocatalytic/hydrophilic property of TiO₂ NPs. Therefore, as-synthesized composite membrane can be utilized as an economically friendly filter media for water purification.     

Cellulose acetate–silica fume membrane: characterization and application for separation of starch and maltose

Maltose is one of the starch derivatives. Maltose can be produced by starch hydrolysis using any kind of hydrolytic process. One of the methods to separate a mixture of both compounds is using porous membrane. In this research, a novel type of hybrid membrane was prepared from a mixture of cellulose acetate and silica fume. Silica fume is widely used in the domain of construction as cement material, whereas in this research silica fume was successfully used as membrane material. Various compositions of membrane dope solutions were prepared for obtaining the membranes used for separation of starch and maltose. Such synthesized membranes demonstrate a good performance in separation processes. The best performance is achieved when the composition of cellulose acetate in membrane dope solution is 15 % (w/w) in N,N-dimethylacetamide solvent and the mass ratio between cellulose acetate and silica fume is 4:1. For this composition, the rejection of membranes towards starch and maltose is 87 and 2 %, respectively, at working pressure of 3 bar and compaction time of 2 h. Infrared spectrum indicates no new peaks are found compared to raw materials’ spectral peaks. Thus, it can be concluded that the interaction between the cellulose acetate and silica fume is merely a physical type. From the observation of cross-sectional SEM images, we can remark that the morphology of such a membrane is porous. X-ray diffractogram indicates that the synthesized membranes are amorphous.     

Fabrication of oriented electrospun cellulose nanocrystals–polystyrene composite fibers on a rotating drum

Nitrobenzene (CNC-1), trifluoromethyl benzene (CNC-2) modified and polystyrene-grafted (CNC-g) cellulose nanocrystals in polystyrene (PS)-N,N dimethylformamide (DMF) solutions were electrospun and collected as stretched and aligned fibers on a rotating drum. Scanning electron microscope pictures showed significant alignment in the case of unmodified and nitrobenzene-modified CNC-1/PS nanocomposite fibers once the linear speed of rotor reached to 15 m s⁻¹. Fiber diameter decrease was more strong with rotor speed increase in the case of trifluoromethyl benzene modified (CNC-2) and polystyrene-grafted (CNC-g) cellulose nanocrystals/PS systems. Dynamic mechanical analysis including storage and elastic modulus of electrospun-oriented fibers were performed on surface-modified and polymer-grafted CNC/PS samples. According to α transition peak, the increase in the glass-transition temperature with filler concentration was the highest in polymer-grafted CNC-g/PS composite fibers. It was due to the interpenetration of grafted polymer brushes and free polymer chains in continuous phase and resulted in restrictions of motions of polymer chains in the PS matrix. The elastic moduli of nitrobenzene (CNC-1) and trifluoromethyl benzene (CNC-2)-modified CNC-filled PS composite fibers agreed well with percolation model, which indicates the CNC–CNC interactions and network formation with an increase in concentration. Magnitude of the elastic modulus of polymer grafted CNC-g at 0.33 vol % in PS was significantly higher than the prediction from percolation theory. It was due the immobilized polymer chains around CNC-g particles. However, grafted polymer chains, at higher CNC concentrations acted like stickers among CNC particles and caused CNC agglomerates with entrapped free polystyrene from the matrix, thus caused a decrease in the elastic modulus. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48942.     

Investigating the wicking behavior of micro/nanofibrous core-sheath PET–PAN yarn modified by dimethyl 5-sodium sulfoisophthalate

The present research aims at imparting an improved wicking ability to the recycled multifilament yarns by wrapping composite nanofibers to attain an efficient material for filtration purposes. Therefore, polyacrylonitrile nanofibers containing dimethyl 5-sodium sulfoisophthalate nanoparticles were wrapped around the recycled poly(ethylene terephthalate) yarn by means of a novel electrospinning technique. Several tests were performed to investigate the parameters affecting wicking rise and moisture regain of the samples. Taguchi method was used in two separate designs (with or without nanoparticles). Some factors such as polymer solution concentration, mass ratio of nanoparticles, take-up rate, and number of filaments were considered as the variable factors while yarn wicking rate and moisture regain were the response factors. It was found that the hydrophilic nature of nanoparticles together with the ultrafine structure of nanofibers provide yarns with enhanced wicking properties. Although solution concentration is the predominant factor in wicking rate of the yarns containing nanoparticles, the most effective factor in wicking rise and moisture regain for other cases is the number of filaments. The mechanism of nanoparticle effect on fluidic jet during electrospinning process is explained by theory of nanofluids stability which has never been validated experimentally in previous research studies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48185.     

Synthesis and characterization of facile industrially scalable and cost effective WO3 micro–nanostructures for electrochromic devices and photocatalyst

A novel strategy for the synthesis of tungsten trioxide (WO₃) micro–nanostructures by thermal annealing of tungsten powder under ambient conditions is reported. The as–synthesized WO₃ samples are thoroughly characterized using powder X–ray diffraction, X–ray photoelectron spectroscopy, transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) measurement. The TEM results show that the size of highly crystalline WO₃ particles can be tuned from micro to nano by simply varying the annealing temperatures. The BET results demonstrate that the surface area and pore size of the synthesized WO₃ decreases with increasing annealing temperatures. Furthermore, the WO₃ synthesized at 550?°C (WO–550) exhibits not only higher surface area and pore size, but also excellent photocatalytic activity as well as super hydrophilicity compared to the other prepared and commercially available WO₃. However, among the synthesized WO₃ particles, only WO–550 exhibits moderate electrochromic properties. Our strategy is facile, cheap, rapid, and highly reproducible for large–scale production, and the use of toxic precursors or additional capping agents is also eliminated. We believe that the synthesis of WO₃ by our method could have various practical industrial applications, and yield an excellent alternative to commercial WO₃.