To endow nanofibers with the desirable antibacterial and mechanical properties, a facile strategy using Pickering emulsion (PE) electrospinning is proposed to prepare functional nanofibers with core/shell structure for the first time. The water‐in‐oil (W/O) Pickering emulsion stabilized by oleic acid (OA)‐coated magnetite iron oxide nanoparticles (OA‐MIONs) is comprised of aqueous vancomycin hydrochloride (Van) solution and poly(lactic acid) (PLA) solution. The core/shell structure of the electrospun Van/OA‐MIONs‐PLA nanofibers is confirmed by scanning electron microscopy and transmission electron microscopy observation. Sustained release of Van from the PE electrospun nanofiber membrane is achieved within the time of 600 h. Compared with the neat PLA electrospun nanofiber membrane, 57% increase of tensile strength and 36% elevation of elongation at break are achieved on PE electrospun nanofiber membrane. In addition, the PE electrospun nanofiber membrane demonstrates excellent antibacterial property stemming from the combinational antibacterial activities of OA‐MIONs and Van. The Van‐loaded PE electrospinning nanofibers with sustained antibacterial performance possess potential applications in tissue engineering and drug delivery.
Polymer‐based electrospun fibers have been intensively studied as antimicrobial membranes, drug carriers, and energetic materials. Inorganic fillers or small molecules have been routinely added into polymer matrices in order to enhance product functions. However, the electrospinning process is kinetically controlled and solvent rapidly evaporates due to the large surface‐to‐volume ratio of spinning liquid jet. When electrospinning a multicomponent system, complex phase behavior may occur and give rise to interesting internal structures of resulting products. Such kinetically driven phenomena deserve more attention for optimizing product performance. Here, electrospun poly(ε‐caprolactone)(PCL)/aminopropyl‐heptaisobutyl‐polyhedral oligomeric silsesquioxane (AMPOSS) fibers with AMPOSS content up to 30 wt% are studied as a model system to understand the impact of kinetically controlled phase separation on the fibers' internal structure, properties, and thermal stability. With sufficient AMPOSS loading, the hybrid fibers are found to have an AMPOSS‐shell/PCL‐core structure. The thermal stability of the as‐spun PCL/AMPOSS fibers is therefore greatly enhanced.
Electrospun functionalized polyacrylonitrile grafted glycidyl methacrylate (PAN‐g‐GMA) nanofibers are incorporated between the plies of a conventional carbon fiber/epoxy composite to improve the composite's mechanical performance. Glycidyl methacrylate (GMA) is successfully grafted onto polyacrylonitrile (PAN) polymer powder via a free radical mechanism. Characterization of the electrospun PAN and PAN‐g‐GMA nanofibers indicates that the grafting of GMA does not significantly alter the tensile properties of the PAN nanofibers but results in an increase in the diameter of nanofibers. Statistical analysis of the mechanical characterization studies on PAN‐carbon/epoxy hybrid composites conclusively shows that the composite reinforced with functionalized PAN nanofibers has greater mechanical properties than that of both the neat PAN nanofiber enriched hybrid composite and control composite (without nanofibers). The improved performance is attributed to the grafted glycidyl groups on PAN, leading to stronger interactions between the nanofibers and the epoxy matrix. PAN‐g‐GMA nanofiber reinforced composite outperforms their neat PAN counterparts in tensile strength, short beam shear strength, flexural strength, and Izod impact energy absorption by 8%, 9%, 6%, and 8%, respectively. Compared to the control composite, the improvements resulting from the PAN‐g‐GMA nanofiber incorporation are even more pronounced at 28%, 41%, 32%, and 21% in the corresponding tests, respectively.
Assembly of anisotropic nanoparticles on polymeric templates has attracted much attention recently because of the potential useful applications. In this work, 3D electrospun nanofiber membrane is used as template for the assembly of ex situ synthesized palladium nanocubes. The assembly process is achieved by simple immersion step, in which the electrostatic assembly of the nanocubes occurs. The dense nanocubes on the nanofibers as well as the fibrous nanostructure render the nanocomposite membrane excellent catalytic activity. Moreover, the catalytic membrane can be recycled for at least six times, which makes it possible for practical usage.
3D aligned electrospun fibers hold a promising potential in a wide range of biomedical areas, including biosensors, controlled drug release, tissue engineering, etc. Thus, a cost‐effective and easy way to scale‐up fabrication for 3D aligned nanofibers is highly desired. Herein, a novel yet facile preparation process of 3D aligned nanofibers (3D AFs) by an improved electrospinning technique is reported. The obtained 3D AFs show enhanced controllability on morphology and fiber density, and thus facilitate adhesion and growth of human mesenchymal stem cells within their 3D nanofiber microarchitectures, leading to an excellent in vitro biocompatibility. Moreover, the 3D AFs with aligned morphology can enhance the neuron activities and induce directional cell growth along the direction of nanofiber orientation, thereby providing an excellent cue for the anchorage and migration dependent neurons. Combined with controllable morphology and structure, it is anticipated that this finding can lead to great applications of electrospun fibers in nerve tissue engineering, diagnostics, and other biomedical fields.
This paper presents for the first time that poly(l ‐lactic acid) (PLLA) nanofibers can show the piezoelectricity along the fiber direction (d33) by using an electrospinning method. First, the electrospun fiber bundles are characterized by scanning electron microscope, X‐ray, and piezoelectric coefficient measurements. The data show that the supercritical CO2 treatment can greatly enhance the piezoelectricity of electrospun PLLA fibers, which can be resulting from the increased crystallinity of the fibers. Later, it is found that the electrospun PLLA fiber can generate a current of 8 pA and a voltage of 20 mV by a simple push–release process. Further, a single PLLA fiber‐based blood pulse sensor is also fabricated and tested and shows around a 2 pA output for blood pulse. Due to easy fabrication and relatively simple structure, this device enables a broad range of promising future applications in the medical sensor area.
Supramolecular nanofibers have a great potential to be used as gelating agents, polymer additives, and fibrous material for filtration purposes. To meet the requirements for practical and industrial applications on a large scale, e.g., production of filter media, it is desirable to develop supramolecular systems processable from environmentally friendly water‐based solvent mixtures. Moreover, assessing processing parameters to control the micro‐ and nanofiber diameter is of vital importance. Therefore, an alkoxy‐substituted 1,3,5‐benzenetrisamide, N,N′,N″‐tris(1‐(methoxymethyl)propyl)benzene‐1,3,5‐tricarboxamide is designed that can be self‐assembled into supramolecular nanofibers upon cooling from a water/isopropanol solvent mixture. It is demonstrated that parameters such as stirring velocity and the temperature range during processing allow for a precise adjustment of the cooling profile which in turn enables the control of the supramolecular nanofiber diameters.
Three different dopants are used to fabricate electrospun dopants/polystyrene (dopants/PS) composite fibers from PS solution and PS sol. The relative humidity and the influence of the dopants on the morphologies, diameter, porous structures, and dopant distribution of electrospun PS fibers are investigated. Compared to those obtained from PS solution, electrospun dopants/PS composite fibers from PS sol with hollow‐porous and multichannel hollow‐porous structures present significant advantages due to the multi‐stage degree of interfacial structure and diversity of the internal environment. In comparison to coaxial electrospun PS fibers, the electrospun dopants/PS composite fibers from PS sol obtained in one step have an improved yield and a simplified technological process simultaneously, leading to significant competitiveness in fields such as catalysis, fluidics gas storage, and sensing.
Curdlan (β‐1,3 glucan) (7 wt%) with polyvinyl alcohol (PVA) (10 wt%) is blended at 1:2 weight ratio and electrospun to get nanofibers and is crosslinked with glutaraldehyde vapor to make it insoluble in water. It has a fiber diameter of less than 100 nm and is hydrophilic (contact angle = 35°). It is biodegradable (10% in 14 d) and also has a good swelling behavior (≈170%). More than 100% of L6 cells are viable on this scaffold after 3 d. The scanning electron microscope images also reveal that cells are able to attach and spread in the nanofibrous scaffolds. In vitro scratch assay indicates that the wound closure rate of curdlan/PVA scaffold is better than PVA scaffold probably due to the immunomodulatory properties of the biopolymer. Thus our results indicate that curdlan/PVA scaffold can be an ideal material for wound healing applications.
Proton exchange membranes for fuel cell applications are synthesized by surface‐initiated (SI) atom transfer radical polymerization (ATRP). Poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) is electrospun into 50 µm thick mat, which is then employed as multifunctional initiator for copper‐mediated SI ATRP of 4‐styrene sulfonic acid sodium salt. Fine‐tuning of the ATRP conditions allows adjustment of the membrane's ion exchange capacity by varying the loading of the grafted ionomer. Structure and composition of the membranes are investigated by spectroscopic means and thermogravimetric analysis, respectively. The membrane morphology is probed by scanning electron microscopy. A membrane with proton conductivity as high as 100 mS cm−1 is obtained. Long‐term durability study in direct methanol fuel cells is conducted for over 1500 h demonstrating the viability of this novel facile approach.
The construction of high‐quality 3D polymeric photonic crystal (PC) films featuring fascinating tunable optical properties in a facile and time‐efficient way remains a major concern. Herein, the rapid assembly of highly crystallized brilliant flexible 3D polymeric PC films and their application for multiresponsive colorimetric sensing are demonstrated. Monochromatic PC films with remarkably distinct structural color, narrow half‐band width (27 nm), and broad tunability of band‐gaps (from blue to red) are generated within seconds from highly concentrated and charged colloids (51 vol%, ?57.6 mV) embedded in poly(N‐isopropylacrylamide) matrix. A repulsion‐induced precipitation assembly is found to be responsible for the ultrafast formation of close‐packed PC colloidal arrays. Besides, the resultant PC films exhibit ultrasensitive and fast response to external stimuli, revealed by interesting droplet diffusion experiments. Thus these PC films can serve as efficient colorimetric sensing materials to visually determine diverse species including trace ionic strength (2.9 ppm), minor surfactant (1 × 10?3m ), alcohol, and pH variation (1.0–13.9).
Conductive textiles with exceptional electrical properties have been prepared by coating the conjugated polymer, poly(3,4‐ethylenedioxyphiophene)‐polystyrenesulfonate(PEDOT‐PSS), on polyethylene terephthalate (PET) nonwoven fabrics. Phase segregation from covalent bond formation to surface silica particles generates PEDOT‐PSS coated textiles that hold potential for wearable electronics due to the breathability of the fabric, low toxicity, easy processing and lightweight with high current carrying capacity. The conductive textiles were demonstrated for applications such as electrical connections and resistive heating.
A novel high purity dual‐functional epoxy monomer, diglycidyl ether of 4,4′‐diallyl‐bisphenol‐A, is deliberately designed for the construction of a fishbone‐shaped heterochain polymer by polymerizing it with the methyl phenyl polysiloxane. Their curing reactions with Jeffamine D230 are investigated. The cured fishbone‐shaped heterochain polymer presents a wide transition range spanning over 120 °C with a peak half‐width of 62 °C. In contrast to the traditional epoxy/polysiloxane materials, the cured fishbone‐shaped heterochain polymer takes full advantage of the cooperative effect of epoxy and polysiloxane exhibiting excellent damping properties (tan δ > 0.3) at temperatures near the T g of the polysiloxane. This outstanding low‐temperature damping performance can be ascribed to the fishbone‐shaped structure of the heterochain polymer. These results provide new approach to explore high damping materials used at extremely low temperature (−125 °C).
Polystyrene (PS) commonly exhibits brittle behavior and poor mechanical properties due to the presence of structural heterogeneities promoting localized failure. The removal of this localized failure is shown here by processing PS into fibers with a range of diameters using electrospinning. Mechanical properties of individual electrospun fibers were quantified with atomic force microscopy based nanomechanical tensile testing. The resultant stress–strain behavior of PS fibers highlights considerable enhancement of mechanical properties when fiber diameter decreases below 600 nm such that polystyrene toughness increases significantly by over two orders of magnitude compared to the bulk. Consideration of the network properties of polystyrene is used to demonstrate the increase of draw ratio toward a theoretical limit and is potentially applicable to a range of glassy polymeric materials.
Photo‐reversible polyurethane (PU) coatings based on coumarin diol (CD) are obtained. Initially, pre‐polymers based on different amounts of coumarin (5, 15, and 25 mol%) and 1,6‐hexamethylene diisocyanate are prepared to obtain PUs with a large incorporation of CD and high molecular weight. The pre‐polymer is posterior reacted with poly(ε‐caprolactone) diol (PCL‐diol), either with molecular weight = 530 or 2000 g mol–1. The thermal stabilities of the PUs are studied using thermogravimetric analysis. Polymers with a higher content of CD present higher stability. The thermal transitions and the mechanical response are analyzed using differential scanning calorimetry and strain‐stress tests, respectively. Moreover, the photo‐reversibility of CD‐based PUs is followed by UV absorption. In general, photo‐dimerization induces better mechanical properties of the final PUs. Materials obtained with short PCL‐diol ( = 530 g mol–1) and the highest amount of CD present higher reversibility processes. Therefore, these polymers are promising for application as coating systems.
The direct injection of a drug into a joint can relieve osteoarthritic pain for a short period of time. The problem is that the drug will not stay at the allocated location. Therefore, a proof‐of‐concept in situ is designed forming hydrogel containing liposomes that are covalently linked to the hydrogel network. When the liposomes are filled with a cargo, the formed hydrogel is thus loaded with this cargo, too. Due to the link between the hydrogel and the liposomes, a compression or other mechanical force applied to the hydrogel will rupture the liposomes and release a small percentage of the cargo. Overall, a long‐term intra‐articular drug release is feasible.
Hydrogels, as soft and wet materials, have attracted great attention in the field of functional biomaterials. Most recently, the designed hydrogels, according to the energy dissipation principle, overcome the low mechanical strength, poor toughness, and limited recoverability of common hydrogels and show excellent mechanical properties. However, most of these novel designed hydrogels are lacking of instantaneous recovery and antifatigue properties. In this study, a mesoscopic inhomogeneous hydrogel consisting of carboxymethyl cellulose and polyacrylic acid is synthesized through a facile, one‐pot, visible‐light‐triggered polymerization. The prepared hydrogel can be stretched over 700% with fracture strength as high as 850 kPa, and shows a high elastic modulus (180 kPa). The microgel aggregated structure endows an efficient energy dissipation mechanism to the hydrogel. After the internal network structure stabilizing, the hydrogel exhibits a recovery time within 10 ms and over 92% resilience during impact and cyclic tensile tests, respectively. The hydrogel with such excellent mechanical properties can extend its application in biomaterial fields.
Adsorption of a typical example of a new class of amino cellulose, namely 6‐deoxy‐6‐(2‐aminoethyl)amino cellulose at different pH‐values and in the presence of electrolytes, onto cellulose model substrates is studied with surface plasmon resonance and quartz crystal microbalance with dissipation monitoring. Unexpectedly, adsorption is consistently higher at a higher pH‐value of 10, indicating that solubility and interactions between amine moieties and cellulose are more important than electrostatic interactions. The findings are highly relevant for the process to modify material surfaces with amino cellulose in water‐based systems as a universal tool for changing the surface properties and chemistry. Potential applications for an antimicrobial all biobased material could be found, e.g., as medical textiles or in the biotechnology sector.
Visible light curing of photopolymers has gained increasing interest in recent years. Dental materials are one of the important areas of application, where the bimolecular camphorquinone/amine initiator system is currently state of the art initiator. In this study, the authors describe the synthesis and photochemistry of tetrakis(2,4,6‐trimethylbenzoyl)silane, as cleavable Type I visible light photoinitiator. Besides excellent photobleaching behavior, this photoinitiator can well compete with up to now used long wavelength initiators.
Porous and bulk water‐responsive urethane‐based shape memory polymers (SMPs) containing poly(ethylene glycol) (PEG), poly(caprolactone), and poly(dimethylsiloxane) are fabricated. The copolymers are processed by electrospinning to achieve porous structures. Shape fixation and recovery are achieved via the solvation and recrystallization of the hydrophilic PEG switching segment. Mechanical testing is performed to determine the SMP functionality. Water uptake rate for porous SMP is found to be higher than bulk SMP partly due to higher surface area for water contact. This enables porous structure water‐responsive SMPs to recover faster compared to bulk SMPs. The water‐responsive SMP exhibits good extents of shape fixity and shape recovery when immersed in water (≈35 °C). Different actuation times can be achieved based on the total surface area and efficiency of water‐entry into the polymer.
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