通过2 mM Ni2+孵化辣根过氧化物酶,可制备活化辣根过氧化物酶(Ni2-HRP),实验验证了Ni2-HRP的活性和稳定性,并对Ni2-HRP催化2-二叔丁基苯酚反应的生成物进行了CC/MS,HPLC和核磁共振鉴定,确定为2,4,2′,4′-四羟基-5,5′-二叔丁基联苯,是一种几乎无毒的化合物,可作为制药前体的使用... 相似文献
Improving the conductivity of electrospinning solutions is often achieved by adding small amounts of conductive additives. HMIMCl, a room temperature ionic liquid, and TEBAC, a quaternary ammonium salt, were added to polylactic acid in chloroform and their effects on solution properties, electrospinning, and fiber properties were investigated. Both additives increased the conductivity which decreased the fiber diameter, but differences were observed on the fiber dispersity and fiber morphology. The conductive solutions caused fiber backbuilding with aggregation and fiber fusion. Reasons for the differences in fiber diameter and fiber morphology are discussed.
Electrospinning of blend systems, combining two or more polymers, has gained increasing interest for the fabrication of fibers that combine properties of the individual polymers. Here, a versatile method to produce hydrophobic fibers composed of poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDFhfp) and polyurethane (PUR) is presented. PVDFhfp containing fibers are expected to reduce protein adsorption. In a one‐step process, blend solutions are electrospun into homogeneous nonwoven membranes with fiber diameters in the range of 0.6 ± 0.2 to 1.4 ± 0.7 µm. Surface fluorine concentrations measured by X‐ray photospectroscopy show an asymptotic dependency in function of the PVDFhfp to PUR ratio, reaching values close to pure PVDFhfp at a weight per weight ratio of 10% PVDFhfp to 90% PUR. This fluorine enrichment on the surface suggests a gradient structure along the fiber cross‐section. At increased surface fluorine concentration, the contact angle changes from 121 ± 3° (PUR) to 141 ± 4° (PUR/PVDFhfp). Furthermore, these highly hydrophobic fibers present significantly reduced fibrinogen or albumin adsorption compared to PUR membranes. 相似文献
Aligned and unaligned vanadium (IV) oxide meso-tetraphenyl porphine (VMP)/polyethylene oxide (PEO) hybrid nanofibers have been successfully synthesized by electrospinning technique. The nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy and scanning electron microscopy (SEM). The SEM and AFM analyses of the morphology showed that the nanofibers are cylindrical with diameters ranging from 400–700 nm. The AFM analysis also confirmed that the aligned nanofibers deposited on a small metallic spring are smoother than the unaligned ones deposited on FTO. FTIR analysis showed that the polar environment provided by the phenyl groups of VMP molecules modified the chemical configuration of PEO molecules, and XRD studies indicated that the VMP molecules were homogeneously distributed within the PEO matrix. 相似文献
Ultra‐thin fibers, consisting of blends of a PPE derivative and polystyrene, with average diameters ranging from 430 to 1 200 nm, were produced by electrospinning. The electrospinnability was significantly improved by adding pyridinium formate to the spinning solution. FT‐IR spectroscopy was used to confirm the composition of the electrospun fibers and their morphology was probed by SEM. The optical properties of the as‐prepared solutions, pristine and annealed fibers, and corresponding spin‐coated and solution‐cast films were investigated by UV‐vis spectroscopy. A comparison of the PL emission spectra revealed aggregation of PPE molecules in the electrospun materials but the extent of aggregation can be reduced if the materials are annealed above the glass transition temperature.
Conducting electrospun fiber mats based on PLA and PAni blends were obtained with average diameter values between 87 and 1 006 nm with PAni quantities from 0 to 5.6 wt.‐%. Structural characteristics of fiber mats were compared to cast films with the same amount of PAni and studied by SEM, SAXS, and AFM. Thermal properties of fiber mats and cast films were compared by DSC analyses. Mechanical properties of fiber mats were also evaluated. It was found that electrospinning process governs the crystal structure of the fibers and strongly affects fiber properties. New properties of PLA/PAni blends are reported due to the size fiber reduction.
Abstract A number of poly(vinyl alcohol) fibers with different draw ratios was characterized by measuring the birefringence, crystalline orientational order, crystallinity, tensile strength, and modulus. The birefringence, tensile strength and modulus increased with increasing draw ratio whereas the crystallinity and crystalline order parameters remained constant within narrow limits. The increase in birefringence has to be attributed solely to an increase in chain orientation in the amorphous phase of the semicrystalline fiber. The tensile strength and modulus are therefore directly related to the chain orientation in the amorphous phase. With the aid of a simple two-phase model it was found that the modulus of the amorphous phase in its disordered conformation was 4.8 GPa. The intrinsic birefringence of the amorphous phase was found to be 79 × 10?3, i.e. much higher than the value obtained for the crystalline phase (52 × 10?3). When this value was used in calculations, it was found that the order parameter of the amorphous phase increased from around 0.1 for a draw ratio of 1 to approximately 0.6 for a draw ratio of 5, whereas the order parameter of the crystalline phase was close to 1 for all draw ratios. 相似文献
Understanding the effect of conductivity in electrospinning solutions is crucial in order to improve or control the electrospinning process. In this paper the effect of adding small amounts (0.039–0.259 mol · kg?1) of three different conductive additives to aqueous solutions of polyvinyl alcohol has been investigated. The salts were HMICl (a room temperature ionic liquid), TEBAC (a quaternary ammonium salt) and KCl. Addition of these salts caused a steady increase in the solution conductivity but the fiber diameter was typically greater than that of PVA alone, and exhibited an oscillatory trend. The oscillatory trend on the fiber diameter is attributed to fiber backbuilding and fusion that occurs prior to deposition on the collector.
In bone surgery and orthopedics, bioresorbable materials can be helpful in bone repair and countering post-op infections. Explicit antibacterial activity, osteoinductive and osteoconductive effects are essential to achieving this objective. Nonwoven electrospun (ES) fibers are receiving the close attention of physicians as promising materials for wound dressing and tissue engineering; potentially, in high contrast with dense materials, ES mats hamper regeneration of the bone extracellular matrix to a lesser extent. The use of the compositions of inherently biodegradable polyesters (poly(ε-caprolactone) PCL, poly(lactoglycolide), etc.), calcium phosphates and antibiotics is highly prospective, but the task of forming ES fibers from such compositions is complicated by the incompatibility of the main organic and inorganic ingredients, polyesters and calcium phosphates. In the present research we report the synthesis of hydroxyapatite (HAp) nanoparticles with uniform morphology, and demonstrate high efficiency of the block copolymer of PCL and poly(ethylene phosphoric acid) (PEPA) as an efficient compatibilizer for PCL/HAp mixtures that are able to form ES fibers with improved mechanical characteristics. The materials obtained in the presence of vancomycin exhibited incremental drug release against Staphylococcus aureus (St. aureus). 相似文献
Summary: Ultrafine fibers were spun from poly(D ,L ‐lactide) (PDLA) solution using a homemade electrospinning set‐up. Fibers with diameter ranging from 350 to 1 900 nm were obtained. Morphologies of fibers and distribution of fiber diameters were investigated varying concentration and applied voltage by scanning electron microscopy (SEM). Average fiber diameter and distribution were determined from about 100 measurements of the random fibers with an image analyzer (SemAfore 5.0, JEOL). A more systematic understanding of process parameters of the electrospinning was obtained and a quantitative relationship between electrospinning parameters and average fiber diameter was established by response surface methodology (RSM). It was concluded that the concentration of polymer solution played an important role in the diameter of fibers and standard deviation of fiber diameter. Lower concentration tended to facilitate the formation of bead‐on‐string structures. Fiber diameter tended to increase with polymer concentration and decrease with applied voltage. Fibers with lower variation in diameter can be obtained at lower concentration regardless of applied voltage. Fibers with uniform diameter and lower variation in diameter can be obtained at higher concentration and higher applied voltage. Process conditions for electrospinning of PDLA could be chosen according to the model in this study.
Contour plots of average fiber diameter as a function of concentration and applied voltage. 相似文献
A new target collector was designed for taking up aligned nanofibers by electrospinning. The collector consists of a rotor around which several fins were attached for winding electrospun filaments continuously in large amounts. The alignment of the nanofibers wound on the collector was affected by the electrospinning conditions, such as the needle‐to‐collector distance and the applied voltage, but not by the rotation speed of the collector. At a voltage of 0.5 kV · cm?1, about 60% of the fibers were found to be aligned within an angle of ± 5° relative to the rotational direction of the collector. The fiber alignment was improved to 90% by drawing the fiber bundle 2–3 times at 110 °C. The drawing was also effective for crystal orientation of the fibers as revealed by WAXD. The drawn fibers show improved mechanical properties.
