The morphology and mechanical properties of sodium alginate based electrospun poly(ethylene oxide) nanofibers

The electrospinning of sodium alginate, a natural biopolymer, was performed from aqueous solutions by blending with PEO, a biodegradable polymer. The conductivity and surface tension of solutions of sodium alginate and PEO were investigated by standard methods. The morphology, thermal, and mechanical properties of the electrospun nanofibers were studied using field emission scanning electron microscopy (FE‐SEM), fourier transform infrared spectroscopy (FT‐IR), energy dispersive X‐ray (EDX), differential scanning calorimetry (DSC) and tensile testing. Uniform, smooth, and ultra‐fine nanofibers with diameters of ～140–190 nm were obtained with solution concentrations of 6–7.2% and sodium alginate/PEO volume ratios of 30:70–50:50. The mechanical strength of the electrospun sodium alginate/PEO mats with good morphology was 21 MPa compared to PEO mats which had a strength of only 10 MPa. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Preparation of novel ultrafine fibers based on DNA and poly(ethylene oxide) by electrospinning from aqueous solutions

Novel DNA/Polyethyleneoxide (PEO) electrospun fibers were obtained from aqueous solution. Key solution properties related to electrospinning: conductivity, surface tension and viscosity were determined. The ionic conductivity of the solution increased significantly with the addition of DNA and only slightly with increasing amounts of PEO; the surface tension decreased with the addition of PEO; the viscosity increased with the addition of either DNA or PEO. It was found that solutions containing both DNA and PEO had ideal properties for electrospinning. The use of these solutions resulted in the formation of ultrafine fibrous mats with fiber diameters of 50–250 nm. It was also found that the average diameter of electrospun fibers decreased with decreased feed rate, increased tip-to-collector distance and increase in the potential employed during electrospinning.     

海藻酸钠纤维的电纺性研究

通过与生物相容的合成高分子聚环氧乙烷(PEO)共混,天然高分子海藻酸钠被成功电纺成丝。扫描电镜等测试结果表明:海藻酸钠a/PEO比例为6∶4时得到无串珠的光滑纤维,并且纤维直径分布均匀。用乙醇/氯化钙(CaCl)2处理电纺纤维,其疏水性得到极大改善。     

The effects of solution properties and polyelectrolyte on electrospinning of ultrafine poly(ethylene oxide) fibers

The effects of solution properties and polyelectrolyte on the electrospinning of poly(ethylene oxide) (PEO) solutions were investigated. Ultrafine PEO fibers without beads were electrospun from 3, 4, 7 and 7 wt% PEO solutions in chloroform, ethanol, (dimethylformamide) DMF and water, respectively. At these concentrations, the values of [η]C were ∼10 for all solutions. The average diameters of PEO fibers were ranged from 0.36 to 1.96 μm. The higher the dielectric constant of solvent was, the thinner PEO fiber was. The average diameters of electrospun PEO fibers from PEO/water solutions were decreased and their distributions were narrowed by adding 0.1 wt% poly(allylamine hydrochloride) (PAH) and poly(acrylic acid sodium salt) (PAA) due to the increased charge density in solutions. The addition of PAH and PAA lowered the minimum concentration for electrospinning of a PEO/water solution to 6 wt%.     

The influence of electrospinning parameters on the structural morphology and diameter of electrospun nanofibers

Electrospinning is a simple method of producing nanofibers by introducing electric field into the polymer solutions. We report an experimental investigation on the influence of processing parameters and solution properties on the structural morphology and average fiber diameter of electrospun poly ethylene oxide (PEO) polymer solution. Experimental trials have been conducted to investigate the effect of solution parameters, such as concentration, molecular weight, addition of polyelectrolyte in PEO solution, solvent effect, as well as governing parameter, such as applied voltage. The concentration of the aqueous PEO solution has shown noteworthy influence on the fiber diameter and structural morphology of electrospun nanofibers. At lower concentrations of PEO polymer solution, the fibers showed irregular morphology with large variations in fiber diameter, whereas at higher concentrations, the nanofibers with regular morphology and on average uniform fiber diameter were obtained. We find that the addition of polyelectrolytes, such as sodium salt of Poly acrylic acid (PAA) and Poly allylamine hydrochloride (PAH), increases the conductivity of PEO solutions and thereby decreases the bead formation in electrospun nanofibers. The increase in applied voltage has been found to affect the structural morphology of nanofiber while the addition of ethanol in PEO solution diminishes the bead defects. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of electrospinning of sodium alginate,blended solutions of sodium alginate/poly(vinyl alcohol) and sodium alginate/poly(ethylene oxide)

Alginate is an interesting natural biopolymer for many of its merits and good biological properties. This paper investigates the electrospinning of sodium alginate (NaAlg), NaAlg/PVA‐ and NaAlg/PEO‐ blended systems. It was found in this research that although NaAlg can easily be dissolved in water, the aqueous NaAlg solution could not be electrospun into ultrafine nanofibers. To overcome the poor electrospinnability of NaAlg solution, synthetic polymers such as PEO and PVA solutions were blended with NaAlg solution to improve its spinnability. The SEM images of electrospun nanofibers showed that the alginate (2%, w/v)–PVA (8%, w/v) blended system in the volume ratio of 70 : 30 and the alginate (2%, w/v)–PEO (8% w/v) blended system in the volume ratio of 50 : 50 could be electrospun into finest and uniform nanofibers with average diameters of 118.3 nm (diameter distribution, 75.8–204 nm) and 99.1 nm (diameter distribution, 71–122 nm), respectively. Rheological studies showed a strong dependence of spinnability and fiber morphology on solution viscosity and thus on the alginate‐to‐synthetic polymer (PVA or PEO) blend ratios. FTIR studies indicate that there are the hydrogen bonding interactions due to the ether oxygen of PEO (or the hydroxyl groups of PVA) and the hydroxyl groups of NaAlg. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of poly(ethylene oxide) with different molecular weights on the electrospinnability of sodium alginate

Although sodium alginate (SA) could not be electrospun from its aqueous solution, SA-based electrospun nanofibers can be fabricated with the help of polyethylene oxide (PEO). In this study, the influence of PEO on the electrospinnability of SA aqueous solution was investigated and the roles of chain entanglements and conformations of the blend system were emphasized. It was found that a little amount of PEO100 with high molecular weight could improve the electrospinnability of SA aqueous solution. However, a large amount of PEO2 with low molecular weight had no positive effect on the electrospinnability of SA aqueous solution. Dynamic laser light scattering (DLLS) results showed that only when the PEO molecular chains in aqueous solution were in an entangled state, PEO can enhance the electrospinnability of SA aqueous solution. The further study on rheological measurements showed that SA molecular chains could not form significant entanglements for the electrospinning even when the SA solution concentration approached concentrated regime. SA molecular chains are closely “overlapped” due to its rigid and extended conformation and cannot form effective chain entanglement. The main contribution of PEO100 to improve SA electrospinnability is offering entanglement sites and thereby enhancing the applicable entanglement degree of the blend system. Whereas, although the chain interaction between PEO2 and SA may improve slightly the flexibility of SA chains, the significant chain entanglements of the blend solution is not achieved. Three molecular models are proposed to depict visually the effect of PEO with different molecular weights on chain conformations and entanglements of SA.     

Electrospinning of chitosan-poly(ethylene oxide) blend nanofibers in the presence of micellar surfactant solutions

Nanofibers were fabricated by electrospinning a mixture of cationic chitosan and neutral poly(ethylene oxide) (PEO) at a ratio of 3:1 in aqueous acetic acid. Chitosan ((1 → 4)-2-amino-2-deoxy-β-d-glucan) is a multifunctional biodegradable polycationic biopolymer that has uses in a variety of different industrial applications. Processing conditions were adjusted to a flow rate of 0.02 ml/min, an applied voltage of 20 kV, a capillary tip-to-target distance of 10 cm and a temperature of 25 °C. To further broaden the processing window under which nanofibers are produced, surfactants of different charge were added at concentrations well above their critical micellar concentrations (cmc). The influence of viscosity, conductivity and surface tension on the morphology and physicochemical properties of nanofibers containing surfactants was investigated. Pure chitosan did not form fibers and was instead deposited as beads. Addition of PEO and surfactants induced spinnability and/or yielded larger fibers with diameters ranging from 40 nm to 240 nm. The presence of surfactants resulted in the formation of needle-like, smooth or beaded fibers. Compositional analysis suggested that nanofibers consisted of all solution constituents. Our findings suggest that composite solutions of biopolymers, synthetic polymers, and micellar solutions of surfactants can be successfully electrospun. This may be of significant commercial importance since micelles could serve as carriers of lypophilic components such as pharmaceuticals, nutraceuticals, antimicrobials, flavors or fragrances thereby further enhancing the functionality of nanofibers.     

Formation and properties of nylon-6 and nylon-6/montmorillonite composite nanofibers

Nanocomposite fibers of nylon-6 and an organically modified montmorillonite (O-MMT), Cloisite-30B, were prepared by electrospinning. Dispersion and exfoliation of O-MMT in nylon-6 were achieved by melt-extrusion in a twin-screw extruder prior to dissolving in aqueous formic acid for electrospinning. The effects of O-MMT layers on the properties of the nylon-6 solution and electrospun nanocomposite fibers were investigated. Homogeneous, cylindrical nanocomposite fibers with diameters ranging from 70 to 140 nm could be prepared from the 15% composite solution. The O-MMT layers were well exfoliated inside the nanocomposite fibers and were oriented along the fiber direction. Both the degree of nylon-6 crystallinity and the crystallite sizes increased for the nanocomposite fibrous mats, most significantly for those composed of the smallest fibers electrospun from 15% solution. The mechanical properties of the electrospun fibrous mats and single fibers depended not only on the addition of O-MMT layers but also on the sizes of the fibers. Smaller fibers exhibited higher Young's modulus.     

Characterization of nano-structured poly(ε-caprolactone) nonwoven mats via electrospinning

Nano-structured poly(ε-caprolactone) (PCL) nonwoven mats were prepared by electrospinning process. In this study, three types of solution were used. One dissolved in only methylene chloride (MC), the second dissolved in mixture of MC and N,N-dimethylformamide (DMF), the third dissolved in mixture of MC and toluene. MC, toluene and DMF are a good, poor, and nonsolvent for PCL, respectively. For the MC only, electrospun fibers had very regular diameter of about 5500 nm, but electrospinng is not facilitated. For the mixture of MC and DMF, electrospinning is certainly enhanced as well as fiber diameter decreased dramatically as increasing DMF volume fraction. It was due to high electric properties of solution such as dielectric constant and conductivity. Whereas, as increasing toluene volume fraction, electrospinning is strictly restricted due to very high viscosity and low conductivity. As the results, it has regarded that solution properties is one of the important parameter in electrospinning. Properties such as conductivity, surface tension, viscosity and dielectric constant of the PCL solutions prepared from three types of solvent system were studied. The morphology, crystallinity and mechanical properties of electrospun PCL nonwoven mats were characterized by scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and universal testing method (UTM), respectively.     

Morphology, structure and properties of conductive PS/CNT nanocomposite electrospun mat

The morphologies and properties of Polystyrene (PS)/Carbon Nanotube (CNT) conductive electrospun mat were studied in this paper. Nanocomposite fibers were obtained through electrospinning of PS/Di-Methyl Formamide (DMF) solution containing different concentrations and types of CNTs. The dispersion condition of CNTs was correlated to morphologies and properties of nanocomposite fibers. A copolymer as an interfacial agent (SBS, Styrene-butadiene-styrene type) was used to modify the dispersion of CNTs in PS solution before electrospinning. The results showed that the presence of the copolymer significantly enhances CNT dispersion. The fiber diameters varied between 200 nm and 800 nm depending on CNT type, polymer concentration and copolymer. The final morphological study of the fibers showed that CNT addition caused a decrease in beads formation along fiber axis before percolation threshold. However, addition of CNTs above percolation increased the beads formation, depending on the dispersion condition. The presence of SBS modified the dispersion, reduced the fiber diameter and the number of bead structures. Electrical conductivity measurements on nanocomposite mats of 15-300 μm in thickness showed an electrical percolation threshold around 4 wt% MWCNT; while the samples containing SBS showed higher values of conductivities below percolation compared to the samples with no compatibilizer. Enhancement in mechanical properties was observed by the addition of CNTs at concentrations below percolation.     

A fundamental study of chitosan/PEO electrospinning

A highly deacetylated (97.5%) chitosan in 50% acetic acid was electrospun at moderate temperatures (25-70 °C) in the presence of a low content of polyethylene oxide (10 wt% PEO) to beadless nanofibers of 60-80 nm in diameter. A systematic quantitative analysis of the solution properties such as surface tension, conductivity, viscosity and acid concentration was conducted in order to shed light on the electrospinnability of this polysaccharide. Rheological properties of chitosan and PEO solutions were studied in order to explain how PEO improves the electrospinnability of chitosan. Positive charges on the chitosan molecule and its chain stiffness were considered as the main limiting factors for electrospinability of neat chitosan as compared to PEO, since surface tension and viscosity of the respective solutions were similar. Various blends of chitosan and PEO solutions with different component ratios were prepared (for 4 wt% total polymer content). A significant positive deviation from the additivity rule in the zero shear viscosity of chitosan/PEO blends was observed and believed to be a proof for strong hydrogen bonding between chitosan and PEO chains, making their blends electrospinnable. The impact of temperature and blend composition on the morphology and diameter of electrospun fibers was also investigated. Electrospinning at moderate temperatures (40-70 °C) helped to obtain beadless nanofibers with higher chitosan content. Additionally, it was found that higher chitosan content in the precursor blends led to thinner nanofibers. Increasing chitosan/PEO ratio from 50/50 to 90/10 led to a diameter reduction from 123 to 63 nm. Producing defect free nanofibrous mats from the electrospinning process and with high chitosan content is particularly promising for antibacterial film packaging and filtration applications.     

Wound-dressing materials with antibacterial activity from electrospun gelatin fiber mats containing silver nanoparticles

Ultrafine gelatin fiber mats with antibacterial activity against some common bacteria found on burn wounds were prepared from a gelatin solution (22%w/v in 70 vol% acetic acid) containing 2.5 wt% AgNO₃. Silver nanoparticles (nAg), a potent antibacterial agent, first appeared in the AgNO₃-containing gelatin solution after it had been aged for at least 12 h, with the amount of nAg increasing with increasing aging time. The average diameters of the as-formed nAg ranged between 11 and 20 nm. Electrospinning of both the base and the 12 h-aged AgNO₃-containing gelatin solutions resulted in the formation of smooth fibers, with average diameters of ∼230 and ∼280 nm, respectively. The average diameter of the as-formed nAg in the electrospun fibers from the 12 h-aged AgNO₃-containing gelatin solution was ∼13 nm. The nAg-containing gelatin fiber mats were further cross-linked with moist glutaraldehyde vapor to improve their stability in an aqueous medium. Both the weight loss and the water retention of the nAg-containing gelatin fiber mats in acetate buffer (pH 5.5), distilled water (pH 6.9) or simulated body fluid (SBF; pH 7.4) decreased with increasing cross-linking time. The release of Ag⁺ ions from both the 1- and 3 h-cross-linked nAg-containing gelatin fiber mats - by the total immersion method in acetate buffer and distilled water (both at a skin temperature of 32 °C) - occurred rapidly during the first 60 min, and increased gradually afterwards; while that in SBF (at the physiological temperature of 37 °C) occurred more gradually over the testing period. Lastly, the antibacterial activity of these materials, regardless of the sample types, was greatest against Pseudomonas aeroginosa, followed by Staphylococcus aureus, Escherichia coli, and methicillin-resistant S. aureus, respectively.     

The effect of solution properties on the morphology of ultrafine electrospun egg albumen–PEO composite fibers

Biocompatible composite fibers suitable for food and medical applications were electrospun from egg albumen (EA) and poly(ethylene oxide) (PEO) at a flow rate of 1.8 mL/min, at an applied voltage of 22 kV and a capillary to target distance of 15 cm. The ratio of EA to PEO dispersed in formic acid was varied from 1:0 to 1:0.1, 1:0.3, 1:0.6 and 0:1. The influence of dispersion properties such as viscosity, surface tension and electrical conductivity on the morphology of electrospun fibers was investigated. As the ratio of PEO increased, viscosity, surface tension, and conductivity decreased. Electrospun fibers had diameters of 188 ± 21, 289 ± 33, 470 ± 32 and 202 ± 20 nm for EA–PEO composite ratios of 1:0.1, 1:0.3, 1:0.6, and 0:1, respectively. Pure EA did not form fibers, but was deposited as beads instead. Results were attributed to increasing entanglement of the two polymers as the concentration of PEO in the solution increased leading to larger diameters of electrospun fibers. Compositional analysis of fibers spun from mixed dispersions using FTIR and TGA indicated that fibers were composed of both EA and PEO, but that fibers contained larger concentrations of PEO than the original dispersions. Investigation of thermal properties by DSC showed the absence of a melting point in 1:0.1 and 1:0.3 EA–PEO fibers. At an EA–PEO ratio of 1:0.6, a melting point characteristic of PEO was identified but enthalpy was significantly smaller than that of pure PEO which could possibly be attributed to molecular interactions between the two polymers.     

Electrospinning of heated gelatin‐sodium alginate‐water solutions

Most polymers that are electrospun are dissolved in a solvent and are spun at ambient temperature. Gelatin, a natural polymer, has excellent potential in medical applications as a biodegradable polymer, especially when combined with sodium alginate. Unfortunately, gelatin/water or gelatin/sodium alginate/water solutions cannot be electrospun at ambient temperature without the incorporation of substances that are considered potentially toxic to the human body, such as acetic acid. In this study, gelatin/water solutions with and without sodium alginate were successfully electrospun without the use of additional solvents by using heated water solutions. The effect of electrospinning parameters such as solution concentration and applied voltage on the nanofiber morphology of these solutions was studied. These nanofibers from heated gelatin/water solutions exhibited good morphology with an average size of 291 ± 67 nm at 18% concentration to 414 ± 52 nm at 20% concentration. Similar sizes were observed when sodium alginate was incorporated into the gelatin/water solutions, although the relationship was dependent upon the amount of sodium alginate in the solution as well as the total concentration. Typically, these nanofibers containing sodium alginate were produced at a lower gelatin concentration compared with the gelatin/water nanofibers because of the increase of viscosity and conductivity of the solutions due to the addition of the highly viscous and conductivity sodium alginate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Release characteristics of four model drugs from drug-loaded electrospun cellulose acetate fiber mats

Ultra-fine fiber mats of cellulose acetate (CA; M_w ≈ 30?000 Da; degree of acetyl substitution ≈ 2.4) containing four different types of model drugs, i.e., naproxen (NAP), indomethacin (IND), ibuprofen (IBU), and sulindac (SUL), were successfully prepared by electrospinning from 16% w/v CA solutions in 2:1 v/v acetone/N,N-dimethylacetamide (DMAc). The amount of the drugs in the solutions was fixed at 20 wt.% based on the weight of CA powder. The morphology of the drug-loaded electrospun (e-spun) CA fiber mats was smooth, with the average diameters of these fibers ranging between 263 and 297 nm. No presence of the drug aggregates of any kind was observed on the surfaces of these fibers, suggesting that the drugs were encapsulated well within the fibers. After submersion in the acetate buffer solution at 37 °C for 24 h, the drug-loaded e-spun CA fiber mats swelled particularly well (i.e., 570-630%), while the corresponding solvent-cast film counterparts did not. The release characteristics of the model drugs from both the drug-loaded CA fiber mats and the drug-loaded as-cast CA films were carried out by the total immersion method in the acetate buffer solution at 37 °C. At any given immersion time point, the release of the drugs from the drug-loaded e-spun CA fiber mats was greater than that from the corresponding as-cast films. The maximum release of the drugs from both the drug-loaded fiber mats and films could be ranked as follows: NAP > IBU > IND > SUL.     

Characterization of electrospun poly(N-isopropyl acrylamide) fibers

Poly(N-isopropyl acrylamide) (pNIPAM) is an interesting material in that it shows a thermoresponsive behavior around 32 °C in aqueous solutions. This behavior mimics that of many proteins in solution and as a result, many researchers have studied pNIPAM as a model for protein behavior. Yet, little is known about the processability of pNIPAM into three-dimensional matrices and whether such processing affects polymer conformation. In this work, 3D fibrous mats of pNIPAM were prepared by electrospinning from three different solvents and the resulting morphologies evaluated. Additionally, electrospun pNIPAM was evaluated with polarized Raman and infrared spectroscopies and compared against the spectra of the bulk material. It was found that the electrospinning process did not alter the polymer structure or morphology.     

Preparation and electrochemical characterization of the alkaline polymer gel electrolyte polymerized from acrylic acid and KOH solution

An alkaline polymer gel electrolyte (PGE) film was prepared by solution polymerization of acrylate-KOH-H₂O at room temperature, and the preparation conditions were optimized in view of the mechanical properties and ionic conductivity of the film. The PGE film with the optimized composition of 0.02% K₂S₂O₈, 16.75% acrylic acid and 83.23 wt.% 4 mol l⁻¹ KOH solution is transparent, rubber-like and dimensionally stable with improved mechanical properties as compared with gelled electrolyte. The specific conductivity of the film is 0.288 s cm⁻¹ at room temperature and the conductivity values follow the Arrhenius equation with the activation energy of ∼10 kJ mol⁻¹. These data suggest that the ionic conduction proceeds in the same mechanism as in aqueous alkaline solution. Experimental results from the laboratory Zn/Air, Zn/MnO₂ and Ni/Cd cells using the PGE film as electrolyte demonstrate that the PGE film has almost the same chemical and electrochemical stability as aqueous alkaline solution, and shows good performance characteristics for application of alkaline primary and secondary battery systems.     

Surface modification of electrospun chitosan nanofibrous mats for antibacterial activity

Chitosan (CS) blended with poly(ethylene oxide) (PEO) was electrospun into nanofibrous mats. The spinning solution of 6.7 : 0.3 (% w/v) of CS : PEO was dissolved in a 70 : 30 (v/v) trifluoroacetic acid/dichloromethane solution. The obtained fibers were smooth without beads on their surfaces and average diameter of the fiber was 272 ± 56 nm. N‐(2‐hydroxyl) propyl‐3‐trimethyl ammonium chitosan chloride (HTACC) and N‐benzyl‐N,N‐dimethyl chitosan iodide (QBzCS) were each prepared from the CS/PEO mats. They were identified by Fourier‐transform infrared and X‐ray photoelectron spectroscopy and degree of swelling in water. Both quaternized electrospun chitosan mats exhibited superior antibacterial activity to the unmodified electrospun CS/PEO against Staphylococcus aureus and Escherichia coli at short contact times. After 4 h of contact, the reduction of both bacterial strains by CS/PEO, HTACC, and QBzCS was equal at about 99–100%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40981.     

Coloration of cellulose nanofibres with pigments

Electrospun nanofibrous mats are popular for their wide technological applications as medical, filtration, sensing and high performance textiles. The potential for coloration of electrospun nanofibrous mats for aesthetic purposes has also been explored recently, and the pigment coloration of cellulose electrospun nanofibrous mats is reported for the first time in this paper. Cellulose acetate electrospun nanofibrous mats were fabricated using electrospinning followed by treatment with sodium hydroxide to synthesise regenerated cellulose electrospun nanofibrous mats. Then the cellulose mats were coloured with commercially available pigments by a pad‐dry‐bake method. Excellent K/S and colour fastness to both washing and light were produced with the application of three commercial pigments. The pH and total dissolved solids content of the coloration wastewater, as well as the mechanical properties of the electrospun nanofibrous mats, were also tested. Attenuated total reflection‐Fourier Transform infrared spectroscopy and scanning electron microscopy analysis were used for characterisation.