聚醚砜的静电纺丝研究

采用聚醚砜(PES)的良溶剂二甲基甲酰胺(DMF)和非良溶剂丙酮(AC)为共溶剂体系,研究了溶剂组成、纺丝成形条件对静电纺丝PES纤维的形貌及纤维直径的影响。结果表明:DMF/AC的配比对于静电纺丝PES纤维形貌具有直接的调控作用,随着DMF/AC混合溶剂中AC用量的增加,纤维平均直径变大,纤维毡中串珠数目明显减少,纤维均一性变好;随着纺丝液浓度的升高,纺丝电压的增大,纤维的平均直径变大;接收距离的变化对纤维平均直径影响不大;PES最佳纺丝工艺条件为纺丝溶液质量分数13%,纺丝电压15 kV,接收距离10 cm,mDMF/mAC为8.5/1.5,在此条件下,可以获得纤维平均直径为96 nm的PES纤维毡。     

Electrospinning of polycarbonate urethane biomaterials

Polycarbonate urethane (PCU) nano-fibers were fabricated via electrospinning using N,N- dimethylformamide (DMF) and tetrahydrofuran (THF) as the mixed solvent. The effect of volume ratios of DMF and THF in the mixed solvent on the fiber structures was investigated. The results show that nano-fibers with a narrow diameter distribution and a few defects were obtained when mixed solvent with the appropriate volume ratio of DMF and THF as 1∶1. When the proportion of DMF was more than 75% in the mixed solvent, it was easy to form many beaded fibers. The applied voltage in the electrospinning process has a significant influence on the morphology of fibers. When the electric voltage was set between 22 and 32 kV, the average diameters of the fibers were found between 420 and 570 nm. Scanning electron microscopy (SEM) images showed that fiber diameter and structural morphology of the electrospun PCU membranes are a function of the polymer solution concentration. When the concentration of PCU solution was 6.0 wt-%, a beaded-fiber microstructure was obtained. With increasing the concentration of PCU solutions above 6.0 wt-%, beaded fiber decreased and finally disappeared. However, when the PCU concentration was over 14.0 wt-%, the average diameter of fibers became large, closed to 2 μm, because of the high solution viscosity. The average diameter of nanofibers increased linearly with increasing the volume flow rate of the PCU solution (10.0 wt-%) when the applied voltage was 24 kV. The results show that the morphology of PCU fibers could be controlled by electrospinning parameters, such as solution concentration, electric voltage and flow rate.     

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     

Processing and characterization of electrospun poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) nanofibrous membranes

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) nanofibrous membranes were first fabricated via electrospinning from chloroform (CHCl₃) or CHCl₃/dimethylformamide (DMF) polymer solutions. The electrospinning conditions such as the polymer concentration, the solvent composition, and the applied voltage were optimized in order to get smooth and nano-sized fibers. The crystalline structure, the melting behaviors and the mechanical properties of the obtained nanofibrous membranes were characterized. With pure CHCl₃ as the solvent in the electrospinning process, the finest smooth PHBHHx fibers were about 1 μm in diameter. When DMF is added to CHCl₃ as a co-solvent, the conductivity and volatility of the solution increased and reduced, respectively, and the electrospinnability of the polymer solution increased as a result. The averaged diameters of PHBHHx fibers could be reduced down to 300-500 nm when the polymer concentration was kept at 3 wt%, the ratio of DMF/CHCl₃ was maintained at 20/80 (wt%), and the applied voltage was fixed at 15 kV during electrospinning. WAXD and DSC results indicated that the crystallization of the PHBHHx nanofibers was restricted to specific crystalline planes due to the molecular orientation along the axial direction of the fibers. The crystallization behaviors of the electrospun nanofibers were significantly different from that of the cast membranes because of the rapid solidification and the one-dimensional fiber size effect in the electrospinning process. Mechanically, the electrospun PHBHHx nanofibrous membranes were soft but tough, and their elongation at break averaged 240-300% and could be up to 450% in some cases. This study demonstrated how the size of electrospun PHBHHx fibers could be reduced by adding DMF in the solvent and gave a clue of the presence of oriented molecular chain packing in the crystalline phase of the electrospun PHBHHx fibers.     

Preparation of the chitosan containing nanofibers by electrospinning chitosan–gelatin complexes

Electrospinning is an interesting technique, which provides a facile and an effective mean in producing nonwoven fibrous materials; however, for producing nanofibers, investigation of the electrospinning conditions is very important. In this study, chitosan, gelatin, and their polyelectrolyte complexes (PECs) were electrospun to prepare nonwoven nanofibrous mats. The concentrations of chitosan and gelatin solutions and electric field (kV/cm) were optimized. The solutions were then blended in different ratios (0–100%) to get electrospun nanofibrous mats. Solution concentration and electric field showed pronounced effect on the electrospinnability and fiber diameter of these systems. Mostly large beads coexisted with the fibers were observed for chitosan at 1 wt% solution concentration, which then showed good electrospinnability at 2 wt% (nanofiber diameter was 145 and 122 nm at 15 and 20 kV/10 cm, respectively), whereas gelatin showed no electrospinnability below 15 wt% solution concentration and a homogenous fibers network at 15 wt% (149 nm at 20 kV/10 cm). The morphology and diameter of chitosan–gelatin PEC nanofibers varied with the chitosan/gelatin ratio. The crystallinity of chitosan was also observed to reduce with electrospinning and addition of gelatin. POLYM. ENG. SCI. 50:1887–1893, 2010. © 2010 Society of Plastics Engineers     

Morphology transition in electrospinning polymers by a dual‐capillary system

An experimental investigation of the fiber morphology change of fibers prepared by a dual‐capillary electrospinning system, operated in the cone‐jet mode, was carried out for poly(vinyl acetate) polymers of three molecular weights. The substrate morphology of the electrospun poly(vinyl acetate) could be changed significantly when the polymer's molecular weight, concentration, solvent, and outer liquid flow rate were varied. The onset of bead‐to‐fiber transition was determined by the critical chain overlap concentration. For solutions with a high concentration, the fiber diameter and surface were significantly affected by the physical properties of the solvents. To produce fibers of small diameter, electrospinning with a higher conductivity solution was desirable. On the other hand, a high‐conductivity solution needed to be avoided to keep the fiber uniform in diameter and smooth on the surface. The comparison of electrospun fibers produced by both single‐capillary and dual‐capillary systems was also addressed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of solution properties on nanofibrous structure of electrospun poly(lactic‐co‐glycolic acid)

Electrospinning of poly(lactic‐co‐glycolic acid) (PLGA) in chloroform or 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was investigated, focusing on its solution parameters, to develop nonwoven biodegradable nanofibrous structures for tissue engineering. PLGA nanofibers were obtained by electrospinning of 15 wt % PLGA solution and the resulting average fiber diameters were varied with the range of 270–760 nm, depending on solution property. When small amounts of benzyl triethylammonium chloride (BTEAC) was added to the PLGA/chloroform solution, the average diameter was decreased from 760 to 450 nm and the fibers were densely amounted in a straight shape. In addition, the average fiber diameter (270 nm) of nanofibers electrospun from polar HFIP solvent was much smaller than that (760 nm) of nanofibers electrospun from nonpolar chloroform solvent. Therefore, it could be concluded that conductivity or dielectric constant of the PLGA solution was a major parameter affecting the morphology and diameter of the electrospun PLGA fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1214–1221, 2006     

Effects of processing parameters on morphology of electrospun polystyrene nanofibers

This study focused on the preparation of electrospun polystyrene (PS) nanofibers. PS solutions were prepared in single (dimethylformamide; DMF, dimethylacetamide; DMAc or tetrahydrofuran; THF) and mixed solvent (DMF/THF and DMAc/THF) systems with and without tetrabutylammonium bromide (TBAB) salt. The effects of PS concentration, solvent system, the addition of salt, appearance and diameter of PS fibers were examined. The average diameter of the as-spun fibers increased upon increasing PS concentration. The morphology of the fibers significantly depended on the properties of the solvents. The obtained fibers were smooth without any beads and their diameters were affected by the amount of THF in the solvent and PS concentration. The beads in the fibers disappeared and the fiber diameter significantly decreased after the addition of TBAB. The smallest diameter and the narrowest diameter distribution of PS nanofibers (376±36 nm) were obtained from 15% PS solution in DMAc with 0.025% w/v TBAB.     

Electrospinning of thermoplastic polyurethane microfibers and nanofibers from polymer solution and melt

Electrospinning technique was used to produce ultrafine fibers from thermoplastic polyurethane (TPU). A direct comparison between melt and solution electrospinning of TPU was provided for the evaluation of process–structure relationship. It was found that the deposition rate of melt electrospinning (0.6 g h^?1) is four times higher than that of solution electrospinning (0.125 g h^?1) for TPU under the same processing condition. However, the average fiber diameters of solution electrospun TPUs (220–280 nm) were much lower than those of melt electrospun TPUs (4–8 μm). The effect of processing variables including collection distance and electric field strength on the electrospun fiber diameter and morphology was also studied. The findings indicate that increasing the electric field strength yielded more electrical forces acting on polymer jet and resulted in a decrease in fiber diameter as a result of more fiber drawing in both solution and melt electrospun fibers. It was also demonstrated that increasing the collection distance led to an improvement in the solidification of melt electrospun fibers and thus less fused fibers were obtained. Finally, a close investigation of fiber structures revealed that melt electrospun TPU fibers had smooth surface, whereas solution electrospun TPU fibers showed high intensity of cracks on the fiber surface. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Systematic parameter study for ultra-fine fiber fabrication via electrospinning process

Processing parameters effects on the morphology such as fiber diameter and its uniformity of electrospun polymer nanofibers was investigated. A processing map summarized effects of solutions properties and processing conditions on the electrospun nanofiber morphology was obtained. Polymer concentration, its molecular weight, electrical conductivity of solvents were found as dominant parameters to control the morphology. Based on the systematic parameter study, electrospun PLLA fibers as small as 9 nm were successfully produced.     

Magnetic polyacrylonitrile-Fe@FeO nanocomposite fibers - Electrospinning, stabilization and carbonization

Uniform and bead-free pure polyacrylonitrile (PAN) and its magnetic polymer nanocomposite (PNC) fibers reinforced with different core-shell Fe@FeO nanoparticles (NPs) loadings are prepared using electrospinning method. The morphology of the resulting products is correlated to the corresponding rheological behaviors of the pure PAN and PAN/Fe@FeO solutions. The diameter of the PAN fibers is linearly related to the polymer solution concentration. However, with a fixed PAN concentration of 10 wt%, the Fe@FeO NP loading shows a negligible effect on the morphology of the PNC fibers. Thermogravimetric analysis (TGA) results indicate an enhanced thermal stability of the PNC fibers than that of the pure PAN fibers. Magnetic carbon nanocomposite (MCNC) fibers are prepared through the stabilization and carbonization of the electrospun PNC fibers. The effects of the heating procedures, including the stabilization and carbonization temperature and time, on the fiber morphology are systematically investigated. Both short and long MCNC fibers could be easily produced by changing the heat procedures. Room temperature magnetic properties of the nanocomposite fibers based on different heating procedures are also studied in this work.     

Effect of the addition of a fugitive salt on electrospinnability of poly(?-caprolactone)

Described in this paper is a novel study focused on producing bead-free ultrafine fibers, with narrow fiber diameter distribution, from Poly(?-caprolactone) (PCL) via electrospinning. High quality product is achieved with the use of a new solvent system that involves an acid-base reaction to produce weak salt complexes, which serve to increase the conductivity of the polymer solution. Additionally, the salt formed dissociates easily and evaporates along with the solvent during the spinning process because its respective acid-base components are volatile at room temperature. This results into the formation of pure PCL nanofibers of ultrafine dimensions. Glacial acetic acid was used as the solvent for the polymer and the organic base pyridine was used to initiate the formation of salt complexes in the solution. Pyridine was added at six different levels to vary the conductivity and examine the latter's effect on fiber morphology. Along with the pyridine content, the polymer concentration was also varied to determine how the two interacted in influencing the size of the fiber and the quality of the structure obtained. It was found that bead-free fibers of sizes lying well within the nano range (140-340 nm) could be produced using the conducting solvent system. Two interesting effects were noted. For a given polymer concentration, the mean fiber diameter increased with increase in pyridine amount. And, lower the polymer concentration, higher was the amount of pyridine required to produce bead-free nanofibers. The combination of these effects along with the fact that the reproducibility of the results was high provided a means of producing fibers with predictable sizes.     

Morphology of electrospun nylon‐6 nanofibers as a function of molecular weight and processing parameters

In the present study, the morphology and mechanical properties of nylon‐6 nanofibers were investigated as a function of molecular weight (30,000, 50,000, and 63,000 g/mol) and electrospinning process conditions (solution concentration, voltage, tip‐to‐collector distance, and flow rate). Scanning electron micrographs (SEM) of nylon‐6 nanofibers showed that the diameter of the electrospun fiber increased with increasing molecular weight and solution concentration. An increase in molecular weight increases the density of chain entanglements (in solution) at the same polymer concentration; hence, the minimum concentration to produce nanofibers was lower for the highest molecular weight nylon‐6. The morphology of electrospun fibers also depended on tip‐to‐collector distance and applied voltage concentration of polymer solution as observed from the SEM images. Trends in fiber diameter and diameter distribution are discussed for each processing variable. Mechanical properties of electrospun nonwoven mats showed an increase in tensile strength and modulus as a function of increasing molecular weight. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of biomimetic tussah silk fibroin/chitosan composite nanofibers

Tussah silk fibroin (TSF)/chitosan (CS) composite nanofibers were prepared to mimic extracellular matrix by electrospinning with hexafluoroisopropanol (HFIP) as a solvent. The viscosity and conductivity of TSF/CS blend solution were analyzed and the morphology, secondary structure, and thermal property of TSF/CS composite fibers were investigated by SEM, ¹³C CP/MAS-NMR, X-ray diffraction, and DSC Techniques. The electrospinnability of TSF solution was improved significantly by adding 10 wt% CS, and morphology of electrospun TSF nanofibers changed from flat strip to cylindrical. At the same time, the average fiber diameters decreased from 542 to 312 nm, accompanying by an obvious improvement in fiber diameter uniformity. However, when the CS content in blend solution was more than 15 wt%, the diameter of electrospun TSF/CS nanofibers appeared to be polarized which can be attributed to phase separation of the two components in composite nanofibers. Blending 10 wt% CS did not change the conformation of TSF in TSF/CS composite nanofibers, and TSF in composite nanofibers at various composition ratios had mainly taken the α-helix structure. The thermal decomposition temperature of electrospun TSF/CS composite nanofibers decreased with the increase of CS content due to the lower decomposition temperature of CS. To study the cytocompatibility and cell behavior on the TSF/CS nanofibers, human renal mesangial cells were seeded onto electrospun TSF/CS composite nanofibers. Results indicated that the addition of CS promoted cell attachment and spreading on TSF nanofibers significantly, suggesting that electrospun TSF/CS composite nanofibers could be a candidate scaffold for tissue engineering.     

An investigation into the influence of electrospinning parameters on the diameter and alignment of poly(hydroxybutyrate‐co‐hydroxyvalerate) fibers

Electrospinning is an effective technology for the fabrication of ultrafine fibers, which can be the basic component of a tissue engineering scaffold. In tissue engineering, because cells seeded on fibrous scaffolds with varying fiber diameters and morphologies exhibit different responses, it is critical to control these characteristics of electrospun fibers. The diameter and morphology of electrospun fibers can be influenced by many processing parameters (e.g., electrospinning voltage, needle inner diameter, solution feeding rate, rotational speed of the fiber‐collecting cylinder, and working distance) and solution properties (polymer solution concentration and conductivity). In this study, a factorial design approach was used to systematically investigate the degree of influence of each of these parameters on fiber diameter, degree of fiber alignment, and their possible synergetic effects, using a natural biodegradable polymer, poly(hydroxybutyrate‐co‐hydroxyvalerate), for the electrospinning experiments. It was found that the solution concentration invoked the highest main effect on fiber diameter, whereas both rotational speed of the fiber‐collecting cylinder and addition of a conductivity‐enhancing salt could significantly affect the degree of fiber alignment. By carefully controlling the electrospinning parameters and solution properties, fibrous scaffolds of desired characteristics could be made to meet the requirements of different tissue engineering applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Assessment of parameters influencing fiber characteristics of chitosan nanofiber membrane to optimize fiber mat production

Electrospun chitosan nanofiber mats have been obtained using chitosan solutions in a mixture of trifluoroacetic acid and dichloromethane. The relationship between processing parameters (solvent composition, polymer concentration in the solution, feeding rate, applied voltage, traveling distance between the needle, and the collector) and fiber morphology was studied. Taguchi's methodology was followed to determine which parameters have the strongest influence on mean fiber diameter and fiber homogeneity. Chitosan nanofibers obtained with this procedure were water soluble due to the protonation of amine side groups but were successfully neutralized by immersion in calcium carbonate solutions. It was established that fiber diameter is mainly determined by the solution concentration and the distance from the needle to the collector while other parameters have less influence. The set of parameters that produce the thinnest fibers were a concentration of 8 wt%, a TFA/DCM ratio of 80:20 (v/v%), a voltage of 30 kV, a flow rate of 6.0 mL/h, a gap distance of 10 cm, using a needle diameter of 0.5, allowing to produce randomly oriented mats with a mean fiber thickness of 66 nm. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

不同溶剂对静电纺聚乳酸纳米纤维形态结构的影响

以聚乳酸（PLA）为原料,分别用三种不同的溶剂制得三种纺丝液并采用静电纺丝法,制备了聚乳酸纳米纤维。探讨了溶剂、电压、溶液质量分数对纤维形貌和直径的影响。结果表明,溶剂是决定PLA超细纤维形成的关键因素,三氯甲烷（CHC l3）与二甲基甲酰胺（DMF）混合溶剂（体积比为9∶1）是PLA静电纺丝较为理想的溶剂。在PLA质量分数为6%、极距15 cm、电压25 kV,流量2.5 mL/h的工艺条件下,可制备直径为1 200 nm左右的PLA纤维。     

PHBV/CH2Cl2溶液体系静电纺纤维直径及其分布控制

对β-羟基丁酸酯-co-β-羟基戊酸酯(PHBV)/二氯甲烷(CH2Cl2)溶液进行静电纺丝制备PH-BV纳米纤维毡。采用正交设计实验的方法,对溶液浓度、电压、有机盐(苄基三乙基氯化铵)含量、溶液供给速率、喷丝孔孔径5种因素与纤维直径和直径的多分散性之间的关系进行了研究。通过优化,制备出了平均直径为80nm的纤维。     

Investigation on process parameters of electrospinning system through orthogonal experimental design

Electrospinning is a very simple and versatile method of creating polymer‐based high‐functional and high‐performance nanofibers. But most of the investigations are not systematic and describe the electrospinning process without quantitative accuracy. Inconsistent and even opposite results have been reported, which has hindered the consistent interpretation of the experiments. Orthogonal experimental method was used to investigate qualitative and quantitative correlations between fiber characteristics (diameters and morphologies) and the processing and materials parameters. Uniform fibers can be obtained without any beads by proper selection of the processing parameters, and a lower glass transition temperature was observed for electrospun fibers than that of native polymer. Results of statistical analysis showed that significant influences were observed for polymer molecular weight and solution concentration on fiber diameters, and there were significant effects of polymer molecular weight, solution concentration, and solvent system on fiber morphologies. Meanwhile, solution concentration and polymer molecular weight, and polymer molecular weight and solvent system had obvious interaction effects. Regression analysis revealed quantitative relations of fiber diameters and beads percent, that is, Y₁ = 72.8X₁ ? 8.1X₂ + 138.8, Y₂ = ?3.2X₁ + 0.4X₂ + 60.5, where Y₁ is fiber diameter (nm), Y₂ beads percent (%), X₁ solution concentration (%, w/w), and X₂ polymer molecular weight (kDa). Validation test showed that the experimental values of fiber size and beads percent were in good agreement with the calculated ones. Based on these results, optimal conditions could be obtained for predetermined diameters and morphologies for electrospun fibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3105–3112, 2007     

Influence of self-complementary hydrogen bonding on solution rheology/electrospinning relationships

A series of poly(alkyl methacrylate)s that contained either pendant carboxylic acid or self-complementary multiple hydrogen bonding (SCMHB) groups were synthesized to determine the influence of intermolecular associations on solution rheology and electrospinning performance. The cosolvent composition was varied in order to control the dielectric constant of the electrospinning solvent. By controlling the dielectric constant of the solvent, intermolecular interactions were systematically screened, and the influence of hydrogen bonding on electrospun fiber morphology was determined. While the diameter of the electrospun poly(methyl methacrylate) (PMMA) fibers were in excellent agreement with previously developed predictions, the diameter of the electrospun poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-PMAA) fibers were smaller than predicted when electrospun from dimethyl formamide (DMF). The smaller PMMA-co-PMAA fibers were attributed to dissociation of the carboxylic acid group, which resulted in increased solution conductivity. The poly(methyl methacrylate-co-SCMHB methacrylate) (PMMA-co-SCMHB) displayed significant hydrogen bonding associations with decreasing solvent dielectric constant (D) which resulted in increased viscosity and lower entanglement concentration (C_e). Moreover, strong hydrogen bonding between the SCMHB groups in relatively nonpolar solvents increased the apparent molecular weight of the copolymers, and significantly larger electrospun fibers than predicted were obtained.