Preparation of poly(NaSS‐co‐HEMA) self‐supporting nanofiltration membrane with high cationic permselectivity by electrospinning

A crosslinked nanofibrous cation exchange membrane with high ion permeability and robust mechanical properties was fabricated by electrospinning. Copolymer, poly(sodium styrene sulfonate‐co‐2‐hydroxyethyl methacrylate), was selected as the electrospun material. Fourier transform infrared spectroscopy, ¹H‐nuclear magnetic resonance, and scanning electron microscopy were employed to characterize the copolymer and nanofibrous mat. After a series of preliminary experiments, the proper solvents and their ratio, H₂O/tetrahydrofuran/N,N′‐dimethylformamide (2/1/3 vol/vol/vol), was selected and the electrospinning optimal parameters were determined by orthogonal experiments. Formaldehyde vapor was employed to crosslink the mat. It was observed that the water sorption decreased from 47.9% to 18.4% as the crosslinking time increased from 20 to 32 h. The robust mat with the high tensile strength of 4.85 MPa and 40% elongation at break was obtained at 28 h. The permselectivities of Na⁺, K⁺, and Ca²⁺ were 89%, 85%, and 81%, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45541.     

Influence of humidity,temperature, and annealing on microstructure and tensile properties of electrospun polyacrylonitrile nanofibers

This study investigates the microstructure and mechanical properties of electrospun nanofibers from polyacrylonitrile (PAN)‐dimethylformamide (DMF) solution at different relative humidity (RH) in the range from 14% to 60% and two different temperatures (20°C and 40°C). Nanofibers produced at low RH (22% or less at 20°C) exhibit relatively smooth surface and solid core, whereas at higher RH (30% or higher at 20°C) rough surface and porous core are observed. The resulting morphology is explained by means of H₂O/DMF/PAN ternary phase diagram. At higher RH, the water diffusion into polymer‐solution jet brings thermodynamic instability into the system leading to separation of polymer‐rich phase and polymer‐lean phase, where the later contributes to porosity. Higher process temperature (40°C) yields larger miscibility area in the ternary phase diagram leading to formation of porous structure at relatively higher RH (40%). Tensile strength of nanofibrous yarns is found to vary from 80 MPa to 130 MPa depending on the processing temperature and RH. The amount of porosity is found to affect the tensile properties of nanofibers most significantly, although diameter and crystallinity play important role. Annealing is found to alleviate surface roughness and porosity and increase crystallinity. Tensile strength of nanofibrous yarns is found to improve by up to 25% after annealing. POLYM. ENG. SCI., 58:998–1009, 2018. © 2017 Society of Plastics Engineers     

Main-chain polybenzoxazine nanofibers via electrospinning

Here we report the successful production of nanofibers from main-chain polybenzoxazines (MCPBz) via electrospinning without using any other carrier polymer matrix. Two different types of MCPBz (PBA-ad6 and PBA-ad12) were synthesized by using two types of difunctional amine (1,6-diaminohexane and 1,12-diaminododecane), bisphenol-A, and paraformaldehyde as starting materials through a Mannich reaction. ¹H NMR and FTIR spectroscopy studies have confirmed the chemical structures of the two MCPBz. We were able to obtain highly concentrated homogeneous solutions of the two MCPBz in chloroform/N,N-dimethylformamide (DMF) (4:1, v/v) solvent system. The electrospinning conditions were optimized in order to produce bead-free, uniform and continuous nanofibers from these two MCPBz by varying the concentrations of PBA-ad6 (30–45%, w/v) and PBA-ad12 (15–20%, w/v) in chloroform/DMF (4:1, v/v). The bead-free fiber morphology was evidenced under SEM imaging when PBA-ad6 and PBA-ad12 were electrospun at solution concentration of 40% and 18% (w/v), respectively. The nanofibrous mats of MCPBz were obtained as free-standing material, yet, PBA-ad12 mat was more flexible than and PBA-ad6 mat. Furthermore, the curing studies of these MCPBz nanofibrous mats were performed to obtain cross-linked materials.     

PMIA@PVDF同轴电纺纤维膜的制备及其油水分离性能研究

以聚间苯二甲酰间苯二胺(PMIA)为芯、聚偏氟乙烯(PVDF)为壳,使用22-17G同轴静电纺丝针头制备不同纺丝液芯壳流速比的PMIA@PVDF同轴电纺纤维膜,对纤维膜的芯壳结构、力学性能、热性能及油水分离性能进行了表征.结果表明:在纺丝液芯壳流速比为3:5时,PMIA@PVDF同轴电纺纤维膜具有理想的表面形貌和芯壳结...     

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。     

Electrospun silk fibroin/β-cyclodextrin citrate nanofibers as a novel biomaterial for application in controlled drug release

Abstract

A novel β-cyclodextrin-grafted silk fibroin (SF) nanofibers was successfully fabricated. The morphology and diameter of the electrospun nanofibers were characterized. FE-SEM images showed that the morphology and diameter of the nanofibers were mainly affected by weight ratio of the blend. FTIR, ¹H-NMR, DSC and TGA confirmed the crosslinking reaction between β-cyclodextrin and SF. The release rate of Ciprofloxacin was measured and observed that the SF-g-CD nanofibrous mat provided slower release of the entrapped drug when compared with SF nanofibrous mat. A mathematical analysis of the drug release data suggested that the Higuchi model was the best fitted model.     

Preparation, characterization, and encapsulation/release studies of a composite nanofiber mat electrospun from an emulsion containing poly(lactic-co-glycolic acid)

The aim of this study was to investigate the preparation, characterization, and encapsulation/release performance of an electrospun composite nanofiber mat. The hypothesis was that the composite nanofiber mat with nano-scaled drug particles impregnated in biocompatible and biodegradable polymer nanofibers can serve as an innovative type of tissue engineering scaffold with desired and controllable drug encapsulation/release properties. To test the hypothesis, the composite nanofiber mat electrospun from an emulsion consisting of poly(lactic-co-glycolic acid) (PLGA) Rhodamine B (a model compound to simulate drugs), sorbitan monooleate (Span-80, a non-ionic emulsifier/surfactant that is presumably non-toxic/safe for cell-growth), chloroform, DMF, and distilled water was prepared and characterized; and the Rhodamine B encapsulation/release profile in phosphate buffered saline (pH = 7.4) was recorded and analyzed. For comparison purposes, two additional nanofiber mats electrospun from (1) a solution containing PLGA and Rhodamine B, and (2) a solution containing PLGA, Rhodamine B, and Span-80 were also prepared and assessed as the control samples. The results indicated that the composite nanofiber mat electrospun from the emulsion had the most desired and controllable Rhodamine B encapsulation/release profile and the excellent morphological sustainability; thus, it could be utilized as both a drug encapsulation/release vehicle and a tissue engineering scaffold.     

P123对聚醚砜纳米纤维膜结构和性能的影响

通过静电纺丝法制备了聚醚砜(PES)/聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123,PEO₂₀PPO₇₀PEO₂₀,M_a=5800)纳米纤维膜,考察了P123含量对纺丝液的黏度和表面张力的影响,以及对所制备的纳米纤维膜的结构和性能的影响。实验结果表明:P123含量从3%(质量)增至9%时,其纺丝液的黏度由300 mPa·s增至1000 mPa·s,表面张力在36.5～37.8 mN·m^-1范围内;P123改性的PES纳米纤维直径约为360 nm,分布均匀,其表面也比较光滑,取向趋于一致;此外,该纳米纤维膜具有良好的机械性能和耐溶胀性能,较大的比表面积(>39 m²·g^-1),孔隙率,可用作催化剂载体。     

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.     

Breathable properties of m‐Aramid nanofibrous membrane with high thermal resistance

Electrospinning of m‐aramid in dimethyl acetamide/LiCl solution was investigated to develop thermo‐resistant nanofibrous membranes for breathable waterproof materials. The m‐aramid nanofibers were continuously generated and densely mounted to the membrane without the blockage of the spinning tip during electrospinning. In order to obtain the electrospun m‐aramid nanofibers with different fiber diameters, the polymer concentration in the solution and the spinning distance were varied. Electrospun m‐aramid nanofibrous membranes of various fiber diameters and thicknesses were prepared, and then compared with two commercial expanded polytetrafluoroethylene (ePTFE) membranes with respect to water vapor permeability and pore size. The m‐aramid nanofibrous membrane showed a good water vapor permeability that satisfied the criterion of a breathable membrane, higher than those of the ePTFE porous membranes. Therefore, m‐aramid nanofibrous membrane with thermal and mechanical resistance has great potential for breathable waterproof materials and filters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41515.     

Fabrication of a Nanofibrous Scaffold for the In Vitro Culture of Cardiac Progenitor Cells for Myocardial Regeneration

In this study, random Poly (?-caprolactone) (PCL):Poly glycolic acid (PGA) nanofibrous scaffold with various PCL:PGA compositions were fabricated by electrospinning method. The nanofibrous scaffolds were characterized by SEM, contact angle measurement, ATR-FTIR, and tensile measurements. The results showed that with the increase of the concentration of PGA in spinning blend solution, the average diameter of nanofibers, hydrophilicity, and mechanical properties of the nanofibrous scaffolds increased. An in vitro degradation study of PCL:PGA nanofibers were conducted in phosphate-buffered saline, pH 7.2. The experiments confirm that increasing of PGA provides faster degradation rate in blended nanofibers. To assay the biocompatibility and cell behavior on the nanofibrous scaffolds, cell attachment and spreading of cardiac progenitor cells seeded on the scaffolds were studied. The results indicate that among electrospun nanofibrous scaffolds, the most appropriate candidate for myocardial tissue engineering scaffolds is PCL:PGA (65:35).     

Intercalation of styrene–acrylonitrile copolymer in layered silicate by emulsion polymerization

A well‐defined styrene–acrylonitrile copolymer/montmorillonite (SAN‐MMT) nanocomposite has been prepared by emulsion copolymerization of styrene and acrylonitrile in the presence of sodium ion exchanged montmorillonite (Na⁺‐MMT). This direct and one‐step polymerization technique yielded nanocomposites intercalated with styrene‐acrylonitrile copolymer without occurrence of significant delamination of MMT. The purified products by hot tetrahydrofuran extraction for up to 5 days gave evidences of copolymer intercalation. Those infrared spectra obtained from the purified products revealed the characteristic absorbances due to styrene, acrylonitrile, and MMT. Room temperature powder X‐ray diffraction patterns of the purified product exhibited increased 001 d‐spacing about 1.60 nm. The transmission electron microscopy micrograph of unpurified products confirmed that the 1–2‐nm sized silicate layers are arranged in good order. The onset temperature of purified products are found to be moved to higher temperature, while the thermograms of differential scanning calorimetry show nothing observable transition. The modulus of elasticity of the product was increased with increasing content of MMT, whereas the stress at maximum load was decreased with the increments of MMT. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 179–188, 1999     

Poly(l-lactide-co-?-caprolactone) electrospun nanofibers for encapsulating and sustained releasing proteins

The aim of this study was to investigate coaxial electrospun poly(l-lactide-co-?-caprolactone) [PLLACL] nanofibers for the application in nerve tissue engineering. The hypothesis was that the nanofibrous mats fabricated by coaxial electrospun PLLACL could be effective scaffolds for releasing proteins, such as Bovine Serum Albumin (BSA) or/and Nerve Growth Factor (NGF), in a sustained manner. To test the hypothesis, the coaxial electrospun nanofibers with PLLACL as the shell and BSA/NGF as the core were characterized. Morphologies and mechanical properties of nanofibrous mats were examined. BSA released behavior was studied. The results demonstrated that BSA could be sustainedly released from coaxial electrospun PLLACL nanofibers, however, BSA released from mix electrospun nanofibers present the burst release behavior. Bioactivity of released NGF from coaxial electrospun nanofibers was verified by testing the differentiation of rat pheochromocytoma cells (PC12).     

Solvent-resistant polymeric microfiltration membranes based on oxidized electrospun poly(arylene sulfide sulfone) nanofibers

Polymeric membranes have been widely used in the separation of aqueous system, but there were few studies on the organic solvent-resistant microfiltration (MF) membranes. In this study, organic solvent-resistant oxidized poly(arylene sulfide sulfone)-6 (O-PASS-6) nanofibrous MF membrane with high water flux was prepared through electrospun technology, cold-press, and oxidation treatment. The O-PASS-6 nanofibrous MF membrane was made from the interwoven electrospun uniformly 295 nm nanofibers, and the mean pore size was 0.44 μm. The morphology, chemical structure, and aggregation structure of O-PASS-6 nanofibrous MF membrane were characterized systematically by the scanning electron microscope, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Investigations on the weight loss, swelling ratio, and microstructure change all revealed that the O-PASS-6 membrane had superior stability in strong polar solvents, such as 1,3-dimethyl-2-imidazolidinone (DMI), dimethylformamide (DMF), and tetrahydrofuran (THF). MF performance results showed that the pure water flux of O-PASS-6 nanofibrous membrane was up to 753.34 L·m⁻²·h⁻¹, and the rejection ratio was 99.9% to 0.2 μm particles. More importantly, after treated by aggressive solvents, the membranes still possessed good MF performance: the water flux was 770.08, 775.66, and 766.36 L·m⁻²·h⁻¹ when soaked in DMI, DMF, and THF for 7 days, respectively, and high rejection ratio also maintained (>99%) for both particles investigated. The O-PASS-6 membrane with good solvent resistance proved to be a promising candidate as a prefiltration membrane to eliminate submicron particles in both sewage and aggressive solvents. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48506.     

Enhanced coalescence separation of oil-in-water emulsions using electrospun PVDF nanofibers

A novel and high-efficiency coalescence membrane enhanced by nano-sized polyvinylidene fluoride(PVDF) nanofibers based on polyester (PET) substrate was fabricated using electrospinning method.The properties of the electrospun nanofibers such as roughness and surface morphology greatly affected the oil droplet interception efficiency and surface wettability of the membrane.A series of coalescence units were prepared with different layers of nanofibrous membrane and the separation efficiencies at dif-ferent initial concentrations,flow rates,and oil types were tested.It is very interesting that the obtained nanofibrous membrane exhibited superoleophilicity in air but poor oleophilicity under water,which was beneficial to the coalescence process.The coalescence unit with four membrane layers had excellent per-formances under different initial concentrations and flow rates.The separation efficiency of the 4-layers unit remained above 98.2％ when the initial concentration reached up to 2000 mg·L-1.Furthermore,the unit also exhibited good performance with the increasing oil density and viscosity,which is promising for large-scale oil wastewater treatment.     

Sea‐island polyurethane/polycarbonate composite nanofiber fabricated through electrospinning

Sea‐island polyurethane (PU)/polycarbonate (PC) composite nanofibers were obtained through electrospinning of partially miscible PU and PC in 3 : 7 (v/v) N,N‐dimethylformamide (DMF) and tetrahydrofuran (THF) mixture solvent. Their structures, mechanical, and thermal properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG), and differential scanning calorimetry (DSC). The structures and morphologies of the nanofibers were influenced by composition ratio in the binary mixtures. The pure PC nanofiber was brittle and easy to break. With increasing the PU content in the PU/PC composite nanofibers, PU component not only facilitated the electrospinning of PC but improved the mechanical properties of PU/PC nanofibrous mats. In a series of nanofibrous mats with varied PU/PC composition ratios, PU/PC 70/30 showed excellent tensile strength of 9.60 Mpa and Young's modulus of 55 Mpa. After selective removal of PC component in PU/PC composite nanofibers by washing with acetone, the residual PU maintained fiber morphology. However, the residual PU nanofiber became irregular and contained elongated indents and ridges along the fiber surface. PU/PC composite fibers showed sea‐island nanofiber structure due to phase separation in the spinning solution and in the course of electrospinning. At PC content below 30%, the PC domains were small and evenly dispersed in the composite nanofibers. As PC content was over 50%, the PC phases became large elongated aggregates dispersed in the composite nanofibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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.     

Preparation and characterization of microporous sodium poly(aspartic acid) nanofibrous hydrogel

A novel biodegradable sodium poly(aspartic acid) (PASP) hydrogel with microporous structure was manufactured using electrospun polysuccinimide (PSI) nanofibers. PSI is the intermediate of sodium PASP and could be electospun into nanofibers easily. Firstly, PSI nanofibers were prepared from PSI/N, N-dimethylformamide solution. Then the PSI nanofibrous mats were crosslinked and hydrolyzed to obtain biodegradable microporous sodium PASP nanofibrous hydrogels. The chemical structures, morphologies and pore sizes of PSI nanofibrous mats and microporous sodium PASP nanofibrous hydrogels were investigated. Moreover, the properties of PSI electrospinning solutions, and the swelling ratio and biodegradability of sodium PASP hydrogels were also examined. The results showed that the swelling ratio of microporous sodium PASP nanofibrous hydrogels achieved to 21.0–24.3 g/g and were obviously higher than that of the sodium PASP casting film, reporting a swelling ratio of only 4.6 g/g. When the microporous sodium PASP nanofibrous hydrogel was immersed in water, it exhibited quick absorption and morphological robustness. The microporous sodium PASP nanofibrous hydrogel showed 83 wt% weight loss after 7 days of trypsin catalyzed biodegradation, and the SEM analysis demonstrated the significant morphology change of the microporous sodium PASP nanofibrous hydrogel during the biodegradation.     

苯乙烯-丙烯腈原子转移自由基聚合

采用四氯化碳为引发剂,三氯化铁与丁二酸复合物为催化剂,在N,N-二甲基甲酰胺溶剂中对苯乙烯、丙烯腈进行原子转移自由基共聚合。研究了苯乙烯和丙烯腈物质的量比、引发剂用量、反应时间、温度等工艺条件对共聚物收率的影响。得到最佳反应条件：原料配比n（苯乙烯）：n（丙烯腈）为3：1;引发剂用量为12．5mL,三氯化铁与丁二酸复合催发剂的量分别为0．2865g,0．1180g;反应温度为90％,反应时间48h。     

Spider-net within the N6, PVA and PU electrospun nanofiber mats using salt addition: Novel strategy in the electrospinning process

Electrospun nanofibers are promising candidates in the nanotechnological applications due to the advantages of the nanofibrous morphology. Therefore, many attempts were reported to modify the electrospun mats to gain more beneficial properties. In the present study, we are introducing a strategy to synthesize electrospun polymeric nanofiber mats containing spider-net binding the main nanofibers. Addition with long stirring time of a metallic salt having tendency to ionize rather than formation of sol–gel in the host polymer solution reveals to synthesize a spider-net within the electrospun nanofibers of the utilized polymer. Nylon6, polyurethane and poly(vinyl alcohol) have been utilized; NaCl, KBr, CaCl₂ and H₂PtCl₆ have been added to the polymeric solutions. In the case of nylon6 and poly(vinyl alcohol), addition of the inorganic salts resulted in the formation of multi-layers spider-network within the electrospun nanofibers mats. The synthesized spider-nets were almost independent on the nature of the salt; the optimum salt concentration was 1.5 wt%. The metallic acid led to form trivial spider-nets within both of nylon6 and poly(vinyl alcohol) nanofibers. In a case of polyurethane, few spider-nets were formed after salt addition due to the low polarity of the utilized solvents. According to TEM analysis, the synthesized spider-net consisted of joints; the later issued from the main nanofibers at Taylor's cone zone. The spider-net improved the mechanical properties and the wetability of the nylon6 nanofiber mats, accordingly a mat having amphiphilic feature has been prepared.