Functional Copolymer/Organo-MMT Nanoarchitectures: XXVI. Fabrication and Characterization of Electrospun Nanofibers from PCL/ODA-MMT and Copolymer-g-PLA/ Ag-MMT Blends

We synthesized poly(?-caprolactone)/octadecyl amine-montmorillonite clay nanocomposite as a matrix polymer by solution intercalative method and new amphiphilic poly(maleic anhydrde-alt-1-octadecene)-g-poly(L-lactic acid)/Ag⁺-montmorillonite clay nanocomposite as a partner polymer by interlamellar graft copolymerization of lactic acid onto anhydride copolymer in the presence of silver salt of montmorillonite clay as catalyst-nanofiller. Novel polymer nanofibers were fabricated by electrospinning of matrix/partner blends with different volume ratios. The nanocomposites and nanofibers were investigated by Fourier transform infrared spectroscopy, thermal gravimetric analysis–differential scanning calorimetry, and scanning electron microscope–transmission electron microscope methods. The diameters, morphologies, and thermal behavior of fibers were strongly depended on the partner-polymer nanocomposites loadings. The fabricated biocompatible and biodegradable nanofibers can be utilized for biomedical and filtration applications.     

Structural characterization and dynamic water adsorption of electrospun polyamide6/montmorillonite nanofibers

A facile compounding process, which combined nanocomposite process with electrospinning for preparing novel polyamide6/organic modified montmorillonite (PA6/O‐MMT) composite nanofibers, is reported. In this compounding process, the O‐MMT slurry was blended into the formic acid solution of PA6 at moderate temperatures, where the nanosized O‐MMT particles were first dispersed in N,N‐dimethyl formamide solvent homogeneously via ultrasonic mixing. Subsequently the solution via electrospinning formed nanofibers, which were collected onto aluminum foil. The O‐MMT platelets were detected to be exfoliated at nanosize level and dispersed homogeneously along the axis of the nanofibers using an electron transmission microscope. Scanning electron microscope and atomic force microscope were used to analysis the size and surface morphology of polyamide6/O‐MMT composite nanofibers. The addition of O‐MMT reduced the surface tension and viscosity of the solution, leading to the decrease in the diameter of nanofiber and the formation of rough and ridge‐shape trails on the nanofiber surface. The behavior of the dynamic water adsorption of composite nanofibers was also investigated and discussed in this article. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Optimization of the electrospinning processing‐window to fabricate nanostructured PE‐b‐PEO and hybrid PE‐b‐PEO/EBBA fibers

An electrospinning technique is used to obtain poly(ethylene‐b‐ethylene oxide) block copolymer (PE‐b‐PEO) fibers. Optimization of the electrospinning processing‐window is carried out by varying the concentration of the block copolymer solution and playing with three different electrospinning parameters, applied voltage, solvent and block copolymer solution flow rate. The influence of the concentration of the block copolymer solution over the length and diameter of the fibers is mainly studied and results indicate that the optimum conditions to fabricate PE‐b‐PEO block copolymer fibers are concentrations between 45 and 47 wt% of PE‐b‐PEO block copolymer and chloroform/DMF mixture ratio of 4:1 and 5:1. Moreover, low solvent and block copolymer solution flow rates led to the longest and widest fibers. Hybrid fibers are also fabricated modifying PE‐b‐PEO block copolymer fibers with low molecular weight N‐(4‐ethoxybenzylidene)?4‐butylaniline (EBBA) nematic liquid crystal using coaxial electrospinning technique. The morphology of the fabricated fibers is investigated from micro to nanoscale. Atomic force microscopy (AFM) results show self‐organization of investigated PE‐b‐PEO and hybrid PE‐b‐PEO/EBBA fibers on the nanometric scale, which make them interesting from the point of view of novel applications as template materials. POLYM. ENG. SCI., 57:1157–1167, 2017. © 2017 Society of Plastics Engineers     

Thermo-responsive nanofibers prepared from poly(N-isopropylacrylamide-co-N-methylol acrylamide)

Thermo-responsive nanofibers were successfully prepared via electrospinning in this study. Poly(N-isopropylacrylamide-co-N-methylol acrylamide), poly(NIPAAm-co-NMA), was used as the material for preparing the electrospinning nanofibers. Poly(NIPAAm-co-NMA) copolymers showed thermo-responsive property in aqueous solution, and such copolymers of NIPAAm and NMA were synthesized via random redox copolymerization. Here, NMA provided the thermal crosslinking function for the copolymer. Thermal curing process was then applied on the copolymer nanofibers for thermal crosslinking and the crosslinked nanofibers could keep the fiber morphology and the copolymer characters while soaking in water. The thermal curing conditions led to different swelling performance, LCST, and morphology of copolymer nanofibers while dipping in water. This study demonstrated that novel nanofibers exhibited thermo-responsive characteristics. The nanofibers of these copolymers were suggested for application as a new kind of sensors, drug carriers, and engineering tissues.     

静电纺工艺参数对SEBS纤维形貌和直径的影响

通过静电纺丝,将苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物(SEBS)溶解于四氢呋喃(THF)中的纺丝液制备成SEBS纤维,探索了纺丝液质量分数、纺丝电压和接收距离对纤维形貌及直径的影响.通过扫描电镜观察SEBS纤维的形貌以及Photoshop软件测量了SEBS纤维的直径.结果表明,纺丝液质量分数为25％、纺丝电压为10 k...     

Synthesis and solution rheology of adenine-containing polyelectrolytes for electrospinning

Conventional free radical copolymerization of 9-vinylbenzyladenine (VBA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) with subsequent protonation afforded the synthesis of adenine-containing polyelectrolytes. All adenine-containing polyelectrolytes exhibited classical polyelectrolyte solution rheological behavior with scaling factors near 0.6 and 1.6 in the semidilute unentangled and semidilute entangled regimes, respectively. However, the adenine-containing polyelectrolytes deviated from polyelectrolyte behavior in the concentrated regime with increasing scaling factors as adenine-incorporation increased due to intermolecular association. The electrospinning behavior exhibited a strong dependence on adenine incorporation. Higher adenine-incorporation decreased the normalized concentration for fiber formation from 4.5C_e for PDMAEMA?HCl to 2.9C_e for 35 mol% VBA. The required zero-shear viscosities for electrospinning were 312 cP for PDMAEMA?HCl and 116 cP for the 35 mol% VBA copolymer. Increasing the adenine concentration also increased the fiber diameters presumably due to adenine–adenine interactions. These adenine-decorated electrospun mats exhibit potential in a variety of applications including filtration, purification, and tissue scaffolding.     

Effect of filler content on the structure‐property behavior of poly(ethylene oxide) based polyurethaneurea‐silica nanocomposites

Poly(ethylene oxide) (PEO) based polyurethaneurea‐silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stöber method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO‐2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO‐4600 and PEO‐8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer‐filler interactions. POLYM. ENG. SCI., 58:1097–1107, 2018. © 2017 Society of Plastics Engineers     

Preparation,characterization, and properties of silicate/polyurethaneurea composites based on dipropylene glycol dibenzoate

The silicate/polyurethaneurea composites based on dipropylene glycol dibenzoate were prepared via a room‐temperature‐cured process. Characterization of the composites was accomplished using scanning electron microscope, X‐ray diffraction, Fourier transformation infrared spectrum, and Raman spectroscopy, and the mechanism, mechanical properties and stability were discussed in detail. The obtained results indicated that a durable silicate/polyurethaneurea composite with inorganic‐organic network structure had been successfully prepared. The composites were thermally stable below 210°C and the compressive and flexural strength of the material could reach 42.6 and 29.2 MPa after curing for 6 h, respectively. POLYM. COMPOS., 37–43, 2016. © 2014 Society of Plastics Engineers     

Effects of some electrospinning parameters on morphology of natural silk‐based nanofibers

Natural silk, from Bombyx mori solutions were electrospun into nanofibers, with diameters ranged from 60 to 7000 nm. The effects of electrospinning temperature, solution concentration and electric field on the formation nanofibers were studied. Optical and scanning electron microscope were used to study the morphology and diameter of electrospun nanofibers. It was observed that the nanofibers became flattened with ribbon‐like shape with increasing the electrospinning temperature. The nanofiber diameter increases with the increase in the concentration of silk solution at all electrospinning temperature. With increasing the voltage of electric field at 50°C, morphology of the nanofibers changes from ribbon‐like structure to circular cross section. Referring to the literature the probable mechanism responsible for the change of morphology is pointed out. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of solvent quality and humidity on the porous formation and oil absorbency of SAN electrospun nanofibers

In this study, nanofibrous mat with high oil sorption capability was prepared via one‐step electrospinning process without any further post‐treatments. For this purpose, the fabrication of styrene/acrylonitrile copolymer nanofibers was carried out using various dimethylformamide (DMF)/tetrahydrofuran and DMF/ethanol (DMF/EtOH) binary mixture ratios in an electrospining atmosphere with various relative humidity (RH) levels. Scanning electron microscope micrographs showed that DMF/tetrahydrofuran and DMF/EtOH ratio and RH value could considerably affect the diameter, surface, and interior morphology of the resultant nanofibers. The nanofiber morphology was dependent upon the polymer/solvent(s)/water ternary phase diagram behavior. In overall, the partial hydrophilicity of styrene/acrylonitrile copolymer resulted in electrospun nanofibers with wrinkled surface. In addition, the incorporation of nonsolvent in the spinning solution and using high RH atmosphere forced the polymeric solution jet to intensively phase separate and, therefore, produce the nanofibers with highly interior porous structure during drying process. The maximal capacity and rate of oil sorption (170 g/g) was observed for the nanofibrous mat prepared using EtOH/DMF (2/3: vol/vol) and RH value of 60% showing the highest internal porosity. The results showed that the oil sorption capability and mechanical strength of the fibrous mat are strongly dependent on nanofibers diameter and porous structure, which can be controlled through adjusting the RH and spinning solvent quality. The electrospun mat with highest Young's modulus (7.68 MPa) was prepared using EtOH/DMF (2/3) binary mixture and RH value of 45%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45586.     

Preparation of photochromic poly(vinylidene fluoride-co-hexafluoropropylene) fibers by electrospinning

Photochromic poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) fibers were prepared by electrospinning from a solution of copolymer and ester-functionalized nitrospiropyran (SPEST) molecules. The surface and internal features of the electrospun (ES) fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction (WAXD). The strong segregation of fluorine-rich groups on the fiber surface, which occurs during and/or after the electrospinning process, is driven by the lower surface tension for fluorine-rich groups and leads to encapsulation of SPEST predominantly near the core of the fibers, as confirmed by both X-ray photoelectron spectroscopy (XPS) and dynamic water contact angle (CA) measurements. The photochromic behavior of the spiropyran is preserved in the polymeric fibers, as confirmed by steady-state absorption and emission spectroscopy. Both isomeric forms of the photochrome in SP-PVDF-co-HFP were emissive, an effect that is thought to be due to the steric and/or electrostatic restrictions on the ring-opening reaction imposed by the fiber.     

丙烯酰胺/丁基苯乙烯衍生物疏水缔合共聚物的溶液性能

采用自由基胶束聚合法合成了丙烯酰胺（AM）/丁基苯乙烯（BS）疏水缔合水溶性共聚物(PSAM).凝胶渗透色谱（GPC）测试结果显示,PSAM的重均分子量为1.6868×10⁵,环境扫描电镜（ESEM）照片显示,PSAM在水溶液中形成了疏水缔合网络结构,结果表明,PSAM的增黏能力主要依赖于疏水结构单元的分子间疏水缔合作用.PSAM溶液性能的研究结果表明,溶液质量浓度超过0.1 g·dl^-1时,共聚物具有优良的增黏、耐盐及耐温性能,在80℃时显示良好的抗老化性能;PSAM亚浓溶液为假塑性流体,具有良好的触变性,低剪切速率下在最初一段时间内呈现剪切增稠性质.     

静电纺丝制备TiO2纳米纤维的光催化性能

纳米TiO2材料在光催化、抗菌等方面有着广泛应用。采用尺寸为20～30nm的TiO2颗粒与聚乙烯吡咯烷酮（PVP）的醇溶液混合制得纺丝液,通过静电纺丝技术与烧结工艺,制得TiO2纳米纤维。采用能谱仪、X射线衍射、扫描电子显微镜和投射电子显微镜等分析手段对样品进行了表征,与采用溶胶–凝胶结合静电纺丝技术得到的TiO2纳米纤维进行了形貌对比,并通过亚甲基蓝降解实验研究其光催化性能。结果表明：以TiO2纳米颗粒为原料通过静电纺丝技术制备的TiO2纳米纤维,主要为多晶相的锐钛矿结构,直径为150～250 nm,长度大于20μm,与溶胶–凝胶结合静电纺丝技术制得的TiO2纳米纤维相比,直径分布更为均匀。在紫外光照射90min时,对浓度为4mg/L的亚甲基蓝溶液的分解率为72%,具有较好的光催化效率。     

Low-surface-free-energy polybenzoxazine/polyacrylonitrile fibers for biononfouling membrane

We blended poly(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) (PBA) into polyacrylonitrile (PAN) to generate low-surface-free-energy fibers without fluorine and silicon elements for electrospinning. Liquid-state BA at room temperature can be solidified in electrospinning process using PAN as a medium through their miscible behavior. Results indicate that the mixing below 50 wt% BA into PAN matrix for electrospinning has no significant dropping beads, indicated a miscible PAN/BA system. Above 70 wt% BA in PAN solution could not be solidified completely after electrospinning, revealed apparent beaded fibers. The PAN/PBA blend fibers, obtained after curing at 300 °C, generated a superhydrophobicity because of the low-surface-free-energy PBA. In addition, laser scanning confocal microscope (LSCM) measurements were included to determine the relative amount of antibody that adsorbed to these PAN/PBA fibers to examine the biofouling-resistant property. The results showed an obviously decreased protein adsorption with increasing PBA fraction. The correlations between PAN and PBA would provide insight into the designing and developing of low-surface-free-energy fibers without fluorine and silicon elements to improve biofouling-resistant property.     

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.     

静电纺丝SF/PLGA纤维支架用于血管组织工程的研究

将丝素蛋白（SF）和乳酸-羟基乙酸共聚物（PLGA）溶解在六氟异丙醇中配制成溶液,采用静电纺丝技术制备了SF/PLGA纳米纤维支架,使用扫描电子显微镜（SEM）对纤维支架进行表征,研究了聚合物溶液浓度、纺丝电压、接收距离以及体积流率对纳米纤维形态的影响,从而得到纺丝的最适宜工艺参数。考察了纤维支架表面对HUVECs细胞的相容性。结果表明：HUVECs可以在SF/PLGA纤维支架表面很好的黏附和增殖,支架具有良好的细胞相容性,在组织工程领域有良好的应用前景。     

Photo/pH dual-responsive behavior of azopyridine-containing copolymer vesicles

The amphiphilic diblock copolymer composed of poly(ethylene oxide) as the hydrophilic chain and polymethacrylate with azopyridine moieties in the side groups as the hydrophobic chain self-assembled to vesicles in the mixture of THF/water. The dual photo- and pH-responsive behavior of the copolymeric vesicles was investigated by UV–Vis absorption spectra and optical microscope. It was found that the trans–cis photoisomerization of azopyridine in the vesicles was influenced by the water content in the mixture and the intensity of light irradiation. Regard to the pH-responsive behavior, the copolymer vesicles dissociated into solution gradually triggered by acid, while they reformed in a basic environment. Furthermore, the UV light irradiation accelerated the process of pH-induced dissociation of the vesicles.     

Electrospun nanofibers of block copolymer of trimethylene carbonate and ϵ‐caprolactone

The electrospinning behavior of a block copolymer of trimethylene carbonate (TMC) and ε‐caprolactone dissolved in N,N‐dimethylformamide (DMF) and methylene chloride (MC) was studied. The effects of the blended solvent volume ratio, concentration, voltage, and tip–collector distance (TCD) on the morphology of the electrospun fibers were investigated by scanning electron microscopy. The results indicated that the diameter of the electrospun fibers decreased with a decreasing molar ratio of MC to DMF, but beads formed gradually. With a decreasing concentration of the solution, the fiber diameter decreased; at the same time, beads also appeared and changed from spindlelike to spherical. A higher voltage and larger TCD favored the formation of smaller diameter electrospun fibers. The results of differential scanning calorimetry and X‐ray diffraction showed that the crystallinity and melting point of the electrospun fibers decreased when increasing the TMC content in the copolymer. Compared with the corresponding films, the crystallinity and melting point of the electrospun fibers were obviously increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1462–1470, 2006     

非良溶剂存在下静电纺PVDF和P(VDF-HFP)纤维的可纺性研究

将聚偏氟乙烯(PVDF)和聚偏氢氟乙烯-六氟丙烯共聚物[P(VDF-HFP)]分别溶解于良溶剂N,N-二甲基乙酰胺(DMAc)和非良溶剂丙酮(Act)的混合体系中(DMAc:Act体积比为3:7),用静电纺丝法制备两种超细纤维。考察了在非良溶剂存在的情况下两种溶液浓度和增比粘度(η8p)的依赖关系,测定了两种溶液中的缠结浓度(Ce)。结果表明,PVDF和[P(VDF-HFP)]两种溶液的浓度的对数和8p的对数在一定的浓度范围内存在线性关系,其Ce的质量分数分别为6．8％和4．8％;静电纺纤维经扫描显微镜观察表明,在缠结数评估失效情况下,Ce对两种含非良溶剂的高聚物溶液可纺性也具有半定量的评估作用。两种溶液浓度低于Ce时无法纺出纤维,主要形成聚合物液滴;Ce是电纺出珠状纤维的最小浓度,而纺出均一的无珠纤维溶液浓度为(2-2．5)Ce。     

Influence of solution properties on the roller electrospinning of poly(vinyl alcohol)

In recent years, nanofiber production via electrospinning has gained importance because of superior properties of submicron fibers. In this study, the effect of molecular weight, concentration of solution, electric conductivity, surface tension and solution viscosity of the polymer solution on the roller electrospinning of PVA nanofibers was investigated. One nonspinnable and two spinnable polymer species were studied. The effect of polymer concentration and solution viscosity on the electrospinning process throughput, fiber diameters and quality of nanofiber layers was measured. According to the results there is a significant difference in rheological behavior of nonspinnable and spinnable polymer solutions. Electric conductivity and surface tension of the solutions did not influence both throughput and fiber diameter significantly. Whereas molecular weight has an important effect on the spinnability, concentration of the solutions has not. On the contrary, concentration influences the process throughput considerably and properties of nanofibers and nanofiber layers to some extent. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers