Preparation of a cellulose acetate/organic montmorillonite composite porous ultrafine fiber membrane for enzyme immobilization

Four types of fibrous membranes based on cellulose acetate (CA)—CA membranes with nonporous fibers, CA/organic montmorillonite (O‐MMT) membranes with nonporous fibers, CA membranes with porous fibers, and CA/O‐MMT membranes with porous fibers—were prepared by electrospinning, and then, they were used for enzyme immobilization. The surface morphologies of the composite fibrous membranes were investigated with scanning electron microscopy and transmission electron microscopy. The optimum pH was 3.5 for all of the immobilized enzymes, and the optimum temperature was 50 °C. Compared with the free enzyme, the immobilized enzyme showed better stability for pH and temperature changes. Moreover, the addition of O‐MMT and the pores on the fibers improved the storage stability and the operational stability. Among the four kinds of fibrous membranes, the CA/O‐MMT membranes with porous fibers showed the best stability for the immobilized enzymes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43818.     

Electrospun ultrafine composite fibers from organic‐soluble chitosan and poly(ethylene oxide)

The ultrafine composite fibers had been successfully achieved by electrospinning of chloroform solutions of octadecyl chitosan (O‐CS) and poly(ethylene oxide) (PEO). The ultrafine composite fibers membranes were subjected to detailed analysis by Fourier‐transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and water contact angle (WCA). The FTIR results confirmed that ultrafine composite fibers contained the two polymers. The SEM images showed that the morphology and diameter of the composite fibers were mainly affected by the weight ratio of O‐CS/PEO, the electric field strength, and the collection distance. The WCA data demonstrated that the composite fibers membranes performed a quite hydrophobic character. The special morphology of neck and porous structure was observed experimentally during electrospinning. The neck structure was due to the fibers elongated in the direction of stretching through the electric field, and the porous structure was decided by the competition between the phase separation and the fast evaporation rate of chloroform. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

纳米羟基磷灰石增强聚己内酯/明胶纤维膜的制备及其性能

引导组织再生膜在引导组织再生术中发挥着关键作用,高性能的引导组织再生膜能更好地促进组织再生修复。本文以纳米羟基磷灰石（n-HA）、聚己内酯（PCL）、明胶（Gel）为原料,通过静电纺丝法制备了不同含量n-HA增强的PCL/Gel/n-HA纤维膜,并对其形貌、组成、力学性能及降解性能进行了研究。SEM结果表明,纤维膜中的纤维形态良好,纤维直径大致分布于200～400nm之间,交联后纤维直径明显增加;TEM结果表明,n-HA较均匀分散在纤维中,随着n-HA含量的增加,n-HA在纤维膜表面发生聚集。力学测试结果表明,随着n-HA含量的增加显著提高了纤维膜的拉伸强度和断裂伸长率,当n-HA含量约为15%时,其拉伸强度和伸长率分别达到9.18MPa和180%。n-HA加入后,纤维膜的降解速率明显降低,n-HA含量约为15%的复合纤维膜体外降解12周以后约降解25%。本文制备的PCL/Gel/n-HA纤维膜的力学性能和降解速率能满足临床对引导组织再生膜的性能要求。     

Poly(lactic acid)/poly(vinyl pyrrolidone) membranes produced by solution blow spinning: Structure,thermal, spectroscopic,and microbial barrier properties

Submicrometric and nanometric poly(lactic acid)/poly(vinyl pyrrolidone) (PLA/PVP) fibrous membranes containing 0, 5, 10, 15, and 20 wt % PVP, with or without 20 wt % Copaiba oil (Copaifera sp.), were produced by solution blow spinning (SBS), using polymer injection rate of 120 μL min^?1, gas pressure of 2.4 kPa, working distance of 20 cm, and collector rotation of 200 rpm. The morphological, thermal, and spectroscopic properties of these membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TG), and Fourier transform infrared spectroscopy (FTIR). A method for the evaluation of membrane microbial barrier properties based on resazurin colorimetric method was proposed. Results showed that the addition of both PVP and Copaiba oil produced thicker fibers; otherwise, there was no effect on morphology. Thermal analyses (TG and DSC) indicated the immiscible nature of polymer blends produced, also confirmed by the spectroscopic studies. Antimicrobial barrier properties were related to the antimicrobial effect of Copaiba oil, combined with it hydrophobic nature. The hydrophilic nature of PVP favored degradation of fiber mats, impairing barrier property when higher concentrations of PVP were added. Results indicate that produced spun mats can potentially be used in applications such as wound dressing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44802.     

Electrospun poly(L‐lactide)/poly(ε‐caprolactone) blend fibers and their cellular response to adipose‐derived stem cells

Polymer blending is one of the most effective methods for providing new, desirable biocomposites for tissue‐engineering applications. In this study, electrospun poly(L ‐lactide)/poly(ε‐caprolactone) (PLLA/PCL) blend fibrous membranes with defect‐free morphology and uniform diameter were optimally prepared by a 1 : 1 ratio of PLLA/PCL blend under a solution concentration of 10 wt %, an applied voltage of 20 kV, and a tip‐to‐collector distance of 15 cm. The fibrous membranes also showed a porous structure and high ductility. Because of the rapid solidification of polymer solution during electrospinning, the crystallinity of electrospun PLLA/PCL blend fibers was much lower than that of the PLLA/PCL blend cast film. To obtain an initial understanding of biocompatibility, adipose‐derived stem cells (ADSCs) were used as seed cells to assess the cellular response, including morphology, proliferation, viability, attachment, and multilineage differentiation on the PLLA/PCL blend fibrous scaffold. Because of the good biocompatibility and nontoxic effect on ADSCs, the PLLA/PCL blend electrospun fibrous membrane provided a high‐performance scaffold for feasible application in tissue engineering using ADSCs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Conductive polymers/polyacrylonitrile composite fibers: Fabrication and properties

Polypyrrole/polyacrylonitrile, polyaniline/polyacrylonitrile, and poly(3,4‐ethylenedioxythiophene)/polyacrylonitrile composite fibres were fabricated successfully by in situ polymerization. The morphologic observations confirmed the uniformly‐covered polyacrylonitrile fiber surface by conductive conjugated polymers. These composite fibers exhibited conductivity in the range of 1.4 × 10⁻² to 5.2 × 10⁻¹ S cm⁻¹. Improved thermal stability of the composite fibers was observed from thermogravimetric analysis results. Structural analysis indicated that the interactions of both hydrogen‐bonding and the electrostatic attraction existed between polyacrylonitrile chains and conjugated polymers. These novel composite fibers still possessed original fibrillar morphology and strength properties and showed a good stability to atmosphere and washing. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Fabrication of discontinuous fibers of poly (N‐vinylpyrrolidone) containing metalloporphyrin molecules

This study described the preparation of discontinuous fibers of poly (N‐vinylpyrrolidone) (PVP) containing metalloporphyrin (Manganese (III) tetrakis (1‐methyl‐4‐pyridyl) porphyrin pentachloride) molecules using electrospinning method. SEM images showed that before adding the metalloporphyrin molecules, the electrospun nanofibers are straight and smooth, while after adding metalloporphyrin molecules into the PVP solutions, the SEM images clearly showed that there were two different types of fibers: the thinner fibrous phase and the thicker discontinuous fibers. The chemical composition of the resulting PVP/metalloporphyrin composite fibers was characterized by Fourier‐transform infrared (FTIR) and energy dispersive X‐ray (EDX) analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6017–6022, 2006     

Perfluorinated sulfonic acid ionomer/poly(N-vinylpyrrolidone) nanofiber membranes: Electrospinning fabrication, water stability, and metal ion removal applications

Perfluorinated sulfonic acid ionomer/poly(N-vinylpyrrolidone) (PFSA/PVP) fibrous membranes with varying compositions were prepared by electrospinning. The morphology, physicochemical structure and water stability of these membranes were investigated by SEM, XRD, and FTIR. The crosslinking agent 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt (DAS) was added to the spinning solutions, and its effect on electrospinning behavior and PFSA/PVP membrane morphology was investigated. Thermal annealing of the DAS-containing PFSA/PVP fibrous membranes resulted in improved water stability due to PVP crosslinking. The adsorption properties of the nanofiber membranes were measured by the ability to remove Cu²⁺ and Ca²⁺ ions from water. Nanofiber membranes with higher surface area provide more exposed functional groups and thus better ion removal capability. These functional PFSA/PVP nanofiber membranes show applicability in water treatment and may find potential applications in sensors and drug delivery or as components of the catalytic layer of proton-exchange membrane fuel cells.     

Effects of coagulation bath temperature and polyvinylpyrrolidone content on flat sheet asymmetric polyethersulfone membranes

In this study, effects of coagulation bath temperature (CBT) and polyvinylpyrrolidone (PVP K15) concentration as a pore former hydrophilic additive on morphology and performance of asymmetric polyethersulfone (PES) membranes were investigated. The membranes were prepared from a PES/ethanol/NMP system via phase inversion induced by immersion precipitation in a water coagulation bath. The morphology of prepared membranes was studied by scanning electron microscopy (SEM), contact angle measurements, and mechanical property measurements. Permeation performance of the prepared membranes was studied by separation experiments using pure water and bovine serum albumin (BSA) solution as feed. The obtained results indicate that addition of PVP in the casting solution enhances pure water permeation flux and BSA solution permeation flux while reducing protein rejection. Increasing CBT results in macrovoid formation in the membrane structure and increases the membrane permeability and decreases the protein rejection. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effect of additives concentration on performance of cellulose acetate and polyethersulfone blend membranes

Asymmetric micro porous membranes have been prepared successfully from blending of cellulose acetate (CA) and polyethersulfone (PES) by the phase inversion method with N, N-dimethylformamide (DMF) as solvent. Two additives were selected in this study, including polyethylene glycol 600 (PEG 600) and polyvinylpyrrolidone (PVP). The effects of concentration of additives on CA/PES blend membrane performance and cross-section morphology were investigated in detail. CA/PES membranes were compared with CA/PES/PEG and CA/PES/PVP membranes in the performance such as pure water flux, membrane resistance, porosity and cross-section morphology. The resulting blend membranes were also carried out the rejection and permeate flux of Egg Albumin (EA) proteins with molecular weight of 45 Da. The membranes thus obtained with an additive concentration of 5 wt% of both PEG and PVP exhibited superior properties than the 80/20% blend composition of CA and PES membranes. The permeate flux of protein was increased from 44 to 134 lm² h with increase in concentrations of both PVP and PEG in 80/20% blend composition of CA and PES membranes. Cross-sectional images from scanning electron microscopy showed larger macropores in the bottom layer of the membranes with increasing additives content. Observations from scanning electron microscopy provided qualitative evidence for the trends obtained for permeability and porosity results.     

Structure, mechanical properties and degradation behaviors of the electrospun fibrous blends of PHBHHx/PDLLA

Blends of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(d,l-lactic acid) (PDLLA) with different ratios were fabricated into fibrous membranes by electrospinning processes. Suggested by DSC, WAXD, and SAXS results, the molecular chains of PHBHHx and PDLLA were partially mixed in the amorphous phase, PDLLA didn’t affect the growth of PHBHHx crystalline phase, and PDLLA was excluded from PHBHHx lamella stacks, i.e. in form of interstack segregation, in the blend fibrous matrix. The mechanical properties of the electrospun fibrous membranes depended on the orientation of fibers in the membranes. The electrospun membranes had higher elongation; furthermore, the tensile strength and modulus of the fibers within the membranes were higher than the corresponding cast membranes. As the content of PDLLA increased, the electrospun fibrous membranes of the blends showed higher elongation and lower tensile modulus due to the decreased number of lamellae. According to the change of molecular weight distribution, both PHBHHx and PDLLA portions in the electrospun blend membranes followed bulk erosion and PDLLA degraded faster than PHBHHx during the degradation process. The morphology change of the electrospun fibrous blends during the hydrolytic degradation indicated that the degradation behaviors were strongly influenced by the miscibility and the structural phase segregation of PHBHHx/PDLLA blend in the electrospun fibers.     

利用静电纺丝技术制备多孔聚苯乙烯纤维

利用静电纺丝技术制备聚苯乙烯（PS）聚乙烯吡咯烷酮（PVP）复合纤维,通过除去复合纤维中的PVP成分,成功地制备了PS多孔纤维,并对其进行了SEM谱图分析测试。结果表明,纺丝电压、PS与PVP配比直接影响着复合纤维的微观形态;PS／PVP复合纤维的浸泡时间、浸泡后的干燥方式、PS与PVP配比都会影响PS多孔纤维的表面形态以及纤维的内部结构。     

Effect of Additive Concentration on Cellulose Acetate Blend Membranes-Preparation,Characterization and Application Studies

Abstract

Ultrafiltration techniques have particular advantages for simultaneous purification, concentration, and fractionation of macromolecules. A comparative study is presented on novel ultrafiltration polymeric blend membranes based on cellulose acetate (CA) prepared in the absence and presence of polymeric additives such as polyethylene Glycol 200 (PEG) and polyvinylpyrrolidone (PVP) by phase inversion technique using N,N′-dimethylformamide (DMF) as solvent. Polymer blend composition, additive concentration and casting, and gelation conditions were standardized for the preparation of asymmetric membranes by pore statistics and morphology. These blend membranes were characterized for compaction in ultrafiltration experiments at 414 kPa pressure in order to attain steady state flux and is reached within 4–5 h. The pure water flux was measured at 345 kPa pressure. Membrane hydraulic resistance derived by measuring water flux at various transmembrane pressures and found to be inversely proportional to pure water flux. Water content is estimated by simple drying and weighing procedures and found proportional to pure water flux for all the membranes. The molecular weight cut-offs (MWCOs) of different membranes were determined with proteins of different molecular weights and found to vary from 20 to 69 kDa depending on the PEG 200 and PVP content in the blend in the casting solution. Skin surface porosity of the membranes was analyzed by scanning the samples at various magnifications. The characterized CA, CA/PEG200 and CA/PVP membranes were used for cadmium ion rejection studies at 345 kPa.     

Shape stability enhancement of PVDF electrospun polymer electrolyte membranes blended with poly(2-acrylamido-2-methylpropanesulfonic acid lithium)

The purpose of this study is to overcome the poor dimensional stability of poly(vinylidene fluoride) (PVDF)-based electrospun membranes for polymer electrolytes, a new type of composite fibrous membranes based on PVDF/poly(2-acrylamido-2-methylpropanesulfonic acid lithium) (PAMPSLi) blend systems with different blend ratios were fabricated by electrospinning method. Morphology of the composite fibrous membranes was evaluated by scanning electron microscopy. Average diameters of the membranes were less than 250 nm, which were far less than that of pure PVDF fibrous membrane (400 nm). Fourier transform infrared spectroscopy and Raman scattering were used to characterize the interactions of two polymers. Wide-angle X-ray diffraction and differential scanning calorimetry techniques were applied to investigate the crystal structure of composite fibrous membranes. Owning to the good miscibility between PVDF and PAMPSLi, no phase-separated microstructure was observed in composite fibrous membranes. The membranes possessed a good wettability by liquid electrolytes and exhibited an excellent dimensional stability even at high loading of electrolytes. The polymer electrolyte showed the ionic conductivity of 3.45 × 10^?3 S/cm at room temperature and electrochemical stability up to 5.4 V for the blend ratio of 5/1. PVDF/PAMPSLi (5/1)-based polymer electrolyte was observed much more suitable than polymer electrolytes with other ratios of PVDF/PAMPSLi for application in high-performance lithium rechargeable batteries.     

Biodegradable nanofibrous membrane of zein/silk fibroin by electrospinning

BACKGROUND: Electrospinning of natural polymers offers a promising approach to generate nanofibers with a similar fibrillar structure to that of native extracellular matrix. In the present work, zein/silk fibroin (SF) blends were electrospun with formic acid as solvent to fabricate bicomponent nanofibrous scaffolds for biomedical applications. RESULTS: The zein/SF electrospun nanofibers had a smaller diameter and narrower diameter distribution than pure zein nanofibers, and the average diameter gradually decreased from 265 to 230 nm with increasing SF content in the blend. The predominant presence of α‐helix zein structure and random coil form of silk I in blend fibrous membranes was confirmed from Fourier transform infrared spectral and wide‐angle X‐ray diffraction data, while conversion to the β‐sheet structure of SF was also detected. The tensile strength of the zein/SF fibrous membranes was improved as the content of SF in the blend fibers increased. A preliminary study of in vitro degradation and cytotoxicity evaluated by MTT assay indicated that biodegradable zein/SF fibrous membranes did not induce cytotoxic effects in an L929 mouse fibroblast system. CONCLUSION: Biodegradable zein/SF fibrous membranes with good mechanical properties and cytocompatibility combine the beneficial characteristics of the individual components and may be useful for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Influence of the dilute‐solution properties of cellulose acetate in solvent mixtures on the morphology and pervaporation performance of their membranes

The pervaporation performance of cellulose acetate (CA) membranes prepared from acetone (AC), acetone/tetrahydrofuran (AC/THF), acetone/chloroform (AC/CF), and acetone/cyclohexane (AC/CYH) was studied for separating MeOH/MTBE (methyl tert‐butyl ether) mixture with 5 (wt) % MeOH. The dilute‐solution properties and Huggins constant (K_H) of CA dissolved in AC and AC/solvent mixtures with 15 vol % of the second solvent (tetrahydrofuran, chloroform, or cyclohexane) were examined. J and α of the CA membranes were affected by the types of solvent mixtures used to prepare the casting solutions. Under the same conditions, the membrane with AC/CYH had the highest J value and the lowest α value, and it was followed by the membranes with AC/CF, AC/THF, and AC. The increasing value of J and decreasing value of α for the CA membranes from different solvent mixtures were in good agreement with the increasing value of K_H of CA in corresponding solvent mixtures. Furthermore, differences in the morphology from scanning electron microscopy images of the cross sections or from atomic force microscopy photographs of the surfaces of the membranes existed, and they provided proof of the different pervaporation performances of the CA membranes prepared from AC and AC/solvent mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97:1891–1898, 2005     

Morphology,physical, and mechanical properties of potentially applicable coelectrospun polysulfone/chitosan-polyvinyl alcohol fibrous membranes in water purification

Polysulfone (PSU) is a widely used polymer in water purification membranes. However, its hydrophobicity hinders its practical application. Herein, the wettability of PSU has been improved by producing a coelectrospun fibrous composite membrane using a hydrophilic component, chitosan-polyvinyl alcohol (CS-PVA). First, different proportions of PVA and CS solutions were mixed and electrospun to prepare CS-PVA blend fibers. Scanning electron microscope (SEM) observations revealed that CS-PVA blend fibers with maximum CS content can be obtained in 30:70 CS:PVA weight ratio. The optimum CS-PVA solution was subsequently used alongside PSU solution and were fed into two distinct syringes, which were then electrospun simultaneously at a constant voltage and distance of 15 kV and 15 cm, respectively. Different composite compositions of PSU/CS-PVA were achieved using different feeding rates for each solution. Based on SEM images, the prepared composite fibers were beadless. The ultimate strength of the composite mats decreased by increasing the amount of CS-PVA due to the significant difference in the fiber diameter of each component and the resulting stress concentration. However, the thermal stability of composite membranes remained almost the same as pure PSU fibers. Moreover, samples with higher CS-PVA content showed better wettability and higher water flux.     

Fabrication of continuous aligned polyvinylpyrrolidone fibers via electrospinning by elimination of the jet bending instability

In this study, we successfully fabricated highly aligned polyvinylpyrrolidone (PVP) fibers and crossed mats by restraining and eliminating the jet bending instability through a dual‐opposite‐spinnerets electrospinning (DOSES) method. The DOSES process was photographed by a digital camera, and the morphology of the fibers was analyzed with field emission scanning electron microscopy. We argue that the elimination of the jet whipping and bending instability was achieved by adjusting the concentration of the polymer solution. When the concentration of PVP solution was raised to more than 15 wt %, two individual fibers stuck together were obtained without the appearance of the jet bending instability at a suitable take‐up velocity. This study demonstrated solid improvement in both the alignment of the polymer yarns and the fabrication of individual fibers side by side. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of polyvinylpyrrolidone on morphology and performance of hemodialysis membranes prepared from polyether sulfone

Flat‐sheet hemodialysis membranes were prepared by phase inversion technique using polyether sulfone (PES) dissolved in dimethylacetamide (DMAc) with and without the addition of polyvinylpyrrolidone (PVP). The effect of the composition of the casting solution on membrane morphology and performance were investigated. The performances of membranes were elucidated on the basis of removal of uremic toxins (urea, uric acid, and creatinine) from human blood serum. The membrane prepared from 12 wt % PES with 2.8 wt % PVP demonstrated better performance compared to the other compositions. The membrane performance is a consequence of membrane morphology. Membranes with channel‐like or long finger‐like structures provide superior removal efficiencies. If the morphology turns to a sponge structure, the effectiveness is diminished. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3804–3813, 2004     

Development of Electrospun Composite Fibers in Multiscale Structure and Investigating the Performance on Proliferation and Osteogenic Differentiation of ADSCs

Electrospun composite membranes in multiscale structures are developed for bone tissue engineering. Aligned polycaprolactone (PCL) fibers entrapping CA‐HAp microparticles (containing CaCO₃, hydroxyapatite, and casein in a hierarchical organization) are electrospun to find whether synergistic effects of fiber alignment and CA‐HAp microparticles on improving osteogenic differentiation can be obtained. CA‐HAp microparticles are in a spherical morphology of 1.42 ± 0.26 µm. Their presence increases fiber diameter and does not significantly affect fiber alignment. On all membranes, adipose derived stem cells (ADSCs) from humans spread very well. On a random group, cells distribute randomly and the presence of CA‐HAp microparticles facilitates cell proliferation, especially for the one at CA‐HAp/PCL 50 wt%; the one at CA‐HAp/PCL 20 wt% shows significantly much higher alkaline phosphatase (ALP) activity (112.0% higher) than the pure PCL membrane. On aligned samples, cells align along fibers and expression of ALP is enhanced. However, at the same composition (CA‐HAp/PCL 20 wt%), the random sample has much higher ALP activity than the aligned sample. The expressions of osteogenic marker genes are also evaluated. Combining the results and the applicability of membranes together, the random membrane at CA‐HAp/PCL 20 wt% is the best candidate for bone tissue engineering.