Chitin and chitosan nanofibers: electrospinning of chitin and deacetylation of chitin nanofibers

An electrospinning method was used to fabricate chitin nanofibous matrix for wound dressings. Chitin was depolymerized by gamma irradiation to improve its solubility. The electrospinning of chitin was performed with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a spinning solvent. Morphology of as-spun and deacetylated chitin (chitosan) nanofibers was investigated by scanning electron microscopy. Although as-spun chitin nanofibers had the broad fiber diameter distribution, most of the fiber diameters are less than 100 nm. From the image analysis, they had an average diameter of 110 nm and their diameters ranged from 40 to 640 nm. For deacetylation, as-spun chitin nanofibous matrix was chemically treated with a 40% aqueous NaOH solution at 60 or 100 °C. With the deacetylation for 150 min at 100 °C or for 1day at 60 °C, chitin matrix was transformed into chitosan matrix with degree of deacetylation (DD) ∼85% without dimensional change (shrinkage). This structural transformation from chitin to chitosan was confirmed by FT-IR and WAXD.     

Miscibility of chitosan/poly(ethylene oxide) blends and effect of doping alkali and alkali earth metal ions on chitosan/PEO interaction

The miscibility of Chitosan (CS) and poly(ethylene oxide) (PEO) in their blends and the effect of K⁺ and Ca²⁺ doping on the CS/PEO interaction have been investigated in this work. CS and PEO appeared to be miscible and the DSC analysis suggested the Flory-Huggins interaction parameter χ_AB to be −0.21. Doping of K⁺ and Ca²⁺ into the CS/PEO blend matrix enhanced the cooperative interaction between CS and PEO and this enhancement was larger for Ca²⁺ than for K⁺. The difference between Ca²⁺ and K⁺ possibly reflects a stronger multi-valence interaction of Ca²⁺ with the amino and hydroxyl groups of CS as well as the ether groups of PEO to form a stable CS/Ca²⁺/PEO complex and a less significant interaction of K⁺, as suggested by DSC, WAXD and FTIR results. MD simulations clearly indicated the correlation between the dynamic behavior and the interaction of K⁺ and Ca²⁺ in the CS/PEO blend matrix.     

Evaluation of the permeability and blood‐compatibility properties of membranes formed by physical interpenetration of chitosan with PEO/PPO/PEO triblock copolymers

In order to develop blood compatible membranes with controlled porosity, we have fabricated and examined the properties of physical interpenetrating network (PIN) of chitosan and poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymers (Pluronics^®). Degree of equilibrium swelling, scanning electron microscopy, and electron spectroscopy for chemical analysis (ESCA) were used to characterize the bulk and surface properties. Vitamin B₁₂ and human serum albumin were used as permeability markers. Platelet adhesion and activation were used to determine the blood‐interaction properties of the PIN membranes. Unlike chitosan membranes that were nonporous, the chitosan‐Pluronic PIN membranes were highly porous with the pore size, depending on the type of incorporated Pluronic polyol. ESCA results showed a significant increase in the ? C ? O? signal of C1s spectra on the PIN membranes that correlates with the presence of PEO chains on the surface. The permeability coefficients of vitamin B₁₂ and albumin were higher in the chitosan‐Pluronic PIN membranes than in the control. The number of adherent platelets and the extent of activation were significantly reduced on the chitosan‐Pluronic PIN membranes. The decrease in platelet adhesion and activation correlated positively with the PEO chain length of the incorporated Pluronic polyols. The results of this study show that chitosan‐Pluronic PIN membranes offer a blood‐compatible alternative with a higher‐molecular‐weight cutoff for use in hemodialysis and related applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1274–1284, 2001     

聚乙二醇改性壳聚糖薄膜结构与性质的研究

将壳聚糖与聚乙二醇进行共混,利用溶剂挥发成膜法制备了壳聚糖/聚乙二醇二元共混薄膜。通过红外光谱、偏光显微镜、AFM等研究了共混膜的表面形貌、微结构及力学性能。结果表明:聚乙二醇可明显改善壳聚糖薄膜的脆性,当w(PEO)≤20%时,共混物各组分间有较好的相容性。偏光显微镜照片显示共混膜中聚乙二醇颗粒结晶结构随着聚乙二醇量的增加变得更为完整。     

Effect of chitosan on morphology and conformation of electrospun silk fibroin nanofibers

The electrospinning of silk fibroin(SF)/chitosan(CS) blends with different composition ratios was performed with formic acid as a spinning solvent. The SF/CS blends containing up to the CS content of 30% could be electrospun into the continuous fibrous structure, although pure CS was not able to be electrospun into the fibrous structure. As-spun SF/CS blend nanofibers showed smaller diameter and narrower diameter distribution than pure SF nanofibers, and the diameter gradually decreased from 450 to 130 nm with the addition of CS in blends. However, at the blend compositions with above 40 wt% chitosan, the continuous SF nanofibers containing CS beads were produced. We also investigated the influence of the methanol treatment on the secondary structure of as-spun SF or SF/CS blend nanofibers by means of ATR-IR and solid-state CP-MAS ¹³C-NMR. Comparing with the pure SF nanofibers, the conformational change of the as-spun SF/CS blend nanofibers into β-sheet was faster because the CS with rigid backbone synergistically might promote the conformational transition of SF by an intermolecular interaction.     

Effect of spinning temperature and blend ratios on electrospun chitosan/poly(acrylamide) blends fibers

We report the formation of non-woven fibers without bead defects by electrospinning blend solutions of chitosan and polyacrylamide (PAAm) with blend ratios varying from 75 wt% to 90 wt% chitosan using a modified electrospinning unit wherein polymer solutions can be spun at temperatures greater than ambient up to 100 °C. Electrospinning at elevated temperature leads to further expansion of the processing window, by producing fibers with fewer defects at higher chitosan weight percentage in the blends. Effects of varying blend ratios, spinning temperatures, and molecular weights on fiber formation were studied and optimum conditions for formation of uniform non-woven fiber mats with potential applications for air and water filtration were obtained. Uniform bead-less fiber mats with fiber diameter as low as 307 ± 67 nm were formed by spinning 90% chitosan in blend solutions at 70 °C.     

Morphological and kinetics study of PEO/PVC blends

The kinetics of spherulite radial growth and the morphology of the compatible system PEO/PVC have been studied by optical microscopy. The usual spherulite radial growth behaviour has been found for compatible blends with PEO content higher than 70%. For lower composition, distortion of the usual spherulite morphology has been observed; the anomalies have been attributed to partial miscibility of the components.     

PEO在聚合物锂离子电池中的应用

聚氧化乙烯（PEO）可与锂盐形成具有离子导电性的络合物,但PEO的高结晶性使其与锂盐构成的固体电解质在室温下电导率很低,不能满足实际应用要求,因此需对PEO基固体电解质进行改性。简介PEO的特点和离子传导机理,重点介绍提高PEO基固体电解质室温导电性能目前所采取的措施,包括形成共聚物、生成交联聚合物、掺杂复合物盐、加入增塑剂、加入无机填料和制备侧链含PEO链段高聚物。     

静电纺丝制备PANi/PEO微/纳米纤维的研究

采用静电纺丝制备了PANi/PEO微/纳米纤维,研究了纺丝液中PANi/PEO的质量比、纺丝电压、注射流速和喷丝针头孔径对纤维形貌的影响.研究结果表明,PEO含量的增加不仅会增强纺丝液的成纤能力,也会增大纤维的平均直径;纺丝电压的提高有利于纤维的细化,但断丝现象也增强;纤维的平均直径随注射流速和喷丝头孔径的增大而增大.所制备出的PANi/PEO纤维直径分布为258～843 nm.     

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.     

New solid polymer electrolytes based on PEO/PAN hybrids

Hybrid polymer dry electrolytes comprised of poly(ethylene oxide) (PEO), polyacrylonitrile (PAN), and LiClO₄ were investigated. The impedance spectroscopy showed that the effect of PAN on the ion conductivity of PEO‐based electrolytes depends on the concentration of lithium salt. When the mole ratio of lithium to oxygen is 0.062 (15%LiClO₄‐PEO), adding PAN will increase the ionic conductivity. Differential scanning calorimetry, NMR, and IR data suggested that the enhanced conductivity was due to both the decreasing of the PEO crystallinity and increasing of the degree of ionization of lithium salt. There was obviously no interaction between PAN and lithium ions, and PAN acts as a reinforcing filler, and hence contributes to the mechanical strength besides reducing the crystallinity of the polymer electrolytes. When the LiClO₄‐PEO‐PAN hybrid polymer electrolyte was heated at 200°C under N₂, PAN crosslinked partially, which further decreased the crystallinity of PEO and increased the ionic conductivity, and at the same time prevented the recrystallization of PEO upon sitting at ambient environment. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1530–1540, 2006     

静电纺PVA/PEO/多壁碳纳米管超细纤维的制备与性能

采用超声波辅助溶液共混的方式制备聚乙烯醇/多壁碳纳米管(PVA/MWCNT)复合溶液,并将该溶液与聚氧化乙烯(PEO)溶液共混,利用静电纺丝技术制备PVA/PEO/MWCNTs复合超细纤维。运用扫描电子显微镜(SEM)、X-射线衍射仪(XRD)、示差扫描量热仪(DSC)方法对不同MWCNTs含量的PVA/PEO/MWCNTs复合纤维的微观形貌、结构和热性能进行了观察分析。结果表明:随着MWCNTs含量的增加,纤维直径显著变细,MWCNTs的加入降低了纤维的结晶性,纤维的热稳定性有所提高。     

Effects of gamma irradiation on the thermal and mechanical properties of chitosan/PVA nanofibrous mats

Chitosan/poly(vinyl alcohol) (PVA) nanofibrous mats were prepared by the electrospinning method. The morphology and structure of electrospun nanofibers were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. SEM images showed that the uniform and bead-free fibers were obtained at concentrations greater than 8 wt%. Chitosan/PVA mats were irradiated with different doses (50–200 kGy) of ⁶⁰Co gamma rays. The effect of irradiation dose on the mechanical and thermal properties of these films was also investigated. Increasing the irradiation dose led to a decrease in tensile strength. FT-IR and DSC demonstrated that there were strong intermolecular hydrogen bonds between the chitosan and PVA molecules.     

PEO/PBS共混物的共混结晶行为研究

通过差示扫描量热仪、偏光显微镜、原子力显微镜等研究了质量比80/20的聚环氧乙烷(PEO)与聚丁二酸丁二酯(PBS)的共混结晶热力学、结晶形貌、多次熔融重结晶行为。实验结果表明,共混不利于二者的结晶,但熔点低的PEO起到溶剂化作用,使PBS分子链更加规整的折叠排列,晶体完善度提高。共混物熔融结晶时PBS为PEO结晶提供了环带球晶框架:过冷度低时PEO片晶沿着PBS片晶生长,且晶体致密;过冷度高时,PEO片晶的生长不能完全复制PBS的片晶生长方式,在遵循形成环带球晶框架的基础上,PEO片晶按物质自身需求方式生长。此外,共混物在多次经历135℃→80℃→40℃的热处理时,PEO会发生团聚,共混物球晶不再是环带球晶,球晶半径逐渐增大。而PEO在屡次加热中被氧化,以无定形态聚集在两个共混物球晶之间。     

Structure and thermal properties of multilayered Laponite/PEO nanocomposite films

The structures and thermal properties of a series of nanocomposite poly(ethylene oxide)/Laponite films have been investigated by differential calorimetric and thermal analysis and complemented by microscopy and X-ray diffraction experiments. The crystalline structures of the nanocomposite multilayered films can be tuned by controlling the composition, polymer Mw and the water content. We study the concentration, polymer Mw and humidity dependence of polymer crystallinity in selected nanocomposite multilayered films. Results show that the exact sample preparation and history are important in controlling structure and properties and in developing new materials. Complementary microscopy is used to monitor the structural changes.     

PEO在芳纶纸基复合材料开发中的应用研究

芳纶纸基复合材料是目前最高档绝缘材料之一,同时也是航空、航天、国防、电子、通讯等领域中的重要材料。针对国内芳纶纸研制中长期存在的匀度不良而导致的性能不佳的问题,重点研究了开发过程中关键技术助剂PEO的应用。探讨了PEO的用量与纸张性能的关系,以及PEO的作用机理。采用特殊的分散技术与纸页成型工艺及设备,提高成纸的匀度,解决以往芳纶纸制备中存在的纸页匀度差、强度低、性能不够稳定等问题,目前研制的芳纶纸产品性能已接近杜邦同类产品性能标准。     

Preparation of ordered TiO2 nanofibers/nanotubes by magnetic field assisted electrospinning and the study of their photocatalytic properties

Ordered-and-oriented TiO₂ nanofibers and nanotubes were prepared by magnetic field-assisted electrospinning, and photocatalytic properties of all samples were analyzed under UV–Vis shine. TiO₂ nanofibers/nanotubes prepared by magnetic field-assisted electrospinning showed better degradation effect on rhodamine B, reduced the band gap, increased the contact area of organic pollutants with the sample and higher photocatalytic activity than TiO₂ nanofibers/nanotubes prepared by classical electrospinning. The product obtained after high temperature annealing was a mixed phase of rutile phase and anatase phase and could be advantageous to the segregate of photogenic electron hole pairs and enhance the high dye absorption capacity; Surface roughness could increase more active sites and accelerate the reaction rate of photocatalytic activity; the addition of magnetic field regulated the morphology of TiO₂, and narrowed the band gap to favor photocatalytic performance. The magnetic field-assisted electrospinning study prepared in this paper was an easy-to-use and versatile method for the preparation of ordered TiO₂ nanomaterials, which could be easily extended to practical applications or other materials for photocatalysis and water cleavage.     

PEO嵌段分子自组装研究新进展

综述了近年来多醚链(PEO)嵌段分子自组装的研究进展,阐述了不同形状的化合物与其自组装结构的关系,展望了这类多醚链嵌段分子自组装研究体系的潜在应用价值及其发展方向。     

Facile preparation and characterization of poly(vinyl alcohol)/chitosan/graphene oxide biocomposite nanofibers

Poly(vinyl alcohol) (PVA)/chitosan (CS)/graphene oxide (GO) biocomposite nanofibers have been successfully prepared using aqueous solution by electrospinning. CS colloidal gel in 1% acetic acid can be changed to homogeneous solution by using electron beam irradiation (EBI). The uniform distributions of GO sheets in the nanofibers were investigated by field emission scanning electron microscopy (FESEM) and Raman spectroscopy. FESEM images illustrated that the spread single GO sheet embedding into nanofibers was formed via self-assembly of GO sheet and PVA/CS chains. And the average diameters of the biocomposite nanofibers decreased (200, 173, 160 and 123 nm) with increasing the contents of GO (0.05, 0.2, 0.4 and 0.6 wt%). Raman spectra verified the presence of GO in the biocomposite nanofibrous mats. The mechanical properties of as-prepared materials related with GO contents. It revealed that the highest tensile strength was 2.78 MPa, which was 25% higher than that of neat PVA/CS nanofibers. Antibacterial test demonstrated that the addition of GO to PVA/CS nanofiber had great ability to increase inhibition zone till 8.6 mm. Overall, these features of PVA/CS/GO nanofibers which were prepared by eco-friendly solvent can be a promising candidate material in tissue engineering, wound healing and drug delivery system.     

PEO/Na-MMT粉体与聚氯乙烯复合材料的制备及性能研究

通过溶胶凝胶法,制备了聚氧乙烯(PEO)和钠基蒙脱土的复合粉体PMMT,经XRD和透射电镜分析,蒙脱土在聚氯乙烯中基体进行了纳米级的分散;通过对材料力学性能、毛细管流变和TGA测试表明,PMMT对聚氯乙烯具有增韧和增强的效果,同时使PVC的流变性和热稳定性也有一定的提高。