CRYSTALLIZATION, MORPHOLOGY, AND DYNAMIC MECHANICAL BEHAVIOR OF SUPRAMOLECULAR [60]FULLERENE-CONTAINING POLY(ETHYLENE-co-ACRYLIC ACID)

A multifunctional [60]fullerene derivative AEAF was melt-mixed with poly(ethylene-co-acrylic acid) (PEAA20). The strong interaction between AEAF and PEAA20, as shown by x-ray photoelectron spectroscopy, enables AEAF to be well dispersed in the amorphous phase of PEAA20. WAXD revealed that the crystallinity of PEAA20 is reduced and the crystallites are deformed by the addition of AEAF. The storage modulus and dynamic glass transition temperature of the polymer increase upon the incorporation of AEAF. Unlike C₆₀ and a monofunctional C₆₀ derivative, AEAF is able to sustain its reinforcing effect in the glass-rubber transition region.     

CRYSTALLIZATION,MORPHOLOGY, AND DYNAMIC MECHANICAL BEHAVIOR OF SUPRAMOLECULAR [60]FULLERENE-CONTAINING POLY(ETHYLENE-co-ACRYLIC ACID)

ABSTRACT

A multifunctional [60]fullerene derivative AEAF was melt-mixed with poly(ethylene-co-acrylic acid) (PEAA20). The strong interaction between AEAF and PEAA20, as shown by x-ray photoelectron spectroscopy, enables AEAF to be well dispersed in the amorphous phase of PEAA20. WAXD revealed that the crystallinity of PEAA20 is reduced and the crystallites are deformed by the addition of AEAF. The storage modulus and dynamic glass transition temperature of the polymer increase upon the incorporation of AEAF. Unlike C₆₀ and a monofunctional C₆₀ derivative, AEAF is able to sustain its reinforcing effect in the glass-rubber transition region.     

Role of jet path on uniformity of electrospun nanofibers

This paper reports on the role of jet path in obtaining uniform and bead free nanofibers during electrospinning process. Polyethylene oxide (PEO) nanofibers were electrospun by varying the molecular weight of PEO and concentration of poly allylamine hydrochloride (PAH) in the spinning solution. Different modes of fiber formation were captured by a camera and analyzed further by image processing technique in order to assess their influence in the formation of uniform and bead free nanofibers. Two different jet paths during fiber formation, namely straight and whipping were assessed. The length of the straight jet path during the fiber formation played a major role in the formation of uniform nanofibers in comparison to the length of the whipping path. The diameter and surface morphology of the nanofibers were characterized by SEM. Nanofibers spun using higher concentration of PAH exhibited longer straight jet path and therefore more uniform nanofibers in comparison to that spun at lower concentration of PAH. Flow simulations of the electrically charged polymer solutions were carried out to observe the changes in the solution flow rate and Taylor cone shape. Increased flow rate and changes in the Taylor cone shape with the increasing PAH concentration in low molecular weight polymer were observed.     

The influence of electrospinning parameters on the morphology and diameter of poly(vinyledene fluoride) nanofibers- effect of sodium chloride

Electrospinning was used to produce PVDF nonwoven fiber mats under varying parameters of polymer concentration, applied voltage, salt content, and spinning distance. The results indicated that both the polymer and salt concentration had a noteworthy influence on both the morphology and diameter of the nanofibers. Improved fiber morphology and increased PVDF fiber diameter were observed as the PVDF concentration was increased. Adding different concentrations of NaCl to the PVDF polymer solution resulted in improved electrospinnability of PVDF resulting in better morphology and with increasing salt content, smaller fiber diameter. In particular increasing the salt content led to well defined fibers in otherwise nonfiber-producing formulations. The applied voltage and spinning distance were also seen to have an influence on the properties of the PVDF nanofibers. Nanofibers without beads were formed under the improved conditions of the different parameters studied.     

Poly(ethylene-co-acrylic acid) stationary phases for the separation of shape-constrained isomers

A new approach for the synthesis of long alkyl chain length stationary phases for use in reversed-phase liquid chromatography is described. Poly(ethylene-co-acrylic acid) copolymers (i.e., (-CH2CH2-)x[CH2CH(CO2H)-]y) with different levels of acrylic acid were covalently bonded to silica via glycidoxypropyl or aminopropyl linkages. 13C cross polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy was used to characterize the new reversed-phase materials. Aspects of shape selectivity were evaluated for six different columns with Standard Reference Material (SRM) 869a, Column Selectivity Test Mixture for Liquid Chromatography. Selectivity for isomer separations was enhanced for stationary phases prepared with poly(ethylene-co-acrylic acid) containing a mass fraction of 5% acrylic acid. The relationship between alkyl conformation and chromatographic properties was studied by 13C magic angle spinning (MAS) NMR measurements, and correlations were made with the composition of the polymer. Finally, the effectiveness of this phase is demonstrated by the separation of several beta-carotene isomers.     

Synthesis of aluminum oxy-hydroxide nanofibers from porous anodic alumina

A novel method for the synthesis of aluminum oxy-hydroxide nanofibers from a porous anodic oxide film of aluminum is demonstrated. In the present method, the porous anodic alumina not only acts as a template, but also serves as the starting material for the synthesis. The porous anodic alumina film is hydrothermally treated for pore-sealing, which forms aluminum oxy-hydroxide inside the pores of the oxide film as well as on the surface of the film. The hydrothermally sealed porous oxide film is immersed in the sodium citrate solution, which selectively etches the porous aluminum oxide from the film, leaving the oxy-hydroxide intact. The method is simple and gives highly uniform aluminum oxy-hydroxide nanofibers. Moreover, the diameter of the nanofibers can be controlled by controlling the pore size of the porous anodic alumina film, which depends on the anodizing conditions. Nanofibers with diameters of about 38-85?nm, having uniform shape and size, were successfully synthesized using the present method.     

Large-scale synthesis of self-doped polyaniline nanofibers

Self-doped polyaniline (SPAN) nanofibers with the diameter of 60–70 nm, and length up to several micrometers have been synthesized by copolymerization of aniline (AN) and m-aminobenzenesulfonic acid (SAN) in aqueous solution using cetyltrimethylammonium bromide (CTAB) as structure directing agent and ammonium peroxydisulfate (APS) as oxidant. The morphology and structure of SPAN nanofibers have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy. The influences of the concentration of the surfactant and the pH value on the resulting products are investigated. It is found that the diameters of SPAN nanofibers decrease with the concentration of CTAB decreased.     

Fast dissolving electrospun polymeric films of anti-diabetic drug repaglinide: formulation and evaluation

Abstract

Objective: Repaglinide is a well-known FDA approved drug from category of meglitinide; used for the treatment of diabetes. However, its use is limited because of its poor water solubility which leads to erratic drug absorption. Present work focuses on formulation and evaluation of polyvinyl alcohol (PVA)-polyvinyl pyrrolidone (PVP) nanofibers to counter this problem of poor water solubility.

Significance: Prepared nanofibers with hydrophilic polymers were expected to tackle the problem of poor water solubility.

Methods: Nanofibers were prepared by electrospinning technique with the optimization of parameters affecting final product. Further prepared formulation was characterized using various techniques.

Results: Successful development of drug loaded nanofibers was commenced utilizing electrospinning technique. Further casted film of same polymeric blend was prepared and compared with nanofibers. Optimized nanofibers showed an average diameter of 600–800?nm with smooth surface morphology. Prepared nanofibers and casted film was analyzed in terms of surface morphology, mechanical strength, solid state of drug present, effects of hydrogen bond formation and drug release profile. Results from the glucose tolerance test suggested both the formulations to be having better control over glucose levels as compared to free drug.

Conclusion: Overall developed nanofibers presented themselves to be potential drug delivery candidates for drugs having poor water solubility.     

Pd/PANI纳米纤维的液相合成及其对乙醇的电化学行为

以苯胺为单体、PdCl₂为金属前驱体、过硫酸铵为氧化剂,在避光条件下液相化学氧化合成Pd/PANI纳米纤维,用XRD、FESEM、TEM、SAED、HRTEM、FT-IR和UV-vis等手段对其表征,研究了 Pd/PANI纳米纤维修饰玻碳电极对乙醇的电化学行为。结果表明,Pd/PANI纳米纤维的平均直径为20 nm,长度为500 nm;平均直径为6 nm的纳米Pd颗粒单分散分布在PANI纤维中;Pd/PANI纳米纤维修饰电极的ECSA值为54.76 m²/g_Pd,是商用Pd/C催化剂(6.08 m²/g_Pd)的9倍,其j_f/j_b值为1.192。     

电纺制备明胶/壳聚糖/羟基磷灰石/氧化石墨烯抗菌复合纳米纤维的研究

本研究模拟细胞外基质成分与结构, 采用静电纺丝法成功制备出明胶/壳聚糖/羟基磷灰石/氧化石墨烯四元复合纤维。重点考察该体系中物质浓度对复合纤维形貌及抗菌性能的影响。结果表明: 明胶浓度增大会增大纤维的直径, 但浓度过大会出现粘连现象, 其最佳浓度为15~20%; 加入壳聚糖(CS)会出现细纤维分支, 其浓度为1%左右较佳; 增加羟基磷灰石(HA)浓度, 可提高电纺液的导电性, 降低纤维中的珠状物和粘联现象发生, 粒径为12 μm的HA浓度为5%时纤维形态较好; 加入氧化石墨烯后可使纤维形态均匀、光滑。最后对四元复合纤维进行了抗菌性能考察, 发现氧化石墨烯的加入增强了复合纤维的抗菌性。明胶/壳聚糖/羟基磷灰石/氧化石墨烯四元复合纤维对金黄色葡萄球菌和大肠杆菌均具有较好的抗菌效果。     

Polyacrylonitrile nanofibers prepared using coaxial electrospinning with LiCl solution as sheath fluid

A modified coaxial electrospinning process including an electrolyte solution as sheath fluid was used for preparing high quality polymer nanofibers. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing a coaxial electrospinning containing LiCl in N, N-dimethylacetamide (DMAc) as the sheath fluid. FESEM results demonstrated that the sheath LiCl solutions have a significant influence on the quality of PAN nanofibers. Nanofibers with smaller diameters, smoother surfaces and uniform structures were successfully prepared. The diameters of nanofibers were controlled by adjusting the conductivity of the sheath fluid over a suitable range and this was determined by varying LiCl concentrations. The influence of the effect of LiCl on the formation of PAN fibers is discussed and it is concluded that coaxial electrospinning with electrolyte solutions is a convenient and facile process for achieving high quality polymer nanofibers.     

连续的旋转电极式无针尖静电纺丝

连续供液的旋转电极式无针尖静电纺丝采用圆柱滚筒电极代替喷丝头实现了高产量纳米纤维制造．该方法避免了喷丝头的堵塞问题,同时也实现了纳米纤维的连续生产．本文利用扫描电镜（SEM）探讨了该制作过程中的关键参数。如溶液浓度、偏置电压、旋转速度以及溶液厚度等对纳米纤维直径的影响．实验结果表明,纳米纤维的平均直径随溶液浓度、圆柱滚筒电极旋转速度和溶液厚度的增大而增大,但随着偏置电压、圆柱滚筒电极直径的增大而减小．圆柱滚筒电极长度为12cm、直径为60mm时制备的纳米纤维产量高达8．7g／h,且纳米纤维的直径均小于500nm．     

Localization of nanofibers on polymer surface using interface transfer technique

A new method to localize polymer nanofibers on a polymer surface was verified using interface transfer technique of nanofibers between immiscible polymer pairs. Nanofibers of poly(butylene terephthalate) (PBT) were prepared in a molten polypropylene (PP) by melt-stretching and subsequent quenching. The obtained composite of PP containing PBT nanofibers was compressed into a flat sheet and piled with a sheet of high-density polyethylene (HDPE). During annealing procedure of the piled sheets at the temperature between melting points (Tm’s) of PP and PBT, PBT nanofibers were transferred from PP to HDPE. Consequently, PBT fibers was confirmed on the surface of HDPE. Similarly, polytetrafluoroethylene (PTFE) nanofibers dispersed in a molten poly(lactic acid) (PLA), which were obtained by mechanical blending process, were found to immigrate to PP during annealing procedure at the temperature between Tm’s of PLA and PTFE. This movement leads to the modification of surface tension for PP. Furthermore, the piled sheets of PP/PBT and HDPE as well as those of PLA/PTFE and PP were easily separated each other because of the immiscible nature.     

Encapsulation of purple membrane patches into polymeric nanofibers by electrospinning

The formation of beaded nanofibers containing purple membrane (PM) by electrospinning of polymer solutions is reported. Electrospinning is known as a versatile method to produce polymeric fibers with diameters on the nanometer scale. Embedding of particles significantly larger than the fiber diameter is unexpected because a breakdown of the spinning process is expected when microscaled particles in the polymer solution pass the nozzle. Presumably due to the flexibility of PM patches, the embedding of the membrane patches into the fibers becomes possible. Embedding into nanofibers may be an alternative to microencapsulation for biomolecules.     

Synthetic-based blended electrospun scaffolds in tissue engineering applications

Journal of Materials Science - Electrospinning, as one of the most common methodologies in nanofibers production, involves applying high voltages to a polymeric solution that is entrapped in a...     

YBCO nanofibers synthesized by electrospinning a solution of poly(acrylic acid) and metal nitrates

A versatile approach to the synthesis of YBCO (high temperature superconductor ceramics) nanofibers via electrospinning a polymer precursor solution is reported. The aqueous polymer precursor solution consists of poly(acrylic acid) (PAAc) and a mixture of yttrium nitrate, barium nitrate, and copper nitrate, henceforth termed (Y,Ba,Cu)–N. The conductivity of the polymer precursor solution at 27.1 °C was 14.70 mS/cm, its zero shear viscosity was 52.00 cP, and its pH was 1.88. Typical YBCO nanofibers were 50–100 nm in diameter and around of 10 μm length. The nanofibers also contain relatively small amounts of yttrium oxide and copper yttrium oxide.     

A simple one-step fabrication of short polymer nanofibers via electrospinning

Short polymer nanofibers were successfully fabricated by electrospinning, a solution composed of a polymer cellulose acetate, acetone, and dimethyl acetamide. The concentration of the polymer in the solution ranged from 13 to 15 wt% and was the most important factor in the fabrication of short nanofibers. The lengths of the short nanofibers were changed via the flow rate of the polymer solution along with the applied voltage. The length was increased by increasing the flow rate of the solution, and it was decreased with an increase in the applied voltage, resulting in a length of short nanofibers that could be controlled at 37–670 μm. The polymer solution jet ejected straight from the needle tip, but then it was spread due to lateral perturbations on the surface of the polymer solution. A rapid increase in the repulsive force from surface charges combined longitudinal forces from the applied voltage split the solution jet and segmented the nanofibers.     

Phase Separation and Theta-compositions of PPES/NMP/non-solvent Systems

Poly (phthalazinone ether sulfone) (PPES) with 1:1 and 1:3 ratios of bisphenol A (BPA) unit to phthalazinone unit were selected as samples. Polymer precipitation curves for the ternary systems PPES (1:1)/NMP/ non-solvent and PPES (1:3)/NMP/non-solvent were determined by a titration method. Comparison between two sets of data is made. Non-solvents used were H2O, ethyl ether (EE), diethylene glycol (DEGC), ethyleneglycol methylether (EGME) and butanone (BO). NMP/non-solvent theta-compositions for PPES (1:1) and PPES (1:3) were also estimated. It was found that the volume ratio of non-solvent to NMP at the property mutation or worsening of PPES membrane is close to the theta-composition.     

Modeling and optimization of electrospun polyvinylacetate (PVAc) nanofibers by response surface methodology (RSM)

Response surface methodology (RSM), a collection of statistical and mathematical techniques, has been widely used to optimize and design operating conditions. Although this method is suitable for optimizing experimental conditions, very few attempts have been made on the electrospinning process. In this work, RSM was used to model and optimize of the electrospinning parameters for polyvinylacetate (PVAc) nanofibers. PVAc solution in acetone was electrospun under various conditions such as concentration of spinning solution and applied voltage. The experimental results indicate that concentrations of solution and applied voltage played an important role on the diameter size of PVAc nanofibers. The second order polynomial function was used to correlate the fiber diameter with the production variables. The predicted fiber diameters were in good agreement with the experimental results.     

Polyamide 6.9 nanofibres electrospun under steady state conditions from a solvent/non-solvent solution

Nanofibres can be processed into several high-end applications due to their unique characteristics, especially when based on a diversity of polymers with specific properties. This, however, requires that the nanofibrous structures are produced in a highly reproducible way. The article gives focus to polyamide (PA) 6.9, a less exploited PA though with interesting properties such as a very low moisture absorption. To trace and understand the dominant parameters that allow for the aimed reproducible characteristics, the influence of the solution parameters on the steady state behaviour during electrospinning as well as the resultant fibre morphology is followed by scanning electron microscopy and differential scanning calorimetry. Results show a significant effect of the amount of non-solvent acetic acid, added to the solvent formic acid, on the steady state behaviour and the fibre morphology. The non-solvent acetic acid broadens the steady state window by making the electrospin solutions more suitable to obtain uniform and reproducible nanofibrous structures with a narrow nanofibre diameter distribution. The mixture of the solvent formic acid and the non-solvent acetic acid strongly contributes to the future potentials of PA 6.9 nanofibres, with its leading to a smaller fibre distribution and moreover highly reproducible in time.