Nanofiber Network Structure Research Articles

Formation of electrospun nylon-6/methoxy poly(ethylene glycol) oligomer spider-wave nanofibers

A methoxy poly(ethylene glycol) (MPEG) oligomer with a viscous nylon-6 supporting solution was fabricated and polymerized simultaneously to form a nanofiber network structure via electrospinning. This network consisted of thin MPEG nanofibers and thick nylon-6 nanofibers, which were arranged in a spider-web like structure. These two different nanofibers were separated from the electrospun mat by extraction of MPEG using water. This result showed that the hybrid nanocomposite mat consisted of two different interconnecting polymeric nanofibers. We propose that this interconnection is due to the formation of hydrogen bonds between MPEG and nylon-6 molecules. This spider-web structure formed by electrospinning was responsible for increasing the mechanical strength and the wetability of nylon-6 mat in the presence of small amounts of MPEG.

Preparation and enhanced electrochemical properties of nano-sulfur/poly(pyrrole-co-aniline) cathode material for lithium/sulfur batteries

Abstract Poly(pyrrole-co-aniline) (PPyA) copolymer nanofibers were prepared by chemical oxidation method with cetyltrimethyl ammonium chloride (CTAC) as template, and the nano-sulfur/poly(pyrrole-co-aniline) (S/PPyA) composite material in lithium batteries was achieved via co-heating the mixture of PPyA and sublimed sulfur at 160 °C for 24 h. The component and structure of the materials were characterized by FTIR, Raman, XRD, and SEM. PPyA with nanofiber network structure was employed as a conductive matrix, adsorbing agent and firm reaction chamber for the sulfur cathode materials. The nano-dispersed composite exhibited a specific capacity up to 1285 mAh g −1 in the initial cycle and remained 866 mAh g −1 after 40 cycles.

Supramolecular hydrogel-based protein and chemosensor array

The development of protein and sensor arrays is crucial for rapid and high-throughput assays of biological events, markers, environmental pollutants, and others. We describe supramolecular hydrogel as a unique material for use as a matrix for immobilizing proteins, peptides, substrates, chemosensors, and mesoporous silica particles, and thereby array them on solid supports. The semi-wet conditions provided by the gel, which consists of 3D supramolecular nanofiber network structure, are suitable for entrapping such substances whilst retaining their activity and function. Moreover, the hydrophobic interior of the nanofibers of the supramolecular hydrogel can reversibly entrap hydrophobic molecules, which allows the development of various read-out systems, such as fluorescence enhancement and fluorescence resonance energy transfer (FRET), by which one can monitor the signal changes associated with, for instance, molecular recognition and enzyme activity.

Polycondensation and Stabilization of Chirally Ordered Molecular Organogels Derived from Alkoxysilyl Group- Containing l-Glutamide Lipid

A lipophilic L-glutamide-derived lipid with a triethoxysilyl headgroup (Si-lipid) was newly synthesized as a self-assembling organogelator to stabilize the chirally ordered state of the aggregates. The Si-lipid formed nanofibrous network structures in various organic solvents such as benzene, cyclohexane, and dimethylformamide and entrapped them to form gels. The gels were transformed to sols by heat, and this gel-to-sol transition was thermally reversible. Polycondensation of the triethoxysilyl groups was carried out by acid-catalyzed hydrolysis and condensation in a benzene gel and confirmed by 29Si CP/MAS NMR and FT-IR measurements. After polycondensation, a gel state was maintained, and the thermal and mechanical stabilities of the aggregates increased markedly. Interestingly, polycondensation in chloroform and acetonitrile induced gelation, whereas no gelation was observed before polycondensation. Xerogel, which was prepared by freeze drying organogels, had fibrous network structures similar to those of the original gels. A strong CD signal was observed around the amide bonds in a cyclohexane gel at 20 degrees C, indicating that the gel contained chirally oriented structures based on intermolecular hydrogen bonds. An enhanced CD signal was observed even after polycondensation of the ethoxysilyl group of Si-lipid (poly(Si-lipid)) and was maintained at 70 degrees C, which is above the temperature of the gel-to-sol phase transition of the original gel. These results indicate that the formation of siloxane network structure among the fibrous aggregates stabilizes the chiral orientation of lipid aggregates.

Processing and Structure of Carbon Nanofiber Paper

A unique concept of making nanocomposites from carbon nanofiber paper was explored in this study. The essential element of this method was to design and manufacture carbon nanofiber paper with well‐controlled and optimized network structure of carbon nanofibers. In this study, carbon nanofiber paper was prepared under various processing conditions, including different types of carbon nanofibers, solvents, dispersants, and acid treatment. The morphologies of carbon nanofibers within the nanofiber paper were characterized with scanning electron microscopy (SEM). In addition, the bulk densities of carbon nanofiber papers were measured. It was found that the densities and network structures of carbon nanofiber paper correlated to the dispersion quality of carbon nanofibers within the paper, which was significantly affected by papermaking process conditions.

Dependence of carbon fiber morphology with deposition conditions

Carbon fibers with different morphologies including carbon nanotubes, short crossed carbon fibers, carbon nanofiber network structures, and nodular carbon fibers covered with carbon microbeads were synthesized using a floating catalyst method by changing the flow rate of xylene solution containing ferrocene, the concentration of ferrocene in xylene, and carrier gas. The general tendency is: Higher flow rate of xylene solution contributed to the formation of short crossed carbon fibers and deteriorated the graphitic crystalline of carbon fibers, which might play a critical role in their connection. Lower ferrocene concentration in xylene solution improved the graphitization of carbon nanofibers and changed the connection way of carbon nanofibers. Nodular carbon fibers covered with microbeads were obtained in N 2 ambience. Carbon nanotubes with well graphitic crystal were prepared with the concentration of ferrocene in xylene 1.5 g/100 ml, the flow rate of xylene solution 0.12 ml/min and hydrogen 150 ml/min.

Formation and Novel Thermomechanical Processing of Biocompatible Soft Materials

We demonstrated for the first time the thermo-mechanical processing of the organogels of dibutyllauroyl glutamide as a small molecule gelling agent (SMGA) in a biocompatible solvent, isostearyl alcohol. The study focused on the impact of novel thermomechanical processing parameters such as temperature, strain, and the cooling rate on the microstructure and macroscopic properties of gels. The properties of the gels were analyzed by dynamic light scattering and by rheological and electron microscopy methods. The modification of the thermoreversibility and viscoelastic properties of the gels can be associated with the changes in the micro-/nanofiber network structures. The micro-/nanofiber network structures are stable over a wide range of frequencies. Two temperature domains associated with distinct gelation behaviors and rheological properties were identified for the first time in the gelation of organic solvents using SMGA. The transition from one temperature domain to the next can be linked to the changes in the micro-/nanostructure.

Structure design of polysaccharides: novel concepts, selective syntheses, high value applications

Using protecting silyl groups, catalyzed transesterification, and stereochemically controlled SN2 mechanisms examples of well-defined 2-, 3-, 6-, and 2,6-ethers, esters, resp. amino derivatives of cellulose, starch, and related polysaccharides have been synthesized and characterized by two-dimensional NMR spectroscopy. Supramolecularly structured polymer matrices useful in biosensors could be developed by immobilization of enzymes like glucose oxidase and aromatic redox-chromogenic structures at 6-deoxy-6-(4-aminophenyl)-aminocellulose. Cellulose tubes “grown” biotechnologically from D-glucose in the culture medium of Acetobacter xylinum represent novel types of artificial blood vessels because of their unique highly-swollen nanofiber network-structure.

Designing bearing fatigue life tests for improving the use of testing resources: Miller, B. and Hester, D. ASTM J. Test. Eval. May 1989 17, (3), 137–156

The further development of flexible electronics inevitably requires conductive materials to have numerous foldable properties; however, that has not been realized. Here, inspired by silkworm cocooning processes, we prepare a super-foldable conductive carbon material with layered nanofiber network structures through an improved electrospinning/carbonization technique. It can remarkably bear 1,000,000 times repeated true-folding without structural damage and conductivity fluctuations. The root of such performance breakthrough is revealed through real-time SEM folding observation and mechanical simulations. Its structures featuring appropriate pores, non-crosslinked junctions, slidable nanofibers, separable layers, and a compressible network can act synergistically to generate a ε-like folding construction at crease under true-folding, which can completely disperse stress via bulged layers, dispersed arcs, and slidable grooves in ε. Consequently, each nanofiber avoids directly facing with 180° folding when the whole material is true-folded. This work embodies structure innovation, performance breakthrough, and mechanism reveal, which has great scientific significance and application prospects.