We study the effect of the gap size on the molecular orientation and crystalline structure of uniaxially well‐aligned nylon‐6 nanofibers produced in the gap between negatively charged metal plates. ...The relative intensities of several absorbance bands are found to be different in the parallel‐ and perpendicularly polarized FTIR spectra. X‐ray analysis indicates that the metastable γ‐form is predominant in as‐spun nylon‐6 nanofibers, and is transformed into the thermodynamically stable α‐form by increasing the gap size. The polymer chains are thought to be oriented perpendicular to the fiber direction, and the molecular orientation to the fiber axis is enhanced on increasing the gap size.
Polarized FTIR spectroscopy and WAXD of macroscopically well‐aligned electrospun nylon‐6 nanofibers suggest that the polymer chains are oriented perpendicular to the fiber direction in uniaxially aligned electrospun nylon‐6 nanofibers. The degree of molecular orientation relative to the fiber axis was enhanced by increasing the gap size of the collector electrode during electrospinning.
In this study, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofiber membranes with different amounts of polyethylene glycol (PEG) and polyethylene glycol dimethacrylate (PEGDMA) ...oligomer were fabricated via electrospinning. The obtained nanofiber membranes were subsequently thermal treated to produce physically bonded structures and chemically cross-linked networks, which were confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) and wide-angle X-ray diffraction (WAXD). Young’s modulus of electrospun nanofiber membrane with the composition of PVDF-HFP/PEG/PEGDMA (6/1/3, w/w/w) was approximately three times for the case of nanofiber membrane and four times for the case of single nanofiber higher than that of pure PVDF-HFP nanofiber, respectively. The characteristic of cell cycling performance was demonstrated as the possibility of its application at ambient temperature. The electrospun PVDF-HFP nanofiber membrane presented great electrolyte uptake because the membrane had higher porosity due to the structural features of nonwoven fabric, and the amorphous regions in PVDF-HFP could trap large amounts of liquid electrolyte. Also, the cell performance of the membrane as the separator declared high discharge capacity. As the result, the reinforced electrospun composite nanofiber membrane was found to be a promising candidate as a separator for lithium-ion batteries.
In this study, nylon-6 nanofiber mats containing Fe super(2+) ions were fabricated via electrospinning. The resultant electrospun nylon-6/FeCl sub(2) nanofiber mats were characterized by SEM, TEM, ...Fourier transform IR spectroscopy, wide angle XRD and DSC. Unique morphological features, such as spider's-web-like morphologies, were observed and became evident with increasing additive Fe super(2+) ions. The metastable gamma form was predominant in the as-spun nylon-6 nanofibers. The relative intensity of such gamma form gradually decreased with increasing additive Fe super(2+) ions, indicative of transformation of the crystalline structure in the electrospun nylon-6/FeCl sub(2) nanofibers due to strong molecular interactions between the nylon-6 backbone and the additive Fe super(2+) ions. The effects of additive Fe super(2+) ions on the mechanical properties of both nonwoven nanofiber mats and single nanofibers were investigated. In particular, Young's modulus of nylon-6/FeCl sub(2) single nanofibers gradually increased from 1.46 to 5.26 GPa with increasing additive Fe super(2+) ions. copyright 2013 Society of Chemical Industry The crystallinity and mechanical properties of the nylon-6/FeCl sub(2) nanofibers were significantly influenced by the Fe super(2+)-ion additives. Unique morphological features, such as spider-net like morphologies, were observed at higher sub(Fe) ( greater than or equal to 15 wt%).
We studied the thermal insulation, antibacterial and mold properties of the nanofiber laminated wallpapers prepared by laminate-coating using electrospinning method. The thermal insulation capability ...of the nanofiber laminated wallpapers was evaluated by using a home-made insulated environmental chamber under different environmental conditions. It was found that the nanofiber laminated wallpapers exhibited better thermal insulation performance than the conventional silk wallpaper, which was commercialized silk wallpapers prepared by polyacrylic resin, suggesting that the laminate-coated nanofiber layer played an effective role in thermal insulation. Compared to the normal silk wallpaper, the nanofiber laminated wallpaper also exhibited good moisture vapor transmission rate (MVTR) due to excellent vapor permeability. In addition, TiO2-containing nanofiber laminated wallpapers exhibited good antibacterial activity against both E. Coli and P. Aeruginosa.
NAD kinase is a crucial enzyme for production of NADP
+
.
Myxococcus xanthus
is a gram-negative soil bacterium that forms fruiting bodies and spores under starvation, and it accumulates polyphosphate ...(poly(P)) during early development. We found that
M. xanthus
NAD kinase (PanK) utilized both ATP and poly(P) as phosphoryl donors; therefore, PanK was designated as a poly(P)/ATP-NAD kinase. Unlike other poly(P)/ATP-NAD kinases, PanK hardly exhibited NADH kinase activity. The NAD kinase activity of PanK was inhibited by NADPH, but not NADH. Replacement of Thr-90 in the GGDGT motif of PanK with Asn decreased both ATP- and poly(P)-dependent NAD kinase activities; however, poly(P)-dependent NAD kinase activity was further decreased by approximately 6- to 10-fold compared with ATP-dependent NAD kinase activity, suggesting that Thr-90 in the GGDGT motif of PanK may be important for poly(P) utilization. PanK preferred ATP and short-chain poly(P) as phosphoryl donors. The
K
m
of PanK for ATP, poly(P)
4
, and poly(P)
10–15
was 0.66 mM, 0.08 mM, and 0.71 mM, respectively, and the catalytic efficiency (
k
cat
/
K
m
) for poly(P)
4
was 2.4-fold higher than that for ATP, suggesting that
M. xanthus
under starvation conditions may be able to efficiently generate NADP
+
using PanK, ATP, and poly(P).
PDF
