Facile fabrication and characterization of polyimide nanofiber reinforced photocured hybrid electrolyte for Li‐ion batteries

In this study, a novel ion conductive polyimide (PI) nanofiber reinforced photocured hybrid electrolyte has been fabricated. Polyimide fibers were fabricated with the reaction between 4,4′‐oxydianiline (ODA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) followed by electrospinning and thermal imidization methods. Then, PI electrospun fibers were dipped into hybrid resin formulation containing bisphenol A ethoxylate dimethacrylate (BEMA), poly (ethylene glycol) methyl ether methacrylate (PEGMA) and 3‐(methacryloyloxy) propyltrimethoxysilane (MEMO) and then photocured to prepare PI nanofiber reinforced electrolyte membrane. Photocured membranes were soaked into lithium hexafluorophosphate (LiPF₆) before measuring electrochemical stability and ionic conductivity of hybrid polyelectrolyte. The chemical structure and electrochemical performance of the electrolytes were examined by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and scanning electron microscopy (SEM) analysis. The incorporation of MEMO into organic matrix effectively increased the modulus from 2.83 to 5.91 MPa. The obtained results showed that a suitable electrolyte for Li‐ion batteries with high lithium uptake ratio, high conductivity (7.2 × 10^?3 S cm^?1) at ambient temperature and wide stability window above 5.5 V had been prepared. Copyright © 2017 John Wiley & Sons, Ltd.     

Enhanced Catalytic Activity of Cobalt Porphyrin in CO2 Electroreduction upon Immobilization on Carbon Materials

In a comparative study of the electrocatalytic CO₂ reduction, cobalt meso-tetraphenylporphyrin (CoTPP) is used as a model molecular catalyst under both homogeneous and heterogeneous conditions. In the former case, employing N,N-dimethylformamide as solvent, CoTPP performs poorly as an electrocatalyst giving low product selectivity in a slow reaction at a high overpotential. However, upon straightforward immobilization of CoTPP onto carbon nanotubes, a remarkable enhancement of the electrocatalytic abilities is seen with CO₂ becoming selectively reduced to CO (>90 %) at a low overpotential in aqueous medium. This effect is ascribed to the particular environment created by the aqueous medium at the catalytic site of the immobilized catalyst that facilitates the adsorption and further reaction of CO₂. This work highlights the significance of assessing an immobilized molecular catalyst from more than homogeneous measurements alone.     

New acetylated flavone C-glycosides from Iris lactea

Chemical investigation of the aerial parts of Iris lactea afforded three new flavone C-glycosides including 4?-O-acetyl-embinin (1), 2?,4?-O-diacetyl-embinin (2) and 6″,4?-O-diacetyl-embinin (3) along with the known analogue embinin (4). Their structures were elucidated by 1D and 2D NMR spectroscopic analysis as well as by HRESIMS data. The sugars were characterized following acid hydrolysis of the respective glycosides and TLC analysis compared to known standards. Duplicated signals can be observed in the NMR spectra, indicating the presence of rotamers caused by rotational hindrance around the glycosyl-flavone CC linkage. All isolated compounds were tested for their antimicrobial and cytotoxic activities but found to be inactive.     

Investigating cyclic sotolon,maple furanone and their dimers in solution using optical rotation,electronic circular dichroism and vibrational circular dichroism

The experimental optical rotation (OR), electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra of (R)-3-hydroxy-4,5-dimethylfuran-2(5H)-one (sotolon, 1) and (R)-5-ethyl-3-hydroxy-4-methylfuran-2(5H)-one (maple furanone, 2) taken in chloroform were compared to their spectra calculated with time-dependent density functional theory (TDDFT). Sotolon was shown to exist as a dimer in chloroform while maple furanone remains a monomer. Transition state barriers for the enol/keto tautomerization of sotolon were calculated and found to be high. The VCD method offers promise to ultimately distinguish between the presence of monomers or dimers.     

Rapid,efficient and solvent-free synthesis of (un)symmetrical xanthenes catalyzed by recyclable sulfated polyborate

The present study describes a rapid, simple and straightforward approach to the synthesis of 1,8-dioxo-octahydroxanthenes, 14-phenyl-14H-dibenzo[a,j]xanthene and tetrahydrobenzoxanthene-11-ones under solvent-free conditions using sulfated polyborate as a highly efficient catalyst. The procedure offers several advantages including cleaner reaction profile, mild reaction condition, economic, recyclable and environmentally benign catalyst, high yields, simple experimental and workup procedures. While non-extractive work up/purification, along with reusability of catalyst make this method economically affordable for large scale.     

Three-component synthesis and optical properties of triarylpyridines containing a buta-1,3-diene-1,1,3-tricarbonitrile fragment

The synthesis of triarylpyridine derivatives containing a buta-1,3-diene-1,1,3-tricarbonitrile fragment via the base-promoted reactions of aromatic aldehydes, 2-phenylacetophenone and a malononitrile dimer in the presence of an oxidant is described. The influence of aryl substituents in the 4-position on the optical properties is also reported.     

Uranium-bearing francolites present in organic-rich limestones of NW Greece: a preliminary study using synchrotron radiation and fission track techniques

Synchrotron radiation techniques (μ-XRF and μ-XANES) were applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. The UL ₃-edge of μ-XANES spectra showed that uranium was present in tetravalent form. U-bearing francolite crystals were separated from the rock and characterized by Raman spectroscopy and microprobe. The analysis of the crystals also indicated the presence of sodium and sulfur. The uranium presence in the crystals was also visualized, after neutron irradiation and etching, by the observation of the fission tracks.

     

O-methylcyclovirobuxine-D — A new alkaloid fromBuxus sempervirens

The amounts and compositions of the essential oils in the leaves and fruit of Meyer's lemon in the various vegetation periods have been studied. It has been established that as the fruit ripens the amount of essential oils and of monoterpene hydrocarbons in its peel and in the leaves increases.Institute of Plant Biochemistry, Academy of Sciences of the Georgian SSR. Sukhumi Zonal Experimental Station of Essential-Oil Crops. Sukhumi Experimental Station of Subtropical Crops, All-Union Institute of Plant Growing. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 784–787, November–December, 1985.     

SOCl2 and POCl3 as reducing agents for TcO 4 − formation and EPR detection of Tc(VI)-compounds

Pertechnetate, TcO ₄ ^– , is reduced by thionyl chloride and phosphoryl chloride, respectively, to yield semistable Tc(VI) intermediates which can easily be detected by EPR spectroscopy. Spectra are recorded in liquid and frozen solutions. EPR data as well as chemical behaviour suggest the compounds obtained to be oxochloro complexes of technetium(VI).     

Challenge and Solution of Characterizing Glass Transition Temperature for Conjugated Polymers by Differential Scanning Calorimetry

Thermomechanical properties of polymers highly depend on their glass transition temperature (T _g). Differential scanning calorimetry (DSC) is commonly used to measure T _g of polymers. However, many conjugated polymers (CPs), especially donor–acceptor CPs (D–A CPs), do not show a clear glass transition when measured by conventional DSC using simple heat and cool scan. In this work, we discuss the origin of the difficulty for measuring T _g in such type of polymers. The changes in specific heat capacity (Δc _p) at T _g were accurately probed for a series of CPs by DSC. The results showed a significant decrease in Δc _p from flexible polymer (0.28 J g^?1 K^?1 for polystyrene) to rigid CPs (10^?3 J g^?1 K^?1 for a naphthalene diimide‐based D–A CP). When a conjugation breaker unit (flexible unit) is added to the D–A CPs, we observed restoration of the Δc _p at T _g by a factor of 10, confirming that backbone rigidity reduces the Δc _p. Additionally, an increase in the crystalline fraction of the CPs further reduces Δc _p. We conclude that the difficulties of determining T _g for CPs using DSC are mainly due to rigid backbone and semicrystalline nature. We also demonstrate that physical aging can be used on DSC to help locate and confirm the glass transition for D‐A CPs with weak transition signals. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1635–1644