Synthesis and properties of ortho‐linked aromatic polyimides based on 1,2‐bis(4‐aminophenoxy)‐4‐tert‐butylbenzene

A bis(ether amine) containing the ortho‐substituted phenylene unit and pendant tert‐butyl group, 1,2‐bis(4‐aminophenoxy)‐4‐tert‐butylbenzene, was synthesized and used as a monomer to prepare polyimides with six commercial dianhydrides via a conventional two‐stage procedure. The intermediate poly(amic acid)s had inherent viscosities of 0.78–1.44 dL/g, and most of them could be thermally converted into transparent, flexible, and tough polyimide films. The inherent viscosities of the resulting polyimides were in the range of 0.46–0.87 dL/g. All polyimides were noncrystalline, and most of them showed excellent solubility in polar organic solvents. The glass‐transition temperatures of these polyimides were in the range of 222–259 °C in differential scanning calorimetry and 212–282 °C in thermomechanicl analysis. These polyimides showed no appreciable decomposition up to 500 °C in thermogravimetric analysis in air or nitrogen. A comparative study of the properties with the corresponding polyimides without pendant tert‐butyl groups derived from 1,2‐bis(4‐aminophenoxy)benzene is also presented. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1551–1559, 2000     

Syntheses and properties of organosoluble polyimides based on 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4, 7‐methanohexahydroindan

A series of organosoluble aromatic polyimides (PIs) was synthesized from 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4,7‐methanohexahydroindan (3) and commercial available aromatic dianhydrides such as 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA), 4,4′‐sulfonyl diphthalic anhydride (SDPA), or 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropanic dianhydride (6FDA). PIs (III_c–f), which were synthesized by direct polymerization in m‐cresol, had inherent viscosities of 0.83–1.05 dL/g. These polymers could easily be dissolved in N,N′‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylformamide (DMF), pyridine, m‐cresol, and dichloromethane. Whereas copolymerization was proceeded with equivalent molar ratios of pyromellitic dianhydride (PMDA)/6FDA, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA)/6FDA, or BTDA/SDPA, or ½ for PMDA/SDPA, copolyimides (co‐PIs), derived from 3 and mixed dianhydrides, were soluble in NMP. All the soluble PIs could form transparent, flexible, and tough films, and they showed amorphous characteristics. These films had tensile strengths of 88–111 MPa, elongations at break of 5–10% and initial moduli of 2.01–2.67 GPa. The glass transition temperatures of these polymers were in the range of 252–311°C. Except for III_e, the 10% weight loss temperatures (T_d) of PIs were above 500°C, and the amount of carbonized residues of the PIs at 800°C in nitrogen atmosphere were above 50%. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1681–1691, 1999     

A graphene oxide facilitated a highly porous and effective antibacterial regenerated cellulose membrane containing stabilized silver nanoparticles

Regenerated nanocomposite cellulose membranes embedded with silver nanoparticles (AgNP) and AgNP-graphene oxide (AgGO) were prepared in this study. The as-synthesized AgNP and AgGO were added respectively to a cellulose solution that was prepared by dissolving cellulose in a precooled NaOH/urea (NU) solvent. The solution mixtures were further regenerated into nanocomposite membranes through coagulation in an acidic solution. UV-Vis and TEM results revealed the improved stability of the AgGO compared to that of the AgNP in NU solutions. As revealed by FESEM, the AgGO nanocomposite membrane possessed a more porous structure than a membrane containing AgNP. Antibacterial tests demonstrated that the cellulose membrane of AgGO inhibited the growth of both Staphylococcus aureus and Escherichia coli more effectively than the AgNP nanocomposite membrane, with a lower concentration of AgGO. This work provides a proven and effective method to prepare novel functional cellulose membranes with antibacterial properties, thus broadening the applications of cellulose.     

Ascorbic Acid‐Assisted Synthesis of Mesoporous Sodium Vanadium Phosphate Nanoparticles with Highly sp2‐Coordinated Carbon Coatings as Efficient Cathode Materials for Rechargeable Sodium‐Ion Batteries

Herein, mesoporous sodium vanadium phosphate nanoparticles with highly sp²‐coordinated carbon coatings (meso‐Na₃V₂(PO₄)₃/C) were successfully synthesized as efficient cathode material for rechargeable sodium‐ion batteries by using ascorbic acid as both the reductant and carbon source, followed by calcination at 750 °C in an argon atmosphere. Their crystalline structure, morphology, surface area, chemical composition, carbon nature and amount were systematically explored. Following electrochemical measurements, the resultant meso‐Na₃V₂(PO₄)₃/C not only delivered good reversible capacity (98 mAh g^?1 at 0.1 A g^?1) and superior rate capability (63 mAh g^?1 at 1 A g^?1) but also exhibited comparable cycling performance (capacity retention: ≈74 % at 450 cycles at 0.4 A g^?1). Moreover, the symmetrical sodium‐ion full cell with excellent reversibility and cycling stability was also achieved (capacity retention: 92.2 % at 0.1 A g^?1 with 99.5 % coulombic efficiency after 100 cycles). These attributes are ascribed to the distinctive mesostructure for facile sodium‐ion insertion/extraction and their continuous sp²‐coordinated carbon coatings, which facilitate electronic conduction.     

Luminescent Dinuclear Bis‐Cyclometalated Gold(III) Alkynyls and Their Solvent‐Dependent Morphologies through Supramolecular Self‐Assembly

A series of luminescent bis‐cyclometalated gold(III) complexes containing bridging alkynyl ligands of different natures has been synthesised and characterised. The photophysical properties of the complexes have been investigated through electronic absorption spectroscopy and emission studies. The vibronic emission bands are found to originate from the triplet intraligand (IL) π–π* excited states of the bis‐cyclometalating ligands with some mixing of ³IL π–π* character of the alkynyl ligands. The electrochemical study of a nonsymmetric dinuclear complex shows two successive reduction processes originating from the reductions of the two different cyclometalating ligands. The complexes are found to undergo supramolecular self‐assembly processes driven by π–π stacking and hydrophobic/hydrophilic interactions to give honeycomb nanostructures, as revealed from the SEM images. Solvent‐dependent morphological transformations have also been observed, which have been studied by SEM and ¹H NMR spectroscopy.     

Synthesis and FET characterization of novel ambipolar and low‐bandgap naphthalene‐diimide‐based semiconducting polymers

A novel series of naphthalene‐diimide‐based semiconducting polymers ( P1–P4 ) containing benzodithiophene or dithienopyrrole were successfully synthesized for ambipolar semiconducting materials showing near infrared absorptions. The incorporation of a 3‐hexylthiophene (3HT) spacer extended the intramolecular charge‐transfer (ICT) peak from λ_onset = 739 nm ( P1 ) to 785 nm ( P3 ). Moreover, about 250 nm red‐shift of the ICT peaks was observed in P2 and P4 compared to P1 and P3 due to the increased high‐lying HOMO energy levels. The grazing incidence X‐ray scattering of the P3 and P4 films proved the slightly improved crystalline order in the π?π stacking direction, indicating that the planar backbone is probably due to the introduced 3HT. The P1–P4 ‐based field‐effect transistor showed n‐type dominant ambipolar characteristics. The P2 and P4 showed higher electron mobilities up to 1.5 × 10^?2 cm² V^?1 s^?1 than P1 and P3 , which might be influenced by the orientation of the polymer backbone and the intermolecular orbital overlap. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 359–367     

Di‐nuclear zinc complexes containing tridentate imino‐benzotriazole phenolate derivatives as efficient catalysts for ring‐opening polymerization of cyclic esters and copolymerization of phthalic anhydride with cyclohexene oxide

Zinc catalysts incorporated by imino‐benzotriazole phenolate ( IBTP ) ligands were synthesized and characterized by single‐crystal X‐ray structure determinations. The reaction of the ligand precursor ( ^C1DMeIBTP ‐H or ^C1DIPIBTP ‐H) with diethyl zinc (ZnEt₂) in a stoichiometric proportion in toluene furnished the di‐nuclear ethyl zinc complexes [(μ‐ ^C1DMeIBTP )ZnEt]₂ ( 1 ) and [(μ‐ ^C1DIPIBTP )ZnEt]₂ ( 2 ). The tetra‐coordinated monomeric zinc complex [( ^C1PhIBTP )₂Zn] ( 3 ) or [( ^C1BnIBTP )₂Zn] ( 4 ) resulted from treatment of ^C1PhIBTP ‐H or ^C1BnIBTP ‐H as the pro‐ligand under the similar synthetic method with ligand to metal precursor ratio of 2:1. Single‐crystal X‐ray diffraction of bimetallic complexes 1 and 2 indicates that the ^C1DMeIBTP or ^C1DIPIBTP fragment behaves a NON‐tridentate ligand to coordinate two metal atoms. Catalysis for ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL), β‐butyrolactone (β‐BL), and lactide (LA) of complexes 1 and 2 was systematic studied. In combination with 9‐anthracenemethanol (9‐AnOH), Zn complex 1 was found to polymerize ε‐CL, β‐BL, and L‐LA with efficient catalytic activities in a controlled character. This study also compared the reactivity of these ROP monomers with different ring strains by Zn catalyst 1 in the presence of 9‐AnOH. Additionally, Zn complex 1 combining with benzoic acid was demonstrated to be an active catalytic system to copolymerize phthalic anhydride and cyclohexene oxide. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 714–725     

Synthesis,characterization and photocatalytic properties of CaNb2O6 with ellipsoid-like plate morphology

Ellipsoid-like two-dimensional (2D) plates of calcium niobate (CaNb₂O₆) were synthesized via the hydrothermal route without any surfactants or templates by controlling the reaction conditions, viz. the pH value, reaction time and temperature. The prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fluorescence spectroscopy, and diffuse reflectance UV–vis spectroscopy. It was found that the plates were consisted of uniaxially aligned nanorods and can absorb UV light with wavelengths of less than 340 nm. Compared with the powder of the same material prepared by the solid-state reaction method, the ellipsoid-like 2D plates exhibited a much lower room temperature luminescence intensity and higher photocatalytic activity for the degradation of Rhodamine B dye solution under UV light irradiation. The enhanced photocatalytic activity of the plates was assigned to their higher optical absorption capability, higher diffusion rate of charge carriers and higher surface area resulting from their reduced dimensionality.     

等离子辅助分子束外延技术研究生长在Si(111)衬底的氮化镓pn结

利用等离子辅助分子束外延系统研究了生长在硅(111)衬底的氮化镓pn结,并将其应用于光学器件．硅和镁分别用做n和p掺杂,反射高能电子衍射图像显示氮化镓pn结层具有良好的表面形貌,结层厚度约为0.705 nm,且为六方结构．室温下X射线衍射对称摇摆曲线中(0002)面的ω/2θ显示,半峰宽为0.340,说明氮化镓pn结质量高．另外,在硅和镁掺杂样品中没有A1峰淬灭．光致发光光谱表明pn结样品具有良好的光学性能．镍和铝作为分别作为正面和背面的电极接触应用于光学器件,该器件的电流电压特性显示了典型的异质结整流特性．正向接触镍经过氮气中退火处理10 min,结果表明,600 oC处理的样品比400 oC处理和未经处理的样品具有更高的增益．