Synthesis, Crystal Structure and Fluorescent Property of One New Complex [Na2（2-benzoylbenzoato）4（Phen）2（H2O）2]·H2O

One binuclear sodium(Ⅰ) complex [Na2(2-benzoylbenzoato)4(Phen)2(H2O)2]·H2O has been synthesized with 2-benzoylbenzoic acid and 1,10-henanthroline as ligands. The crystal structure was determined by X-ray diffraction. The crystal belongs to the triclinic system with space group P , a = 1.08096(8), b = 1.09619(8), c = 1.09740(8) nm, α = 79.0600(1), β = 71.0450(1), γ = 62.0540(1)o, V = 1.08533(1) nm3, Dc = 1.421 g/cm3, Z = 2, F(000) = 484, GOOF = 1.036, the final R = 0.0363 and wR = 0.0961. The crystal structure shows that two neighboring sodium(Ⅰ) ions are linked together by two bridging water molecules, and each end position is coordinated with one 1,10-phenanthroline molecule and one 2-benzoylbenzoato to form a binuclear structure. Each sodium(Ⅰ) ion in the molecule is coordinated with five atoms to give a distorted trigonal bipyramid. The fluorescence property of the title complex is also discussed.     

Thin-film polymerization and characterization of Sumitomo's Sumikasuper®-type liquid crystalline polymers

Using the thin film polymerization approach, we have studied the texture evolution when synthesizing a novel liquid crystalline polymer (LCP) system based on Sumikasuper^® LCPs. The main monomers used were p-acetoxybenzoic acid (ABA), 4,4′-biphenol (BP), isophthalic acid (IA), phthalic acid (PA) and terephthalic acid (TA). Polarizing optical microscopy (POM), FTIR, X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to study the thin film polymerization process and characterize the products. The generation and evolution of liquid crystal phases were monitored; the results revealed that there exists a composition range for the monomers to react and form liquid crystal materials. The critical temperature for LC formation in ABA/BP/IA system decreased with increasing ABA content. FTIR results confirmed the formation of polymers. AFM investigation suggested a similar process of morphological change to that observed using POM. An increasing surface roughness of the thin films with the progress of polymerization was also obtained from AFM analysis. A nematic LC texture of the polymer system was suggested by XRD examination. Results obtained by replacing BP with acetylated BP, and by conducting polymerization using two-monomer systems, suggest that BP units are included in polymers obtained by the thin film polymerization method.     

Analysis of operation mode of reflective twisted nematic liquid crystal display devices with rear film compensation

The rear film compensated reflective twisted nematic liquid crystal display device was studied in normally black and normally white operation conditions using a dynamic parameter space method. The electro-optical responses and reflectance spectra were also studied for different operation modes. A comparison was made between rear film and front film compensated reflective twisted nematic liquid crystal displays. We show that high quality normally white or normally black modes can be obtained by placing the fast axis of a quarter wave plate at 45° or 0° to the input director direction. The viewing angle characteristics of the optimum modes were also studied.     

Sulfur-linked cyanobiphenyl-based liquid crystal dimers and the twist-bend nematic phase

ABSTRACT

The synthesis and characterisation of two series of cyanobiphenyl-based liquid crystal dimers containing sulfur links between the spacer and mesogenic units, the 4?-[1,ω-alkanediylbis(thio)]bis-[1,1?-biphenyl]-4-carbonitriles (CBSnSCB), and 4?-({ω-[(4?-cyano[1,1?-biphenyl]-4-yl)oxy]alkyl}thio)[1,1?-biphenyl]-4-carbonitriles (CBSnOCB) are described. The odd members of both series show twist-bend nematic and nematic phases, whereas the even members exhibit only the nematic phase. An analogous cyanoterphenyl-based dimer, 3⁴-{6-[(4?-cyano[1,1?-biphenyl]-4-yl)thio]-hexyl}[1¹,2¹:2⁴,3¹-terphenyl]-1⁴-carbonitrile (CT6SCB), is also reported and shows enantiotropic N_TB and N phases. The transitional properties of these dimers are discussed in terms of molecular curvature, flexibility and biaxiality. The same molecular factors also influence the birefringence of nematic phases. Resonant X-ray scattering studies of the twist-bend nematic phase at both the carbon and sulfur absorption edges were performed, which allowed for the determination of critical behaviour of the helical pitch at the transition to the nematic phase, the behaviour was found to be independent of molecular structure. It was also observed that despite the different molecular bending angle and flexibility, in all compounds the helical pitch length far from the N-N_TB transition corresponds to 4 longitudinal molecular distances.     

Crystallization of calcium carbonate controlled by Pluronic P123 in room-temperature ionic liquid

The crystallization of calcium carbonate (CaCO₃) controlled by Pluronic P123 in a room-temperature ionic liquid, ethylamine nitrate (EAN), was investigated. The CaCO₃ aggregates were obtained by rapid mixing of ammonium carbonate ((NH₄)₂CO₃) and calcium chloride (CaCl₂). Cubic calcite, spherical vaterite, and bagel-like vaterite were obtained easily by changing P123 concentration and reaction temperature. The morphologies of the as-prepared CaCO₃ aggregates were investigated by transmission electron microscopy and scanning electronic microscopy. The phase change of the obtained crystals was confirmed by X-ray diffraction and Fourier transform infrared spectroscopy. It was shown that higher P123 concentration and higher reaction temperature favor the formation of vaterite in EAN. Unusual bagel-like vaterite was first obtained at 60 °C in the presence of 5 g/L P123 in EAN. Mineralization of CaCO₃ regulated by P123 in EAN is a simple, novel, and environment-friendly strategy for vaterite synthesis.     

Facile synthesis of gemini surface-active ATRP initiator and its use in soap-free AGET ATRP mini-emulsion polymerisation

A novel cationic gemini surfactant has been readily synthesised in 70 % total yield. The functional gemini surfactant can act both as an emulsifier and an atom transfer radical polymerisation (ATRP) initiator in mini-emulsion polymerisation of methyl methacrylate (MMA), in which no other emulsifier was required. 1-(Dimethylamino)dodecane (N,N-dimethyldodecylamine, DMDA) was found to be a good ligand in the activator generated by electron transfer (AGET) ATRP reaction. Kinetic studies indicated that the polymerisation featured controlled/living radical polymerisation.     

A quantum mechanics/molecular mechanics study on the hydrolysis mechanism of New Delhi metallo-β-lactamase-1

New Delhi metallo-β-lactamase-1 (NDM-1) has emerged as a major global threat to human health for its rapid rate of dissemination and ability to make pathogenic microbes resistant to almost all known β-lactam antibiotics. In addition, effective NDM-1 inhibitors have not been identified to date. In spite of the plethora of structural and kinetic data available, the accurate molecular characteristics of and details on the enzymatic reaction of NDM-1 hydrolyzing β-lactam antibiotics remain incompletely understood. In this study, a combined computational approach including molecular docking, molecular dynamics simulations and quantum mechanics/molecular mechanics calculations was performed to characterize the catalytic mechanism of meropenem catalyzed by NDM-1. The quantum mechanics/molecular mechanics results indicate that the ionized D124 is beneficial to the cleavage of the C–N bond within the β-lactam ring. Meanwhile, it is energetically favorable to form an intermediate if no water molecule coordinates to Zn2. Moreover, according to the molecular dynamics results, the conserved residue K211 plays a pivotal role in substrate binding and catalysis, which is quite consistent with previous mutagenesis data. Our study provides detailed insights into the catalytic mechanism of NDM-1 hydrolyzing meropenem β-lactam antibiotics and offers clues for the discovery of new antibiotics against NDM-1 positive strains in clinical studies.     

Synthesis of high molecular weight and narrow molecular weight distribution poly(acrylonitrile) via RAFT polymerization

Well‐defined polyacrylonitrile (PAN) of high viscosity‐average molecular weight (M_η = 405,100 g/mol) was successfully synthesized using reversible addition‐fragmentation chain transfer polymerization. The polymerization exhibits controlled characters: molecular weights of the resultant PANs increasing approximately linearly with monomer conversion and keeping narrow molecular weight distributions. The addition of 0.01 equiv (relative to monomer acrylonitrile) of Lewis acid AlCl₃ in the polymerization system afforded the obtained PAN with an improved isotacticity (by 8%). In addition, the influence of molecular weights and molecular weight distributions of PANs on the morphology of the electrospun fibers was investigated. The results showed that, under the same conditions of electrospinning, average diameter (247–1094 nm) of fibers increased with molecular weights of PANs, and it was much easier to get “uniform” diameter fibers while using PANs with narrow molecular weight distributions as the precursor of electrospinning. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Electrical properties of La0.6Ca0.4MnO3–Bi3.4Nd0.6Ti3O12 thin films derived by a sol–gel process

Magnetoelectric (ME) xLa_0.6Ca_0.4MnO₃–(1 ? x)Bi_3.4Nd_0.6Ti₃O₁₂ (LCMO–BNT) composite thin films have been prepared by a sol–gel process and spin-coating technique. The effects of LCMO content on the microstructure, leakage current density, ferroelectric properties, fatigue endurance and ME voltage coefficient of LCMO–BNT thin films derived by sol–gel method were studied. It was found that the composite thin films have better fatigue endurance properties and lower leakage current densities compared with pure BNT thin films, as well as large ME voltage coefficients.     

Fabrication of ZIF‐8@SiO2 Core–Shell Microspheres as the Stationary Phase for High‐Performance Liquid Chromatography

The unique features of high porosity, shape selectivity, and multiple active sites make metal–organic frameworks (MOFs) promising as novel stationary phases for high‐performance liquid chromatography (HPLC). However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOF‐packed columns. Herein, the fabrication of monodisperse MOF@SiO₂ core–shell microspheres as the stationary phase for HPLC to overcome the above‐mentioned problems is reported. Zeolitic imidazolate framework 8 (ZIF‐8) was used as an example of MOFs due to its permanent porosity, uniform pore size, and exceptional chemical stability. Unique carboxyl‐modified silica spheres were used as the support to grow the ZIF‐8 shell. The fabricated monodisperse ZIF‐8@SiO₂ packed columns (5 cm long × 4.6 mm i.d.) show high column efficiency (23 000 plates m^?1 for bisphenol A) for the HPLC separation of endocrine‐disrupting chemicals (bisphenol A, β‐estradiol, and p‐(tert‐octyl)phenol) and pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole, and pymetrozine) within 7 min with good relative standard deviations for 11 replicate separations of the analytes (0.01–0.39, 0.65–1.7, 0.70–1.3, and 0.17–0.91 % for retention time, peak area, peak height, and half peak width, respectively). The ZIF‐8@SiO₂ microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF‐8 crystals.