Dicarboxylic acid promoted immortal copolymerization for controllable synthesis of low‐molecular weight oligo(carbonate‐ether) diols with tunable carbonate unit content

Low‐molecular weight oligo(carbonate‐ether) diols are important raw materials for polyurethane formation, which with tunable carbonate unit content (CU) may endow new thermal and mechanical performances to polyurethane. Herein, facile synthesis of oligo(carbonate‐ether) diols with number average molecular weight (M_n) below 2000 g mol^?1 and CU tunable between 40% and 75% are realized in high activity by immortal copolymerization of CO₂/propylene oxide (PO) using zinc‐cobalt double metal cyanide complex (Zn‐Co‐DMCC) in the presence of sebacic acid (SA). M_n of the oligomer is in good linear relationship to the mole ratio of PO and SA (PO/SA) and hence can be precisely controlled by adjusting PO/SA. Besides, the molecular weight distribution is quite narrow due to the rapid reversible chain transfer in the immortal copolymerization. High pressure and low temperature are favorable for raising CU. In all the reactions, the weight fraction of propylene carbonate (W_PC) can even be controlled as low as 2.0 wt %, and the catalytic activity of Zn‐Co‐DMCC is above 1.0 kgg^?1 cat. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Bis(β‐ketoamino)copper(II)/methylaluminoxane systems for homo‐ and copolymerizations of methyl acrylate and 1‐hexene

Two bis(β‐ketoamino)copper [ArNC(CH₃)CHC(CH₃)O]₂Cu ( 1 , Ar = 2,6‐dimethylphenyl; 2 , Ar = 2,6‐diisopropylphenyl) complexes were synthesized and characterized. Homo‐ and copolymerizations of methyl acrylate (MA) and 1‐hexene with bis(β‐ketoamino)copper(II) complexes activated with methylaluminoxane (MAO) were investigated in detail. MA was polymerized in high conversion (>72%) to produce the syndio‐rich atactic poly(methyl acrylate), but 1‐hexene was not polymerized with copper complexes/MAO. Copolymerizations of MA and 1‐hexene with 1 , 2 /MAO produced acrylate‐enriched copolymers (MA > 80%) with isolated hexenes in the backbone. The calculation of reactivity ratios showed that r(MA) is 8.47 and r(hexene) is near to 0 determined by a Fineman‐Ross method. The polymerization mechanism was discussed, and an insertion‐triggered radical mechanism was also proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1113–1121, 2010     

Novel organometallic aromatic polyester based on ferrocene

<正>A novel polyester containing ferrocenyl was prepared by low-temperature interface polycondensation of 1,1'-ferrocenedicarboxylic acid chloride with 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ),which is a twisted non-coplanar heterocyclic bisphenol-like monomer.The newly generated polymer was evaluated based on characterization of its solubility,viscosity measurements,elemental analysis,FTIR spectroscopy,differential scanning calorimetric and thermogravimetric studies.     

Study of structural stabilities and optical properties of HgTe under high pressure

A theoretical investigation on the structural stabilities and electronic properties of HgTe under high pressure was conducted using first principles based on density functional theory. Our results demonstrate that the sequence of the pressure-induced phase transitions of HgTe is from the zinc blende, to cinnabar, rocksalt, orthorhombic, and CsCl-type structures. The pressure effects on the optical properties were discussed and compared with previous calculations and experimental data whenever available.     

Electrodeposited molybdenum-doped Co3O4 nanosheet arrays for high-performance and stable hybrid supercapacitors

Journal of Solid State Electrochemistry - Long-cycle stability and high-energy density are big challenges for developing high-performance hybrid supercapacitor (HSC) electrode materials. In this...     

A black hole preying on the star for a gamma-ray burst of GRB080503: Evidence for the second event in this new class

In this paper, we critically assess GRB080503, a short gamma-ray burst with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike). The light curve of the prompt γ-ray emission of GRB080503 resembles that of GRB 060614 which has been suggested to be due to an event from an intermediate mass black hole (IMBH) preying on a star. We therefore propose that GRB080503 is also due to a similar event; the mass of the IMBH is estimated to be about 4.6×10⁴ solar masses, and the engulfed star had about the same mass and size as the Sun. We also estimate that the total burst energy is about 7.67 × 10⁵⁰ ergs.

     

Dynamic quality of transmission optimization and global impairments control in reconfigurable transparent WDM networks:schemes and demonstrations

<正>Two novel dynamical quality of transmission(QoT) optimization schemes with explicit optimization targets and accurate end-to-end QoT estimation are proposed for reconfigurable transparent wavelength-division multiplexing(WDM) networks.Numerical simulations show that the scheme of quality(Q) best has the best Q factor improvement with large attenuation adjustment.The scheme of Q allowable can achieve minimized number of tuning sites and attenuation adjustment and also improve the Q factor of light path to the required value.In addition,the idea of dynamic QoT optimization and global impairment control has been experimentally demonstrated on a simple mesh network by the cooperation of a control plane and tunable devices.