Oligomerization and Polymerization of Ethylene Initiated by a Novel Ni(Ⅱ)-Based Acetyliminopyridine Complexes as Single-Site Catalysts

Novel Ni(Ⅱ)-based acetyliminopyridine complexes 1b, 2b, 3b (1-3b), which are synthesized from ligands 1a, 2a, 3a (1-3a) and [NiCl2(DME)], are suitable precursors for the catalysts that are necessary for ethylene oligomerization and polymerization reactions, activated by methylaluminoxane (MAO). The MAO-treated 1-3b presents an active catalytic center, which may oligomerize and polymerize ethylene to produce linearα-olefins and polyethylene, respectively. The molecular weight distributions of oligomers that are obtained are in good agreement with the Schulz-Flory rules for oligomers>C4. The activity of 3b-MAO complex is 6.3×107 g/(molNi·h) at 50℃. The activities and molecular weight distributions of oligomers show significant reliance on the structures of catalyst precursors.     

Quantitative Determination of Oxalic Acid Using Victoria Blue B Based on a Catalytic Kinetic Spectrophotometric Method

A sensitive catalytic method is developed for the spectrophotometric determination of oxalic acid. The procedure is based on the effect of oxalate on the oxidation of Victoria blue B by dichromate in dilute sulfuric acid medium. The reaction is quantitatively estimated by measuring the decrease in absorbance of Victoria blue B at the maximum wavelength of 610nm after quenching the reaction with tap water. The factors effecting the sensitivity and reproducibility of the reaction were studied. The method is not interfered with by foreign species generally associated with oxalate and oxalic acid. The described method is simple, specific, inexpensive and suitable for oxalic acid concentrations of between 0.06 and 9.0µgmL^–1. It was validated with satisfactory results by determining oxalic acid content in water extracts from plant materials such as spinach and Lathyrus sativus.     

An Investigation on the Production of Random Copolymer with Monothiocarbonate and Trithiocarbonate Units over Cyclic Thiocarbonate via Metal‐free Catalysis

Synthesis of poly(thiocarbonate)s from the copolymerization of epoxides and carbon disulfide (CS₂) remains a tough challenge, due to inevitable oxygen‐sulfur atom scrambling process. In this work, we utilized the oxygen‐sulfur exchange reaction (O‐S ER) to synthesize a random copolymer with monothiocarbonate and trithiocarbonate units from CS₂ and phenyl glycidyl ether (PGE) via metal‐free Lewis pairs. The copolymers contained monothiocarbonate and trithiocarbonate units of which the molar fraction could be tuned by varying either the types of Lewis pairs or the reaction temperature. Keeping track on the intermediate provided an insight in the process of O‐S ER and thus gave a hint to control the product structure. Production and consumption of phenyl thioglycidyl ether was the key process to regulate the chain structure. Remarkably, the oxygen atoms of PGE could be excluded out of the chain, resulting in the nearly complete production of poly(trithiocarbonate)s. Correspondingly, the refractive index of this kind of copolymer could be regulated in a wide range of 1.73—1.79 (at 590 nm).     

化学计量一级站量值传递工作及经验

介绍了国防科工委化学计量一级站为保证化学量值的准确与统一,在计量标准建立、标准物质研制、测量方法研究等方面所做的工作和经验。     

Hydrogen-bonding-directed layer-by-layer assembly of poly(4-vinylpyridine) and poly(4-vinylphenol): effect of solvent composition on multilayer buildup

This paper describes the buildup of hydrogen-bonding-directed poly(4-vinylpyridine)/poly(4-vinylphenol) (PVPy/PVPh) multilayer film that was fabricated by layer-by-layer (LbL) assembly of PVPy and PVPh from an ethanol solution. UV-visible spectroscopy and Fourier transform infrared (FT-IR) spectroscopy revealed a uniform deposition process. The interaction between PVPy and PVPh was identified as hydrogen bonding through FT-IR spectroscopy and temperature-dependent IR spectral changes of the hydrogen-bonded multilayer. Notably, we discussed the effect of solvent conditions on the growth of PVPy/PVPh multilayer films monitored by UV-visible spectroscopy. It was found that increasing the ratio of N,N-dimethylformamide (DMF) in the mixed ethanol/DMF solvents resulted in a marked decrease of the amount of polymers adsorbed, which was attributed to the increased polarity of the adsorption solutions. Furthermore, the solvent stability of PVPy/PVPh multilayer film in mixed ethanol/DMF solvents with different DMF ratios was also investigated. As a result, a new method for tuning the structure of hydrogen-bonding-directed multilayer film was developed.     

Synthesis and characterization of a novel main chain oxadiazole-based copolymer for n-type solar cell material

A novel oxadiazole-based copolymer has been successfully synthesized through the palladium-catalyzed cross-coupling polycondensation method.The copolymer P is soluble in common organic solvents.Its structure has characterized by ~1H NMR,~(13)C NMR,gel permeation chromatagraphy (GPC),UV-vis absorbance (Abs) and photoluniminescence (PL) spectroscopy,and cyclic voltammetry (CV).Investigation of its optical properties revealed that it is yellow emitting material,and the electrochemical analysis showed that P was well suited poly (2,5-dioctyloxy-p-phenylenevinylene) (PDOCPV) for photovoltaic devices,so the copolymer P is able to act as an electron acceptor in combination with PDOCPV as the electron donor to quench photoluminescence of the copolymer in the blend,indicative of the efficient photoinduced electron transfer from the PDOCPV to the P.     

Novel assembly of cyclic ethers by coupling alpha-chlorosulfides and alcohols

A novel protocol for assembling polycyclic ethers was developed and successfully applied to the synthesis of the EFGH ring system of ciguatoxin CTX3C. A key transformation involves construction of an O,S-acetal through coupling of alpha-chlorosulfide and a secondary alcohol under mild conditions. The method is highly applicable to use with sensitive substrates and will enable the synthesis of various natural and artificial polycyclic ethers. [reaction: see text]     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

Synthesis of Molecularly Imprinted Polymer Particles by Suspension Polymerization in Silicon Oil

Molecular imprinting is a method to prepare polymers with recognition site of desired and predetermined selectivity1. Molecularly imprinted polymers (MIP) are prepared by copolymerizing functional and cross-linking monomers in the presence of a molecular …     

Self－assembly of Novel Hetero[3]rotaxane, [2]Rotaxanes and [2]Catenane

One linear template 13 and one cyclophane template 15, both incorporating two electron rich 1,4‐dialkoxybenzene units and one diamide unit, have been synthesized. By utilizing donor‐acceptor interaction and/or intermolecular hydrogen bonding assembling principles, one novel hetero[3]rotazane 22·4Cl, possessing one neutral and one tetracationic ring components, has been synthesized from 13, through neutral [2]rotaxane 21 as intermediate. With 15 as template, tetracationic [2]catenane 23·4PF₆ was assembled by using donor‐acceptor interaction, but no neutral [2]rotaxane could be obtained under the typical conditions of hydrogen bonding assembling principle. The interlocked supramolecular compounds have been characterized and their spectral properties are investigated.