茂金属烯烃聚合催化剂Ⅱ.丙烯茂金属催化剂结构对称性和立体选择性的关系

介绍了茂金属催化剂的研究进展及茂金属催化剂在乙烯、丙烯和苯乙烯等聚合反应中的应用。     

超浓乳液聚合研究近况

总结了国内外在超浓乳液聚合研究方面的近况 ,包括新的聚合体系及聚合产物结构和性能的研究 ,展示了其在新的聚合物材料开发和应用中的前景和价值。     

Catalytic Activity and Performance of Copper-Based Complexes Mediating Atom Transfer Radical Polymerization

The factors affecting the performance of the atom transfer radical polymerization (ATRP) catalyst, i.e., its activity, ability to control the polymerization, and its propensity to participate in side complexation or redox reactions are summarized in this brief review. The effect of the ligand, transferable halogen atom, and the reaction solvent can be understood and quantified by formally splitting the overall atom transfer equilibrium into contributing reactions, including the homolysis of a carbon halogen bond, reduction of the halogen atom to a halide ion (electron affinity), oxidation of the lower oxidation state metal complex (activator), and formation of the radical deactivator via coordination of a halide anion to the higher oxidation state metal complex (halidophilicity).     

Anodic Films on Aluminium and its Alloys for Protection against Corrosion

The effect of periodic reversal of current upon concentration over-potential and current efficiencies in electrolysis has been investigated for a metal depositon reaction which is purely diffusion-controlled. In the cathodic part of the cycle the onset of limiting diffusion conditions is deferred, and the current efficiency and average rate of metal deposition are increased. The magnitude of the effect depends upon the ratio of the quantities of electricity passed in anodic and cathodic pulses, and it is greatest under conditions such that diffusion away from the electrode of anodically-formed ions is minimised. Quantitative theoretical treatment is possible in a limiting case to which actual experimental results approximate. Supplementary experiments have been carried out in more complex cases of metal deposition.     

Synthesis of ω‐amino‐α‐phenylcarbonate alkanes and their polymerization to [n]‐polyurethanes

Aliphatic [n]‐polyurethanes have recently been synthesized from ω‐isocyanato‐α‐alkanols or, more traditionally, by cationic ring‐opening polymerization of cyclourethanes or by the Bu₂Sn(OMe)₂‐promoted polycondensation of ω‐hydroxy‐α‐O‐phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. In contrast, the polymerization of ω‐amino‐α‐phenylcarbonate alkanes is expected to occur under milder conditions. ω‐Amino‐α‐phenylcarbonate alkanes have been synthesized from 6‐aminohexanol (1) and 3‐aminopropanol (6). The procedure involves the N‐Boc protection of the amino group, followed by activation of the alcohol. Removal of the N‐Boc affords the corresponding ω‐amino‐1‐O‐phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]‐polyurethanes. The procedure described is useful for the preparation of stable ω‐amino‐α‐phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]‐polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. Copyright © 2010 Society of Chemical Industry     

The Properties of Nickel Electrodeposited from a Sulphamate Bath

The properties of nickel electrodeposited from a nickel sulphamate bath and the effect of some experimental variables upon them are described. The optimum conditions for minimum internal stress are defined. The tensile properties of sulphamate nickel deposits and their effect on the fatigue strength of En 25 (Ni/Cr/Mo) steel of 80 ton/in² U.T.S. are directly compared with the properties of nickel deposited from a Watts type solution.     

Synthesis of PEGylated single wall carbon nanotubes by a photoinitiated graft from polymerization

A considerable amount of research has been devoted to carbon nanotubes because of their unique electrical, mechanical, optical, and chemical properties. Here, in this report, we introduce a novel, simple ultraviolet initiated “graft from” polymerization method to synthesize PEGylated carbon nanotubes. This grafting procedure significantly enhanced nanotube aqueous dispersibility and long term stability in solution. Mass of grafted polymer chains was easily modulated by adjusting polymerization reaction time, and nanomaterials containing up to 80% polymer by weight were synthesized. Nanotube morphology was characterized by SEM, TEM before and after the functionalization. In addition, the covalent bonding of polymer chains to the nanotubes structure was elucidated by Raman, ATR‐FTIR, and XPS spectroscopy. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

<Emphasis Type="Italic">In-situ</Emphasis> polymerized nanosilica/acrylic/epoxy hybrid coating: Preparation,microstructure and properties

An in-situ polymerization method was employed to synthesize the nanosilica/acrylic/epoxy (SAE) hybrid coating on AISI 430 stainless steel (430SS), as compared with a traditional blending method. Microstructures of the blending SAE hybrid coating (BC) and in-situ SAE hybrid coating (ISC) were characterized by transmission electron microscopy (TEM). Corrosion resistance of BC and ISC on 430SS was evaluated by the neutral salt spray test and potentiodynamic polarization technique. Failure mechanism of the BC on 430SS was suggested by the microstructures and corrosion behaviors. Serious aggregation of nanosilica particles in the BC impairs its structural uniformity and induces the flaws formation. These flaws in the BC initiates the failures of pitting, filiform corrosion and peeling which are accelerated by the O₂ concentration cell and H⁺ self-catalysis in chlorine-containing moist environments. The ISC-coated 430SS shows a more advantageous corrosion resistance than that of the BC-coated. The ISC-coated 430SS can suffer the salt spray over 1000 h. Besides, it exhibits a high corrosion potential beyond 0.925 V and good passivation characteristics during the potentiodynamic polarization. Supported by the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619305) and the National Natural Science Foundation of China (Grant No. 50571044)     

Method for super Fresnel resolution in electromagnetic diagnostics of inhomogeneous plasma

The method of electromagnetic diagnostics is suggested, which promises to perform super Fresnel resolution of plasma inhomogeneities, that is resolution, distinguishing details smaller than Fresnel radius. To realize super Fresnel resolution it is suggested to represent the wave field of the source in the form of double weighted Fourier transform (DWFT), deals with Fourier transform simultaneously in coordinates of the sources and in coordinates of receivers. Important property of DWFT is that DWFT transfers into geometrical optics (GO) approximation for smooth inhomogeneous media and becomes equivalent to the Rytov or to small angle Born approximation in the case of weak inhomogeneities. As a result, inverse DWFT allows obtaining linear integral of plasma density both for large scale inhomogeneities, as in GO approximation, and also for inhomogeneities, whose transverse sizes are small as compared with Fresnel radius. DWFT embraces also the results of the phase screen method and allows to take into account phenomenon of micro-multirayness and to describe strong amplitude fluctuations.Using inverse DWFT algorithm, the authors study resolution of systems consisting of discrete sources and receivers. Both analytical estimates and the results of numerical modeling evidence opportunity to observe small scale plasma inhomogeneities with super Fresnel resolution.