Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. VI. Charge‐transfer complex (2)

The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (E_a) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent E_a's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), E_a's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, E_a's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, E_a's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005     

Interaction of inositol phosphate with calcite

The interaction of myo-inositol hexaphosphate with calcite was studied to evaluate the adsorption mechanisms and the electrochemical modifications induced by interaction of a molecule at such a high-charge density. In addition to quantitative information through the construction of adsorption isotherms, FT-IR and Laser Doppler Velocimetry - Photon Correlation Spectroscopy (LDV-PCS) were employed to investigate the nature of the adsorbent-adsorbate bonds and to determine the electrophoretic mobility and size of the particles before and after sorption. The experiments were also run with orthophosphate (Pi) for comparison. The amount of sorbed P increased to reach a plateau at 17.8 mol m^-2 for inositol hexaphosphate (IHP) while for Pi rose 1.4 mol m^-2 but at C_e > 610^-4 M it had a sharp increase reaching 155 mol m^-2. As expected, for Pi, adsorption predominated up Ce 610^-4 M by covering about 20% of total surface. The adsorption occurred at sites that behaved as nucleus of formation of the clustering of Ca- and PO₄-ions with the ending formation of calcium phosphate precipitates at C_e higher than 610^-4 M. The reaction of inositol hexaphosphate with calcite involves, besides adsorption, precipitation of Ca salts and hence calcite dissolution also at the lowest added IHP concentrations, accounting for the large amount retained by calcite. Sorption of IHP on calcite caused aggregation of particles at low concentrations followed by an increase of their negative charge and hence re-dispersion at higher concentrations. These results indicate a great IHP-fixing capacity of calcite that can affect its accumulation in soils and P bioavailability, and a considerable change of calcite electrochemical properties and particle size distribution that can modify aggregate stability.     

Local orders,lattice distortions,and electronic structure dominated mechanical properties of (ZrHfTaM1M2)C (M = Nb,Ti, V)

High-entropy carbides (HECs) are regarded as potential candidate structural materials with attractive mechanical properties due to their ultra-high hardness. It is essential to reveal the atomic and electronic basis for strengthening mechanism in order to develop the advanced HECs. In the present work, C (M = Nb, Ti, V) are selected as case studies. The effects of transition metals (M) on the lattice parameters, bulk modulus, enthalpy of formation, electron work function (EWF), and bonding morphology/strength of HECs are comprehensively studied by first-principles calculations. It is found that the lattice parameters, equilibrium volumes, and bulk modulus of HECs are improved with the increase of M atomic volumes. The atomic-size differences among various groups of elements not only result in the lattice mismatch/distortion but also contribute to the formation of weak spots. In the view of bonding charge density, the electron redistributions caused by the coupling effect of the lattice distortion and valance electron differences can be revealed obviously, which identify the different bonding strength. Moreover, in terms of EWF, the proposed power-law-scaled hardness of HECs is validated and matches well with those reported theoretical and experimental results, providing a strategy to design advanced HECs with excellent mechanical properties.     

21世纪先进发射药(2):低敏感高能发射药--新配方、装药、点火和理论模拟技术

研究开发低敏感高能发射药必将成为2l世纪发射药及其装药发展的趋势。讨论和分析了低敏感高能发射药的新配方、装药及点火设计、理论模拟等方面的最新研究进展和成果，展现了新一代先进发射药的优异性能。     

飞机碱性电瓶充放电参数测量仪的设计与研究

电瓶是民航飞机可靠供电的最后保证。飞机制造厂家提高了对电瓶的性能和容量检测要求,传统的电瓶充放电装置已经无法满足新的要求。利用单片机技术研制的飞机电瓶参数测试仪,实现了对电瓶各种参数的实时侧量和分析,为飞机电瓶维护和检测提供依据。     

带取代基硝酮化合物光环化反应的研究

本工作合成了一系列取代的硝酮类化合物。其中部分化合物仅一侧的苯环上带有取代基,而另部分化合物则两个苯环上均带有取代基。研究工作表明:取代基处于一侧的硝酮类化合物,不论取代基是给出电子或接受电子的,均有利于化合物光环化反应的进行。而当两个苯环分别带有给电子及接受电子的取代基形成推拉结构时,则大大减弱了化合物光环化反应的发生。文章对上述结果进行了初步讨论。     

Synthesis of copolymers of tert‐butyl vinyl ether with maleic and citraconic anhydrides

In the present study, the effects of charge‐transfer complex formation and intramolecular fragmentation (side‐chain lactonization) in radical copolymerization of tert‐butyl vinyl ether (t‐BVE) with anhydrides of maleic (MA) and citraconic (CA) acids and the structure–thermal behavior relationships of the resulting copolymers were examined using the ¹H‐NMR, FTIR, DSC, and TGA analysis methods. It was shown that copolymerization under the chosen conditions proceeded through intramolecular fragmentation with the formation of γ‐lactone units. Side‐chain fragmentation of t‐BVE–MA and t‐BVE–CA copolymers also was confirmed by TGA and DSC analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2455–2463, 2006 2006     

Thermal characterization of n‐alkyl maleate‐styrene‐allyl propionate terpolymers

Thermal characterization of maleic anhydride‐styrene‐allyl propionate (MA‐St‐AP) terpolymer and its ester derivatives named as n‐alkyl maleate and shown as nPr MA‐St‐AP, nBu MA‐St‐AP, nPn MA‐St‐AP, and nBz MA‐St‐AP was carried out. The thermal characterization was performed using thermal analysis techniques such as TGA, DTA, DSC, and TMA. Different results were observed between the original terpolymer and its ester derivatives. Thermal stabilities of the terpolymer and its ester derivatives were compared by using various measurements plotted as TGA, DTA, DSC, and TMA curves. The increase in the alcohols' carbon numbers added to the original terpolymer results in ester derivatives with different thermal stability behavior. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 600–604, 2007     

EFFECT OF NONSOLVENT ADDITIVES ON THE PORE SIZE AND THE PORE SIZE DISTRIBUTION OF AROMATIC POLYAMIDE RO MEMBRANES

In this paper discussions are made on the effect of nonsolvent swelling agents on the average pore size and pore size distributions at the surface of polyamide membranes which result from casting solutions involving above nonsolvent swelling agents.

The size of the polymer aggregate in the film casting solution and the size of polymer network pores are correlated to physicochemical data of ions which constitute the electrolytes used as nonsolvent swelling agents. As such ionic properties the charge density and the free energy of transition of ions from polyamide phase to water phase were considered. The validity of the correlation is limited in a range of casting solution composition where the polymer concentration in the casting solution is close to the limiting concentration of polymer at the phase boundary and the molar ratio of the nonsolvent swelling agent to the amide group involved in the polyamide polymer is equal to or slightly more than 0.7.     

Charge reduction and regeneration in K+, Na+, Mg2+, Ni2+ and Co2+-exchanged Wyoming Bentonite

Controlled calcination of ion-exchanged Wyoming Bentonite in the presence and absence of ammonia leads to layer charge reductions. Detailed chemical analyses of both unexchangeable and exchangeable species lead to the conclusion that in no case is there migration of the original interlamellar cations into the octahedral region of the layers although, in terms of ionic radius alone, Mg²⁺, Ni²⁺ and, possibly Co²⁺, might be expected to do so. The production of unexchangeable Mg, Ni or Co, is identified as resulting from high temperature hydrolysis leading to hydroxide or oxide formation.