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121.
P Rabindra Reddy P R Prasad Reddy M Harilatha Reddy 《Journal of Chemical Sciences》1987,99(5-6):297-303
Studies on interaction of La(III), Pr(III), Nd(III), Sm(III), Gd(III), Dy(III) and Er(III) with inosine and xanthosine in
a 1:1 ratio have been carried out by potentiometric equilibrium measurements at 35±0·1°C and 0·1 M (KNO3) ionic strength. Investigations were also made for the interaction of these metal ions and nucleosides with the biologically
important secondary ligands glycine and histidine. These investigations were undertaken with a view to assess the influence
of charge on the structure and stability of 1:1 metal-inosine/xanthosine systems.
DBT/India overseas Fellow at Harvard University (1986–88). 相似文献
122.
F. Gugumus 《Polymer Degradation and Stability》2007,92(1):143-157
The experimental kinetics for γ-lactone formation shows more complexity than that for acids. Nonetheless, it can be concluded to the existence of a constant rate of formation from the beginning of the experiments with polyethylene melts. There is an additional term contributing to γ-lactone formation in the initial stages that is cubic in processing time. In the advanced stages of processing, in the high temperature range (170-200 °C), the concentration of γ-lactones increases linearly with the processing time.There are many mechanisms susceptible to give γ-lactones on polyethylene melt processing. Some of them are based on decomposition of intermediates formed directly on chain propagation. This is so for the α,γ-keto-hydroperoxides in 4-position to hydroxyl groups. Since decomposition of these intermediates is very fast, the reaction might account for a constant rate of γ-lactone formation from the beginning of polyethylene processing. Decomposition of the α,δ-keto-hydroperoxides formed on intramolecular reactions on chain propagation is not so fast as that of the α,γ-keto-hydroperoxides. Nonetheless, it might account for part of the delayed formation of γ-lactones. The same is valid for the mechanisms based on peroxidation of aldehydes and γ-hydroxy trans-vinylene groups that involve intermediates that are formed on polyethylene peroxidation. They might be important for explaining the cubic term as well as γ-lactone formation in the advanced stages of polyethylene processing. 相似文献
123.
用裂解气相色谱-质谱联用方法研究了橡胶产品中使用的增塑剂邻苯二甲酸二甲酯(DMP)在不同温度条件下的热裂解行为.对不同温度条件下裂解产物的分析表明,在初始阶段DMP的裂解产物主要为二氧化碳、苯、甲苯和苯甲酸甲酯.随着温度的升高苯甲酸甲酯进一步裂解成为分子质量更小的自由基,并发生稠环化反应形成更稳定的菲、蒽、间-联三苯、三亚苯等芳香族多环化合物.根据分析实验提供的裂解产物信息和有机物热裂解化学反应的原理对DMP的热裂解反应机理作了探讨,表明在废旧合成橡胶热裂解回收过程中,增塑剂DMP的高温裂解会产生多环芳烃污染物.应选择合适裂解工艺和裂解温度,以减少对环境的污染. 相似文献
124.
Theresa J. Hermel-Davidock H. Sean Tang Daniel J. Murray Stephen F. Hahn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):3338-3348
It has been found that by the addition of low concentrations of an amphiphilic block copolymer to an epoxy resin, novel disordered morphologies can be formed and preserved through curing. This article will focus on characterizing the influence of the block copolymer and casting solvent on the templated morphology achieved in the thermoset sample. The ultimate goal of this work is to determine the parameters that would control the microphase morphology produced. Epoxy resins blended with a series of amphiphilic block copolymers based on hydrogenated polyisoprene (polyethylene-alt-propylene or PEP) and polyethylene oxide (PEO), specifically, were investigated. In this article, the cure-induced order–order phase transition from the spherical to wormlike micelle morphology will also be discussed. It is proposed that the formation of the wormlike micelle structure from the spherical micelle structure is similar to the phase transition behavior that occurs in dilute block copolymer solutions as a function of the influence of the solvent on micelle morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3338–3348, 2007 相似文献
125.
Khaled A. Aamer Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1109-1121
Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007 相似文献
126.
Structural characterisation of such bio-objects as fibrinogen solution, yeast cells, wheat seeds and bone tissues has been done using two versions of cryoporometry based on the integral Gibbs-Thomson (IGT) equation for freezing point depression of pore liquids and the measurements by 1H NMR spectroscopy (180-200 < T < 273 K) and the thermally stimulated depolarisation current (TSDC) method (90 < T < 273 K) of structured water. The IGT equation was solved using a self-consisting regularization procedure including the maximum entropy principle applied to the distribution function of pore size (PSD). Both methods give clear pictures of changes in the structural characteristics caused, e.g., by hydration and swelling of wheat seeds and yeast cells, coagulation and interaction of fibrinogen with solid nanoparticles in the aqueous media, and the human bone tissue disease. 相似文献
127.
Rodrigo París José Luis de la Fuente 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3538-3549
Different diblock copolymers constituted by one segment of a monomer supporting a reactive functional group, like allyl methacrylate (AMA), were synthesized by atom transfer radical polymerization (ATRP). Bromo‐terminated polymers, like polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were employed as macroinitiators to form the other blocks. Copolymerizations were carried out using copper chloride with N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as the catalyst system in benzonitrile solution at 70 °C. At the early stage, the ATRP copolymerizations yielded well‐defined linear block copolymers. However, with the polymerization progress a change in the macromolecular architecture takes place due to the secondary reactions caused by the allylic groups, passing to a branched and/or star‐shaped structure until finally yielding gel at monomer conversion around 40% or higher. The block copolymers were characterized by means of size exclusion chromatography (SEC), 1H NMR spectroscopy, and differential scanning calorimetry (DSC). In addition, one of these copolymers, specifically P(BA‐b‐AMA), was satisfactorily modified through osmylation reaction to obtain the subsequent amphiphilic diblock copolymer of P(BA‐b‐DHPMA), where DHPMA is 2,3‐dihydroxypropyl methacrylate; demonstrating the feasibility of side‐chain modification of the functional obtained copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3538–3549, 2007 相似文献
128.
Masaharu Asano Jinhua Chen Yasunari Maekawa Takahiro Sakamura Hitoshi Kubota Masaru Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2624-2637
A novel process comprising the UV‐induced photografting of styrene into poly(tetrafluoroethylene) (PTFE) films and subsequent sulfonation has been developed for preparing proton‐conducting membranes. Although under UV irradiation the initial radicals were mainly generated on the surface of the PTFE films by the action of photosensitizers such as xanthone and benzoyl peroxide, the graft chains were readily propagated into the PTFE films. The sulfonation of the grafted films was performed in a chlorosulfonic acid solution. Fourier transform infrared and scanning electron microscopy were used to characterize the grafted and sulfonated membranes. With a view to use in fuel cells, the proton conductivity, water uptake, and mechanical properties of the prepared membranes were measured. Even through the degree of grafting was lower than 10%, the proton conductivity in the thickness direction of the newly prepared membranes could reach a value similar to that of a Nafion membrane. In comparison with γ‐ray radiation grafting, UV‐induced photografting is very simple and safe and is less damaging to the membranes because significant degradation of the PTFE main chains can be avoided. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2624–2637, 2007 相似文献
129.
We report on a new type of Fano effect, named as Andreev-Fano effect, in a hybrid normal-metal/supeeconductor (N/S) interferometer embedded with a quantum dot. Compared with the conventional Fano effect, AndreevFano effect has some new features related to the characteristics of Andreev reflection. In the Iinear response regime, the line shape is the square of the conventional Fano shape, while in the nonlinear transport, a sharp resonant structure is superposed on an expanded interference pattern, which is qualitatively different from the conventional Fano effect. The phase dependence of the hybrid N/S interferometer is also distinguished from those of all-N or all-S interferometers. 相似文献
130.
Bart M. J. M. Suijkerbuijk Duncan M. Tooke Anthony L. Spek Gerard van Koten Robertus J. M. Klein Gebbink Prof. Dr. 《无机化学与普通化学杂志》2007,633(15):2649-2653
A tin(IV) porphyrin was combined with two axial NCN‐pincer platinum(II) fragments by utilizing the oxophilicity of the apical positions on the tin atom and the acidic nature of the NCN‐pincer platinum derived benzoic acid. The solid‐state structure determined by X‐ray crystallography revealed some close contacts between the pincer complexes and the meso‐p‐tolyl subsitutents of the porphyrin. It was shown by 1H NMR spectroscopy that these close contacts were not present in solution and that this compound can potentially act as a novel building block for supramolecular architectures. 相似文献