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241.
Summary The equilibrium mechanical behaviour of weak diepoxide-monoepoxide-diamine networks, prepared with an excess of diamine and measured in the rubbery state, was compared with theoretical predictions obtained by using the theory of branching processes. The experimental equilibrium moduli fit well the shape of theoretical curves over a broad range of crosslinking density regardless of whether the contribution by trapped entanglements is considered or not. The data fit equally well the theoretical dependence for the front factor A = 1 without entanglement contribution and forA = (f
e
- 2)/f
e
, (f
e
is the average effective functionality of a junction) with an entanglement contribution based on the contact probability between any two units within elastically active network chains (Langley).Dedicated to Prof. Dr.G. Rehage on the occasion of his 60th birthday.With 5 figures 相似文献
242.
Xie Yongshu Ni Jia Liu Xueting Liu Qingliang Xu Xiaolong Du Chenxia Zhu Yu 《Transition Metal Chemistry》2003,28(3):367-370
Novel 1:2 and 1:1 (M:L) copper(II) complexes have been prepared from the tridentate ligand 2-(1-methyl-2-aza-5-oxapentyl)phenol (H2L1). The crystal structure of [Cu(HL1)2] (1) exhibits a noncentrosymmetric square-planar geometry with a slightly tetrahedral distortion. The CuII atom is coordinated by two amino N and two phenoxo O atoms of two (HL1)– ligands. The phenoxo and the alkoxy groups are involved in two strong intramolecular hydrogen bonds. The coordination moieties are further connected to a 1D linear structure by the action of intermolecular hydrogen bonds between the alkoxyl and the amino groups. The importance of steric hindrance introduced by the methyl group in the molecular structure and the packing of the complex molecules has been demonstrated. The e.p.r. parameters of (1) have been obtained: g
= 2.231, g
= 2.005, g
iso = 2.080, A
= 185.0 G, A
iso = 86.5 G, A
= (3A
iso – A
)/2 = 37.3 G. These results confirm a distorted square planar stereochemistry with a (
)1 ground state. 相似文献
243.
HongBingJI DuGuiHE JunSONG YuQIAN 《中国化学快报》2004,15(10):1241-1244
Clean liquid oxidation of aldehydes can be accomplished using solid catalyst in the presence of molecular oxygen at room temperature, which is a valuable alternative to traditional counterparts. 相似文献
244.
Josep Castells Elisabet Duñach Fernando Geijo Francisco López-Calahorra Margarita Prats Olga Sanahuja Laura Villanova 《Tetrahedron letters》1980,21(23):2291-2294
Triethylamine catalyzed Michael additions of benzoins to chalcone can prevail over the expected Michael-Stetter additions when certain thiazolium ion conjugate bases - prepared from the pertinent thiazolium salts and triethylamine- are used as catalysts. 相似文献
245.
A unique cyano-bridged copper(II)-copper(I) mixed-valence polymer, {[Cu(3)(CN)(4)(H(2)O)(3)](H(2)O)(2)}(n) (1), has been prepared and structurally determined by X-ray diffraction. The cyanide anions with (mu(2),eta(2)) and (mu(3),eta(2)) bridging modes connect the copper centers into a complicated zeolite-like 3-D network. Of further interest, coordinated and lattice water molecules in this structure form 1-D hydrogen-bonded water tapes consisting of linked cyclic pentamer clusters. 相似文献
246.
Du J Chen Y Zhang Y Han CC Fischer K Schmidt M 《Journal of the American Chemical Society》2003,125(48):14710-14711
Presented in this communication is a novel hybrid vesicle with a cross-linked polyorganosiloxane wall based on a new reactive block copolymer, poly(ethylene oxide)-block-poly(3-(trimethoxysilyl)propyl methacrylate) (PEO-b-PTMSPMA), which was synthesized by atom transfer radical polymerization. The vesicles were prepared first by self-assembly of the block copolymer in a selective solvent, and then the PTMSPMA block was subjected to hydrolysis and polycondensation reaction to fix vesicle wall in the presence of triethylamine as a catalyst. Transmission electron microscopy, scanning electron microscopy, NMR, and light scattering have been used to characterize the vesicles. 相似文献
247.
Vesna Radulovi? Alessia Bacchi Giancarlo Pelizzi Du?an Sladi? Ilija Br?eski Katarina Andjelkovi? 《Monatshefte für Chemie / Chemical Monthly》2006,23(3):681-691
Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide
were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized
by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure
was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex
is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation. 相似文献
248.
Wang Y Liu Z Han B Huang Y Zhang J Sun D Du J 《The journal of physical chemistry. B》2005,109(25):12376-12379
We report a facile route to pattern polymer surfaces with the aid of compressed CO(2), termed the compressed-CO(2)-assisted imprint method. In this method, compressed CO(2) serves as a plasticizer for polymers (such as poly(methyl methylate) and polystyrene), which leads to a tremendous reduction in the glass transition temperature and viscosity of the polymers. Nylon fabrics and anode aluminum oxide porous membranes are used as molds, respectively, to pattern the softened polymers at relatively low temperatures, resulting in patterns at the scale of micrometers and nanometers on the surface of polymer films. The patterned structures can be tuned by changing CO(2) pressure and temperature in the imprinting process. This method is simple and environmentally benign. It also can be operated at low temperatures, for instance, ambient temperature. 相似文献
249.
Milena Jelikić-Stankov Dejan Stankov Dušan Malešev Zorica Radović 《Mikrochimica acta》1991,103(1-2):65-70
By means of spectroscopic methods it has been found that demeclocycline reacts with molybdate ions forming a complex compound [MoO3HDMTC]2–. The relative stability constant of this compound has been determined by applying spectrophotometric methods. Under optimum conditions for complex formation a very sensitive spectrophotometric method for the estimation of demeclocycline in the concentration range 5.0–35.1 g/ml is proposed. The detection limit of the method is 2.5 g/ml of demeclocycline. The relative standard deviation (n=10) varies between 0.76% and 1.46%. The method proved to be accurate and sensitive for the analysis of the demeclocycline content in tablets. 相似文献
250.
CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of \(B_d^0 - \bar B_d^0 \) system. We discuss two feasible experimental circumstances: the symmetrice + e ? collisions (i) on theZ 0 resonance to produce incoherent \(B_d^0 \bar B_d^0 \) states, and (ii) just above the ?(4S) resonance to produceC=even \(B_d^0 \bar B_d^0 \) states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb \(\bar b\) pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB d 0 , \(\bar B_d^0 \to p\bar p\) , \(\Delta ^ + \bar \Delta ^ - \) , \(p\bar \Delta ^ - \) , \(\Delta ^ + \bar p\) , \(n\bar n\) , \(\Delta ^0 \bar \Delta ^0 \) , \(n\bar \Delta ^0 \) , \(\Delta ^0 \bar n\) , \(\Sigma _c^ + \bar \Sigma _c^ - \) , \(\Lambda _c^ + \bar \Lambda _c^ - \) , \(\Sigma _c^ + \bar \Lambda _c^ - \) , \(\Lambda _c^ + \bar \Sigma _c^ - \) , \(\Sigma _c^0 \bar \Sigma _c^0 \) , \(\Xi _c^0 \bar \Xi _c^0 \) , which should be interesting for experimental observation. 相似文献