Materials Literature
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Abstract The effects of various imperfections such as slow initiation, termination, transfer and slow exchange on kinetics, molecular weights and polydispersities in chain growth polymerizations are simulated. The simukations demonstrate that well defined polymers polymers can be prepared in systems with chain‐breakin…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagneto-structural correlations in .mu.2-1,1-azide-bridged dicopper(II) complexes. 2. Dominant antiferromagnetic coupling with azide bridge angles exceeding 108.degree.. X-ray Structures of [Cu2(PAP)(.mu.2-N3)Br3].cntdot.CH2Cl2, [Cu2(PAP6Me)(.mu.2-N3)(.mu.2-Br)Br2].cntdot.1.…
Abstract— For tetrasulfonated aluminum phthalocyanine (AlPcS 4 ), dimer formation is characterized in the absorption spectrum by a broadening of the Q‐band and the appearance of a new band at the red edge of the spectrum. The high concentrations required to produce dimers, however, often leads to anomalous observation…
Abstract Pumice‐supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x‐ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica‐ and alumina‐supported nickel catalysts, a preferential interaction of Ni 2+ with Al 3+ of the support ha…
Pressureless sintered alumina compacts with a submicrometer microstructure exhibit a hardness that approaches or even exceeds the level of advanced hotpressed composites of Al 2 O 3 + 35 vol% TiC, whereas the strength of both ceramics is approximately the same. The combination of reduced dislocation mobility (due to t…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHomogeneous Catalysis. Mechanisms of the Catalytic Mukaiyama Aldol and Sakurai Allylation ReactionsT. Keith Hollis and B. BosnichCite this: J. Am. Chem. Soc. 1995, 117, 16, 4570–4581Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published…
The probability of finding a nearest neighbor at some radial distance from a given particle in a system of interacting particles is of fundamental importance in a host of fields in the physical as well as biological sciences. A procedure is developed to obtain analytical expressions for nearest-neighbor probability fu…
Fibrous and crystal structures of a helical polymer, poly-L-lactic acid (PLLA), were analyzed by using x-ray diffraction experiments. It was confirmed that the molecular residues were arranged on a nonintegral 10/3 helix as De Santis and Kovacs [Biopolymers 6, 299 (1968)] reported. The atomic positions in a monomeric…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnprotected Peptides as Building Blocks for the Synthesis of Peptide Dendrimers with Oxime, Hydrazone, and Thiazolidine LinkagesJun Shao and James P. TamCite this: J. Am. Chem. Soc. 1995, 117, 14, 3893–3899Publication Date (Print):April 1, 1995Publication History Published o…
Polyaniline films are found to expand and contract by electrochemical oxidation and reduction, respectively. Two polyaniline films are used as cathode and anode muscles. In this system, the proton transfer between the films are essential chemical reaction. Two types of actuators, viz., “Backbone-type” and “Shell-type”…
Lactic acid-based aliphatic polyesters (PLAs) are well known biocompatible bioresorbable polymers which are being increasingly used as biomaterials for temporary therapeutic applications. Because of their sensitivity to water and the formation of degradation by-products which can be easily metabolized by microorganism…
Magnetic refrigeration, an emerging new technology for cooling and gas liquefaction, needs magnetic materials with specific thermomagnetic behavior. Depending on the thermodynamic cycle selected, the isothermal magnetic entropy change or the adiabatic temperature change upon field application needs to be a preselected…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMorphology and Thermodynamics of Symmetric Poly(A-block-B-block-C) Triblock CopolymersReimund Stadler, Clemens Auschra, Joerg Beckmann, Udo Krappe, Ingrid Voight-Martin, and Ludwik LeiblerCite this: Macromolecules 1995, 28, 9, 3080–3097Publication Date (Print):April 1, 1995P…
No abstract.
Manufacturing of bulk ceramic components from materials in the system Si‐Me‐C‐N‐O (Me = Ti, Cr, V, Mo, Si, B, CrSi 2 , MoSi 2 , etc.) from preceramic organosilicon polymers ‐ such as poly(carbosilanes), poly(silazanes), or poly(siloxanes) ‐ has become possible by incorporating reactive filler particles into the liquid…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDrop Breakup and Coalescence in Polymer Blends: The Effects of Concentration and CompatibilizationUttandaraman Sundararaj and C. W. MacoskoCite this: Macromolecules 1995, 28, 8, 2647–2657Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Publ…
Very strong antiferromagnetic coupling exists between the Fe centers in the N-bridged complexes 1 and 2. In 1 (shown on the right), which contains a symmetrical [FeIV = N = FeIV] unit, this results in an S = 0 ground state, while in 2, which has an unsymmetrical FeIII–N = FeIV bridge, it leads to an S = 3/2 ground sta…
Cyclotetramerization of a hydroxymethylphenanthropyrrole afforded a highly conjugated porphyrin 1 with four annelated phenanthrene rings. The 68 carbon atoms in the dication of this highly symmetrical heptadecacycle–the neutral compound is virtually insoluble in most organic solvents–produced only nine resonances in t…
We present a new formulation of ab initio molecular dynamics which exploits the efficiency of plane waves in adaptive curvilinear coordinates, and thus provides an accurate treatment of first-row elements. The method is used to perform a molecular dynamics simulation of the CO_2 molecule, and allows to reproduce detai…
Recent neutron scattering experiments on the microscopic dynamics of polymers below and above the glass transition temperature T(g) are reviewed. The results presented cover different dynamic processes appearing in glasses: local motions, vibrations, and different relaxation processes such as alpha- and beta-relaxatio…