Materials Literature
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The long-term confusing glass transition temperature, T g, and specific heat capacity, Δ C p, of the 4,4‘-diisocyanatodiphenylmethane (MDI) and 1,4-butanediol (BD) hard segment in segment polyurethanes have been clearly evidenced by using a new series of completely phase-mixed polyurethanes while being extrapolated to…
The calorimetric titration of H 3 PW 12 O 40 (H 3 PW) with a series of bases in CH 3 CN gives equilibrium constants and enthalpies for the three deprotonation steps. These results show that solutions of H 3 PW in any solvent whose basicity is equal to or weaker than CH 3 CN will only furnish one strong proton per mole…
We studied the dependence of the dynamic properties on the generation G of a star-burst dendrimer model. The Rouse approximation for the mobility matrix was used for simplicity. We categorized all normal-mode displacements and considered various time-dependent correlation functions and the intrinsic viscosity. We dete…
Optical switching behavior of low-molecular-weight and polymer azobenzene liquid crystals (LCs) was explored by means of reflection-mode analysis. Reflectivity changed on pulse irradiation under various conditions of orientations of LC molecules with respect to incident probe light, either s-polarization or p-polariza…
▪ Abstract Recent progress in the field of mechanical behavior of layered ceramics is reviewed. Several processing techniques are described with reference to the fabrication of ceramic laminates. These include tape-casting, centrifugal casting, slip-casting, electrophoretic deposition (EPD), and the production of fibr…
Three metal complexes of one particular homochiral porphyrin were investigated as catalysts for enantioselective epoxidation of unfunctionalized olefins under various reaction conditions. Much better results were obtained with the iron and ruthenium complexes than with the manganese derivative. The absence of any effe…
The crystal structure of [Pt(trpy)(MeCN)](SbF 6 ) 2, where trpy denotes 2,2‘:6‘,2‘‘-terpyridine, shows that the platinum complex packs as a monomer; however, the 3 π−π* emission of the solid occurs at surprisingly long wavelengths at room temperature. At lower temperatures new, shorter-wavelength maxima appear. Of the…
The stress‐rupture properties of precracked minicomposites were determined in air at temperatures in the range of 700°‐1200°C. The minicomposite systems consisted of a single tow of Nicalon or Hi‐Nicalon fibers with carbon or boron nitride (BN) interphases and a chemical‐vapor‐infiltrated silicon carbide (CVI‐SiC) mat…
The cspD gene of Escherichia coli encodes a protein of high sequence similarity with the cold shock protein CspA, but cspD expression is not induced by cold shock. In this study, we analyzed the regulation of cspD gene expression. By using a cspD-lacZ fusion and primer extension analysis, the expression of cspD was fo…
Abstract A genetic algorithm (GA) based method for solving crystal structures directly from powder diffraction data has been developed. The method is based around fitting the diffraction data generated from trial structures against the measured diffraction data and has the ability to handle flexible molecules and mult…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDendrimers Containing Organometallic Moieties Electronically CommunicatedIsabel Cuadrado, Carmen M. Casado, Beatriz Alonso, Moisés Morán, José Losada, and Vitaly BelskyView Author Information Departamento de Química Inorgánica, Universidad Autónoma de Madrid, 28049-Mad…
We examine the influence of attractive interactions on the phase behavior of rodlike colloids. We model the rodlike particles by spherocylinders, for which the phase diagram, in the absence of attraction, is known for arbitrary aspect ratio. We consider the case that the attraction is due to depletion forces caused by…
Crystal structures of ( E )-azobenzene (1), ( E )-2,2′- dimethylazobenzene (2), ( E )-3,3′-dimethylazobenzene (3) and ( E )-4,4′-dimethylazobenzene (4) were determined by X-ray diffraction at various temperatures. An apparent shrinkage of the N=N bond and its temperature dependence were observed and are interpreted in…
Low-water content reverse micelles have been formed in cyclohexane employing Triton X-100 or AOT (bis(2-ethylhexyl) sulfosuccinate sodium (salt) as the surfactant. Steady-state and time-resolved luminescence quenching studies, using Ru(bpy) 3 2+ as the luminophore and Fe(CN) 6 3 - or MV 2+ as the quencher, have shown…
A survey was compiled of several characteristics of the intersubunit contacts in 58 oligomeric proteins, and of the intermolecular contracts in the lattice for 223 protein crystal structures. The total number of atoms in contact and the secondary structure elements involved are similar in the two types of interfaces.…
Microphase separation in semicrystalline block copolymers can be driven by two forces: thermodynamic incompatibility between the blocks in the melt or crystallization of one or more blocks. The diblock copolymers investigated here are polyethylene- b -poly(3-methyl-1-butene), all containing ≈26 wt % ethylene, prepared…
This work synthesizes new adamantane-based polyimides by reacting 1,3-bis[4-(4-aminophenoxy)phenyl]adamantane ( 4 ) with various aromatic tetracarboxylic dianhydrides. The poly(amic acid)s have number-average molecular weights ( M n ) of 39 000−139 000. The M n 's of soluble polyimides 7 d and 7 e are 108 000 and 89 0…
The molecular-dynamics technique involving the rapid cooling of a liquid to simulate an amorphous solid has been used for several years. Despite the success of the technique, the method has lacked a physical justification, and the cooling rates have been assumed to be too fast. In this paper an analysis of thermal spi…
There has been a controversy about the self-aggregation of 5,10,15,20-tetrakis[4-( N -methyl)pyridinium]porphyrin (TMPyP(4)) in water. In order to make clear whether TMPyP(4) forms a dimer in water, 1 H NMR and UV−vis spectroscopic studies of 5-phenyl-10,15,20-tris[4-( N -methyl)pyridinium]porphyrin (TriMPyP), 5,10-di…
Macromolecular architecture is receiving increasing interest as the search for new tailor-made polymeric materials with strictly specified properties intensifies. Many research groups are now focusing their interest on dendritic macromolecules [dendron (Greek) = treelike, highly branched] i.e. dendrimers and hyperbran…