Materials Literature
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We present a theoretical study of the conformations of a polymer brush (made of linear macromolecules chemically anchored to a flat, solid interface) when it is exposed to a molten, compatible polymer. At large brush grafting densities σ and melt molecular weights P, the melt only penetrates the brush over a distance…
Rheological and dielectric behavior was examined for concentrated solutions of a styrene−isoprene−styrene (SIS) triblock copolymer in monomeric and polymeric I-selective solvents, n -tetradecane (C 14 ) and a low- M homopolyisoprene (I-1; M = 1.4K). The I blocks had symmetrically once-inverted dipoles along the block…
The preparation and characterization of poly(aryl ether sulfone) (PES) PolyHIPE (polymerized high internal phase emulsion) materials is described. A maleimide-terminated aryl ether sulfone macromonomer was copolymerized with styrene, divinylbenzene (DVB), or a bis(vinyl ether) species, in the continuous phase of a HIP…
Abstract Raman microscopy of the kaolinite polymorphs was used to study single crystals and bundles of aligned crystals of kaolinite. The spectra of the hydroxyl stretching region were both sample and orientation dependent. Kaolinites can be classified into two groups according to the ratio of the intensities of the 3…
The first part of this article concerns the thermodynamics of point defects. In the traditional analysis of reactions in which point defects are involved, point defects are assumed to be ideally diluted, which leads to familiar mass‐action‐type equations. In this article, situations in which deviations from ideal mass…
The melting behavior of paracetamol and polyethylene glycol (PEG) 4000, both individually and as binary systems, has been studied using differential scanning calorimetry. The appearance of the PEG peaks was shown to be highly dependent on scanning rate, with evidence for the existence of once-folded and extended chain…
Crack‐growth resistance‐curve (R‐curve) behavior for small (<400 μm) surface cracks and long (>3 mm) through‐thickness cracks is examined in two silicon carbide (SiC) ceramics that have sharply contrasting fracture properties. The first, an in‐situ toughened material designated ABC‐SiC, fails by intergranular fracture…
Magnetization and neutron-diffraction measurements were performed on a single crystal of ${\mathrm{Cu}}_{2}{\mathrm{MnSnS}}_{4}.$ This quartenary magnetic semiconductor has the stannite structure (derived from the zinc-blende structure which is common to many II-VI dilute magnetic semiconductors), and it orders antife…
We have successfully grown smooth diamond thin films epitaxially on (001) iridium surfaces through a direct-current plasma chemical vapor deposition process with two steps: ion irradiation pretreatment and diamond growth. The epitaxial areas of diamond thin films with a mean thickness of about 1.5 µ m seem to act as o…
The thermal conductivity κ and diffusivity α of high-strength and high-modulus crystalline polymer fibers (polybenzobisoxazole (Zylon \circR ) and polyethylene (Dyneema \circR )) and their fiber-reinforced plastics (FRPs) were measured in directions parallel and perpendicular to the molecular chain axis of the fibers.…
The effect of zirconium segregation on hardening in the creep of fine‐grained alumina was studied by using the tensile creep test. To avoid the effect of zirconia particle dispersion on creep, 100‐ppm‐zirconium‐doped alumina and 1000‐ppm‐zirconium‐doped alumina were fabricated by using a zirconium‐containing precursor…
The tetraaza macrocycles 2-oxa-3-oxotetramesitylporphine (|H(2) 1|) and 2-oxa-3-oxotetrakis(2,6-dichlorophenyl)porphine (|H(2) 2|) and the corresponding iron complexes (|Fe(III)(X) 1| and |Fe(III)(X) 2|; X= Cl(-), OH(-), or SO(3)CF(3)(-)) have been synthesized. These macrocycles are derived from porphyrins by transfor…
Alcaligenes faecalis penicillin G acylase is more stable than the Escherichia coli enzyme. The activity of the A. faecalis enzyme was not affected by incubation at 50 degrees C for 20 min, whereas more than 50% of the E. coli enzyme was irreversibly inactivated by the same treatment. To study the molecular basis of th…
A new immobilization technique for homogeneous catalysts is represented by the title process. Polyethers that are covalently attached to silica surfaces (shown schematically on the right) act as solvent and/or ligands for the catalysts, in this case polyoxometalates (POM). Such systems allow, for example, the quantita…
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A novel polynuclear lanthanum complex of the DOTA ligand has been prepared and its X-ray crystal structure determined. This complex provides the first evidence of an “inverted square antiprismatic” geometry in the solid state for a lanthanide DOTA derivative.
A series of novel aromatic diamines ( 1 − 3 ) containing kinked cyclohexylidene moieties was synthesized by a reaction of excess aniline and corresponding methyl-substituted cyclohexanone derivatives. The structures of ( 1 − 3 ) were identifield by 1 H NMR, 13 C NMR, and FT-IR. The polymers were synthesized from the o…
Using transmission electron microscopy a systematic study of the dislocation microstructure after cyclic deformation of nickel single crystals was undertaken in order to describe quantitatively the influence of deformation temperature on microstructural parameters. The frequency distributions of the heights and length…
A new levitation apparatus coupled to a synchrotron-derived x-ray source has been developed to study the structure of liquids at temperatures up to 3000 K. The levitation apparatus employs conical nozzle levitation using aerodynamic forces to stably position solid and liquid specimens at high temperatures. A 270 W CO2…
The possibility of processing MPS 3 (M = Mn, Cd) layered materials as thin films capable of intercalating nonlinear optical chomophores is investigated. Two different synthetic routes are presented. The first method (solution approach) involves the coprecipitation of transition-metal ions Mn 2+ with ligands (P 2 S 6 4…