Materials Literature
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ABSTRACT: Theoretical and experimental evidence for the occurrence of multiple relaxation regimes in polymers far above the glass transition temperature is presented and interpreted in terms of the Kohlrausch-Williams-Watts (KWW) stretched exponential expression. Intramolecular effects responsible for the observation…
Vibrational Raman spectroscopy was used successfully for the quantitative determination of the cubic and monoclinic phases of zirconia. Pressed pellets with known composition were prepared using monoclinic and cubic powders from different manufacturers and were used as standard mixtures. An intensity ratio plot of the…
Abstract High valent species formed from iron(III) meso-tetra-(pentafluorophenyl)porphyrin was first prepared in dichloromethane and characterized by low-temperature UV-vis absorption spectra, proton NMR and ESR. These measurements showed the formation of oxo iron(IV) porphyrin π-cation radical, not iron(V) porphyrin.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPyrophosphate Structures and Reactions: Evaluation of Electrostatic Effects on the Pyrophosphates with and without Alkali CationsBuyong Ma, Cynthia Meredith, and Henry F. Schaefer IIICite this: J. Phys. Chem. 1994, 98, 33, 8216–8223Publication Date (Print):August 1, 1994Publ…
We have investigated the crystal structures of 186 polar molecular organic compounds with the aim to consider the occurrence of ferroelectric state. There are 16 crystals suspected of ferroelectricity. The results of tentative experimental investigations are also included.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTChain Core Isomerism in dppm-Bridged Polymetallic Complexes. Synthesis, Reactivity, and Structure of Fe-Hg-Pt, Fe-Sn-Pt, and Fe-Pd-Sn Arrays (dppm = Ph2PCH2PPh2)Pierre Braunstein, Michael Knorr, Martin Strampfer, Antonio Tiripicchio, and Franco UgozzoliCite this: Organometal…
The nucleation and growth of diamond films on Nicemented carbide is investigated. Substrates made of WC with 6 wt% of Ni were submitted to grinding, and then to different pretreatments (scratching, etching, and/or decarburization) before diamond deposition. Diamond synthesis was carried out by hot‐filament chemical va…
We are concerned with a family of minimization problems arising in Quantum Chemistry for the modelling of the ground state of a molecule. We study the multiconfiguration methods, which are an extension of the well known Hartree–Fock method. We propose a general approach to prove the existence of the ground state in th…
Angular predictions of directional scattering distributions for metal and dielectric surfaces with length scales of the order of the wavelength are made from rigorous electromagnetic scattering theory. The theoretical and numerical formulation of the electromagnetic scattering solution based on the extinction theorem…
Poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers synthesized via living carbocationic polymerization using a di- or tricumyl chloride/TiCl4/pyridine initiating system in 60/40 (v/v) hexane/methyl chloride cosolvents. The kinetics of formation of the PIB block at − 80°C were found to be first order in iso…
The thermal conductivity has been measured in the temperature range 5–400 K for a series of chemical-vapor-deposited diamond samples differing only in thickness. By analyzing the conductance, a local conductivity is extracted as a function of height z above the substrate on which the samples were grown. An analysis of…
A statistical dynamic theory is presented to describe the effects of relaxation of the microstructure, frequency, and volume fraction (\ensuremath{\varphi}) on the complex shear viscosity of concentrated colloidal dispersions. On the basis of a fluid lattice model, the relationship between the memory function and rela…
Abstract Acetoxypropylcellulose (APC) and propionic, n ‐butyric, isobutyric, valeric, isovaleric, hexanionic, and heptanionic acid esters of hydroxypropylcellulose (HPC) (respectively PPC, BPC, iBPC, VPC, iVPC, HexPc, and HepPc) were prepared and characterized by differential scanning calorimetry, chromatography, pola…
Abstract Infrared spectroscopy was used to study the structure and deformation behaviour of a series of model poly(ether‐urethane) (PEU) elastomers. These materials contain (molecularly) uniform hard segments obtained from piperazine and the bischloroformate of 1,4‐butanediol with a poly(oxytetramethylene) soft segmen…
Abstract N ‐alkyl‐substituted itaconimides (RII) and N ‐(alkyl‐substituted phenyl)itaconimides (RPhII) with various alkyl substituents were prepared and polymerized in the presence of a radical or anionic initiator to give high molecular weight polymers in high yields. The effects of the alkyl substituents on the poly…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSegregation Study of a BAB Triblock Copolymer at the A/B Homopolymer InterfaceKevin H. Dai, Junichiro Washiyama, and Edward J. KramerCite this: Macromolecules 1994, 27, 16, 4544–4553Publication Date (Print):August 1, 1994Publication History Published online1 May 2002Publishe…
The effect of /sup 60/Co radiation on the leakage current behavior of hydrogenated amorphous silicon photodiode sensors has been investigated. These sensors, with an n-i-p construction, are identical to those used on two-dimensional, pixelated imaging arrays currently under development. Sensor leakage current is repor…
Epitaxial p-type Schottky diodes have been fabricated on p/sup +/-substrate. While the activation energy of the epitaxial layer conductivity is 390 meV, that of the substrate is only 50 meV. At forward bias the substrate conductivity dominates above 150/spl deg/C, leading for a 5/spl times/10/sup -5/ cm/sup 2/ area co…
Abstract The interaction energies between PS, Pα‐MS, and PMMA with several bisphenol‐A‐based polycarbonates were quantitatively determined from oligomer/oligomer, oligomer/homopolymer, and homopolymer/copolymer blends. Interaction energies were calculated from the Flory‐Huggins theory and the Sanchez‐Lacombe equation…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTToward New Magnetic, Electronic, and Optical Materials: Synthesis and Characterization of New Bimetallic Tetrathiafulvalene Tetrathiolate Building BlocksRichard D. McCullough and John A. BelotCite this: Chem. Mater. 1994, 6, 8, 1396–1403Publication Date (Print):August 1, 199…