Materials Literature
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Abstract The fractionation of polydimethylsiloxane (PDMS) using supercritical CO 2 was studied to determine the parameters of pressure and temperature required to separate specific molecular weights. On a laboratory scale, we show that this fractionation method can quickly provide gram quantities of the polymer with a…
Abstract The effect of Sb 2 O 3 , which is used as the main catalyst in the production of poly(ethylene terephthalate) (PET) by melt polymerization, was studied on solid‐state postpolycondensation. It was observed that the catalyst works efficiently even in the solid state. The number‐average molecular weight of a PET…
Abstract Polychloroprene and compounds of polychloroprene with ZnO and MgO were crosslinked by heating in a DSC at a programmed rate. The reaction was stopped at points along the thermogram and the crosslink density of the compound determined. The amount of chlorine evolved during reaction was measured as ZnCl 2 and/o…
Abstract The injection molding of an isotactic polypropylene was computer‐simulated with both quiescent and shear‐induced crystallization taken into account. A one‐dimensional finite difference model was used to simulate the filling, packing, and cooling stages of the injection‐molding cycle. The Spencer‐Gilmore equat…
Abstract Various material data for an isotactic polypropylene were acquired for the simulation of the injection molding of this material. Viscosity as a function of shear rate and temperature was measured using a capillary rheometer at high shear rates and a cone‐and‐plate rheometer at low shear rates. Heat‐flow prope…
Results of recent density functional theory calculations for alkali metal adsorbates on close-packed metal surfaces are discussed. Single adatoms on the (111) surface of Al and Cu are studied with the self-consistent surface Green-function method by which the pure adsorbate-substrate interaction may be analyzed. Highe…
Abstract A study was undertaken of the effect of sample preparation conditions, especially moisture content, annealing conditions, and degree of neutralization, on the dynamic mechanical properties of poly(styrene‐ co ‐sodium methacrylate) ionomers. Water plasticizes the ionic cores; however, very small amounts of wat…
Abstract Two stereoregular polygluconamides, one ( 3 ) of polypeptide‐type and the other ( 16 ) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D‐glucosamine and D‐glucose, respectively. The new polyamides were characterized by elemental analysis, a…
Abstract Aliphatic polyamides (Nylon‐66 and a Nylon‐6, ‐66, ‐610 terpolymer) were isothermally precipitated from formic acid solution by immersing in an aqueous nonsolvent bath or a solvent/nonsolvent mixture. Depending on the composition of the polymer solution and nonsolvent bath, phase separation by nucleation and…
Metastable pseudomorphic Ge0.12Si0.88 films were grown by molecular beam epitaxy on Si(100) substrates and then implanted with 100 keV 31P at room temperature for a dose of 5×1013/cm2. Samples were subsequently annealed by rapid thermal annealing (RTA) in nitrogen and by steady-state furnace annealing in vacuum. Both…
Amorphous Ga2O3 films have been deposited in situ on (100) GaAs layers grown by molecular beam epitaxy in ultrahigh vacuum. The Ga2O3–GaAs interface is stable during photoexcitation and the photoluminescence (PL) intensity, measured at 514.5 nm excitation wavelength, is enhanced drastically by a factor of 420 as compa…
Abstract Contrast for transmission electron microscopy (TEM) of microphase‐separated saturated hydrocarbon diblock copolymers has been obtained using ruthenium tetroxide (RuO 4 ). This technique exploits differences in the rate of transport of the oxidizing stain in rubbery amorphous versus semicrystalline, or glassy,…
Abstract Differential scanning calorimetry and high temperature x‐ray diffraction were used to study the perfectly alternating copolymer of ethene and carbon monoxide (polyketone; POKC2). It was found that oriented POK‐C2 fibers show a crystalline phase transition at a temperature between 110–125°C with a 10% change i…
Smooth and continuous diamond films have been heteroepitaxially grown on β-type silicon carbide (β-SiC) (001) surfaces. The smooth films can be obtained in the thickness of less than 6 μm which is the smallest in heteroepitaxial diamonds. The epitaxial growth is composed of three steps; (i) Bias enhanced nucleation on…
The very highly conducting state of polypyrrole is investigated. A Drude metallic response, similar to the behavior of usual metals, is determined, based on the coincidence of dc and microwave conductivities, measurement of a huge and negative microwave dielectric constant, and the optical determination of an unusual…
The relation between fast ion conductivity, glass forming ability, and structure in ${(\mathrm{AgI})}_{x}{(\mathrm{AgP}{\mathrm{O}}_{3})}_{1\ensuremath{-}x}$ glasses has been studied using neutron and x-ray diffraction and extended x-ray-absorption fine structure spectroscopy. Reverse Monte Carlo models based on the d…
A mathematical model is presented for the dynamical strain-stress response of shape memory wires. This model is based on a free boundary problem for the heat equation which incorporates bistable potentials together with a physical constant, independent of stress or temperature, which accounts for mechanically dissipat…
I present the exact dispersion relations for certain low-lying states of the one-dimensional Heisenberg ferromagnet. These states are bound complexes of $M$ overturned spins, and in fact are the states with the lowest energy for given values of the total spin, $z$ component of spin and momentum.
Abstract The GPC method is used widely to measure molecular weights of linear polymers. High‐quality GPC data contains detailed information on many aspects of the polymer's molecular weight distribution (MWD). This information can be extracted from the data using computer analysis. Equations have been derived for the…
Scanning tunneling microscopy observations on epitaxial Cu/Ru(0001) show the relaxation of (tensile) lattice strain to occur in four different stages with increasing film thickness, from pseudomorphic to unilaterally contracted to (quasi-)isotropically contracted film structures, with decreasing lattice strain and inc…