Materials Literature
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The SAC(symmetry adapted cluster)/SAC-CI method is applied to the calculations of the ground, excited, and ionized states of the free base porphin. The electronic spectrum of porphin is well reproduced and new assignments for the B (Soret), N, L, and M bands are proposed. The present result shows that the four-orbital…
The polybutadiene (PB) content and its microstructure in different grades of high impact polystyrene (HIPS) has been studied by various spectroscopic techniques. PB is characterized by deformation bands in FTIR spectroscopy at 994, 967, 912, and 729 cm−1. FT-Raman was used for higher constant resolution over the range…
1,4-Bis(2,3-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, bis(2,3-dicarboxyphenoxy)sulfide dianhydride, bis(3,4-dicarboxyphenoxy)sulfide dianhydride, and 2,3,3′,4′-tetracarboxy diphenyl sulfide dianhydride were synthesized from 3-chlorophthalic anhydride and 4-chlorophthalic a…
Abstract The self‐assembly of alkaline folates in isotropic water solutions, with or without added salts, has been investigated by small‐angle neutron‐scattering, circular‐dichroism, and NMR techniques. The assembled species are chiral, cylindrical aggregates of finite length, composed of stacked tetramers; each tetra…
The low-temperature properties of block copolyetheresters with hard segments of poly(alkylene p,p′-bibenzoate) and soft segments of poly(tetramethylene ether) were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). In the temperature range of −100 to 60°C, two transition tem…
Ionizing radiation induces various changes in the molecular structure of elastomers; consequently, the macroscopic properties of the irradiated elastomers will be modified. The newly formed products and the alteration of the initial chemical structure are the result of free-radical reactions which provide the crosslin…
This work studies the bulk and nonisothermic polymerization of styrene (S) using mixtures of mono- and bifunctional initiators. The effects on polymerization rate and on molecular weight averages after changes in the global initiator concentration and in the nature of the initiator mixtures were experimentally and the…
Interaction Between Fillers and
The isothermal crystallization and melting behavior of the poly(ε-caprolactone)(PCL)/poly(ethylene oxide)(PEO) diblock copolymer has been studied by WAXD, SAXS, and DSC methods. Only the PCL block is crystallizable; the PEO block of weight fraction 20% cannot crystallize, although its corresponding homopolymer has str…
Ab initio molecular-dynamics simulations have been used to investigate the structure, dynamics and electronic properties of the liquid alloy Ag(1-x)Se(x) at 1350 K and at the three compositions x=0.33, 0.42 and 0.65. The calculations are based on density-functional theory in the local density approximation and on the…
Reactions of (silylamino)silanetriols RN(SiMe 3 )Si(OH) 3 (R = 2,4,6-Me 3 C 6 H 2 ( 1 ) and 2,6-Me 2 C 6 H 3 ( 2 )) with i -Bu 2 AlH in 1:1 molar ratio at −78 °C afford aluminosiloxanes [RN(SiMe 3 )Si(OH)O(OAlBu- i ·dioxane)] 2 (R = 2,4,6-Me 3 C 6 H 2 ( 3 ) and 2,6-Me 2 C 6 H 3 ( 4 )) and [RN(SiMe 3 )Si(OAlBu- i )(OAl…
Diffusion in homogenous membranes molecular simulations of sorption and diffusion in amorphous polymers free-volume theory transport phenomena in polymer membranes supermolecular structure of polymer solids and its effects on penetrant transport translational dynamics of macromolecules in melts.
In order to access the dynamics of surface diffusion or of surface chemical reactions it is necessary to determine the spatial probability distributions of the adsorbed atoms or molecules rather than their average positions. Here we demonstrate how such a distribution can be determined from scanned-energy mode photoel…
Zwei gegabelte Wasserstoffbrückenbindungen legen die Vorzugskonformation I des unten gezeigten Catenans im Festkörper und in unpolaren Lösungsmitteln fest; in polaren Lösungsmitteln ist Konformation II die dominierende. magnified image
The microstructure of (001)p-oriented (subscript p indicates the choice of a pseudocubic unit cell) potassium niobate (KNbO3) thin films grown by metalorganic chemical vapor deposition on (100)p lanthanum aluminate and having a large second-order nonlinear optical response is examined. Transmission electron microscopy…
An efficient, electrically conductive, chemical barrier for the integration of piezoelectric Pb(Zr,Ti)O3 (PZT) films on reactive metal substrates has been developed, opening new possibilities for PZT integration on micromechanical and semiconductor devices. Very reactive zirconium films have been taken in order to tes…
The disorder-to-order transition in asymmetric diblock copolymers of polystyrene/polyisoprene is studied using small angle x-ray scattering. In between the homogeneously disordered state at high temperature and the bcc ordered array of spheres we find a stable state of liquidlike order between the spherical domains. Q…
Si ions were implanted into thermally grown SiO2 films on crystalline Si at an energy of 120 keV and with a dose of 1016 cm−2. Under an ultraviolet excitation of ∼5.0 eV, the implanted films exhibit blue luminescence with a peak of ∼2.7 eV at room temperature. The blue emission is caused by oxygen vacancies in the fil…
The electronic structures of the perovskite oxides, ${\mathrm{LaMnO}}_{3}$ and ${\mathrm{CaMnO}}_{3}$, are studied using density-functional methods. Antiferromagnetic insulating (AFI) solutions are obtained for both compounds within the local-density approximation (LDA). For ${\mathrm{LaMnO}}_{3}$ the Jahn-Teller dist…
Polycrystalline diamond films have been grown by microwave assisted chemical vapor deposition from methane/hydrogen gas mixtures. The addition of small amounts of nitrogen with concentrations below 50 ppm to the process gas was found to drastically increase the deposition rate depending on the microwave power. At 4.2…