Materials Literature
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Samples of poly(syndiotactic styrene- co -butadiene) (sPS−B) have been prepared using methylalumoxane (MAO) activated CpTiCl 3 under a range of experimental conditions. Copolymerization activities were low (24−36 kg mol -1 of cat. h -1 ) and nearly constant over the range of polymerization temperatures investigated (2…
Using the Monte Carlo lattice-simulation technique, we present numerical evidence of the formation of gyroid and nongyroid tricontinuous cubic phases in high polymeric systems of ABC/A/C triblock copolymer and homopolymer blends. By increasing the volume fraction of homopolymer, a remarkable phase sequence G (gyroid)…
The low-temperature specific heat of single-walled carbon nanotubes (isolated and bundled) and multiwalled carbon nanotubes is calculated within force-constant dynamical models. It is shown that, due to the quadratic dependence of the frequency $\ensuremath{\omega}$ of the transverse-acoustic phonons on the wave numbe…
We develop an efficient simulation scheme to study a model suspension of equally sized colloidal hard spheres and nonadsorbing ideal polymer coils, both in bulk and adsorbed against a planar hard wall. The many-body character of the polymer-mediated effective interactions between the colloids yields a bulk phase diagr…
Abstract Fluorescence was used to characterize the glass transition in thin and ultrathin supported polymer films with common chromophores. The temperature dependence of the fluorescence intensity exhibits a transition or break upon cooling from the rubbery state to the glassy state, and this is identified as the glas…
Electronic states of P donors in Si nanocrystals (nc-Si) embedded in insulating glass matrices have been studied by electron spin resonance. Doping of P donors into nc-Si was demonstrated by the observation of optical absorption in the infrared region due to intraconduction band transitions. P hyperfine structure (hfs…
We have used density functional calculations on model peptides to study conformational effects on (15)N, (13)C alpha, (13)C beta, and (13)C' chemical shifts, associated with hydrogen bonding, backbone conformation, and side-chain orientation. The results show a significant dependence on the backbone torsion angles of…
The detailed structure of a new dense amorphous ice, VHDA, is determined by isotope substitution neutron diffraction. Its structure is characterized by a doubled occupancy of the stabilizing interstitial location that was found in high density amorphous ice, HDA. As would be expected for a thermally activated unlockin…
The photooxidation of various olefins in homogeneous solution under an oxygen atmosphere, by use of visible light, a dye sensitizer, and an oxygen-transfer catalyst, has been investigated. The oxygen transfer from molecular oxygen to olefin involves the following steps: i) photoinduced singlet-oxygen formation, ii) al…
Atomistic configurations of yttria-stabilized zirconia between 3 and 10 mol % ${\mathrm{Y}}_{2}{\mathrm{O}}_{3}$ were relaxed using the pseudopotential technique. The results showed a phase transition to the cubic (c) $({\mathrm{ZrO}}_{2}{)}_{100\ensuremath{-}x}({\mathrm{Y}}_{2}{\mathrm{O}}_{3}{)}_{x}$ at $x\ensuremat…
L -Tyrosine (C9H11NO3), having morphology of spherulitic needles and long needles, an amino acid constituent of urinary stone, is crystallized in silica gel under suitable pH conditions and by single diffusion and double diffusion methods. The grown crystals were characterized by density measurement, Fourier transform…
Photochromic dithiazolylethenes [1,2-bis(5-methoxy-2-phenylthiazol-4-yl)perfluorocyclopentene (1a) and (5-methoxy-2phenylthiazol-4-yl)-2-(5-methyl-2-phenylthiazol-4-yl)perfluorocyclopentene (2a)] having methoxy substituents at the reaction centers were synthesized and their photochromic reactivity was compared with 1,…
A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of t…
Four new porphyrin derivatives are described: one (1) with a methoxyphenyl group and three pyridinium units (for comparison only), and three others with either adenine (2, 3) or thymine (4) bases. The synthetic strategies vary from known literature procedures in that the methylation of pyridinium subunits takes place…
Density functional theory (DFT) was applied to describe the magnetic and electron-transfer properties of dinuclear systems containing the [MnO2Mn]n+ core, with n=0,1,2,3,4. The calculation of the potential energy surfaces (PESs) of the mixed-valence species (n=1,3) allowed the classification of these systems according…
A novel method, combining chemical vapor deposition and pyrolysis of trimethoxyborane under ammonia atmosphere, has been developed to synthesize spherical boron nitride particles with a uniform diameter distribution from 50 to 400 nm; chemical composition and high-resolution transmission electron microscopy analyses i…
A diffuse interface model for the one-phase Hele–Shaw problem is derived from a gradient flow characterization due to Otto (1998 Arch. Rat. Mech. Anal. 141 63). The resulting dynamical model yields a generalized form of Darcy's law, and reduces to a degenerate version of the well-known Cahn–Hilliard equation. Formal a…
[Fe(hyptrz)3](4-chloro-3-nitrophenylsulfonate)22 H2O (1; hyptrz=4-(3-hydroxypropyl)-1,2,4-triazole) has been synthesized and its physical properties have been investigated by several physical techniques including magnetic susceptibility measurements, calorimetry, and Mössbauer, optical, and EXAFS spectroscopy. Compoun…
A facile synthesis of highly soluble, axially substituted titanium(IV) phthalocyanines is described. The reaction of tetra-tert-butylphthalocyaninatotitanium oxide tBu4PcTiO with the chelating agents 3a−3i containing oxygen or sulfur as donor atoms leads to the formation of axially substituted tBu4PcTiX (X = functiona…
The influence of electric field on crystal nucleation in a saturated solution has been studied both theoretically and experimentally. The classical equations for nucleation have been used to determine the free energy of formation, critical radius of the cluster and the concentration of the critical nuclei. The theory…