Materials Literature
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Abstract Two series of novel phosphorus‐containing poly(alkylene) amines with or without aromatic groups were synthesized via reacting phosphoryl chloride derivatives with commercially available polyetheramines, ethylenediamine and N‐phenyl‐1,4‐phenylenediamine, respectively. Chemical structures of the amines were cha…
Dynamic secondary ion mass spectrometry was used to investigate the chain mobility of polystyrene (MW ranging from 4.3 to 957 kg/mol) at the free surface. The data show that the diffusion coefficient was reduced relative to the bulk value within a distance, d < or = 4R(g), from the surface and scaled as 1/N(2.5) at fi…
One of the simplest models describing the ion transport in disordered ionic conductors on a microscopic level is the random barrier model. Using Monte Carlo techniques, we simulate, for the first time, the low-temperature particle dynamics in random barrier model systems with long-range Coulomb interactions between th…
This paper deals with X-ray fluorescence (XRF), X-ray diffraction (XRD), and 29 Si nuclear magnetic resonance ( 29 Si NMR) measurements of rice husk silica treated under hydrothermal conditions in autoclave and steam-explosion processes. An understanding of the structural behavior of rice husk silica provides insight…
Abstract Poly(vinyl acetate) (PVAc) was added to the crystalline blends of poly(ethylene oxide) (PEO) and poly( L ‐lactide) (PLLA) (40/60) of higher molecular weights, whereas diblock and triblock poly(ethylene glycol)–poly( L ‐lactide) copolymers were added to the same blend of moderate molecular weights. The crystal…
The vibrational density of states (VDOS) of bulk nanocrystalline Ni and Cu (model) samples with grain diameters between 5 and 12 nm are derived from molecular-dynamics simulations. The results show an enhancement of the density of states at low and high energies. Because of large system sizes and a decomposition of th…
We show that adsorption of dye molecules control the light-induced alignment of dye-doped nematic liquid crystal (LC) on a nonphotosensitive polymer surface. The dependencies of light-induced twist structures on exposure, thermal baking, thickness, and aging before irradiation of the LC cells allowed us to propose the…
[structure--see text] As an attempt to rationally design organogelators, an amphiphilic porphyrin bearing four beta-D-galactopyranoside groups at its periphery was synthesized. This compound tends to aggregate in a one-dimensional direction, resulting in very robust gels in DMF/alcohol mixed solvents. Spectroscopic st…
Dynamics of thin films of poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) have been investigated by dielectric relaxation spectroscopy in the frequency range from 0.1 Hz to 1 MHz at temperatures from 263 to 423 K. The alpha process, the key process of glass transition, is observed for thin films of PVA…
Abstract Polypropylene/clay (PP/clay) nanocomposites were synthesized via intercalative polymerization. The nanostructure of the composites was investigated by wide‐angle X‐ray diffractometry (WAXD) and transmission electron microscopy (TEM). The WAXD patterns of the PP/clay nanocomposites indicated that the character…
Raman spectra of the MgB2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 1…
The question addressed in this paper is that of the influence of the density of dislocations on the spin tunneling in Mn12 clusters. We have determined the variation in the mosaicity of the crystal structure of fresh and thermally treated single crystals of Mn12 by analyzing the widening of low angle X-ray diffraction…
The Kohn-Luttinger envelope-function method is generalized to the case of heterostructures with atomically sharp heterojunctions based on lattice-matched layers of related semiconductors with zinc-blende symmetry. For electron states near the Γpoint in (001) heterostructures the single-band effective-mass equation is…
The van der Waals liquid ortho -terphenyl has long been used as a model system in the study of the glass transition. Motivated by mode-coupling theory, extensive experiments have been undertaken to monitor the onset of structural relaxation on microscopic time- and lengthscales. Using in particular quasielastic neutro…
A ferroelectric monoclinic phase of space group Cm ${(M}_{A}$ type) has been discovered in $0.65{\mathrm{P}\mathrm{b}(\mathrm{M}\mathrm{g}}_{1/3}{\mathrm{Nb}}_{2/3}{)\mathrm{O}}_{3}{\ensuremath{-}0.35\mathrm{}\mathrm{PbTiO}}_{3}$ by means of high-resolution synchrotron x-ray diffraction. It appears at room temperature…
The thermal reaction of single-wall carbon nanotubes with in situ generated aryl diazonium compounds is described and is compared to a previously reported, electrochemically induced reaction with preformed aryl diazonium salts.
Optimal co-doping concentrations and dynamics of energy transfer processes for Tm3+-Tb3+ and Tm3+-Eu3+ in LiYF4 crystal hosts, J T Vega-Durán, L A Díaz-Torres, M A Meneses-Nava, J L Maldonado-Rivera, O Barbosa-García
Fluorescence upconversion experiments were performed on monomer solutions of a number of structurally similar thiacarbocyanine dyes. The results from these time-resolved experiments combined with the data obtained from steady-state absorption and emission and 1 H NMR spectra allowed us to assign the components with di…
Spontaneous pattern formation in hybrid nematic liquid-crystal films on glycerol was studied with both polarized transmission and unpolarized monochromatic reflected light microscopy. These observations reveal that the patterns that are found in 1 to 10-microm-thick films are due to a combination of film topography, g…
Polyaniline (PANI) zeolite composites have been prepared by oxidative polymerization of anilinein the presence of zeolite 13X, producing composite materials with PANI/zeolite weight ratios from about 0.5 to 55. The DC conductivity of the composite materials decreased exponentially with zeolite weight fraction. Pure PA…