Materials Literature
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The purpose of this brief review is to describe some recent, preliminary attempts to prepare nanocomposites in which polymer chains thread through the cavities or channels of several types of inorganic materials, specifically zeolites, a mesoporous hexagonal form of silica, and silica nanotubes. One goal is to determi…
Abstract
SUMMARY An unconstrained 3-D micromagnetic model for magnetite grains with resolutions up to 23 × 23 × 63 is presented. The model has been used to investigate the magnetic domain states of submicron parallelepipeds with various elongations. The method of fast Fourier transformation (FFT) has been implemented in three…
The adsorption of CO on Co(0001) has been investigated in situ by polarization modulation infrared reflection absorption spectroscopy (PM-RAIRS), which has been applied for the first time in a study of a model system for a heterogeneous catalyst. The CO/Co(0001) system was studied in the pressure range from 10 -10 to…
In this perspective some general phenomena of ligand-stabilized transition-metal clusters and colloids are introduced before some recent results on the special behaviour of such particles in catalysis are given.
Abstract Polymerizations of lactides via cationic, anionic, and insertion mechanisms are described. The usefulness of these three mechanisms for preparative purposes is evaluated. The polymerization mechanisms initiated by Al‐alkoxides or Sn(II)‐2‐ethylhexanoate are discussed in more detail. Furthermore, the usefulnes…
The depression of the glass transition temperature of a wheat gluten film by water was studied by dynamic mechanical thermal analysis and differential scanning calorimetry. Wheat gluten film behaved as a typical amorphous polymer, and the large plasticizing effect of water did not fit simply on the prediction of the C…
Spread monolayers of poly(styrene)−poly(ethylene oxide) diblock copolymers (PS m −PEO n, m = 38, n = 90, 148, 250, and 445) have been studied at the air−water interface by measuring the surface pressure−area (π− A ) isotherms at several temperatures. The π− A isotherms exhibit several regions which can be ascribed to…
Abstract High purity and a large amount of β‐modification can be produced in polypropylene (PP) by adding a bicomponent β‐nucleator consisting of equal amounts of pimelic acid and calcium stearate. Wide angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), static tensile tests, Izod impact tests, and ins…
Hydrotalcites, which are anionic clays, have been synthesized by the sol−gel technique from magnesium ethoxide, aluminum tri-sec-butoxide, and aluminum acetylacetonate. Initially a colloidal solution is obtained which gels and is thermally stabilized. The local and average structure are studied comparing the electron…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSoluble Alkyl-Substituted Poly(ethylenedioxythiophenes) as Electrochromic MaterialsAnil Kumar and John R. ReynoldsView Author Information Department of Chemistry, Center for Macromolecular Science and Engineering, University of Flor…
A new class of porphyrins in which intervening ethynyl moieties connect aryl groups to the porphyrin 5- and 15-positions is described. The synthesis and optical spectroscopy of five new compounds are reported: [5,15-bis[(4‘-dimethylaminophenyl)ethynyl]-10,20-diphenylporphinato]zinc(II), [5,15-bis[(4‘-methoxyphenyl)eth…
Polymerization of l -lactide in dichloromethane at 25 °C using an initiating system comprising tris(2,6-di- tert -butylphenoxy)yttrium and 2-propanol was first order in monomer and initiator. A propagation rate constant of 1.92 × 10 3 L mol -1 min -1 was determined using in situ UV spectroscopy. In the first step the…
Supramolecular liquid-crystalline networks have been prepared by self-assembly of multifunctional H-bond donor and acceptor molecules through the formation of intermolecular hydrogen bonds. Two tricarboxylic acids, 1,3,5-tris(2-(2-(4-carboxyphenoxy)ethoxy)ethoxy)benzene ( 1 ) and 3,4-bis(2-(2-(4-carboxyphenoxy)ethoxy)…
Part I - Layered Solids and their Intercalation Chemistry. Part II - Molecular Sieves: Inclusion Chemistry and Reactivity. Layered solids and their intercalation chemistry (G. Alberti, U. Constantino). Graphite intercalation compounds (F. Okino, H. Touhara). Layered metal chalcogenides and their intercalates (J. Rouxe…
The spreading of aqueous mixtures of a number of surfactants, including “superspreading” trisiloxane surfactants, has been investigated as a function of surfactant concentration, substrate surface energy, temperature, humidity, and substrate roughness. The substrate surface energy, characterized in terms of the contac…
Over the past two decades the “pressure and material gaps” separating ultrahigh-vacuum surface science and technical catalysis has been bridged by coupling an apparatus for the measurement of reaction kinetics at elevated pressures with an ultrahigh-vacuum system for surface analysis. Studies with this combined method…
A combination of small-angle X-ray scattering and optical microscopy was used to investigate the influence of diluent mobility and polymer−polymer interactions on diluent segregation in a series of “model” melt-miscible poly(ethylene oxide) (PEO) blends. The amorphous polymeric diluents were selected with regard to th…
We report experimental data on the mechanical stability of the silica mesoporous material MCM-41. Using X-ray diffraction and nitrogen adsorption we show that the ordered mesoporous structure of MCM-41 can be affected considerably by mechanical compression at pressures as low as 86 MPa and essentially destroyed at 224…
We report atomistically detailed molecular dynamics simulations of benzene−polystyrene systems (0−84.2 wt % polystyrene). We have calculated solvent diffusion coefficients and have found that their composition dependence not only shows good agreement with experiment but also follows quite well the predictions by latti…