Materials Literature
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Studies were undertaken to gain mechanistic information on lactone ring-opening polymerization reactions using porcine pancreatic lipase (PPL) as the catalyst and ε-caprolactone (ε-CL) as the monomer. Polymerizations were carried out at low water levels (0.13 mmol) and supplemented with either butanol or butylamine. R…
A look inside the silk spinning process along the length of a silk gland has been achieved by the cryogenic quenching and subsequent microtoming of live silk-spinning animals, Nephila clavipes (spider) and Bombyx mori (silkworm). Observations made using transmission electron microscopy, electron diffraction and atomic…
ZnO films were prepared on silica glass substrates by the sol-gel method from Zn(CH3COO)2⋅2H2O-2-methoxyethanol solutions containing monoethanolamine (MEA) or diethanolamine (DEA). Smooth and transparent ZnO films were obtained by heating at temperatures from 200 to 500°C for 10min after each coating and finally at th…
Phase separation in a polymerizing diacrylate/LC mixture is shown to be driven by liquid−gel demixing rather than by liquid−liquid demixing. The structure of the gel strongly influences the initial morphology: “early” phase separation (at low conversion) produces spherical domains, whereas “late” phase separation (at…
We studied the viscoelasticity of two lyotropic lamellar systems prepared in the so-called “onion phase”. This state consists of monodisperse multilamellar vesicles filling up space. The elastic ( G ‘) modulus is measured as a function of the frequency in the linear regime (small amplitude of the oscillations) for dif…
A description is given of a modeling technique that is used to explore three-dimensional image distributions formed by high numerical aperture (NA > 0.6) lenses in homogeneous, isotropic, linear, and source-free thin films. The approach is based on a plane-wave decomposition in the exit pupil. Factors that are due…
The synthesis and characterization of siloxane-containing perfluorocyclobutane (PFCB) aromatic polyethers, a new class of fluorosiloxane polymers possessing a well-defined linear structure of alternating disiloxanyl- p -phenylene ( cis / trans) -1,2-disubstituted perfluorocyclobutyl ether linkages with known fluoroole…
In an effort to assess the applicability of various competing theoretical models, we have examined the temperature dependence of the viscosity \ensuremath{\eta}(T) and of the \ensuremath{\alpha}-relaxation times of a wide variety of supercooled liquids. The overall best fits over the entire temperature range above the…
The orientation of functional groups, side chains, and repeat units at the surface of a liquid crystal (LC) alignment layer (AL) polyimide was changed by rubbing with a cotton velvet cloth. It was discovered that rubbing induced polar functional groups and repeat units to reorient out-of-the-plane of the surface, and…
Acetylene coupling to benzene on the Pd{111} surface is greatly enhanced by the presence of catalytically inert Au atoms. LEED and Auger spectroscopy show that progressive annealing of Au overlayers on Pd{111} leads to the formation of a series of random surface alloys with continuously varying composition. Cyclizatio…
Complexes of the type Re(X)(CO) 3 (α-diimine) (X = Cl, Br, I; α-diimine = bpy, iPr-PyCa, iPr-DAB) exhibit a significant influence of X on the energies and intensities of their lowest-energy electronic transitions. Resonance Raman experiments revealed a change in character of the lowest energy transitions of these comp…
We present a phenomenological theory of randomly cross-linked polymer networks based on the separation of solid-like and liquid-like degrees of freedom and taking into account the frozen inhomogeneity of network structure. The complete solution of the statistical mechanics of this model is given, and the monomer densi…
Macromolecules incorporating a highly branched polystyrene core and a poly(ethylene oxide) shell were synthesized. A comb-branched (generation G = 0) polystyrene was prepared by initiating the polymerization of styrene with sec -butyllithium, capping with 1,1-diphenylethylene, and titrating the living anions with a so…
A vector generalization of the Jiles-Atherton model (1986) of ferromagnetic hysteresis is proposed. It gives a differential equation relating vector magnetization to vector magnetic field and essentially retains the simplicity of the original scalar model. The model can handle both the isotropic and anisotropic case a…
A series of trivalent metal cation containing mesoporous silicas have been synthesized using a primary alkylamine, e.g., hexadecylamine as organic templating surfactant. Using this synthesis route, it was possible to prepare materials where trivalent cations were tetrahedrally coordinated, with Si/Me ratios as low as…
Mn 2+ -doped CdS nanocrystals (1−2 nm in size) dispersed in organic−inorganic silica xerogels are prepared by combining a controlled precipitation of nanocrystals in inverted micelles, a separation as a pure capped cluster powder, and a dispersion in hydrolyzed silicon alkoxide. ESR study identified two Mn 2+ sites, o…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTThe Synthesis and Solubilization of Amide Macrocycles via Rotaxane FormationAndrew G. Johnston, David A. Leigh, Aden Murphy, John P. Smart, and Michael D. DeeganView Author Information Department of Chemistry, University of Manchester Institute of Science and Technolog…
Ceramic‐metal composites have been made to near net‐shape by reactive penetration of dense ceramic preforms by molten Al. In contrast to processes involving physical infiltration of a porous medium, this process works with dense ceramic preforms. Ceramic‐metal composite formation by reactive metal penetration is drive…
Single crystalline n‐type GaP was made porous by anodic etching in the dark in sulfuric acid solution. The morphology and (photo)electrochemical properties of the porous layer were investigated. Submicron pits 10 to 30 μm apart were formed at the surface. Below the surface, the pits acted as the nuclei of distinct por…
SiO 2 and SnO 2 colloids are capped with a cationic dye, rhodamine 6G, by electrostatic interaction. The close packing of these dye molecules on the negatively charged SiO 2 or SnO 2 colloid results in the formation of H-aggregates. These aggregates are nonfluorescent but can inject electrons from the excited state in…