Materials Literature
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Heat-resistant flexible-film optical waveguides were fabricated from fluorinated polyimides. These waveguides operated in single mode and had low optical loss (0.3 dB/cm) at a wavelength of 1.3 microm for TE and TM polarizations. They also had good flexibility: The optical loss did not significantly change above a min…
Using rheometry and light scattering, we have studied the viscoelasticity of gels formed by the kinetically arrested phase separation in an emulsion−polymer mixture; to prevent the gels from collapsing under their own weight, we have used an isopycnic solvent. At constant osmotic pressure (set by the polymer concentra…
A new method is presented to generate and to fixate compositional gradients in blends of two miscible and amorphous polymers. A compositional gradient is introduced into a solution of a polymer in a monomer by use of a centrifugal field, and this gradient is subsequently fixated by polymerization of the solvent-monome…
Molecular reorientation in the two amorphous phases of triphenyl phosphite, namely the supercooled liquid (phase aI) and the newly discovered second amorphous phase (phase aII), was investigated by dielectric relaxation and by two-dimensional (2D) nuclear magnetic resonance spectroscopy (NMR) in the time and frequency…
Ikaite, calcium carbonate hexahydrate, has by means of X-ray diffraction analyses of frozen samples been identified as the mineral component of the white spots formed in the shell of frozen shrimp during storage. When the shrimp thaw and the shell material is dried and kept at room temperature, ikaite rapidly transfor…
The valence change of samarium from trivalent to divalent in strontium hexaborate (SrB 6 O 10 ) prepared in air is observed. The temperature dependence of the luminescence and vibronic transitions of Sm 2+ are studied. The Sm 2+ ions occupy three crystallographic sites. With increasing temperature, the 5 D 0 → 7 F 0 t…
Nonlocal density functional theory [DFT] has been used to compute vibrational frequencies and intensities of nickel porphine and of several isotopomers via a scaled quantum mechanical [SQM] force field [FF]. The results support and extend those obtained from a revised empirical FF. The force constants are similar for…
The thermally stable second-order nonlinear optic (NLO) hybrid materials were successfully prepared by a sol−gel process using dye-attached sol−gel monomers (ormosils) of difunctionalized or trifunctionalized second-order NLO chromophores attached to silicon atoms. The dye-attached sol−gel monomers were synthesized by…
A layered double hydroxide with the hydrotalcite-like structure containing Ni(II) and Fe(III) cations in the brucite-like layers with the formula [Ni 0.7 Fe 0.3 (OH) 2 ](CO 3 ) 0.15 ·0.94 H 2 O has been prepared by coprecipitation. On hydrothermal treatment, a coproduct, identified as a NiFe 2 O 4 spinel, is formed. B…
We revisit the transport properties of La-Ca manganites in detail, since they have been confirmed in a number of CMR-exhibiting materials. We also discuss new data considered the hallmark of an unusually high electron-phonon coupling responsible for charge localization and small polaron transport.
A versatile single source thermal ablation (SSTA) technique is demonstrated, enabling the deposition of high-quality films of organic−inorganic hybrid materials. The SSTA process involves rapidly heating the organic−inorganic compound using a resistively heated sheet. The organic and inorganic components ablate from t…
Dimensionality plays a critical role in determining the properties of materials due to, for example, the different ways that electrons interact in three-dimensional, two-dimensional (2D), and one-dimensional (1D) structures.1-5
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPreparation of Narrowly Distributed Stable and Soluble Polyacetylene Block Copolymer NanoparticlesChi Wu, Aizhen Niu, Louis M. Leung, and T. S. LamView Author Information Department of Chemistry The Chinese University of Hong Kong Shatin, N.T., Hong Kong The Open Labor…
Nanotubes of hexagonal boron nitride ( h -BN) have been synthesized by arc discharge between ZrB 2 electrodes in a nitrogen atmosphere. A new morphology of BN nanotubes at their tips, exhibiting a “triangular flag” like shape, was observed by transmission electron microscopy. This morphology suggests the presence of e…
We have studied the isothermal cold crystallization of poly(ether−ether−ketone) (PEEK) by atomic force microscopy, densitometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small- and wide-angle X-ray scattering (SAXS and WAXS). A two-stage process was clearly evidenced. The first s…
Chiral acyclic allylic alcohols 1 have been chemo-, regio-, and diastereoselectively epoxidized to the corresponding epoxy alcohols 2 by catalysis with the achiral manganese(salen) and iron(porphyrin) complexes 3 and 4 and iodosyl benzene as oxygen donor. The threo diastereoselectivities establish that hydrogen bondin…
Spherulitic growth rates for poly(ethylene oxide) and four model, melt-miscible blends were measured over a range of crystallization temperatures. The miscible diluents fall into two classes: those exhibiting relatively weak intermolecular interactions with PEO and those exhibiting strong interactions. Generally, at a…
In supercooled o -terphenyl (OTP), subsets of probe molecules in more mobile environments can be selectively photobleached. The time required for the remaining slower-than-average probes to be redistributed into an equilibrium set of environments has been measured. At T g + 4 K ( T g = 243 K), this exchange time is 6…
Structural and enzymological studies have shown the importance of Glu144 and Glu164 for the catalysis by 2-enoyl-CoA hydratase-1 (crotonase). Here we report about the enzymological properties of the Glu144Ala and Glu164Ala variants of rat mitochondrial 2-enoyl-CoA hydratase-1. Size-exclusion chromatography and CD spec…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrganic Materials Challenges for 193 nm ImagingElsa Reichmanis, Omkaram Nalamasu, and Frank M. HoulihanView Author Information Bell Laboratories, Lucent Technologies, 600 Mountain Avenue, Murray Hill, New Jersey 07974 Cite this: Acc. Chem. Res. 1999, 32, 8, 659–667Publicatio…