Materials Literature
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ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTAn Efficient Rhodium(I) Initiator for Stereospecific Living Polymerization of PhenylacetylenesYasuhisa Kishimoto, Tatsuya Miyatake, Takao Ikariya, and Ryoji NoyoriView Author Information ERATO Molecular Catalysis Project, Research D…
We use scaling arguments to determine the patterns that form when Y-shaped AB copolymers are grafted onto a flat surface. One “arm” of the Y is an A homopolymer, and the other arm is an incompatible B chain, and the short “stem” tethers the entire copolymer to the surface. We investigate the behavior of the brush form…
This study focuses on interfacial bonding between intergranular silicon carbide particles and an alumina matrix, to determine the creep inhibition mechanism of alumina/ silicon carbide nanocomposites. It is revealed that the silicon carbide/alumina interface possesses much stronger bonding than the alumina/alumina int…
An investigation of the surfaces of linear, segmented block copolymers of poly(dimethylsiloxane−urea−urethanes) by dynamic contact angle analysis is reported. The polymer films are immersed in water, the time-dependent advancing and receding contact angles are observed, and the contact angle hysteresis is reported. Th…
We have determined by forced Rayleigh scattering the diffusion coefficients D of several photochromic tracers with van der Waals radii between 0.38 and 8 nm (the largest ones being photolabeled polystyrene micronetworks) in 10 glass-forming liquids at temperatures between the glass temperature T g and ∼1.2 T g . The r…
A phenomenological theory for the cholesteric phase induced by a chiral solute in a nematic solvent is derived from (i) the continuum representation of twist deformation of the nematic solvent, and (ii) the surface anchoring energy approximation for the interactions between the solvent and a solute of given shape. Thi…
${\mathrm{KTaO}}_{3}$ was investigated using density functional methods. These local-density approximation calculations correctly show the absence of a ferroelectric instability in this compound. Phonon frequencies and bulk properties in good agreement with existing measurements are obtained. A highly anharmonic low-f…
The diameter containing a fraction of the current is used as the measure of the charged particle probe size. This has, particularly in the case of analytical microscopies, proven to be a more practical measure than those based on widths of the current density distribution. The diameter of current carrying beams of fin…
The structure of bovine liver cytochrome b(5), a soluble 93-residue proteolytic fragment of a 16 kDa membrane-bound hemoprotein, initially solved at 2.0 A resolution, has been refined at 1.5 A using data collected on a diffractometer. Refinement to 2.0 A resolution used the Hendrickson-Konnert procedure PROLSQ and was…
Structural, thermal, and optical studies on regioregular poly[3-oligo(oxyethylene)-4-methylthiophene] have revealed interesting thermochromic and ionochromic effects related to a planar/nonplanar transition of the conjugated backbone. This first-order-like conformational transition (formation of twistons) seems driven…
Photochemical and thermal surface modifications of diamond powders and (100), (110), and (111) oriented single crystals were achieved. Clean, hydrogen-terminated diamond was chlorinated by heating in Cl 2 (g) or by UV irradiation in Cl 2 (g). The surface chlorine titer was shown to correlate with the dangling bond den…
Transmission electron imaging and diffraction are used to probe the atomic-level structure of single-layer carbon nanotubes. The nanotubes bend, fold, kink, and radially deform. They have a tendency to form parallel bundles of tubes, and this bundling process has been observed in real time. In addition, the electron b…
Homogeneous precipitation from solution by hydrolysis of urea at elevated temperatures (T= 120 °C) yields novel ammonia-intercalated α-type hydroxide phases of the formula M(OH)x(NH3)0.4(H2O)y(NO3)2 –x where x= 2,y= 0.68 for M = Ni and x= 1.85, y= 0 for M = Co. These triple-layered hexagonal phases (a= 3.08 ± 0.01 Å,…
Thin films of cubic BaTiO 3 were processed hydrothermally at 40°–80°C by reacting thin layers of titanium organo metallic liquid precursors in aqueous solutions of either Ba(OH) 2 or a mixture of NaOH and BaCl 2 . All films (thickness ∼1 μm) were polycrystalline with grain sizes ranging from nano‐ to micrometer dimens…
Solid-state 13 C CP-MAS NMR spectroscopy has been used to investigate highly crystalline, partially crystalline, and amorphous poly( l -lactide) (PLLA). The amorphous domains have broad resonances with Gaussian line shapes, while the crystalline domains have narrower resonances with a high degree of Lorentzian charact…
The surface composition of styrene polymers capped at one or both ends by perfluoro groups has been determined by ISS, XPS, and static SIMS. The homopolymers, with M n 29 000−59 000, have an excess of the perfluoro end groups at the surface that is inversely proportional to the chain length and is commensurate with on…
Dimanganese-substituted gamma-Keggin heteropoly tungstates have been synthesized by reaction of the lacunary species gamma-[(SiO(4))W(10)O(32)](8)(-) with appropriate mixtures of Mn(II) and MnO(4)(-). The crystal structure of [(CH(3))(3)(C(6)H(5))N](4)[(SiO(4))W(10)Mn(III)(2)O(36)H(6)].2CH(3)CN.H(2)O (anion 1) was det…
A process for micromachining arbitrary structures with high aspect ratios in bulk silicon utilizing standard microelectronic processes is presented. It is based on electrochemical macropore formation on n‐type silicon in electrolytes containing hydrofluoric acid. Very regular pore arrays with pore diameters and distan…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTUnprecedented Two-Dimensional Polymers of Mn(II) with TCNQ-• (TCNQ = 7,7,8,8-Tetracyanoquinodimethane)Hanhua Zhao, Robert A. Heintz, Kim R. Dunbar, and Robin D. RogersView Author Information Department of Chemistry and the Center for Fundamental Materials Research Mich…
Fluorescence line-narrowing spectroscopy is used to characterize the effect of metal cation codopants (Sr 2+, La 3+, Gd 3+, Y 3+, Lu 3+, Sc 3+, and Ga 3+ ) on the state of aggregation of Eu 3+ in sol−gel silica. Significant Eu 3+ clustering occurs in samples doped only with Eu 3+ . The addition of codopants inhibits t…