Materials Literature
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We report results of a large-scale Monte Carlo study of a grafted-polymer "brush" composed of two types of chains of length N = 100 segments under near-melt conditions, with respulsive interactions of strength χ acting between segments of the two species. Following a quench from χ = 0 to χ = 1, we observe the formatio…
The current-voltage relationship I(V) for several different ferroelectric thin films often exhibits an apparent negative differential resistivity. In the present paper we show that in lead zirconate-titanate (PZT) this is a spurious artifact arising from rapid (parametric) measurement techniques and that it disappears…
Pyriporphyrins like the isolable porphyrin analogue 1 react unexpectedly upon oxidation. Depending on the reaction conditions either a ketone (C = O instead of CH2) or a dimer is formed. A conjugated [18]annulene derivative is, however, not obtained.
The multiphonon relaxation (MR) rates for a large number of 3- to 5-phonon transitions of ${\mathrm{Er}}^{3+}$ ions in ${\mathrm{LiYF}}_{4}$ and ${\mathrm{LaF}}_{3}$ crystals were measured at 77 K. The MR rates of ${\mathrm{Nd}}^{3+}$ and ${\mathrm{Er}}^{3+}$ ions in these crystals have been analyzed with a point-char…
Abstract The influence of thermal annealing on molecular weight, microphase mixing, and multiple melting behavior of a segmented block copolyurethane is reported. The material studied contained 55% of hard segment consisting of 4,4'‐diphenylmethane diisocyanate and butanediol, and a poly (propylene oxide) diol of mole…
Abstract Metal phthalocyanines (M = Cu, Ni, Co, SnCl 2 ) 3–6 containing four 14‐membered tetraaza macrocycles have been prepared. Detosylation of the aza functions has provided donor sites for binding four Ni 2+ ions giving a pentanuclear complex which is extremely soluble in polar solvents. The mass spectrum of the […
Sublimation of 1,2,3,5-dithiadiazolyl in vacuo affords a triclinic phase of the dimer [HCN2S2]2. The crystals belong to the space group P¯1, a = 6.816(3), b = 13.940(2), c = 14.403(3) Å, α = 116.830(14), β = 98.64(3), γ = 99.18(3)°, FW = 212.4 (for [HCN2S2]2·[N2]0.08) Z = 6. The crystal structure consists of stacked d…
The electronic structure and interband transitions of α‐Al 2 O 3 have been studied using temperature‐dependent vacuum ultraviolet spectroscopy from 5 to 43 eV, at temperatures ranging from 293 up to 2167 K, which is approaching the melting point of 2327 K. The energy range of the spectra spans the full range of interb…
The phase content, size, and distribution have a marked effect on the thermomechanical properties of a 9 mol% MgO‐ZrO 2 (Mg‐PSZ) alloy. The work undertaken in this study is the first investigation to simultaneously measure and characterize the quantitative bulk phase contents and correlate these parameters to the frac…
A phenomenological model is proposed for the description of the sequences of ferroelectric, antiferroelectric, and ferrielectric smectic phases reported in liquid crystals of the MHPOBC [4-(1-methylheptyloxycarbonyl)phenyl-4'-octyloxybiphenyl-4-carboxylate] type. The model assumes a bilayer smectic ordering and a mech…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and Structure of Dialuminiohexaeuropiopentakis(hexaniobate): a High-Nuclearity Oxoniobate ComplexTomoji Ozeki, Toshihiro Yamase, Haruo Naruke, and Yoshinori SasakiCite this: Inorg. Chem. 1994, 33, 3, 409–410Publication Date (Print):February 1, 1994Publication Histo…
We study the quasistatic behavior of the lamellar phase of diblock copolymers under uniaxial compression and tension along the normal direction of the layers, in both the weak segregation limit (WSL) and the strong segregation limit (SSL). In the SSL, we derive a (nonlinear) continuum free energy description of the sy…
The adsorption and desorption of hydrogen from diamond films were studied in ultrahigh vacuum using high resolution electron energy loss spectroscopy as a probe of surface vibrations. Auger electron and energy loss spectroscopies were also used to characterize the diamond surface. The samples studied were boron-doped…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTWater-Saturated Mesoporous MCM-41 Systems Characterized by 1H NMRDuncan Akporiaye, Eddy Walther Hansen, Ralf Schmidt, and Michael StockerCite this: J. Phys. Chem. 1994, 98, 7, 1926–1928Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Pub…
A color change from yellow to red is observed on heating the bipyridinium salt of squaric acid (1). This reversible process is based on a proton transfer during the phase change. According to the Bürgi–Dunitz structure-correlation principle, the structure of the anion in solid 1 represents a point on the reaction coor…
The synthetic compound 4',7-dihydroxyflavylium chloride shows an interesting photochronic effect at moderately acidic pHvalues. Pale yellow solutions of this compound, equilibrated in the dark atpH3.4, become bright yellow upon irradiation with 313-nm light. Switching off the light, gives back the initial pale yellow…
A temperature-driven anchoring transition strongly influenced by ionic impurities appears in a nematic liquid crystal composed of centrosymmetric molecules. Two anchoring parameters, the tilt angle and the anchoring strength, were measured. The observed phenomena are explained as a result of a balance between the orie…
We describe an in vitro test of the hypothesis that viscoelastic properties of the collagen fiber network of skin are influenced by interactions between the macromolecular components in the extracellular matrix. Native type I collagen gels were investigated as a mechanical analog for connective tissue. A series of gel…
A model of ferroelectric switching in thin films which also exhibit semiconducting properties is presented. The two principle assumptions upon which the model is based are (1) that the threshold field for reverse domain nucleation, E cm, is much greater than the field required for domain wall motion, E cm, and (2) tha…
Measurements are presented of the long-time self-diffusion coefficient and of the low shear limiting viscosity of dispersions of charge stabilized colloidal silica spheres. Long-time self-diffusion coefficients were measured using fluorescence recovery after photobleaching (FRAP), the theory of which is presented and…