Materials Literature
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Two disc-shaped multialkynyl arene ethers (1 and 2) with unusual thermo-mesomorphic properties are presented. Conoscopic studies show that the nematic phases of these new low molecular weight liquid crystals are biaxial and that the sign of their biaxiality is negative. The diether 2 is the first discotic twin liquid…
Part 1 Dimensional instabilities due to volume relaxation: general outline of volume relaxation volume-relaxation data for a number of polymers consequences for optical and electrical properties methods to reduce the volume-relaxation effects. Part 2 Dimensional instability due to the stresses acting during processing…
Abstract New monomers are described for the synthesis of rod‐like poly(1,4‐phenyleneethynylene)s with long flexible aliphatic side chains. By palladium catalyzed polycondensation soluble polymers with melting points around 100°C could be obtained. The molecular weight was estimated by GPC, VPO and elemental analysis:…
Abstract Biological structures consist of mechanical load carriers, which are highly optimized in terms of mechanical strength and minimum weight. It is demonstrated on some selected examples that a constant Mises‐stress at the surface of the biological component can be accepted as significant biological design rule.…
Abstract Investigation of the morphology and properties of ternary composites of polypropylene, ethylene‐propylene‐diene terpolymer, and filler has shown that in such systems two kinds of structures can be formed: separate dispersion of the components or encapsulation of the filler by the elastomer. A thermodynamic an…
When preparing homogeneous, fine barium titanate powders, the major difficulty is to avoid the spontaneous self‐condensation between the Ti‐OH groups. In the usual way of preparing fine barium titanate powders, chelating agents (citrate, oxalate) or simply unidentate ligands (alkoxy or carboxyl groups) are used to com…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThermally irreversible photochromic systems. Reversible photocyclization of 1,2-diselenenylethene and 1,2-diindolylethene derivativesYasuhide Nakayama, Koichiro Hayashi, and Masahiro IrieCite this: J. Org. Chem. 1990, 55, 9, 2592–2596Publication Date (Print):April 1, 1990Pub…
Luminescence spectra and SIMS measurements of Er-doped silicon are presented in this paper. Luminescence was found to be stronger in Czochralski-grown Si crystals, known to contain up to 10 18 cm -3 of oxygen center. Direct role played by oxygen impurities in the optical activation of the 1.54 µm luminescence was demo…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOff-lattice Monte Carlo simulations of polymer melts confined between two plates. 2. Effects of chain length and plate separationSanat K. Kumar, Michele Vacatello, and Do Y. YoonCite this: Macromolecules 1990, 23, 8, 2189–2197Publication Date (Print):April 1, 1990Publication…
Near‐phase pure perovskite lead magnesium niobate (PMN) with MgO or PbO additives was produced by reacting PbO with MgNb 2 O 6 at 800°C and sintering at 1200°C. Dense ceramics were characterized by scanning electron microscopy, X‐ray diffraction, and dielectric measurements. The microstructural studies showed that exc…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and optical properties of conformationally constrained trimeric and pentameric porphyrin arraysToshi Nagata, Atsuhiro Osuka, and Kazuhiro MaruyamaCite this: J. Am. Chem. Soc. 1990, 112, 8, 3054–3059Publication Date (Print):April 1, 1990Publication History Published…
A current-estimation approach to support the analysis of electromigration (EM) failures in power supply and ground buses of CMOS VLSI circuits is discussed. It uses the original concept of probabilistic simulation to efficiently generate accurate estimates of the expected current waveform required for electromigration…
Abstract The thermal behavior of poly(etheretherketone)(PEEK) film heated in an open differential scanning calorimetry (DSC) pan at 20°C/min is distorted by relaxation of the strained film. PEEK film in a closed pan or quenched PEEK in open or closed pans shows a glass‐transition temperature ( T g ) around 144°C, cold…
Analyse statistique de l'energie et des modes d'empilement des cristaux d'hydrocarbures. Discussion des effets de la taille moleculaire, de la forme et de la stœchiometrie sur l'energie d'empilement. Estimation des effets du rapport carbone/hydrogene sur l'empilement. Evaluation du nombre de coordination moleculaire
The complex resonance eigenvalue can easily be obtained by scaling the internal coordinates of the Hamiltonian by a complex factor since then the resonance eigenfunction ${\mathrm{\ensuremath{\Psi}}}_{\mathrm{\ensuremath{\theta}}}$ is square integrable. The back-transformation of ${\mathrm{\ensuremath{\Psi}}}_{\mathrm…
An inorganic pyroelectric crystal is predicted to be ferroelectric if it satisfies the structural conditions that no atom within the unit cell be displaced more than about 1 Å from the position it would occupy in the paraelectric state and that the largest such displacement be greater than about 0.1 Å. In addition, th…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFormation and structure of alkyl peroxide complexes of germanium(IV) porphyrins from direct reactions with alkyl hydroperoxides and by photolysis of alkylgermanium(IV) porphyrins in the presence of dioxygenAlan L. Balch, Charles R. Cornman, and Marilyn M. OlmsteadCite this:…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIdeal polymer chains of various architectures at a surfaceM. K. KosmasCite this: Macromolecules 1990, 23, 7, 2061–2065Publication Date (Print):April 1, 1990Publication History Published online1 May 2002Published inissue 1 April 1990https://pubs.acs.org/doi/10.1021/ma00209a03…
Abstract In a series of MSnI 3 compounds (M = K, NH 4 , Rb, Cs, CH 3 NH 3 ) two types of coordination around the central Sn(II) were found by 127 I-NQR and powder X-ray diffraction techniques. They are square pyramidal (for M = NH 4 , Rb) and octahedral (for M = CH 3 NH 3 ). CsSnI 3 , on the other hand, showed a drast…
The electrochromic behavior of amorphous films prepared by electron‐beam deposition has been studied. SIMS analysis has revealed that lithium accumulates in amorphous films during reversible coloring and bleaching in propylene carbonate solution of . When a large quantity of lithium has been injected into films, an ab…