Materials Literature
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConjugated liquid-crystalline polymers - soluble and fusible poly(phenylenevinylene) by the Heck coupling reactionZhenan Bao, Yongming Chen, Rubing Cai, and Luping YuCite this: Macromolecules 1993, 26, 20, 5281–5286Publication Date (Print):September 1, 1993Publication Histor…
Abstract Replacement of kaolinite by dickite has been observed to occur with increasing depth of burial in sandstones from three different basins on the Norwegian continental shelf. In the Garn Formation (Middle Jurassic) of Haltenbanken, samples from 1.4-2-7 km below the sea floor (110°C) contain kaolinite, whereas d…
This paper describes a computational method for the determination of all possible phonon modes in framework crystal structures that leave the fundamental structural units (tetrahedra and octahedra) undistorted. Such rigid-unit modes (RUMs) are prime candidates as soft modes for displacive phase transitions, such as in…
Abstract Conducting polyfluorene derivatives with alkyl chains—poly(9‐alkylfluorene)s and poly‐(9,9‐dialkylfluorene)s—have been synthesized by chemical polymerization utilizing FeCl 3 as an oxidizing agent. The polymers obtained are found to be soluble in conventional organic solvents such as chloroform and have been…
Solid‐state 27 Al and 29 Si magic angle spinning NMR spectroscopy has been combined with electron energy loss spectroscopy carried out in the transmission electron microscope to determine the location of Al substituting in a semicrystalline C‐S‐H gel present in a hydrated synthetic slag glass. The gel is found to cont…
The dinucleating ligand bis[ 1- methyl-2-(6'- [ 1”-(3,5 imethoxybenzyl)benzimidazol-2~'-ylp]y rid-2'-y1)benzimidazol- 5-yllmethane (L) reacts with lanthanide perchlorates to give dinuclear 2:3 complexes [Lnz(L)#+ (Ln = La, Eu, Gd, Tb, and Lu). Detailed ES-MS, lH-NMR, luminescence, and spectrophotometric measurements i…
The classical theory of elasticity describing three- and lower-dimensional systems is generalized to higher-dimensional spaces. The elastic properties of quasicrystals can be derived from this theory, appropriately. The practical application is given to pentagonal, octagonal, dodecagonal, and icosahedral quasicrystals…
The inclusion of anisotropic surface free energy and anisotropic linear interface kinetics in phase-field models is studied for the solidification of a pure material. The formulation is described for a two-dimensional system with a smooth crystal-melt interface and for a surface free energy that varies smoothly with o…
Abstract A simple, convenient and reliable calorimetric efficiency scale is proposed for the evaluation of nucleating additives for polymers. The scale is based on conventional differential scanning calorimetry cooling runs and makes use of a crystallization range determined in self‐nucleation experiments. It can be c…
The rare earth cryptates are used as long-lived fluorescent labels. They are formed by inclusion of a europium ion in the intramolecular cavity of a macropolycyclic ligand containing bipyridine groups as light absorbers. The use of fluoride ions in the measuring medium allows a total shielding of the label fluorescenc…
Infrared transmission spectra of molecules adsorbed on silver island films evaporated on CaF 2 have been investigated. The spectra are remarkably simple compared with those of the molecules in the solid state (KBr pellets). Only the vibrational modes which give dipole changes perpendicular to the metal surface are inf…
The dielectric behavior and structure of the Sr(Zn1/3Nb2/3)O3-Ba(Zn1/3Nb2/3)O3 solid solution have been investigated with the intention of understanding the relationship between the structural changes and the temperature coefficient of the relative permittivity τε. A correlation between the value of τε and the occurre…
J aggregate of a water-soluble porphyrin, 5,10,15,20-tetra(4-sulfophenyl)porphyrin (H2TPPS44−), formed in acidified aqueous solutions, exhibits sharp and intense absorption bands at 491 and 707 nm. These characteristic transitions, J bands, are of linear oscillators polarized in the long axis of rodlike aggregate. The…
The tissue response and in vivo molecular stability of injection-molded polyhydroxyacids--polylactides (PLA), poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/VA, 5-22% VA content)--were studied. Polymers were implanted subcutaneously in mice and extirpated at 1, 3, and 6 months in…
Abstract The crystallization behavior after partial or complete melting of the α phase of iPP is examined by combined differential scanning calorimetry (DSC) and optical microscopy: calorimetric results are directly correlated with corresponding morphologies of microtome sections of DSC samples. On partial melting at…
In kilogram quantities ; pure poly(propylene imine) dendrimers can be prepared in an extremely simple reaction sequence comprising Michael addition (primary amines to acrylonitrile) and heterogeneous hydrogenation with a Raney cobalt catalyst. Both steps proceed quantitatively and selectively and can be employed with…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExpanding roles for templates in synthesisSally Anderson, Harry L. Anderson, and Jeremy K. M. SandersCite this: Acc. Chem. Res. 1993, 26, 9, 469–475Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https…
Abstract A polyimide hybrid with montmorillonite clay mineral has been synthesized from a dimethylacetamide (DMAC) solution of poly(amic acid) and a DMAC dispersion of montmorillonite intercalated with an ammonium salt of dodecylamine. Montmorillonite consists of stacked silicate sheets about 2000 Å in length, 10 Å in…
Deviations from thermally activated and from exponential response are typical features of the vitrification phenomenon and previously have been studied using viscoelastic, dielectric, calorimetric, optical, and other techniques. Linear response data from literature on about 70 covalent glass formers, ionic melts, supe…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallitesC. B. Murray, D. J. Norris, and M. G. BawendiCite this: J. Am. Chem. Soc. 1993, 115, 19, 8706–8715Publication Date (Print):September 1, 1993Publication H…