Search results for "X-Ray"

2-Acylamino- and 2,4-bis(acylamino)pyrimidines as supramolecular synthons analysed by multiple non-covalent interactions. DFT, X-ray diffraction, and…

2012

Intermolecular interactions of ten 2-acylamino and 2,4-bis(acylamino)pyrimidines (7 of which are previously unknown) have been investigated by X-ray structural, quantum chemical (DFT), and NMR spectral methods. Especially the concentration dependencies of the (1)H NMR chemical shifts and titrations with other molecules capable of multiple hydrogen bonding provided useful information regarding their association via triple or quadruple hydrogen bonding, which is controlled by the conformational preferences of 2-acylamino- and 2,4-bis(acylamino)pyrimidines. On comparison of the properties of 2-acylamino- and 2,4-bis(acylamino)pyrimidines with the corresponding pyridines, an additional nitrogen…

2020

Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied.

Micropatterning of neurons using organic substrates in culture

1997

Abstract In this study, we have used spatially defined surfaces of organic thin films to micropattern the outgrowth of central nervous system neurons in culture. Glass substrates were first chemically modified with synthetic peptides derived from an extra-cellular matrix protein laminin to couple a functionality that promotes a neuron-substrate interaction. The modification procedure was verified using X-ray photoelectron spectroscopy. The functionality of the modified glass surfaces was examined by growing neurons dissociated from mammalian central nervous tissues in culture. Spatially defined surfaces of the peptide were then fabricated by selectively attaching the peptide to coplanar sur…

Heads or Tails? Sandwich-Type Metallo Complexes of Hexakis(2,3-di-O-methyl)-α-cyclodextrin

2020

Native and synthetically modified cyclodextrins (CDs) are useful building blocks in the construction of large coordination complexes and porous materials with various applications. Sandwich-type co...

Effects of pressure and of thermal history on the structural phase transition of KCN

1992

The cubic-noncubic structural phase transition of a KCN single crystal is studied as a function of thermal history and of hydrostatic pressure up to 2 kbar. The standard sequence of phases is cubic-monoclinic-orthorhombic on cooling and orthorhombic-cubic on heating. The monoclinic phase is also absent in first cooling runs at low pressures (p≦250 bar). The width of the monoclinic field inp, T phase diagram is increased in second cooling runs. The effects are discussed in terms of a martensitic transformation behavior and random strain fields.

Laponite clay in homopolymer and tri-block copolymer matrices

2007

Macromolecule/laponite nanomaterials were studied by DSC and X-ray diffraction techniques. The matrices are poly(ethylene) glycols at various molecular masses and poly(ethylene oxides)-poly(propylene oxides)-poly(ethylene oxides) tri-block copolymers. The latter were tuned by modulating the molecular masses, at constant hydrophilic/hydrophobic ratio, and the hydrophilicity. For all the investigated systems, the enthalpy of melting (ΔH m) is nearly constant up to a given composition thereafter it increases monotonically reaching the value of the pure macromolecule. We proposed a model to interpret the DSC data. Briefly, it was invoked a mechanism of interaction following which some segments …

X-ray topographic study of solid-state polymerized poly-[1,2-bis-(p tolylsulphonyloxymethylene)-1-butene-3-inylene]

1976

Local extinction contrast effects have been observed in macroscopic polymer crystals, using Berg-Barrett X-ray topography. Results from as-polymerized crystals indicate that the crystals are perfect enough for defect regions to be imaged. As-polymerized crystals exhibited apparent defects lying along [021]. [010] slip traces in the (100) surface of a crystal were imaged; the slip system here appears to be consistent with (h01) [¯10h], forh, l ≠ 0 and [010] the chain direction.

Structure and Chemical Bonds in Black Ti(C, N, O) Thin Films

2010

Different kinds of solid solutions in the V2O5-ZrSiO4-NaF system by sol-gel processes and their characterization

1993

Abstract In the V2O5-ZrSiO4-NaF system, three kinds of substances have been identified by sol-gel methods depending on the V2O5 amounts in the composition. Their characterization by X-ray diffraction, measurements of unit cell parameters, UV-visible (UV-V) spectroscopy, differential thermal analysis and lab colour parameter determination allow the consideration of three kinds of solid solution in the zircon lattice: (a) V+5,V+4-ZrSiO4, thermally stable and with a deep green colour; (b) V+4-ZrSiO4, thermally stable and blue coloured, made by the sol-gel method and with V2O5 amounts lower than 0·03 mol per formula weight; and (c) Na+,F−,V+4-ZrSiO4, a solid solution with a deep blue-turquoise …

Suivi par diffraction de rayons X “in situ” de l'évolution du paramètre de maille du ferrite nanométrique γ-Fe2O3lors de l'isotherme d'adsorption d'e…

2002

La methode de synthese par chimie douce a ete utilisee pour synthetiser des nanoparticules de maghemite γ-Fe 2 O 3 dans une gamme de taille allant de 9 a 14 nm. Ces poudres, parfaitement cristallisees en phase spinelle, exemptes d'impuretes, avec une stoechiometrie en oxygene parfaitement controlee, ont servi de materiaux modeles pour cette etude. Le parametre de maille de ce materiau (0,8346 nm) s'avere etre non dependant de la taille. Cependant, le suivi en Diffraction de Rayons X in-situ revele des variations de ce parametre avec la modification de la surface en presence de vapeur d'eau. Les phenomenes de chimisorption et de physisorption jouent un role preponderant dans les evolutions o…