Solid States (solid + states)

Distribution by Scientific Domains

Selected Abstracts

Structural characteristics of clay-dominated soils of a marsh and a palaeosol in a crossed diagram

M. Bernard
Summary Although the shrink-swell phenomenon of clays has been thoroughly studied, the in situ relation of the shrinkage curve to the structure profile is rarely presented from the shrinkage limit to the liquid limit. We studied the consolidated structure of clay-dominated (<2 ,m) soils formed on ,pseudo-liquid' marsh sediments in the ,Marais de l'Ouest' (France). The profiles were studied in a grassland field and in a sunflower field from unsaturated surface soils down to deeper, saturated, levels characterized by a very large water content (100% by weight). The consolidation states were quantified recording cone resistance (Qd) profiles using a dynamic penetrometer in successive seasons. These Qd profiles were compared with the associated wet density and gravimetric water-content profiles. Two consolidation depths were evident, the surface soil and a 130-cm deep palaeosol. The seasonal Qd profiles demonstrate the partial irreversibility of the consolidation peaks associated with the surface soil and with the palaeosol. The shrinkage properties were established through drying curves of undisturbed test samples. In the void ratio (e) - water content (W) and water content (W) - saturation index (Sr) diagrams, the profiles as a whole exhibit only one clay soil behaviour from their pseudo-liquid to plastic to solid states. Each Qd profile is represented by a hyperbolic curve in the e/Qd diagram. Represented in a (e , W , Qd ,Sr) crossed diagram, the vertical evolution of the successive profiles shows the soil structure behaviour from the initial pseudo-liquid sediment to the consolidated soil. A simple cone resistance recording associated with gravimetric water-content profiles, characterizes the evolution of structural layers of soils for the seasonal drying-wetting cycles, for the over-consolidation associated with the palaeosol, and also for the effect of ploughing. [source]

Tris(4-cyanophenyl)amine: Simple Synthesis via Self-assembly; Strong Fluorescence in Solution, Nano/microcrystals, and Solid,

A. Patra
Abstract The threefold symmetric molecule, tris(4-cyanophenyl)amine (TCPA) is synthesized from 4-fluorocyanobenzene by treatment with potassium carbonate in dimethylsulfoxide; the occurrence of the reaction without any amine reagent suggests the involvement of a novel self-assembly process. A reprecipitation strategy provides stable colloids containing highly monodisperse nano/microcrystals with well-defined cubic morphology and sizes tunable from 250 to 500,nm. The solution, colloid, and solid states of TCPA exhibit strong blue fluorescence; the colloid shows dual emission with an unusually small Stokes shift. Computational investigations are carried out on the molecule and supramolecular assemblies derived from the crystal structure. Coupled with detailed spectroscopic studies, they show that the emission in the colloidal and solid states can be attributed to energy levels resulting from the intermolecular interactions within different aggregation motifs in the condensed phase and energy cascades between them. The computations also reveal the presence of cooperative interactions in the molecular crystal contributing to its high thermal stability. The strong light emission exhibited by TCPA, concurrently in the solution, nano/microcrystal, and solid states establishes it as a novel molecular material of potential practical utility; it has led to the exploration of the underlying mechanism that describes the phenomena observed in the different physical states. [source]

Solution, thermal and optical properties of novel poly(pyridinium salt)s derived from conjugated pyridine diamines,

Alexi K. Nedeltchev
Abstract Several novel poly(pyridinium salt)s with heterocyclic pyridine moieties in their backbones with tosylate and triflimide counterions were prepared by either ring-transmutation polymerization reaction of phenylated-bis(pyrylium tosylate) with isomeric pyridine diamines of 4-phenyl-2,6-bis(4-aminophenyl)pyridine in dimethyl sulfoxide (DMSO) for 48 h at 130,140 C or by metathesis reaction of the respective tosylate polymers with lithium triflimide in DMSO at about 60 C. Their chemical structures were characterized by FTIR, 1H, 13C NMR spectroscopy, and elemental analysis. Their number-average molecular weights (Mn) were in the range of 8,000,51,000 and their polydispersities in the range of 1.18,2.13 as determined by gel permeation chromatography. They had excellent thermal stabilities of 340,458 C and high glass transition temperatures >200 C. As they showed good solubilities in common organic solvents, their solution properties were also characterized for their lyotropic liquid-crystalline properties with polarizing optical microscopy (POM) studies. Their photoluminescent properties were examined by using a spectrofluorometer in both solution and solid states. Their quantum yields were rather low, which were in the range of 1.3,2.0%. Additionally, hand-drawn fibers from the melts were examined to determine their morphologies with a number of microscopic techniques including POM, scanning electron microscopy, and transmission electron microscopy. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source]

Dendrimers based on [1,3,5]-triazines

Mackay B. Steffensen
Abstract A comprehensive and chronological account of dendrimers based on [1,3,5]-triazines is provided. Synthetic strategies to install the triazine through cycloaddition, cyclotrimerization, and nucleophilic aromatic substitution of cyanuric chloride are discussed. Motivations and applications of these architectures are surveyed, including the preparation of supramolecular assemblies in the solution and solid states and their use in medicines, advanced materials, and separations when anchored to solid supports. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3411,3433, 2006 [source]

Synthesis of Dendritic Oligo-Spiro(fluorene-9,9,-xanthene) Derivatives with Carbazole and Fluorene Pendants and their Thermal, Optical, and Electroluminescent Properties

Zengze Chu
Abstract Two novel spiro-configured ter(arylene-ethynylene) derivatives, TSF-Cz and TSF-F, have been designed and synthesized using spiro(fluorene-9,9,-xanthene) (SFX) as building blocks, introducing a hole-transporting carbazole and a fluorene chromophore as the peripheral functional group into the backbone through an oxygen atom. The two well-defined oligomers possess good solubility, film-forming quality, and high Tg's at 140 and 126,C, respectively. In addition, these oligomers exhibit blue photoluminescence (PL) emission both in solution and solid states. The double-layered devices fabricated using the two materials as the emitter show a sky-blue emission with a brightness and a current efficiency of 7,613,cd,,m,2 and 1.11,cd,,A,1 for TSF-Cz, and 1,507,cd,,m,2 and 0.36,cd,,A,1 for TSF-F, respectively. [source]

Structure determination and conformation analysis of symmetrical dimers

Alexei V. Buevich
Abstract Conformational and stereochemical analysis of six new symmetrical dimers was performed using proton,proton vicinal coupling measured from 1H NMR and 13C satellites of 1H NMR signals, natural abundance 13C-edited nuclear overhauser effect (NOE) experiments, comprehensive NOE analysis and molecular modeling. The 13C satellite analysis and 13C-edited NOE experiments were carried out to extract spectral information between equivalent protons. Molecular modeling was applied for estimations of three-dimensional parameters of the studied dimers, which were subsequently used to generate a set of theoretical NOE for each possible conformation. The J -coupling, 13C-edited NOE and quantitative NOE analyses showed the predominance of gauche conformation for three dimers, whereas a mixture of gauche and anti conformations (45:55) for three other dimers was established by quantitative NOE analysis. X-ray crystallographic study confirmed the stereochemistry of one of the dimers and revealed a discrepancy in conformation stability between liquid and solid states. Copyright 2004 John Wiley & Sons, Ltd. [source]

Influence of co-monomer structure on properties of co-polyamide packaging films

P. Scarfato
Abstract In this work a series of co-polyamides were prepared by random polymerization of ,-caprolactam in presence of four different co-monomers at a percentage of 5% w/w, with the aim of verifying their suitability as film-forming materials. The effects of structural changes induced in the ,-caprolactam homopolymer by co-monomers were evaluated in both molten and solid states. Rheological tests in shear and elongational flow were performed to evaluate the processability of co-polyamides. Cast films were obtained and their thermal, mechanical and transport properties were evaluated to establish the performances of the co-polyamides in view of packaging applications. The results indicate that co-polyamide films having a partially aromatic structure display the best mechanical performances and show a significant improvement in barrier properties to gases compared to the homopolymer. Copyright 2002 John Wiley & Sons, Ltd. [source]

Molecular Materials with Contrasting Optical Responses from a Single-Pot Reaction and Fluorescence Switching in a Carbon Acid

A. Patra
Abstract Three for the price of one: The reaction of tetracyanoquinodimethane with an aromatic amine is shown to follow an unusual course leading to three products in a single pot. The product molecules form a family of materials with contrasting optical responses, in that they exhibit light emission of different colors and emission switching that is sensitively triggered by acidic/basic environments (see scheme). A wide variety of amines are known to react with 7,7,8,8-tetracyanoquinodimethane (TCNQ) to yield push,pull diaminodicyanoquinodimethanes with a strongly zwitterionic structure and significant optical and nonlinear optical properties. A novel course of reaction is observed now with the amine 2-methyl-4-chloroaniline, which leads to three well-defined products, A,C, in a single pot. A and B are formed through the replacement of one cyano group in TCNQ by the amine; A is a carbon acid and B is its corresponding salt. C is the conventional product in which two cyano groups in TCNQ are replaced by the amine. The products are characterized structurally and spectroscopic studies reveal contrasting optical responses. A is nonfluorescent, whereas B and C show red and green emission, respectively, in the solution and solid states. The acid/conjugate-base pair A and B can be interconverted through facile, reversible, and repeated deprotonation/protonation cycles, which are accompanied by instantaneous switching of the fluorescence. The current study illustrates an interesting case of a single-pot reaction yielding different optical materials with attributes that can be switched through simple approaches such as protonation or tuned through modification of the push,pull characteristics. [source]

Inclusion Behavior of ,-Cyclodextrin with Bipyridine Molecules: Factors Governing Host-Guest Inclusion Geometries

Yan-Li Zhao Dr.
Abstract Guest Effect: The differences of nitrogen atom positions and the bridge bonds linked to two pyridine rings of some bipyridine guests can significantly affect the binding abilities and inclusion geometries of ,-cyclodextrin with the guests in both the solution and solid states. The 1:1 complexation of ,-cyclodextrin (,-CD) with structurally similar bipyridine guests which lead to the formation of six inclusion complexes (1,6) of ,-CD with 4,4,-vinylenedipyridine, 2,2,-vinylenedipyridine, 1-(2-pyridyl)-2-(4-pyridyl)ethylene, 4,4,-ethylene-dipyridine, 4,4,-dithiodipyridine, and 2,2,-dithiodipyridine has been investigated comprehensively by X-ray crystallography in the solid state and by 1H,NMR spectroscopy and microcalorimetric titration in aqueous solution. The complex formation constants (KS) for the stoichiometric 1:1 host,guest inclusion complexation of ,-CD with the bipyridine derivatives were determined in aqueous solution by microcalorimetry and the host,guest inclusion geometries of the complexes were deduced from 1H ROESY NMR spectroscopy. It transpires that the guest bipyridine molecules are included in the ,-CD cavity with a range of different inclusion geometries. In the solid state, the crystal superstructures for the ,-CD complexes 1, 4, and 5 are characterized by the triclinic crystal system (space group P1) commensurate with AAAA type supramolecular aggregation. By contrast, the ,-CD complexes 2, 3, and 6 display either monoclinic (space group P21) or orthorhombic (space group C2221) crystal systems, characteristic of ABAB type supramolecular aggregation. The results demonstrate that the relative locations of the nitrogen atom positions and the bridge-bond links between the two pyridine rings in these bipyridine guests, not only lead to distinct crystal systems and space groups, but also to different binding geometries and thermodynamical parameters on complexation of the bipyridines with ,-CD. The knowledge obtained from this research improves our understanding of the molecular recognition and self-assembly processes exhibited by ,-CD, both in the solid state and in aqueous solution. [source]