Polymer induced crystallization III. PEO-CdCl2 and in situ formation of PEO-CdS composite
TL;DR: In this article, the formation of cadmium sulphide in polyethylene oxide matrix has been studied starting with its complex with Cadmium chloride and it has been found that the complex crystallizes in orthorhombic configuration with lattice parameters of a = 8.42 A, b = 15.39 A, and c = 18.49 A.
About: This article is published in Journal of Crystal Growth.The article was published on 1994-08-02. It has received 17 citations till now. The article focuses on the topics: Cadmium chloride & Crystallization.
Citations
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TL;DR: In this article, the structure development and crystallization behavior of polypropylene (PP) containing nanoparticles of calcium phosphate prepared by a new route based on matrix mediated control of growth and morphology was investigated by X-ray diffraction (XRD), optical microscopy and DSC techniques.
195 citations
TL;DR: In this article, X-ray diffraction and transmission electron microscopy techniques were used to characterize the tensile strength, tensile modulus, elongation at break, and impact strength of polystyrene with calcium phosphate nanoparticles.
Abstract: Calcium phosphate nanoparticles were prepared by matrix-mediated synthesis and were characterized using X-ray diffraction and transmission electron microscopy techniques. The particle size was found to be around 10 nm. Nanocomposites of polystyrene with calcium phosphate were prepared by a melt mixing technique. Mechanical properties of the nanocomposites such as tensile strength, tensile modulus, elongation at break, and impact strength were determined. Tensile strength and modulus showed 50 and 80% increase for 5% filled composites, respectively. Careful differential scanning calorimetric measurements were performed to evaluate the changes in heat capacity (Cp) as a function of filler loading. The ΔCp values decreased dramatically as a function of filler loading indicating the existence of strong interaction between the nanofiller and polystyrene. A three-phase model consisting of a rigid amorphous phase has been proposed to illustrate the strong polymer−filler interaction.
47 citations
TL;DR: The structure, growth and morphology of calcium sulphate prepared in situ of a polymer has been investigated using polyethylene oxide as the growth medium as mentioned in this paper, and the results have been explained on the basis of polymer mediated crystallization and large interaction between the filler and the matrix.
Abstract: The structure, growth and morphology of calcium sulphate prepared in situ of a polymer has been investigated using polyethylene oxide as the growth medium The structure was predominantly the dihydrate type with monoclinic configuration for these samples as compared to the anhydrite type with orthorhombic structure obtained in commercial samples The crystal morphology consisted of sharp needle shape, having aspect ratio of more than 10 The concentration of the polymer used had a profound effect on the crystal size and its distribution The size distribution became narrow and the average crystal size reduced with the increase of polymer concentration Highly oriented crystals could be obtained with application of, small shearing force on the samples These results have been explained on the basis of polymer mediated crystallization and large interaction between the filler and the matrix © 1998 Chapman & Hall
23 citations
TL;DR: In this article, a new technique based on matrix mediated control of growth and morphology using polymer blends was used to obtain nanosize particles of calcium phosphate. But their crystal structure and size were confirmed by X-ray diffraction and electron microscopy.
20 citations
TL;DR: In this article, the effect of poly(ethylene oxide)−metal salt complexation on the dynamics and microstructure of PEO−nickel chloride [NiCl2] systems is investigated by rheology and X-ray scattering.
Abstract: The effect of poly(ethylene oxide) [PEO]−metal salt complexation on the dynamics and microstructure of PEO−nickel chloride [NiCl2] systems is investigated by rheology and X-ray scattering. Annealed PEO−nickel salt systems exhibit network properties above the melting temperature of PEO, characterized by a second elastic plateau, beyond the reptation time of PEO chains. The level of the second plateau strongly depends on the annealing conditions and the ion content. In PEO−NiCl2 networks, the linear viscoelastic region is experimentally out of reach, meaning that their viscoelastic properties strongly depend on strain and strain rate as well as any deformation history. The network can be broken down by large-amplitude shear and reversibly reformed under quiescent conditions. X-ray scattering reveals formation of distinct crystalline structures of PEO−NiCl2 complexes, which are different from those of both neat PEO and nickel salt. The combined rheology and X-ray scattering results indicate that the network results from a small fraction of trapped PEO chains, which are bridging the crystalline domains of PEO−NiCl2 complexes
19 citations
References
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TL;DR: The algorithm can be used as a building block for solving other distributed graph problems, and can be slightly modified to run on a strongly-connected diagraph for generating the existent Euler trail or to report that no Euler trails exist.
13,828 citations
TL;DR: In each case, the specificity of interaction is determined by complementarity in size, charge and molecular shape, often generated by the interplay of structural, stereochemical and dynamical relationships as discussed by the authors.
Abstract: Molecular recognition is a term used widely in many branches of chemistry and biochemistry. It encompasses a multitude of molecular systems ranging from the small molecule-small molecule interactions of macrocyclic ligands with metal cations, through macromolecular processes involving enyzme-substrate reactions, protein-protein coupling and antibody-antigen specificity to supramolecular events involving cell-cell communication. In each case, the specificity of interaction is determined by complementarity in size, charge and molecular shape, often generated by the interplay of structural, stereochemical and dynamical relationships. The fact that these processes are intrinsic to biochemical reactions in solution and within membrane assemblies suggests that all functional systems evolved from chemical recognition.
897 citations
TL;DR: A biomimetic approach based on these principles could lead to the development of new strategies in the controlled synthesis of inorganic nanophases, the crystal engineering of bulk solids, and the assembly of organized composite and ceramic materials.
Abstract: Crystallization is an important process in a wide range of scientific disciplines including chemistry, physics, biology, geology, and materials science. Recent investigations of biomineralization indicate that specific molecular interactions at inorganic-organic interfaces can result in the controlled nucleation and growth of inorganic crystals. Synthetic systems have highlighted the importance of electrostatic binding or association, geometric matching (epitaxis), and stereochemical correspondence in these recognition processes. Similarly, organic molecules in solution can influence the morphology of inorganic crystals if there is molecular complementarity at the crystal-additive interface. A biomimetic approach based on these principles could lead to the development of new strategies in the controlled synthesis of inorganic nanophases, the crystal engineering of bulk solids, and the assembly of organized composite and ceramic materials.
680 citations
TL;DR: In this article, the development of bulk optical properties as a function of crystallite size for the inorganic direct gap semiconductor CdS was studied in situ at extreme dilution.
Abstract: This paper reports experimental studies of the development of bulk optical properties as a function of crystallite size for the inorganic direct gap semiconductor CdS. Small crystallites are synthesized via colloidal chemical techniques, and their optical properties are studied in situ at extreme dilution. The crystallites are characterized via high resolution transmission electron microscopy. Direct images show (111) lattice planes, and establish the crystallite structures as close to those of excised fragments of bulk CdS (zinc‐blende cubic). Large crystallites (> 100 A average diameter) show an optical absorption, in colloidal solution, close to that of bulk crystalline material. However, small crystallites of 30 A average diameter show a large blue shift (∼0.8 eV) in absorption edge (effective band gap), and an intensification of edge absorption relative to absorption at higher energy regions. These observations can be understood as quantum size effects resulting from confinement of an electron and hole in a small volume. 40 A average size crystallites show a smaller shift (∼0.25 eV), and corresponding changes in their fluorescence, and resonance Raman excitation, spectra.
636 citations
TL;DR: A methodology is described for using ``tailor-made'' additives designed to interact stereospecifically with crystal surfaces during growth and dissolution that has led to the discovery of a new ``relay'' mechanism explaining the effect of solvent on crystal growth.
Abstract: Nucleation, growth, and dissolution of crystals have been studied by stereochemical approach involving molecular recognition at interfaces. A methodology is described for using ``tailor-made99 additives designed to interact stereospecifically with crystal surfaces during growth and dissolution. This procedure was instrumental in controlling crystal morphology and in revising the concept of the structure and symmetry of solid solutions. Consequently, it was applied to the transformation of centrosymmetric single crystals into solid solutions with polar arrangement displaying second-harmonic generation and to the performance of asymmetric synthesis of guest molecules inside centrosymmetric host crystals. The method has led to a discovery of a new ``relay99 mechanism explaining the effect of solvent on crystal growth. Finally, it allowed for the design of auxiliary molecules that act as promoters or inhibitors of crystal nucleation that can be used to resolve enantiomers and crystallize desired polymorphs.
408 citations