914 resultados para DNA-organic hybrid materials, polymer colloidsm


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The Problem/Opportunity: To define, identify, and guide design-based materials collections in academic settings and foster community among those with existing collections and/or those considering creating and supporting one. Contents and topics: What is a materials collection? Why have a materials collection? Acquisition strategies Organizational approaches Programming possibilities Symposium summary Resources

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Faculty from Rhode Island School of Design representing Interior Architecture, Industrial Design, and Textiles detail their thoughtful interactions with materials.

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Designers respond to issues and synthesize ideas from throughout the day as voices from the field who directly encounter the need for recently graduated students to possess the ability to investigate and interrogate materials.

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Educators representing interactions with materials speak to critical approaches, life-cycle concerns, critical thinking of composition/process/properties.

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Organic-inorganic hybrid materials based on the assembly between inorganic 2D host structure and polymer have received considerable attention in the last few years. This emerging class of materials presents several applications according to their structural and functional properties. Particularly, among others, layered double hydroxides (LDHs) provide the opportunity of preparing new organically modified 2D nanocomposites. Pyrrole carboxylic acid derivatives, namely 4-(lH-pyrrol-1-yl)benzoate, 3-(pyrrol-i-yl)-propanoate,7-(pyrrol-1-yl)-heptanoate, and aniline carboxylic acid derivative, namely 3-aminobenzoic acid, have been intercalated in LDHs of intralamellar composition Zn2Al(OH)(6). The LDHs were synthesized by the co-precipitation method at constant pH followed by hydrothermal treatment for 72 h. The materials were characterized by powder X-ray diffraction patterns (PXRD), transmission electron microscopy (TEM) thermogravimetric analysis (TGA), and electron spin resonance (ESR). The basal spacing found by the PXRD technique gives evidence of the formation of bilayers of the intercalated anions. ESR spectra present a typical signal with a superhyperfine structure with 6 + 1 lines (g = 2.005 +/- 0.0004), which is assigned to the interaction between a carboxylate radical from the guest molecules and a nearby aluminium nucleus (I = 5/2) from the host structure. Additionally, the ESR data suggest that the monomers are connected to each other in limited number after thermal treatment. (c) 2007 Elsevier Ltd. All rights reserved.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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C-13 exchange solid-state NMR methods were used to study two families of siloxane/poly-(ethylene glycol) hybrid materials: Types I and II, where the polymer chains interact with the inorganic phase through physical (hydrogen bonds or van der Waals forces) or chemical (covalent bonds) interactions, respectively. These methods were employed to analyze the effects of the interactions between the organic and inorganic phases on the polymer dynamics in the milliseconds to seconds time scale, which occurs at temperatures below the motional narrowing of the NMR line width and around the polymer glass transition. Motional heterogeneities associated with these interactions and evidence of both small and large amplitude motions were directly observed for both types of hybrids. The results revealed that the hindrance to the slow molecular motions of the polymer chains due to the siloxane structures depends on the chain length and the nature of the interaction between the organic and inorganic phases.

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Organic-inorganic hybrid materials were prepared from an ureasil precursor (ureapropyltriethoxysilane designated as UPTES) and acrylic acid modified zirconium (IV) n-propoxide. Thin films containing rhodamine 6G (Rh6G) were prepared by spin-coating on glass substrates with different Zr:Si molar ratios (Zr:Si = 75:25, 50:50 and 25:75). Refractive index, thickness, number of propagating modes and attenuation coefficient were measured at 543.5, 632.8 and 1550 nm wavelengths by the prism coupling technique. Distributed feedback (DFB) laser effect was observed and studied as a function of films thickness and refractive index.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Two groups of hybrid organic-inorganic composites exhibiting ionic conduction properties, so called ORMOLYTES (organically modified electrolytes), have been prepared by the sol-gel process. The first group has been prepared from mixture of a lithium salt and 3-isocyanatopropyltriethoxysilane(IsoTrEOS),O,O′-bis(2-aminopropyl) polypropyleneglycol. These materials produce chemical bonds between the organic (polymer) and the inorganic (silica) phases. The second group has been prepared by an ultrasonic method from a mixture of tetraethoxysilane (TEOS), polypropyleneglycol and a lithium salt. The organic and inorganic phases are not chemically bonded in these samples. The Li+ ionic conductivity, σ, of all these materials has been studied by AC impedance spectroscopy up to 100°C. Values of σ up to 10-6 Ω-1·cm-1 have been found at room temperature. A systematic study of the effects of lithium concentration, polymer chain length and the polymer to silica weight ratio on σ shows that there is a strong dependence of σ on the preparation conditions. The dynamic properties of the Li+ ion and the polymer chains as a function of temperature between -100 and 120°C were studied using 7Li solid-state NMR measurements. The ionic conductivity of both families are compared and particular attention is paid to the nature of the bonds between the organic and inorganic components.