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Organic Moieties (organic + moiety)
Selected AbstractsCover Picture: Functionalized Gold Nanoparticles Mimic Catalytic Activity of a Polysiloxane-Synthesizing Enzyme (Adv. Mater.ADVANCED MATERIALS, Issue 10 200510/2005) Abstract A system that acts as a biomimetic of the silica-synthesizing enzyme found in a marine sponge is reported by Morse and co-workers on p.,1234. Gold nanoparticles (GNPs) are functionalized with the same organic moieties that are found in the enzyme's catalytic site. Interaction between the nucleophilic (OH-terminated) and hydrogen-bonding (imidazole-terminated) GNPs, as shown on the cover, is required for the hydrolysis of a silicon alkoxide precursor and subsequent polycondensation to form silica at a low temperature and near-neutral pH. Replacement of either of the required functional groups by a non-reactive methyl group abolishes catalysis in this synthetic system, as it does in the biological enzyme. Cover art provided by Peter Allen. [source] Architecture and performance of mesoporous silica-lipase hybrids via non-covalent interfacial adsorptionAICHE JOURNAL, Issue 2 2010Shan Lu Abstract To investigate the effects of surface property of mesoporous supports on the lipase immobilization and the performance of immobilized lipase, the mesoporous molecular sieve SBA-15 is functionalized with three organic moieties, dimethyl (DM), diisopropyl (DIP), and diisobutyl (DIB), respectively, by post-synthesis grafting and one-pot synthesis methods. Porcine pancreas lipase (PPL) is immobilized on SBA-15 supports through hydrogen bonding and hydrophobic interaction. The hydrophobic adsorption involves no active sites of PPL, and neither hyper-activation nor total inactivation occurs. The study on the intrinsic stability of PPL, including thermal stability, pH stability, and storage stability, indicates that the entrapment in mesoporous supports, and especially in organic-functionalized supports, makes PPL more resistant to temperature increment but more sensitive to pH change. The reusability investigation shows that the organic modification of mesoporous surface inhibits the enzyme leaching to some extent, resulting in a better operational stability. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] A Scalable Route to Highly Functionalized Multi-Walled Carbon Nanotubes on a Large ScaleMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2008Xianhong Chen Abstract A scalable and solvent-free chemical process to obtain highly functionalized and dispersible multi-walled carbon nanotubes is reported. Highly functionalized multi-walled carbon nanotubes have been prepared using in situ generated aryl diazonium salts in the presence of ammonium persulfate and 2,2,-azoisobutyronitrile by solvent-free techniques. In the Raman spectra of the resulting materials, characteristic peaks, the D- and G-bands, are shifted by about 10 cm,1 to lower frequencies. At the same time, the relative intensity ratios between the D- and G-bands increase in comparison to that in the spectrum of the purified product. Fourier-transform infrared spectroscopy reveals the presence of the functional groups on the surface. Transmission electron microscopy images directly confirm the significant build-up of sidewall organic moieties on the treated materials. The weight loss of various functional moieties determined by thermogravimetry,differential scanning calorimetry analysis is about 18,33%. The dispersibility of the functionalized materials in solvents, such as chloroform, tetrahydrofuran, and water, is obviously improved. [source] Morphology and surface properties of some siloxane,organic copolymersPOLYMER INTERNATIONAL, Issue 6 2009Maria Cazacu Abstract BACKGROUND: It is well known that, due to their extremely low polarity, polysiloxanes are incompatible with almost any organic system. This incompatibility leads to phase separation in mixed siloxane,organic systems. RESULTS: Three siloxane,organic copolymers, poly[(5,5,-methylene-bis-salicylaldehyde)-imine-(1,3-bis(propylene)tetramethyldisiloxane)] (Paz1), poly[(2,5-dihydroxy-1,4-benzoquinone)-imine-(1,3-bis(propylene)tetramethyldisiloxane)] (Paz2) and poly[1,3-bis(propylene)tetramethyldisiloxane diamide] (Pam), were prepared by the reaction of 1,3-bis(3-aminopropyl)tetramethyldisiloxane with appropriate organic partners (5,5,-methylene-bis-salicylaldehyde, 2,5-dihydroxy-1,4-benzoquinone and oxalyl chloride, respectively). The morphologies dictated by the incompatibility between siloxane and polar organic moieties were investigated using differential scanning calorimetry and scanning electron microscopy. The surface activity of the copolymers and water vapour sorption capacity were also measured. CONCLUSION: Even though the polar sequences are very short ones, the highly flexible siloxane-containing sequence permits the self-assembly of these into more or less polar domains. Such an organization influences the properties of the resulting materials, an important place being occupied by the surface properties. Copyright © 2009 Society of Chemical Industry [source] Layered silicate/epoxy nanocomposites: synthesis, characterization and propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004Nehal A. Salahuddin Abstract Novel epoxy-clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T-403), primary polyethertriamine (Jeffamine T-5000) and three types of polyoxypropylene diamine (Jeffamine D-230, D-400, D-2000) with different molecular weight were used to treat Na-montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na+ in MMT with the organic ammonium group in Jeffamine compounds. X-ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine-MMT intercalates. Jeffamine D-230 was used as a swelling agent for the organoclay and curing agent. It was established that the d001 spacing of MMT in epoxy-clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000-MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5,nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140,nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three-fold increase in the energy required for breaking the test specimen was found for T5000-MMT/epoxy containing 7,wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd. [source] A new chain structure: catena -poly[4,4,-(ethane-1,2-diyl)dipyridinium bis[[aquadifluoridooxidovanadate]-,-fluorido]]ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010David W. Aldous The title compound, {(C12H12N2)[V2F6O2(H2O)2]}n, features a novel extended-chain moiety, [VOF2F2/2(H2O)]n, comprising trans vertex-connected VOF4(H2O) octahedra. The octahedra themselves show the characteristic distortion due to the off-centring of the V4+ ion, such that a short terminal V=O bond and an elongated trans V,OH2 bond are present. Hydrogen bonding from the water molecules to terminal F atoms in adjacent chains generates associated chain dimers, which are loosely linked into sheets via additional hydrogen bonding involving the organic moieties. Structural relationships with previously described vanadium oxyfluoride species are briefly discussed. [source] Two hydrates of 6-methoxypurineACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2004Natalya Fridman 6-Methoxypurine crystallizes from N,N -methylformamide as the hemihydrate, C6H6N4O·0.5H2O, and from water as the trihydrate, C6H6N4O·3H2O. Both forms crystallize in the triclinic crystal system. Upon heating the trihydrate, molecules of water are liberated successively; the hemihydrate is formed at 383,K. In the hemihydrate, the H atom on the imidazole N atom is disordered between the two N atoms. The water molecule in the hemihydrate and the H atoms of a water molecule in the trihydrate are also disordered. In the hemihydrate, the organic moieties are connected by N,H,N hydrogen bonds, while they are connected via water molecules in the trihydrate. [source] Self-Assembling of Er2O3,TiO2 Mixed Oxide Nanoplatelets by a Template-Free Solvothermal RouteCHEMISTRY - A EUROPEAN JOURNAL, Issue 45 2009Beatriz Julián-López Dr. Abstract An easy solvothermal route has been developed to synthesize the first mesoporous Er2O3,TiO2 mixed oxide spherical particles composed of crystalline nanoplatelets, with high surface area and narrow pore size distribution. This synthetic strategy allows the preparation of materials at low temperature with interesting textural properties without the use of surfactants, as well as the control of particle size and shape. TEM and Raman analysis confirm the formation of nanocrystalline Er2O3,TiO2 mixed oxide. Mesoscopic ordered porosity is reached through the thermal decomposition of organic moieties during the synthetic process, thus leading to a template-free methodology that can be extended to other nanostructured materials. High specific surface areas (up to 313,m2,g,1) and narrow pore size distributions are achieved in comparison to the micrometric material synthesized by the traditional sol,gel route. This study opens new perspectives in the development, by solvothermal methodologies, of multifunctional materials for advanced applications by improving the classical pyrochlore properties (magnetization, heat capacity, catalysis, conductivity, etc.). In particular, since catalytic reactions take place on the surface of catalysts, the high surface area of these materials makes them promising candidates for catalysts. Furthermore, their spherical morphology makes them appropriate for advanced technologies in, for instance, ceramic inkjet printers. [source] A Zeolite-Like Zinc Phosphonocarboxylate Framework and Its Transformation into Two- and Three-Dimensional StructuresCHEMISTRY - AN ASIAN JOURNAL, Issue 12 2007Zhenxia Chen Abstract Three zinc phosphonocarboxylates, Zn2(pbc)2,Hdma,H3O,2H2O (1), Zn(pbc),Hdma (2), and Zn4.5(pbc)3(OH)(H2O)0.5,Hdma (3) (H3pbc=4-phosphonobenzoic acid, dma=dimethylamine) were synthesized by the mixed solvothermal reaction of Zn(Ac)2,2H2O and 4-phosphonobenzoic acid in N,N -dimethylformamide (DMF) and water. The zigzag and ladderlike chains completely constructed by triply fused 4-membered rings (denoted SBU-1) are linked by the organic moieties to form the 3D zeolite-like structure 1 and the layered structure 2, respectively. As for structure 3, a new second building unit (SBU-2) formed by the inset of the [Zn3O12] trimer into the 4-membered ring as well as SBU-1 is observed. The connections between the two types of SBUs lead to a "zinc phosphate" layer, which is linked by the organic groups to generate a 3D pillar-layered structure. Both solution-mediated and solid-state transformations of 1 to 2 and 3 were observed. A possible mechanism for the transformation is proposed. Gas sorption studies show that 1 has accessible pores for methanol and water and exhibits size selectivity for alcohols. [source] Benzylamines as Versatile Agents for the One-Pot Synthesis and Highly Ordered Stacking of Anatase NanoplateletsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2008Georg Garnweitner Abstract The simple reaction of titanium isopropoxide in benzylamine is shown to lead to remarkably complex, highly ordered hybrid structures. These structures consist of anatase nanoplatelets that were stacked in a lamellar fashion with a small organic layer in between. By careful characterization of these structures, we show that indeed solely the benzylamine solvent is present in the organic moiety between the nanocrystals, which thereby provides both shape control and alignment of the inorganic crystals. The solvent also plays a central role during the anatase formation itself; hence, it enacts control on the forming materials on a multitude of levels.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Preparation and characterization of mesoporous materials based on silsesquioxane by block copolymer templating,POLYMER INTERNATIONAL, Issue 11 2002Byeong-Gyu Park Abstract Nanoporous materials were prepared by using silsesquioxane containing three alkoxy groups and a non-hydrolysable organic moiety. The influences of pH and precursor ratios of silsesquioxane and tetraethyl orthosilicate (TEOS) on the preparation of organo-modified periodic mesoporous materials were investigated. These materials were characterized using small angle X-ray scattering, infrared spectroscopy and thermogravimetric analysis. A non-ionic triblock copolymer was used as a structure-directing agent to provide large pores with a high density of silanol groups. It was found that silsesquioxanes could form ordered nanoporous materials in the presence of TEOS by controlling the pH and the co-precursors ratio, despite their structural irregularity. © 2002 Society of Chemical Industry [source] | |||||||||||||