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No description available.

No description available.

No description available.

No description available.

Poly(dimethylsiloxane) (PDMS) fluids containing magnetite nanoparticles stabilized with carboxylic acid-functionalized PDMS were prepared. PDMS-magnetite complexes were characterized using transmission electron microscopy, elemental analysis, and vibrating sample magnetometry. PDMS-magnetite complexes containing up to 67 wt% magnetite with magnetizations of ~52 emu gram-1 were prepared. The magnetite particles were 7.4 ± 1.7 nm in diameter. Calculations suggested that the complexes prepared using mercaptosuccinic acid-functionalized PDMS (PDMS-6COOH) complexes contained unbound acid groups whereas the mercaptoacetic acid-functionalized PDMS (PDMS-3COOH) complexes did not. Calculations showed that the PDMS-3COOH and PDMS-6COOH covered the same surface area on magnetite. Calculations were supported by molecular models and FTIR analyses. The complexes were dispersed into PDMS carrier fluids by ultrasonication, resulting in magnetic PDMS fluids with potential biomedical applications. Magnetite particles (100 nm to 1 mm in diameter) were prepared by crystallization from goethite/glycol/water solutions under pressure. Two methods for particle growth were investigated in which the crystallization medium was varied by adjusting the amount of water or by adding itaconic acid. Particle surfaces were analyzed by x-ray photoelectron spectroscopy (XPS). Particles with clean surfaces were coated with carboxylic acid-functionalized poly(e-caprolactone) stabilizers. Adding itaconic acid to the reactions afforded particles ~100 nm in diameter. The magnetite particles displayed magnetic hysteresis. The particles were dispersed into vinyl ester resins by ultrasonication and it was demonstrated that the ~100 nm particles remained dispersed for three days without agitation. These dispersions have applications in magnetic induction heating for composite repair. Living polymerizations of hexamethylcyclotrisiloxane were terminated with dimethylchlorosilane, phenylmethylchlorosilane, or diisopropylchlorosilane (DIPCS). Platinum-catalyzed hydrosilation of the hydrosilane-terminated PDMS with allyloxyethanol afforded a systematic series of hydroxyalkyl-terminated PDMS. The reactions were successful except for the hydrosilation of the sterically-hindered DIPCS-functionalized PDMS where no reaction was observed. Hydroxyalkyl-terminated PDMS oligomers were successful in initiating the stannous octoate-catalyzed copolymerization of e-caprolactone, which afforded PDMS-b-PCL diblock copolymers of controlled composition. / Ph. D.

Mesoporous monocrystalline metal oxides (e.g. Co₃O₄, Cr₂O₃, NiO, CeO₂, In₂O₃ and WO₃) templated by SBA-15 or KIT-6 were synthesised successfully by using a simple solvent-free approach, the so-called solid-liquid method, which was the principal development of methodology in this project. A metal-containing precursor, whose melting point is lower than its decomposition temperature, was directly ground with a mesoporous silica and impregnated into the pores of the silica template after melting when the temperature was increased above its melting point. The liquid precursor then decomposed to form metal oxide inside the silica pores when the temperature was further increased to its decomposition temperature and crystallization temperature of the oxide. The structural characterisations of these porous metal oxides were performed by using TEM, XRD and N₂ adsorption/desorption techniques. The solid-liquid method is convenient and solvent-free. On the other hand, its limitation is that the precursor must have a melting point lower than its decomposition temperature. A novel porous single crystal of rutile TiO₂ as well as anatase nanocrystal-silica composite was also synthesised successfully for the first time using SBA-15 and KIT-6 as templates. These materials have interesting properties of proton conductivity, Li insertion and photoactivity. Likewise, the characterisation of porous TiO₂ was achieved by using XRD, TEM, SAED and N₂ adsorption/desorption. The residual SiO₂ component in porous TiO₂ was detected by using the EDX technique. Porous cubic metal oxides of Co₃O₄, NiO, CeO₂ and In₂O₃ were prepared using novel mesoporous silicas FDU-12 and SBA-16, which contain spherical nanocavities linked together by smaller windows. These porous materials have larger surface areas than those templated by SBA-15 and KIT-6. Unlike the cubic metal oxides, syntheses of porous crystals of non-cubic metal oxides such as rhombohedral Cr₂O₃, Fe₂O₃ and hexagonal TiO₂, WO₃ were not successful when using cage-containing mesoporous silicas as templates. The three-dimensional arrangements of nanospheres in porous crystals of cubic oxides mentioned above were observed by TEM and the corresponding larger surface areas were confirmed by N₂ adsorption/desorption technique. Additionally, fabrication of porous crystals of other metal oxides such as MgO, ZnO and ZrO₂ were unsuccessful by using either mesoporous silicas or mesoporous carbons as templates. Possible drawbacks of using mesoporous silica and carbon as templates were discussed.

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No description available.