Student Number : 0107507J - PhD thesis - School of Chemistry - Faculty of Science / Periodic mesoporous organosilica (PMO) materials (consisting of ethane groups in the framework) and bifunctional periodic mesoporous organosilica materials (consisting of ethane groups in the framework and either glycidoxypropyl groups or aminopropyl groups in the channels) were synthesized by the sol-gel method under basic conditions. Ethanesilica materials were synthesized by condensation of 1,2-bistrimethoxysilylethane (BTME) and by co-condensation of BTME with tetraethylorthosilicate (TEOS). Bifunctional periodic mesoporous organosilica materials were synthesized by the co-condensation of BTME with either 3- glycidoxypropyltriethoxysilane (GPTS) or 3-aminopropyltriethoxysilane (APTS). Cetyltrimethylammonium bromide was used as the structure-directing template. Cobalt ion incorporated ethanesilica and modified ethanesilica materials were synthesized in situ by adding cobalt nitrate to the reaction mixture. Cobalt was also supported on ethanesilica materials and APTS-modified materials by using the incipient wetness impregnation method. Raman spectroscopy and diffuse reflectance infrared spectroscopy (DRIFTS) results confirmed the formation of organosilica materials and showed that the surfactant was removed by solvent extraction. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the ethane portion of the materials (originating from the bridging ethane group in BTME) only decomposed at temperatures > 400 oC. These techniques also showed that the surfactant is removed by solvent extraction. Cobalt ion incorporation was confirmed by Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. Powder powder X-ray diffraction (XRD) and nitrogen adsorption data indicated that the mesophase and textural properties of the materials are dependent on the reaction conditions (i.e. ageing duration, ageing temperature, amount of silica precursor(s), amount of water and amount of base (NH4OH)). The periodicity of the materials was indicated by the presence of low angle diffraction peaks in powder X-ray diffraction patterns. Cubic and hexagonal mesophases were identified using powder X-ray diffraction. When solvent extraction is prolonged, the BET surface area and the pore volume increase, while the average pore diameter decreases. Materials with more dominant XRD structural features and larger d values, higher surface areas, lower pore volumes and average pore diameters are obtained when low ageing temperatures are used. For samples prepared from a mixture of BTME and TEOS at a given temperature, the surface area was found to increase with increasing amount of TEOS added. This trend was observed for materials with and without cobalt. Type IV isotherms, typical of mesoporous materials, were obtained for ethanesilica and modified ethanesilica materials prepared without cobalt. For cobalt incorporated periodic mesoporous ethanesilica materials, the XRD lattice parameter (d100) increased whereas surface area and pore volume decreased with increasing cobalt loading. Nitrogen gas adsorption on samples with varying ratios of BTME:GPTS or BTME:APTS revealed that increasing the amount of GPTS or APTS affects pore size, surface area and pore volume as well as shapes of the isotherms and hysteresis loops. The hysteresis loops of the Type IV isotherms obtained for GPTS-modified ethane silica materials (without cobalt) change from Type H3 to Type H4. There is a tendency for pore sizes to change from mesopore to micropore when the amount of GPTS is increased. Isotherms of cobalt incorporated GPTS-modified ethane silica materials changed from Type IV to Type I. The surface area, pore volume and pore diameter decreased with increasing loading of GPTS or APTS as well as after cobalt incorporation.

Synthesis and Applications of Novel Periodic Mesoporous Organosilicas by Chun Xiang (Cynthia) LIN Abstract This dissertation is concerned with the synthesis, functionalization, and applications of periodic mesoporous organosilica (PMO) with a unique hollow spherical morphology, with the main objectives as follows: • Developing new techniques to synthesize mesoporous silica and organosilica materials • Designing different approaches to modify PMO and silica materials to meet various applications • Developing innovative applications of novel PMO materials in biological fields. The key features that have been achieved in this work are highlighted as follows: • A series of studies has been carried out and resulted in a new strategy for the synthesis of PMO material with a novel hollow morphology. This new approach employs both hydrocarbon and fluorocarbon surfactants as mixed structure-directing-agents in alkaline medium. Moreover, a vesicle and liquid crystal "dual-templating" mechanism has been proposed. • Detailed observation on the formation mechanism of hollow PMO has revealed that the demixing temperature (Td) plays an important role on the formation of highly ordered mesostructure of PMO hollow spheres. Beside that, dissimilarity on the hydrophobic nature of silica - organic silica precursors has brought differences in the resulted materials. • Different approaches in the modification of PMO hollow spheres with several functional groups and commercial magnetic ferrite nanoparticles have shown some unique features of this material. It was found that different reactive sites of each functional group bring different disruptive effect on the mesopore geometry of hollow PMO. Furthermore, hollow PMO material show different behavior on encapsulating the commercial magnetic ferrite nanoparticles compared to superparamagnetic particles, where different techniques should be applied, which involved several factors that need to be carefully adjusted. • Applications of hollow PMO in biological field were performed on drug and DNA delivery. A comparison between periodic mesoporous silica (PMS) and PMO as drug carriers showed the differences in wall composition between pure silica and hybrid organic silica, also the morphology (hollow and solid spheres) play important roles in controlling adsorption capacity and drug release rate. In addition, different pH value of release medium also brings significant effect on release profile. As a carrier of DNA, magnetic modified hollow PMO material showed biocompatibility towards sugarcane callus. Moreover, this study has introduced a new innovative technique on delivering DNA into plant cell through the application of modified hollow PMO with barium magnetic core and enzyme digestion approach.

There is currently a great interest in the field of porous organosilica materials because of the high surface areas (> 1000 m²/g) and narrow pore size distributions which are beneficial for applications such as chromatography, chiral catalysis, sensing or selective adsorption. Periodic mesoporous organosilicas (PMOs) represent an interesting class of hybrid silica materials because of the wide variety of bridging organic groups which can be incorporated within the precursors [(OR)3Si-R-Si(OR)3] giving rise to materials with exceptional properties. We have synthesized and characterized various aromatic PMOs composed of supporting structural monomers (phenylene- or biphenylenebridged) and functional stilbene monomers (cis and trans) (1, 2). The effect of the different synthetic procedures and varying amounts of functional stilbene monomer on the properties of the materials was examined. The functional transstilbene component was determined to be well distributed in a phenylene-bridged PMO using P123 as a pore template from TEM techniques with Os staining. The trans-stilbene linkers were completely transformed to aryl aldehydes through ozonolysis with dimethylsulfide workup. Further transformation of the carbonyl functionality to an aryl imine showed a moderate level of success. Enantiomeric forms of a novel, chiral PMO precursor (CM) were synthesized and incorporated into biphenylene-bridged PMOs. Under basic pH conditions templated with C18TMACl, although very low levels of CM are incorporated, enantiomeric forms of chiral, porous materials are obtained as was verified by distinct mirror-image circular dichroism spectra. Powder XRD patterns suggest that a tightly packed asymmetric biphenylene arrangement may be necessary for the optical activity. Preliminary results using these materials as a chiral chromatographic phase are promising. Finally, a thin film morphology of an ethane-bridged PMO incorporating a thiol ligand, (3-mercaptopropyl)trimethoxysilane, was prepared on a fibre optic cable and used as a component in a heavy-metal sensing application. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-03-11 17:24:48.997

L'objectif de cette thèse est le développement de nouveaux échangeurs d'anions à base d’ionosilices. Différents matériaux contenant des entités ammoniums ont été synthétisés par la procédure d'hydrolyse-polycondensation à partir de précurseurs silylés d'ammonium. Ces solides, présentant différentes textures, différentes architectures ou des morphologies ont été obtenus en faisant varier des paramètres de réaction, comme par exemple la nature du tensioactif utilisé. Outre les caractérisations structurales et texturales (adsorption-désorption d’azote, DRX, MET / MEB), nous nous sommes concentrés sur les analyses plus détaillée des propriétés physico-chimiques de ces ionosilices. En particulier, elles présentent une contribution hydrophile élevée par rapport aux silices mésoporeuses classiques ou les organosilices du type PMO (Periodic Mesoporous Organosilica). En outre, ces propriétés interfaciales d’hydrophilie peuvent être modulées soit par l'utilisation de différents précurseurs d'ammonium, soit par l'incorporation par échange d'anions hydrophobes. Enfin, nous avons utilisé ces nouveaux matériaux pour la rétention d’espèces anioniques en milieu aqueux. Nos études montrent que ces ionosilices sont des échangeurs d'anions très efficaces présentant une capacité d'adsorption de Cr (VI) élevée (jusqu’à 2.5 mmol g-1). Ces matériaux possèdent également une capacité d’adsorption d’iodure élevée combinée à une bonne stabilité radiolytique pour des applications de rétention de radionucléides. Des résultats similaires ont été obtenus pour des polluants organiques anioniques tels que les principes actifs (le diclofénac, le sulindac et le p-aminosalicylate) ou des colorants (méthyl orange). Outre le grand potentiel d’application de ces matériaux dans les procédés de séparation, cette étude donne un aperçu intéressant de la morphologie des matériaux grâce à l'accessibilité presque complète des sites cationiques. Toutes ces caractéristiques font de ces matériaux des systèmes de choix pour les applications dans le traitement de l’eau polluée, le stockage à long terme des déchets radioactifs et en tant que support de catalyseur. / The objective of this thesis is the development of new anion exchangers based on ionosilica materials. Various materials containing ammonium groups were synthesized by template directed hydrolysis-polycondensation reactions starting from silylated ammonium precursors. Solids displaying different textures, architectures and morphologies were obtained via the modifications of reaction parameters, such as the nature of the used surfactant. Besides the standard structural and textural characterizations (N2 adsorption, XRD, TEM / SEM), we focused on a more detailed physico-chemical analysis of these original and innovative materials. Ionosilicas show an unusually high hydrophilicity compared to classical mesoporous silica or organosilicas of the PMO-type (Periodic Mesoporous Organosilica). Furthermore, the hydrophilicity of ionosilicas can be finely tuned either by the use of various ammonium precursors or the incorporation via exchange of hydrophobic anions. Finally, we used these new anion exchangers for the removal of various anionic species in aqueous media. Our studies show that ionosilicas are highly efficient anion exchanger displaying high capacity for the adsorption of Cr (VI) (up to 2.5 mmol g-1). These materials exhibit also high capacity of iodide combined with high radiolytic stability for radionuclides uptake. Similar results were obtained for organic anionic pollutants, e.g. drugs (diclofénac, sulindac and p-aminosalicylate) and dyes (methyl orange). Besides the high potential of these materials in separation processes, this study gives interesting insights in the materials morphology through the nearly complete accessibility of the cationic sites. All these features make ionosilicas materials of choice for solid-liquid separation processes in water treatment, depollution of industrial wastewater, the nuclear fuel cycle or catalytic support.

Nous visons dans ce travail de thèse à développer une méthodologie de fonctionnalisation par chimie click des silices hybrides synthétisées par voie sol-gel. La réaction click de cycloaddition azoture-alcyne catalysée au cuivre (CuAAC) offre une tolérance exceptionnelle pour les fonctions organiques en plus de conversions très élevées. Dans cette optique, nous avons mis en œuvre en premier lieu des matériaux clickables à base d'organosilice pure (organosilice à mésoporosité périodique (PMO) et silsesquioxanes pontés (BS)) qui ont permis une conversion quasi-quantitative de greffage par CuAAC. Nous avons ensuite utilisé cette particularité pour contrôler les propriétés de surface des BS en modifiant leur caractère hydrophile/lipophile. Dans le second axe de travail, nous nous sommes intéressés à l'apport de la chimie click pour la préparation de nanoparticules mésoporeuses de silice multifonctionnelles, dites mécanisées, pour des systèmes à délivrance contrôlée de principes actifs. / The present work aims to develop a trustful methodology of functionalization for hybrid silica materials made by the sol-gel process using the copper-catalyzed alkyne-azide cycloaddition (CuAAC)Click reaction. This transformation can be highly useful in materials science thanks to its high conversions and the excellent functional group tolerance. In this prospect, we have synthesized fully clickable bridged silisesquioxanes and periodic mesoporous organosilica that show high extents of click grafting. CuAAC was then used for tailoring the surface of bridged silsesquioxane and fine-tuning the hydrophilic/lipophilic balance. Finally, the click reaction was used as an efficient way to obtain multiply functionalized mesoporous silica nanoparticles in order to make nanomachines for controlled delivery of cargo molecules.

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