A new hydrophobic hybrid silica film was synthesized by introducing one silicon precursor (as modifiers) into another precursor (network former). Hybrid films have improved properties. Hydrolysis and condensation of dimethyldiethoxysilane (DMDES) (solvent (EtOH) to DMDES molar ratio R = 4, water to DMDES molar ratio r = 4, 0.01 N HCl catalyst) was analyzed using high-resolution liquid 29Si NMR. It was found that after several hours, DMDES hydrolyzed and condensed into linear and cyclic species. Films from triethoxyfluorosilane (TEFS) have been shown to be promising interlayer dielectric materials for future integrated circuit applications due to their low dielectric constant and high mechanical properties (i.e., Young's modulus (E) and hardness (H)). Co-condensing with TEFS, linear structures from DMDES hydrolysis and condensation reactions rendered hybrid films hydrophobic, and cyclic structures induced the formation of pores. Hydrophobicity characterized by contact angle, thermal stability by thermogravimetric analysis (TGA), Fourier transform Infrared spectroscopy (FTIR), contact angle, and dynamic secondary ion mass spectroscopy (DSIMS), dielectric constant determined by impedance measurement, and mechanical properties (E and H) determined by nanoindentation of TEFS and TEFS + DMDES films were compared to study the effect of DMDES on the TEFS structure. Hybrid films were more hydrophobic and thermally stable. DMDES incorporation affected the dielectric constant, but showed little enhancement of mechanical properties.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Albert E. Stiegman, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.

Esta dissertação versa sobre o estudo de filmes híbridos orgânicos-inorgânicos do tipo ormosil com heteropoliânions do tipo Keggin. O heteropoliânion usado nesse trabalho foi: H3PW12O40 enquanto o ormosil foi obtido a partir do processo sol-gel usando tetraetilortossilicato (TEOS) como agente formador da rede 3D de silicatos e organossilanos contendo grupos oxirana e grupos básicos de Lewis nitrogenados. Realizaram-se testes do uso de Poli (dimetilsiloxano), bis (3-aminopropil) terminados (PDMSa) como agentes modificadores nos filmes. Foram obtidos filmes autossuportados e suportados em lâminas de vidro aluminossilicato. O PDMSa e o silano contendo o grupo oxirana levaram a uma queda na rugosidade média quadrática dos filmes como demonstrado nas micrografias obtidas por Microscopia Eletrônica de Varredura (MEV). Medidas de ângulos de contato estático da água sobre os filmes e de Espectroscopia de Fotoelétrons Excitados por Raios-X mostraram que há segregação do PDMSa ou do silano contendo o grupo oxirana na superfície dos filmes, entretanto os filmes com maior ângulo de contato são aqueles contendo PDMSa. Medidas de Espectroscopia de Absorção na Região do Infravermelho (IV) e Espectroscopia de Ressonância Magnética Nuclear com Rotação em Ângulo Mágico no Estado Sólido (RMN) mostraram que ormosis contendo silanos com grupo amino levam a parcial decomposição dos heteropoliânions, enquanto ormosis contendo silanos com o o grupo nitrila resultam em menor taxa de decomposição. Nos ormosis contendo igual proporção em número de moles destes dois silanos observou-se que estes dois grupos devem estar muito próximos e interagindo entre si via ligação de hidrogênio o que resultou numa queda ainda maior da taxa de decomposição. Os ormosis com silanos dotados de grupos oxirana e nitrila apresentaram maior sensibilidade a radiação UV, ou seja, a maior variação de absorbância e menor tempo de retorno à cor original. Estes filmes mostraram reprodutibilidade e não perderam sua atividade fotocrômica após serem submetidos a 10 ciclos sucessivos de irradiação com UV. Os filmes mostraram resposta linear da função de refletância com a dose de radiação UVB na faixa de 0,80 até 69 MED. Desta forma nós demonstramos a possibilidade de se obter filmes fotocrômicos reprodutíveis e estáveis e como controlar sua sensibilidade usando o processo sol-gel. / This thesis aim to study the organic-inorganic hybrid films of the organosilanes with heteropolyanions of the Keggin type. The heteropolyanion used in this study was H3PW12O40 while the ormosil was obtained by the sol-gel process using tetraethylortossilicate (TEOS) to build the 3D silicate network and organosilanes bearing the oxirane and Basic Lewis nitrogenated groups. Poly (dimethylsiloxane), terminated with (3-aminopropyl) groups, (PDMSa) was essayed as modifiers agents in the film. The films were supported on aluminosilicate glass substrates and self-suported ones. PDMSa or oxirane bearing silanes addition results on smoother filmes reporting lower mean square root roughness based on electron micrographies obtained by Scanning Electron Microscopy (SEM). Water static contact angle measurements and X-ray Photoemission Spectroscopy (XPS) pointed out the surface segregation of the PDMSa and oxirane bearing silane, however higher contact angles were observed for the PDMSa based films. InfraRed Absorption Spectroscopy (IR) and Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy (MAS NMR) results demonstrate that in ormosis with silanes bearing amino groups there was phosphotungstic acid decomposition while in ormosis with nitrile groups such decomposition is much less pronounced. For mixed ormosis with even proportion of amino and nitrile bearing silanes those functional groups are close enough to interact through hydrogen bonding resulting on even lower decomposition of the Phosphotungstate oxocluster. Those films with nitrile functional groups showed higher photochromic activity and faster bleaching time. The films showed high reproducibility and did not loose their photochromic activity after ten cycles of UV irradiation. The films bearing nitrile functionality showed linear response of the reflectance function as a function of the irradiation dose between 0,80 and 69 MED. Therefore, it was demonstrated the possibility to use sol-gel process to obtain photochromic ormosis.

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Agradecemos a compreensão. on 2018-03-21T18:06:58Z (GMT) / Submitted by EZEQUIEL JOSÉ PÉREZ MONTERROZA null (eperez494@gmail.com) on 2018-03-21T19:48:40Z No. of bitstreams: 1 Tese Ezequiel Pérez.pdf: 3206546 bytes, checksum: 195c7ca127a08a51263246b484d38199 (MD5) / Approved for entry into archive by Elza Mitiko Sato null (elzasato@ibilce.unesp.br) on 2018-03-21T21:07:15Z (GMT) No. of bitstreams: 1 perezmonterroza_ej_dr_sjrp.pdf: 3206546 bytes, checksum: 195c7ca127a08a51263246b484d38199 (MD5) / Made available in DSpace on 2018-03-21T21:07:15Z (GMT). No. of bitstreams: 1 perezmonterroza_ej_dr_sjrp.pdf: 3206546 bytes, checksum: 195c7ca127a08a51263246b484d38199 (MD5) Previous issue date: 2018-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O amido é ideal como material de parede na preparação de sistemas de liberação controlada, é barato e considerado GRAS. O amido está constituído por dois biopolímeros de D-glicose, a amilose e a amilopectina, as quais representam 99 % da matéria seca do grânulo. A amilose tem a capacidade de formar complexos com algumas moléculas hidrofóbicas como flavors e ácidos graxos, os quais são capazes de resistir a variações de pH e temperaturas elevadas, tornando-se interessante para a formulação de sistemas de liberação controlada de nutrientes. O objetivo inicial deste projeto foi a utilização de amilose extraída da mandioca e do amido de milho com alto teor de amilose comercial (Hylon VII, 72% de amilose) com o intuito de encapsular bixina e avaliar a formação de complexos de inclusão de V-amilose, bem como a sua caracterização usando difração de raios X (DRX), calorimetria exploratória de varredura, espectroscopia de infravermelho, microscopia eletrônica de varredura (MEV), cor, teor de bixina encapsulado, ensaios reológicos oscilatórios e capacidade de liberação. Foram estudados os efeitos das condições de processo de encapsulação por precipitação em solução ácida e através do tratamento com ultrassom sobre as interações entre a bixina e o amido. O efeito da proteína de soro de leite sobre o processo de encapsulação por precipitação em solução ácida também foi estudado. Finalmente, foi realizado um estudo de otimização usando a metodologia de superfície de resposta para selecionar as melhores condições em ambos os métodos, maximizando a capacidade de carga interior da matriz de amido. Além disso, pelo fato de que os xerogéis e criogéis de amido têm ganhado interesse na indústria como sistemas para a microencapsulação de compostos bioativos, este trabalho também explora a capacidade da amilose de mandioca para encapsular carotenoides usando essas metodologias. Nesse caso foram usados como moléculas-hóspedes os carotenoides presentes no óleo de abacate, luteína e neoxantina. Os resultados da encapsulação da bixina usando Hylon VII e proteína por precipitação de uma solução ácida mostraram que existe interação entre a proteína de soro de leite, o Hylon VII e a bixina, como foi observado na análise por FT-IR, no entanto, os padrões de difração e a análise por DSC não confirmaram a formação de complexos de inclusão do tipo V-amilose com a bixina. Porém, transições endotérmicas com ponto de fusão em 117,2, 105 e 104 °C foram observadas nas amostras preparadas a 90 °C com 0%, 10% e 20% de proteína, respectivamente. Cabe ressaltar que um aumento no conteúdo de proteína causou uma diminuição na entalpia de fusão desta estrutura, assim como um decréscimo em sua cristalinidade relativa, o qual foi causado provavelmente pela interação entre a bixina e a proteína. No grupo das amostras preparadas a 90 °C, o aumento no conteúdo de proteína resultou em uma tendência a aumentar o conteúdo e bixina encapsulado. Os resultados de FT-IR mostraram que as bandas de absorção associadas com as vibrações do grupo -C=C- desaparecem, indicando restrição da cadeia da bixina na matriz, assim como o aumento da disponibilidade para interagir com a proteína, embora, essas interações pareçam ser poucas a altas temperaturas. Os padrões de liberação da bixina foram afetados pelo conteúdo de proteína e a temperatura usada no processo de encapsulação, resultando em diferentes porcentagens de liberação. Nos ensaios de encapsulação da bixina com ultrassom foi avaliado o efeito do tratamento sobre as interações amido-bixina. Os resultados por DSC e DRX não confirmaram a formação de complexos de inclusão tipo V-amilose, no entanto, a análise por FT-IR indicou que as bandas de absorção do grupo funcional -C=O da bixina desapareceram depois do processo de encapsulação, o que sugere a existência de interação entre a bixina e o amido. Aparentemente esta não foi encapsulada eficientemente dentro da cavidade de amilose, provavelmente pelo seu tamanho molecular. Os espectros mecânicos dos géis formados durante o processo de encapsulação por ultrassom mostraram uma leve variação dos módulos de armazenamento (G’) e de perda (G’’), com G’>G’’, indicando tratar-se de géis fracos. O maior teor de bixina encapsulado no interior da matriz foi obtido com potência de ultrassom de 150 W por 60 minutos de tratamento. As amostras submetidas ao ultrassom foram menos susceptíveis à ação do fluido intestinal simulado, provavelmente devido ao aumento das interações entre a bixina e o amido em comparação à amostra controle. Em ambos os métodos de encapsulação a morfologia das partículas apresentou superfície irregular e erodida, com protrusões provocadas pela agregação de amilose. Através da análise estatística, observou-se que nos dois métodos de preparação todos os fatores tiveram efeito significativo (p<0,05) sobre o teor de bixina, tanto na superfície como no interior da matriz de amido. Na encapsulação por precipitação em meio ácido, o maior teor de bixina na matriz foi encontrado com o tratamento a 90 °C usando amilose de mandioca junto com proteína. De forma geral, com o uso de amilose de mandioca obteve se um maior teor de bixina encapsulado no interior da matriz e este sempre aumentou com o uso de proteína. Em relação ao tratamento com ultrassom, o maior teor de bixina encapsulado no interior da matriz foi alcançado com 2% de Hylon 150 W e 20 minutos de tratamento. A eficiência de encapsulação alcançada variou de 13,1% a 62,1% e de 17,3% a 94,5% usando tratamento com ultrassom e precipitação em meio ácido, respectivamente. As condições ótimas foram de 2% Hylon, 150 W e 20 minutos para o tratamento com ultrassom. Em relação ao método por precipitação em meio ácido foram 2% amilose de mandioca com proteína, a 68 °C. Os resultados obtidos no processo de encapsulação de luteína e neoxantina usando xerogéis e criogéis de amilose de mandioca indicaram que não houve formação de complexos de inclusão do tipo V-amilose. Entanto, os padrões de difração de raios X observados são característicos deste tipo de complexos. Foi observado um leve aumento na capacidade de encapsulação nas amostras retrodegradadas a -18°C e liofilizadas. / The starch is considered safe and cheap, ideal as wall material in the formulation of delivery systems. Starch granule consists of two major types of α-glucans, amylose, and amylopectin, which represent about 99% of dry matter. Amylose and some hydrophobic molecules such as flavors and fatty acids, form amylose inclusion complexes. Amylose complexes resist to variations of pH and elevated temperature, being good candidates for the formulation of nutrient delivery systems. The initial objective of this thesis was to use high-amylose corn starch (Hylon VII, 72 % amylose) and amylose from cassava starch as wall material for the encapsulation of bixin, evaluating the formation of V-amylose inclusion complexes, and performing their characterization by using X-ray diffractometry, FT-IR spectrometry, scanning electron microscopy, oscillatory rheological tests, color, encapsulated bixin content, and release profile. The effects of process parametres used in the methods based on ultrasound treatment and precipitation in acid solution on the interaction between amylose and bixin were studied, as well as the effect of whey protein on the encapsulation process by precipitation in acid solution. The process conditions that would maximize the encapsulate bixin content inside of the starch matrix were determined by using desirability function. In addition, considering that xerogels and cryogels have gained interest as potential systems for microencapsulation of bioactive compounds and the use of silica aerogels as delivery systems has been demonstrated with success, this thesis explores the capacity of amylose from cassava starch to encapsulate carotenoids using these methodologies. In this case, the guest molecules were the carotenoids present in the avocado oil, lutein and neoxanthin. The results of FT-IR indicated that there was an interaction between protein, Hylon, and bixin in the encapsulation process by precipitation in acid medium. However, the diffraction patterns and the DSC analysis indicated no formation of V-amylose complexes. Nevertheless, although the set of samples prepared at 90°C with 0%, 10% e 20% of protein respectively, showed endothermal transitions with a melting point about 117,2º, 105º and 104°C The increase in protein content decreased the melting enthalpy and relative crystallinity, probably due to the interaction between bixin and protein. In the set of samples prepared at 90°C, the increase in protein content led to a tendency to increase the encapsulate bixin content inside the matrix. The FT-IR analysis indicated that adsorption bands associated with the vibration of the group -C=C- disappeared due to the restriction of bixin chain into starch matrix and increase in the availability to interacting with the protein. However, these interactions seem to be fewer at the higher temperature. The bixin delivery patterns were affected by protein content and temperature used in the encapsulation process, resulting in different delivery amounts. In the encapsulation of bixin by ultrasound treatment, the effect of sonication power level on the interaction between starch and bixin was studied, nevertheless, the results of DSC and Xray diffraction indicated no formation of amylose inclusion complex. The FT-IR analysis showed that adsorption bands of the -C=O group in bixin disappeared after the encapsulation process, which confirms the interaction between starch and bixin, in spite of bixin having not be entrapped efficiently inside of the amylose cavity, probably due to its molecular size. Frequency sweep tests of gels formed during ultrasound encapsulation process showed a slight frequency dependence of G’ and G” moduli with G’>G’’, with patterns correponding to weak gels. The highest bixin encapsulated content inside of matrix was reached using the combination of ultrasound power of 150 W and 60 min of treatment. The sonicated samples were less susceptible to action of simulated intestinal fluid, probably due to increases interaction between starch and bixin as compared to control sample. The particle morphology of samples prepared by both methods showed protrusions of aggregates of amylose, as well as irregular and eroded surfaces. Statistical analysis showed that in both methods, all factors had a significant effect (p<0.05) on bixin encapsulated content inside or on the surface of the matrix. In the encapsulation by precipitation in acid solution, the combination of 90 °C using amylose from cassava starch and protein leaded to the highest bixin encapsulated content. In general, amylose from cassava starch encapsulated a greater bixin content inside of matrix compared to Hylon, and the presence of protein increased this effect even more. Regarding ultrasound treatment, the combination of 2% of amylose from Hylon, and 20 min of treatment showed the highest bixin encapsulated content inside of matrix. Encapsulation efficiency ranged from 13.1% to 62.1% and 17.3% to 94.5% using ultrasound treatment and precipitation in acid solution respectively. The optimum conditions were 2% amylose, 150 W, and 20 min in the ultrasound treatment, whereas in the method by precipitation in acid solution the best conditions were 2% amylose from cassava starch with protein at 68 °C. The results obtained from DSC and FT-IR spectroscopy in the encapsulation using cryogels and xerogels indicated no formation of inclusion complexes V-type of amylose. Nevertheless, the diffraction patterns were characteristic of this type of complexes. The samples retrograded at -18 °C and dried using freeze-drying had a slightly higher encapsulation degree than the samples retrograded at 8 °C.

Esta dissertação versa sobre o estudo de filmes híbridos orgânicos-inorgânicos do tipo ormosil com heteropoliânions do tipo Keggin. O heteropoliânion usado nesse trabalho foi: H3PW12O40 enquanto o ormosil foi obtido a partir do processo sol-gel usando tetraetilortossilicato (TEOS) como agente formador da rede 3D de silicatos e organossilanos contendo grupos oxirana e grupos básicos de Lewis nitrogenados. Realizaram-se testes do uso de Poli (dimetilsiloxano), bis (3-aminopropil) terminados (PDMSa) como agentes modificadores nos filmes. Foram obtidos filmes autossuportados e suportados em lâminas de vidro aluminossilicato. O PDMSa e o silano contendo o grupo oxirana levaram a uma queda na rugosidade média quadrática dos filmes como demonstrado nas micrografias obtidas por Microscopia Eletrônica de Varredura (MEV). Medidas de ângulos de contato estático da água sobre os filmes e de Espectroscopia de Fotoelétrons Excitados por Raios-X mostraram que há segregação do PDMSa ou do silano contendo o grupo oxirana na superfície dos filmes, entretanto os filmes com maior ângulo de contato são aqueles contendo PDMSa. Medidas de Espectroscopia de Absorção na Região do Infravermelho (IV) e Espectroscopia de Ressonância Magnética Nuclear com Rotação em Ângulo Mágico no Estado Sólido (RMN) mostraram que ormosis contendo silanos com grupo amino levam a parcial decomposição dos heteropoliânions, enquanto ormosis contendo silanos com o o grupo nitrila resultam em menor taxa de decomposição. Nos ormosis contendo igual proporção em número de moles destes dois silanos observou-se que estes dois grupos devem estar muito próximos e interagindo entre si via ligação de hidrogênio o que resultou numa queda ainda maior da taxa de decomposição. Os ormosis com silanos dotados de grupos oxirana e nitrila apresentaram maior sensibilidade a radiação UV, ou seja, a maior variação de absorbância e menor tempo de retorno à cor original. Estes filmes mostraram reprodutibilidade e não perderam sua atividade fotocrômica após serem submetidos a 10 ciclos sucessivos de irradiação com UV. Os filmes mostraram resposta linear da função de refletância com a dose de radiação UVB na faixa de 0,80 até 69 MED. Desta forma nós demonstramos a possibilidade de se obter filmes fotocrômicos reprodutíveis e estáveis e como controlar sua sensibilidade usando o processo sol-gel. / This thesis aim to study the organic-inorganic hybrid films of the organosilanes with heteropolyanions of the Keggin type. The heteropolyanion used in this study was H3PW12O40 while the ormosil was obtained by the sol-gel process using tetraethylortossilicate (TEOS) to build the 3D silicate network and organosilanes bearing the oxirane and Basic Lewis nitrogenated groups. Poly (dimethylsiloxane), terminated with (3-aminopropyl) groups, (PDMSa) was essayed as modifiers agents in the film. The films were supported on aluminosilicate glass substrates and self-suported ones. PDMSa or oxirane bearing silanes addition results on smoother filmes reporting lower mean square root roughness based on electron micrographies obtained by Scanning Electron Microscopy (SEM). Water static contact angle measurements and X-ray Photoemission Spectroscopy (XPS) pointed out the surface segregation of the PDMSa and oxirane bearing silane, however higher contact angles were observed for the PDMSa based films. InfraRed Absorption Spectroscopy (IR) and Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy (MAS NMR) results demonstrate that in ormosis with silanes bearing amino groups there was phosphotungstic acid decomposition while in ormosis with nitrile groups such decomposition is much less pronounced. For mixed ormosis with even proportion of amino and nitrile bearing silanes those functional groups are close enough to interact through hydrogen bonding resulting on even lower decomposition of the Phosphotungstate oxocluster. Those films with nitrile functional groups showed higher photochromic activity and faster bleaching time. The films showed high reproducibility and did not loose their photochromic activity after ten cycles of UV irradiation. The films bearing nitrile functionality showed linear response of the reflectance function as a function of the irradiation dose between 0,80 and 69 MED. Therefore, it was demonstrated the possibility to use sol-gel process to obtain photochromic ormosis.

Chapter 1: Supramolecular gels and their applications Gels are viscoelastic materials composed of a solid-like three dimensional fibrillar network that is embedded in a liquid. Supramolecular gels belong to a class of gels which are derived from low molecular weight compounds (typically < 1000). A variety of non-covalent interactions like H-bonding, π-π stacking, donor-acceptor, metal coordination, solvophobic and van der Waals interactions are involved in the formation of the self-assembled fibrous networks (SAFIN’s) in these gels. These non-covalent interactions are weak in nature and as a result, these gels can be reverted back to sol by heating and this process is reversible. These gels are further classified as hydrogels, organogels and aero/xerogels depending on the medium they encompass. Although low molecular weight gelators were known in the early part of the 20th century, it is only in the last two decades that this field has generated widespread interest among scientists. In the 90s, the investigations on these kinds of gels mainly focused on designing new gelator molecules. However, during the last decade, the research interest in this field has shifted more towards designing functional gels. Such gels Scheme 1. Various applications of functional supramolecular gels have been extensively utilized in the templated synthesis of inorganic nanomaterials, in making hybrid materials, as synthetic light harvesting systems, as sensors, in the field of biomaterials such as drug delivery, screening of enzyme inhibitors and tissue engineering and also in the field of organic optoelectronics. In this chapter a few selected examples from each of these fields are highlighted. Chapter 2: Charge transfer induced organogels from 2,3dialkoxyanthracenes and 2,4,7-trinitrofluorenone 2,3-Di-n-alkoxyanthracenes formed charge transfer (CT) interaction promoted organogels in the presence of electron acceptor 2,4,7-trinitrofluorenone (TNF). These dialkoxyanthracences (in the absence of TNF) have been reported previously to form gels in a variety of organic solvents. The gelation property was found to be dependent on the chain length and the derivatives with C6-C16 chains were found to be gelators. On the other hand derivatives with C5-C1 chains were found to be non-gelators. It was found that TNF not only modulated the gelation property of the efficient organogelators, it also transformed the weak and non-gelators into efficient gelators. This charge transfer induced gelation was observed for the derivatives with C10-C4 chains in alcoholic and hydrocarbon solvents whereas the shorter chain derivatives C3-C1 did not form gels. Several other alkoxy and dialkoxy derivatives with substituents in other positions did not show gelation in the presence of TNF. These results suggested that two structural aspects are necessary for these derivatives to form CT gels- the alkoxy chain length and the position of the alkoxy substituents. The thermal stability of all these gels was found to be maximum with a 1:1 stoichiometry of the donor and the acceptor. The common observation, the intensification of color in going from the sol to the gel phase, supported the crucial role of the charge transfer interaction behind the formation of these gels. The rheological characterization of the gels demonstrated that they Figure 1. Chemical structures of 2,3-dialkoxyanthracenes and TNF (middle) and a fluorescence confocal microscopy image (left) and a photograph (right) of DDOA-TNF gel. behaved like viscoelastic soft solids. Chapter 3: A new class of perfluorinated derivatives of bile acids: Synthesis and gelation properties A new class of bile acid based gelators was designed by connecting the side chains of the facially amphiphilic bile acid with perfluoroalkyl chains of different lengths through two different ester linkages-–O-(CO)-and –(CO)-OCH2-. All these three structural aspects i.e. the bile acid moiety, the fluoroalkyl chain length and the spacer were found to influence the gelation properties of the derivatives. Depending on them, there was a variation in terms of the nature of the solvent gelated, the CGCs, the mechanical properties of the gels, etc among the derivatives. The deoxycholic and lithocholic derivatives with the spacer –O-(CO)-formed gels in aromatic hydrocarbons and also in DMSO depending on the fluoroalkyl chain length. The mechanical properties of the gels formed in DMSO were found to be dependent on the bile acid moiety and the fluoroalkyl chain length. In general, the deoxy analogues showed higher elasticity, stiffness and yield stress values for their gels than the litho derivatives. The perfluorinated derivatives having the spacer –(CO)-OCH2-showed gelation properties in organic-aqueous media and in DMSO. Interestingly, organogelation was observed in the deoxy and lithocholic derivatives from both spacer series whereas in the literature most of the bile acid based organogelators are derived from cholic acid. (b) (c) Figure 2. (a) Perfluorinated derivatives of bile acids, (b) photographs of a few DMSO gels and (c) TEM image of a xerogel of a deoxy derivative Chapter 4: Composite aerogels and organogels from 2,3didecyloxyanthracene and bile-perfluoro derivatives Aerogels are unique materials among solids. They have extremely low densities (up to 95% of their volume is air), large pores and high inner surface area. As a result aerogels have very interesting physical properties such as extremely low thermal conductivity, low sound velocity and high optical transparency. There are only a few reports of aerogel formation by low molecular weight gelators. We have investigated the aerogel formation ability of three long 7 chain perfluoroalkyl esters (two deoxycholic and one lithocholic derivative, chart 1) in supercritical CO2. A deoxy derivative, formed aerogel in sc-CO2. When mixed with DDOA (which has been reported previously to form good aerogels in sc-CO2), the perfluoro compound formed aerogels of better quality. The mixed aerogels were characterized by the presence of very large fibers in the micron range (as observed in the aerogel formed by only the fluoro derivative) as well as fibers of smaller size observed in pure DDOA aerogel. We also investigated the behavior of the composite systems in organic solvents. It was found that in DMSO, another deoxy derivative, Figure 3. SEM images of a mixed aerogel of DDOA-DC23C13F27 (left) and a mixed organogel (DMSO) of DDOA-DC23C11F23 (right). DC23C11F23 formed gels with higher thermal stability and improved mechanical properties compared to the native gels of the perfluoro compound or DDOA. Chapter 5: Hydrogels from lanthanide(III) cholates: Tunable, multiple color luminescence from hydrogels and xerogels In this chapter, facile hydrogel formation by several lanthanide cholates is reported. When sodium cholate was added to aqueous solutions of Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Yb(III) and sonicated, the mixtures formed gels within a few seconds. The gels thus obtained were transparent/translucent and thermoirreversible. Rheological measurements showed that all of them could be classified as viscoelastic soft solids. A naphthalene derivative, 2,3-dihyroxynaphthalene was found to sensitize Tb(III) emission very efficiently in its cholate gel when doped in micromolar concentrations. The importance of the gel matrix behind sensitization of Tb(III) was demonstrated by the inefficiency of the same sensitizer DHN in an SDS micellar solution. In mixed gels of Tb(III)-Eu(III) doped with DHN, a energy transfer pathway was found to occur from the sensitized Tb(III) to Eu(III). By a simple tuning of the ratio of these two lanthanide ions, multiple color emissive gels could be made.The emissive properties of the hydrogels were retained in the xerogels and the suspensions of these xerogels in n-hexane were used for making luminescent coatings on glass surface. Figure 4. Tunable, multi-color luminescent hydrogels and xerogels of lanthanide cholates

Cellulose nanofibrils are a biobased and renewable material with potential to be used in many different applications. Such applications include air filtration, absorption of liquids, and thermal insulation.  To be used for these applications the cellulose nanofibrils must form a porous and dry material. However, maintaining some degree of porosity after drying is difficult, since the fibrils are extracted in liquid and tend to collapse into a dense material upon drying. Certain methods have proven effective for making a dry porous material from cellulose nanofibrils, but these are often expensive and not suitable for large scale production. The aim of this project is to test possible methods for making a highly porous cellulose nanofibril-based material. These methods must be environmentally sustainable and suitable for large scale production. An extensive screening has been conducted with the aim of identifying methods resulting in materials with high porosity. The obtained materials have been analysed further to give a more thorough understanding of the porosity as well as other characteristics. The results indicate that cross-links in the material strengthen the structure, and that drying samples from water always results in complete collapse or very dense materials while drying samples from certain solvents other than water results in more porous materials. The analysed materials had very different porosities, some of which were relatively high. The most porous material analysed by Brunauer-Emmett-Teller gas adsorption had a surface area of 9.5 m2/g. This project gives insight into how cross-linking chemistries and treatment with different solvents and pH affect the resulting cellulose nanofibril-based material, as well as knowledge about which methods can be used to successfully produce dry porous cellulose nanofibril-based materials.

Tato práce se zabývá systematickou studií syntézy a zpracováním pokročilých tepelně stabilních aerogelů pro potenciální vysokoteplotní aplikace. V první části dizertační práce jsou podrobně popsány syntetické implikace pro přípravu aerogelů a jejich aplikace spolu s popisem depozičních metod povlaků vytvořených pomocí sol-gel procesu. Experimentální postup je rozdělen do tří částí. První z nich představuje syntetické protokoly k přípravě ZrO2, YSZ, Ln2Zr2O7 (Ln = La3+, Nd3+, Gd3+, and Dy3+) aerogelů, Ln2Zr2O7 prášků a xerogelů. Dále je popsána depoziční metoda, která byla použita pro přípravu povlaků z aerogelů na kovových substrátech. Poté jsou následně specifikovány techniky, jež byly použity pro charakterizaci. Bylo zjištěno, že množství vody a kyseliny dusičné hraje rozhodující roli v přípravě gelů vhodných pro transformaci na aerogely. Po kalcinaci při 500 °C mají ZrO2 a YSZ aerogely velký povrch, a to až do 114 m2 g-1, avšak při 1000 °C dochází k úplnému zhuštění a ztrácí se tak veškerá jejich porézní struktura. Naopak ve srovnání s ZrO2 and YSZ jsou aerogely Ln2Zr2O7 tepelně stabilnější, protože si zachovávají svou porozitu při vyšší kalcinační teplotě (1000 °C), při které dosahují hodnot > 160 m2 g-1. Experimentálně bylo dále zjištěno, že ve studovaném teplotním rozsahu ZrO2 aerogel tvoří tetragonální komplex monoklinický fázový přechod řízený velikostí krystalitů, zatímco YSZ je tvořena jedinou tetragonální fází. Fázové složení zirkoničitanů vzácných zemin je vysoce závislé na způsobu syntézy; všechny Ln2Zr2O7 materiály jsou pyrochlorické nebo fluoritové krystalické fáze. Přímým odléváním aerogelu na kovový substrát dochází k úplnému rozpraskání povlaku z důvodu smršťování, zatímco máčením kovového substrátu v suspenzi je možné vyrobit homogenní, silné a hrubé povlaky z aerogelu. Tyto povlaky neobsahují fázové změny a zůstávají vysoce porézní i po různých tepelných úpravách.

Ce travail de recherche présente la préparation et la caractérisation de matériaux monolithiques hautement poreux dérivés majoritairement de ressources naturelles. L'objectif était de préparer de nouveaux gels biosourcés jusqu'à 91%, de proposer des alternatives au séchage supercritique au CO2, et d'étudier quelques propriétés d'intérêt de tels gels après séchage, non seulement à l'état organique mais, dans certains cas, après pyrolyse pour obtenir des gels de carbone. A ces fins, le tannin et le soja ont été testés comme précurseurs, à différentes concentrations et différents pH, et trois voies de séchages ont été utilisées : supercritique, lyophilisation et séchage évaporatif. Les gels obtenus ont été caractérisés en termes de densité, porosité, distributions de tailles de pores et surfaces spécifiques, qu'ils soient sous forme organique ou carbonée selon l'application envisagée ou le type de porosité attendue. Leurs propriétés mécaniques et thermiques ont aussi été mesurées. La très large gamme de textures poreuses obtenues a permis de proposer des applications en tant qu'isolants thermiques, supports de catalyseur, ou électrodes de condensateur électrochimiques, selon les cas / This manuscript presents the preparation and the characterization of highly porous monolithic materials mainly derived from natural resources. The objectives were to: (i) develop new gels, biosourced up to the 91% level; (ii) suggest alternatives to supercritical drying in CO2, and (iii) investigate properties of interest for such gels in the organic state and, in some cases, after pyrolysis for obtaining carbon gels. For those purposes, tannin and soy flour were tested as precursors, at different concentrations and different pH, and three ways of drying were used: supercritical drying, freeze drying and evaporative drying. The obtained gels were characterized in terms of density, porosity, pore size distributions and specific surface area, whether in organic or in carbon form, depending on the intended application or expected type of porosity. Mechanical and thermal properties were also measured. The obtained broad range of porous textures allowed suggesting applications such as thermal insulators, catalyst supports or electrodes for electrochemical capacitors

Ce mémoire rapporte la préparation et l'étude de matériaux hybrides organiques-inorganiques à base de titane où les deux réseaux sont liés par des liaisons titane-carbone stables. Différents précurseurs dans lesquels deux groupes cyclopentadienyltitane sont reliés par des espaceurs variés ont été préparés. Ces espaceurs comprennent des groupes aromatiques et hétéroaromatiques linéaires ainsi que des groupes aromatiques disubstitués par des chaînes alkyle. Ces complexes dimétalliques, où le titane est aussi lié à trois groupes labiles, ont été ensuite hydrolysés dans les conditions du procédé sol-gel pour conduire à des hybrides de classe II. Le réseau organique y est lié au réseau inorganique par des liaisons stables titane-carbone. Ces matériaux sont organisés et leur mode d'organisation dépend de la nature de l'espaceur reliant les groupes cyclopentadienyle. Les espaceurs linéaires conduisent à des matériaux à structure en escalier dans lesquels les ligands sont associés par des liaisons p. La longueur des espaceurs n'a pas d'effet sur cette organisation. Par contre, les matériaux à espaceurs substitués latéralement sont organisés par les chaînes alkyle. La calcination de ces matériaux hybrides sous oxygène conduit à la formation de dioxyde de titane nanoporeux sous forme d'anatase dont la cristallinité et la surface spécifique dépendent de la température de calcination. D'une façon similaire des films de dioxyde de titane de même type sont obtenus par la calcination de films minces d'hybrides préparés par spin-coating. / This work aimed to the preparation of titanium-based organic-inorganic hybrid materials where both networks are linked through stable titanium-carbon bonds. The preparation of various di(cyclopentadienyltitanium) precursors in which various organic groups serve as a bridge between the two cyclopentadienyl groups while each titanium atom is equipped with three hydrolysable groups was first achieved. Then, these complexes were hydrolyzed in a sol-gel process that led to new self-assembled titanium-based class II hybrid materials in which the inorganic network is connected to the organic network through stable titanium-carbon bonds. The mode of organization of the nanostructures depends on the spacer bridging the cyclopentadienyl groups. Linear aromatic spacers led to materials having a stair-like structure in which the organic ligands are arranged via p-stacking. The length of the spacer has a little effect on the organization of the nanostructures. The structure of the materials obtained with spacers endowed with long lateral chains is governed by the side chains. The calcination of these materials under oxygen led to the formation of nanoporous anatase titanium dioxide the crystallinity and surface area of which depend on the calcination temperature. Similarly titanium dioxide thin films were prepared by the calcination of hybrid thin films prepared by spin coating.