In this study, we were particularly interested in looking at the possibility that cross metathesis of olefins in melt phase could be used to produce polydimethylsiloxane (PDMS) modified polypropylene (PP). The intention of this project was also to study and quantify relationships among the main experimental factors in the reaction: temperature, catalyst concentration and molar ratio of PP to PDMS, through a 2-level factorial statistical design. In order to examine if PP-PDMS copolymers were synthesized in the melt phase, measurement of the chemical, physical and viscoelastic properties of the synthesized copolymers was necessary. Techniques including proton (¹H)-nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), rheometry and scanning electron microscopy (SEM), were all used to characterize the synthesized copolymers. ¹H NMR measurements confirmed the presence of PDMS in the copolymers. They also provided a quantitative measurement of PP to PDMS molar ratio in copolymers by determining the integration of PP PDMS repeating unit signals in NMR spectra. Compared to virgin PP, a lower melting enthalpy of the PP phase in the copolymer was observed from DSC results. This implied that the PDMS component influenced the thermal behavior of the PP crystalline phase in the copolymers. Moreover, TGA measurements indicated that a higher thermal stability was obtained for PP-PDMS copolymers than that for virgin PP wax and this was expected since PDMS is known for its excellent stability at high temperature. Rheological analysis showed that the presence of PDMS in the copolymers gave lower complex viscosities and loss moduli, but higher storage moduli than those for virgin PP. Furthermore, the morphology of copolymers was examined by SEM and elemental analysis at the surface using an energy dispersive X-ray (EDX) analyzer on the SEM. It was found that micrographs of copolymers showed round domains on the surface, which were not observed in virgin PP wax and those round segments were confirmed to contain silicon. Torque values used in a batch mixer for polymerizations and the remaining weight % of copolymers at 350°C were used to conduct statistical analysis, through which models used to describe the relationships between experimental factors and these physical responses were determined.

Die vorliegende Arbeit befasst sich mit experimentellen Untersuchungen zur physikalisch-chemischen und strukturellen Charakterisierung von neuartigen supramolekularen Kristalleinschlussverbindungen am Beispiel der Clathrate der Wirtverbindung 2,2’-bis(9-hydroxy-9-fluorenyl)biphenyl mit Aceton (polar) sowie Chloroform (unpolar). Durch die Kombination von Röntgenstrukturanalysen mit systematischen Messungen thermodynamischer Größen wie Löslichkeit, Einschluss-, Zersetzungs-, Lösungs- und Kristallisationsenthalpien konnten neue Erkenntnisse bezüglich der Struktur-Eigenschaftsbeziehungen sowie zur Rolle der Wirt-Gast Wechselwirkungen in den existierenden Einschlussverbindungen abgeleitet werden. Die Einschlussbildung bzw. Kristallisation verläuft für alle untersuchten Clathratphasen exotherm. Dies bedeutet, dass die Einschlussverbindungen gegenüber dem reinem Wirt energetisch stark begünstigt sind. Der bestimmende Beitrag hierfür resultiert aus der Bildung eines optimal gepackten Kristallgitters, während spezifische Wirt-Gast Wechselwirkungen nur eine untergeordnete Rolle spielen. Das Zersetzungsverhalten der verschiedenen Clathratphasen kann widerspruchsfrei aus der Packungsstruktur der Kristalle erklärt werden.

Grätzel cells or Dye-Sensitized Solar Cells (DSSCs) are considered one of the most promising methods to convert the sun's energy into electricity due to their low cost and simple technology of production. The Grätzel cell is based on a photosensitizer adsorbed on a low band gap semiconductor. The photosensitizer can be a metal complex or an organic dye. Organic dyes can be produced on a large scale resulting in cheaper dyes than complexes based on rare elements. However, the performance of Grätzel cells based on metal-free, organic dyes is not high enough yet. The dye's performance depends primarily on the electron dynamics. The electron dynamics in Grätzel cells includes electron injection, recombination, and regeneration. Different deactivation processes affect the electron dynamics and the cells’ performance. In this thesis, the electron dynamics was explored by various time-resolved spectroscopic techniques, namely time-correlated single photon counting, streak camera, and femtosecond transient absorption. Using these techniques, new deactivation processes for organic dyes used in DSSCs were uncovered. These processes include photoisomerization, and quenching through complexation with the electrolyte. These deactivation processes affect the performance of organic dyes in Grätzel cells, and should be avoided. For instance, the photoisomerization can compete with the electron injection and produce isomers with unknown performance. Photoisomerization as a general phenomenon in DSSC dyes has not been shown before, but is shown to occur in several organic dyes, among them D149, D102, L0 and L0Br. In addition, D149 forms ground state complexes with the standard iodide/triiodide electrolyte, which directly affect the electron dynamics on TiO2. Also, new dyes were designed with the aim of using ferrocene(s) as intramolecular regenerators, and their dynamics was studied by transient absorption. This thesis provides deeper insights into some deactivation processes of organic dyes used in DSSCs. New rules for the design of organic dyes, based on these insights, can further improve the efficiency of DSSCs.

In this study, we were particularly interested in looking at the possibility that cross metathesis of olefins in melt phase could be used to produce polydimethylsiloxane (PDMS) modified polypropylene (PP). The intention of this project was also to study and quantify relationships among the main experimental factors in the reaction: temperature, catalyst concentration and molar ratio of PP to PDMS, through a 2-level factorial statistical design. In order to examine if PP-PDMS copolymers were synthesized in the melt phase, measurement of the chemical, physical and viscoelastic properties of the synthesized copolymers was necessary. Techniques including proton (¹H)-nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), rheometry and scanning electron microscopy (SEM), were all used to characterize the synthesized copolymers. ¹H NMR measurements confirmed the presence of PDMS in the copolymers. They also provided a quantitative measurement of PP to PDMS molar ratio in copolymers by determining the integration of PP PDMS repeating unit signals in NMR spectra. Compared to virgin PP, a lower melting enthalpy of the PP phase in the copolymer was observed from DSC results. This implied that the PDMS component influenced the thermal behavior of the PP crystalline phase in the copolymers. Moreover, TGA measurements indicated that a higher thermal stability was obtained for PP-PDMS copolymers than that for virgin PP wax and this was expected since PDMS is known for its excellent stability at high temperature. Rheological analysis showed that the presence of PDMS in the copolymers gave lower complex viscosities and loss moduli, but higher storage moduli than those for virgin PP. Furthermore, the morphology of copolymers was examined by SEM and elemental analysis at the surface using an energy dispersive X-ray (EDX) analyzer on the SEM. It was found that micrographs of copolymers showed round domains on the surface, which were not observed in virgin PP wax and those round segments were confirmed to contain silicon. Torque values used in a batch mixer for polymerizations and the remaining weight % of copolymers at 350°C were used to conduct statistical analysis, through which models used to describe the relationships between experimental factors and these physical responses were determined.

Ice structuring proteins (ISPs) naturally exist in many foods consumed as part of the human diet including plants or fish. ISPs from winter wheat grass have gained interest in the pharmaceutical and food industries as a non-toxic, natural and cost-effective product, which is easy to prepare as a crude extract. However, they have not been purified reproducibly and studied in detail to elucidate their structures, mechanism of actions and difference(s). ISPs from the apoplast region of cold acclimated winter wheat leaves were extracted through vacuum infiltration and purified using heat and ethanol precipitations, size exclusion and anionic exchange fast protein liquid chromatography techniques. The ISPs showed both significant inhibition of ice growth and thermal hysteresis activities. The non-acclimated apoplastic extracts from winter wheat leaves contained similar proteins without any abovementioned activities. The ISPs contained disulfide bridges, similar to thaumatin-like proteins (TLPs) and partially similar to ISPs from winter rye leaves and carrot. ISPs remained active after thermal treatment (i.e., pasteurization conditions) and over a wide range of pH (3-12). There are very few quantitative assays to measure the activity of antifreeze proteins (AFPs, or Ice Structuring Proteins, ISPs), which often suffer from various inaccuracies and inconsistencies. Some methods rely only on unassisted visual assessment. When microscopy is used to measure ice crystal size, it is critical that standardized procedures be adopted, especially when image analysis software is used to quantify sizes. Differential Scanning Calorimetry (DSC) has been used to measure the thermal hysteresis activity (TH) of AFPs. In this study, DSC was used isothermally to measure enthalpic changes associated with structural rearrangements as a function of time. Differences in slopes of thermograms between winter wheat ISP or AFP type I containing samples, and those without ISP or AFP type I were demonstrated. ISP or AFP type I containing samples had much higher slopes compared to those without ISP or AFP type I. Samples with higher concentration of ISP or AFP type I showed higher slope values. The proteinaceous activity of ISPs or AFP type I was confirmed by demonstrating changes in samples with and without proteases. A proposed mechanism of this method is discussed.

No description available.

Ce travail de thèse s'inscrit dans les thèmes de la photodégradation et de la biodégradation de polymère pouvant être ou non d'origine renouvelable. Il a pour principal objectif d'étudier la durabilité photochimique de différents polymères ou mélanges de polymères utilisés en particulier dans l'agriculture et donc soumis à un vieillissement climatique. La structure chimique des polymères est un des principaux paramètres susceptible d'influencer la photodégradation. Un ensemble de (co)polyesters comportant des unités aliphatiques, cycliques et / ou aromatiques a été sélectionné dans le but d'exprimer une relation structure / photodurabilité. Le photovieillissement des matériaux a été réalisé en conditions naturelles et en conditions accélérées. Des mécanismes de photo-oxydation ont été proposés pour chacun des matériaux à partir de l'évolution des propriétés viscoélastiques traduisant celle de la structure macromoléculaire. Dans ce contexte, l'étude de la durabilité de ces matériaux respectueux de l'environnement doit s'intéresser à des systèmes extrêmement complexes dont chaque constituant est susceptible d'évoluer. Cette caractéristique exige de mettre au point une méthodologie permettant de déterminer la composition d'un biocomposite et d'en suivre les modifications en cours de vieillissement en même temps que l'évolution de la structuration de ces matériaux.

O leite condensado é um produto amplamente estudado, sendo que os problemas de cristalização ao longo do processo constituem um dos aspectos de interesse quando se considera a produção em escala industrial. No entanto, não foram encontrados estudos que padronizassem técnicas de medida de tamanho de cristais e determinação da cristalinidade total em leite condensado. Este trabalho visa adaptar/desenvolver uma técnica especifica para análise de tamanho de cristais de lactose em leite condensado utilizando de microscopia juntamente com processamento e análise de imagem (software ImageJ). Além disso, acredita-se que o grau de cristalinidade possa se tornar um parâmetro de controle de qualidade em leites condensados, de modo que se propõe o estudo da viabilidade do uso de calorimetria exploratória diferencial para a determinação deste parâmetro. A técnica de processamento e análise de imagem mostrou-se confiável e permitiu realizar comparativo eficiente entre três marcas comerciais de leite condensado. Foi possível, mediante análise estatística, otimizar a metologia existente de preparação de lâminas visando reduzir o tempo e esforço da aplicação da técnica de acompanhamento de tamanho de cristais em ambiente industrial. Para o estudo da viabilidade do uso de analises térmicas para a determinação do grau de cristalinidade em leite condensado foram realizados estudos em térmicos simultâneos (DSC-TGA) e estudos de calorimetria exploratória diferencial em DSC e TMDSC em lactose p.a., sacarose p.a., misturas dos dois açúcares e em leite condensado. Na comparação das técnicas, observou-se que as três apresentam mesmo nível de precisão, porém exatidão distintas. A técnica de DSC foi a que permitiu obter maior definição dos picos identificados ao longo do termograma. Por outro lado, na técnica de MDSC, utilizando porta-amostras com furo, foi possível obter boa repetibilidade também com relação aos processos reversíveis e irreversíveis. A análise quantitativa de cristalinidade a partir de dados de calorimetria para misturas de sacarose e lactose é dificultada pela sobreposição dos picos dos diferentes processos térmicos sofridos pelos dois açúcares e pelo fato que foram encontrados indicativos de efeito sinergético na resposta térmica dos dois carboidratos quando em mistura. Assim como para as misturas de açúcares estudadas, não foi possível determinar o grau de cristalinidade em amostras de leite condensado. / Condensed milk is a widely studied product, given that the crystallization problems throughout the production process constitute one of the aspects of interest as far as the industrial scale production is concerned. However, studies that might enable standardized crystal size measurement techniques and crystallinity determination in condensed milk have not been found yet. This work aims at adapting/developing a specific technique for the analysis of lactose crystals size in condensed milk by using microscopy along with image analysis and processing (ImageJ software). Besides, it is believed that degree of crystallinity may become a quality control parameter in condensed milks, in such a way that it is proposed a viability study of the use of differential exploratory calorimetry for its determination. Processing technique and image analysis have demonstrated to be reliable and allowed to carry out efficient comparison between the three commercially available brands of condensed milk. It was possible, by means of statistical analysis, to optimize the existing thin plate preparation methodology with the aim of reducing time and strain of crystal size monitoring in industrial environment. In view of studying thermal analyses aiming at determining degree of crystallinity in condensed milk, studies in simultaneous thermal instruments (DSC-TGA) along with differential exploratory calorimetry in DSC and TMDSC were carried out in analytical grade sucrose and lactose, mixtures of both sugars and condensed milk. When comparing the techniques, one can observe that all three presented the same level of precision, but different accuracies. DSC technique was the one that allowed higher definition of identified peaks along the thermogram. On the other hand, in MDSC technique, using pierced sample holder, it was possible to obtain good repeatability even in regard to reversible and irreversible processes. Cristallinity quantitative analysis from calorimetry data for sucrose and lactose mixtures is hindered by the superposition of peaks from different thermal processes undergone by both sugars and by the fact that indicatives of synergistic effect were found in the thermal response of the above mentioned carbohydrates when mixed together. As it had occurred for the sugar mixtures studied, it was not possible to determine the degree of crystallinity in condensed milk samples.

O leite condensado é um produto amplamente estudado, sendo que os problemas de cristalização ao longo do processo constituem um dos aspectos de interesse quando se considera a produção em escala industrial. No entanto, não foram encontrados estudos que padronizassem técnicas de medida de tamanho de cristais e determinação da cristalinidade total em leite condensado. Este trabalho visa adaptar/desenvolver uma técnica especifica para análise de tamanho de cristais de lactose em leite condensado utilizando de microscopia juntamente com processamento e análise de imagem (software ImageJ). Além disso, acredita-se que o grau de cristalinidade possa se tornar um parâmetro de controle de qualidade em leites condensados, de modo que se propõe o estudo da viabilidade do uso de calorimetria exploratória diferencial para a determinação deste parâmetro. A técnica de processamento e análise de imagem mostrou-se confiável e permitiu realizar comparativo eficiente entre três marcas comerciais de leite condensado. Foi possível, mediante análise estatística, otimizar a metologia existente de preparação de lâminas visando reduzir o tempo e esforço da aplicação da técnica de acompanhamento de tamanho de cristais em ambiente industrial. Para o estudo da viabilidade do uso de analises térmicas para a determinação do grau de cristalinidade em leite condensado foram realizados estudos em térmicos simultâneos (DSC-TGA) e estudos de calorimetria exploratória diferencial em DSC e TMDSC em lactose p.a., sacarose p.a., misturas dos dois açúcares e em leite condensado. Na comparação das técnicas, observou-se que as três apresentam mesmo nível de precisão, porém exatidão distintas. A técnica de DSC foi a que permitiu obter maior definição dos picos identificados ao longo do termograma. Por outro lado, na técnica de MDSC, utilizando porta-amostras com furo, foi possível obter boa repetibilidade também com relação aos processos reversíveis e irreversíveis. A análise quantitativa de cristalinidade a partir de dados de calorimetria para misturas de sacarose e lactose é dificultada pela sobreposição dos picos dos diferentes processos térmicos sofridos pelos dois açúcares e pelo fato que foram encontrados indicativos de efeito sinergético na resposta térmica dos dois carboidratos quando em mistura. Assim como para as misturas de açúcares estudadas, não foi possível determinar o grau de cristalinidade em amostras de leite condensado. / Condensed milk is a widely studied product, given that the crystallization problems throughout the production process constitute one of the aspects of interest as far as the industrial scale production is concerned. However, studies that might enable standardized crystal size measurement techniques and crystallinity determination in condensed milk have not been found yet. This work aims at adapting/developing a specific technique for the analysis of lactose crystals size in condensed milk by using microscopy along with image analysis and processing (ImageJ software). Besides, it is believed that degree of crystallinity may become a quality control parameter in condensed milks, in such a way that it is proposed a viability study of the use of differential exploratory calorimetry for its determination. Processing technique and image analysis have demonstrated to be reliable and allowed to carry out efficient comparison between the three commercially available brands of condensed milk. It was possible, by means of statistical analysis, to optimize the existing thin plate preparation methodology with the aim of reducing time and strain of crystal size monitoring in industrial environment. In view of studying thermal analyses aiming at determining degree of crystallinity in condensed milk, studies in simultaneous thermal instruments (DSC-TGA) along with differential exploratory calorimetry in DSC and TMDSC were carried out in analytical grade sucrose and lactose, mixtures of both sugars and condensed milk. When comparing the techniques, one can observe that all three presented the same level of precision, but different accuracies. DSC technique was the one that allowed higher definition of identified peaks along the thermogram. On the other hand, in MDSC technique, using pierced sample holder, it was possible to obtain good repeatability even in regard to reversible and irreversible processes. Cristallinity quantitative analysis from calorimetry data for sucrose and lactose mixtures is hindered by the superposition of peaks from different thermal processes undergone by both sugars and by the fact that indicatives of synergistic effect were found in the thermal response of the above mentioned carbohydrates when mixed together. As it had occurred for the sugar mixtures studied, it was not possible to determine the degree of crystallinity in condensed milk samples.

Made available in DSpace on 2016-12-08T17:19:14Z (GMT). No. of bitstreams: 1 Capa.pdf: 33668 bytes, checksum: d1e9564709d38250640540f84c86c175 (MD5) Previous issue date: 2005-07-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The recycling of poly(ethylene terephthalate) (PET) can be carried through by different techniques, one of them is the chemical recycling, where new aliphatic-aromatic copolymers are synthesized from melt reaction of the PET post-consumer with aliphatic homopolymers. The aliphatic polyesters, such as the poly(ethylene adipate) (PEA) are biodegradable. The synthesis of aliphatic-aromatic copolymers reveals a good alternative. Varying the composition of each polymer; it can be gotten materials with superior properties to either of the pure components and possibly biodegradable in soil can be obtained. In this work we characterized these aliphatic aromatic copolyesters in different compositions before and after soil biodegradation tests by infrared spectroscopy (FTIR), differential scanning calorimetric (DSC), thermal analysis (TGA), gel permeation chromatography (GPC) and proton nuclear magnetic ressonance spectroscopy 1H NMR. In addition a new methodology for GPC analyses to aliphatic-aromatic copolyesters at room temperature is being proposal. The results of FTIR characterization did not show any alteration in the samples composition before and after 7 months of soil biodegradation. The samples were analyzed by DSC and TGA to evaluate the alterations in the thermal behavior. DSC curves of samples without degradation showed, through the values of Tg, that samples with higher percentage of PEA are more flexible, while those with higher PET content are more rigid. The TGA results showed that the thermal stability of the copolymers increase with the PET content. No changes were observed to material after degradation tests. GPC analysis showed a significative change in Mn and Mw results for PET-co-PEA 50-50, indicating that the copolymer suffered greater degradation in this composition. The new methodology proposal for GPC analyses demonstrated excellent performance in the attainment of the molar mass results for aliphatic-aromatic copolymers The 1H-NMR results showed that the adipate and terephthalate composition from copolymers are different from the copolymers before degradation. / A reciclagem do poli(tereftalato de etileno) (PET) pode ser realizada por diferentes técnicas, uma delas é a reciclagem química, em que podem ser sintetizados novos copolímeros alifático-aromáticos através da reação em massa do PET pós-consumo com homopolímeros alifáticos. A síntese de copolímeros alifático-aromáticos mostra-se como uma boa alternativa, pois variando os teores de cada componente, pode-se obter materiais com propriedades mecânicas e térmicas superiores aos polímeros puros, passíveis de sofrerem biodegradação em solo. Neste trabalho foi realizada a caracterização do copolímero PET-co-PEA, nas diferentes composições obtidas antes e após testes de biodegradação em solo compostado, através das análises de espectroscopia no infravermelho (FTIR), calorimetria exploratória diferencial (DSC), análise termogravimétrica (TGA), cromatografia de permeação em gel (GPC) e ressonância magnética nuclear de prótons (1H NMR). Também é proposta uma metodologia alternativa para análises de GPC a temperatura ambiente para poliésteres alifático-aromáticos. Os resultados de caracterização por FTIR não mostraram alterações na composição das amostras antes e depois de 7 meses de biodegradação em solo. As amostras foram analisadas por DSC e TGA para avaliar as alterações no comportamento térmico. As curvas de DSC das amostras sem degradação mostraram, através dos valores de Tg, que as amostras com maior porcentagem de PEA são mais flexíveis, enquanto àquelas com maior conteúdo de PET são mais rígidas. As análises de TGA mostraram que a estabilidade térmica dos copolímeros aumenta com o teor de PET. Não se observa alterações antes e após teste de biodegradação nas amostras que apresentam somente um estágio de degradação.Os resultados das análises GPC mostraram uma diferença significativa nos valores de Mn e Mw para a composição de PET-co-PEA 50-50, indicando que foi nesta proporção que o copolímero sofreu maior degradação. A nova metodologia proposta para análises GPC demonstrou ótimo desempenho na obtenção dos resultados de massas molares para os copolímeros alifático-aromáticos. Os resultados de 1H-NMR obtidos mostraram que a composição em adipato e em tereftalato dos copolímeros é diferente daquela dos copolímeros antes da degradação.