Orientador: Carol Hollingworth Collins / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T03:41:41Z (GMT). No. of bitstreams: 1 SilvaJunior_EliasSeveroda_D.pdf: 2576422 bytes, checksum: 19c90c90e1e49e747a75a6260bb45eba (MD5) Previous issue date: 2014 / Resumo: Neste trabalho foram feitos estudos das condições de preparo de fases estacionárias para uso em Cromatografia Líquida de Alta Eficiência em Fase Reversa (CLAE-FR) da mistura de poli(metiloctadecilsiloxano) (PMODS) e poli(dimetilsiloxano) (PDMS), sorvidos e imobilizados por tratamento térmico (em atmosfera inerte) na superfície de sílica Kromasil (esférica, 5 µm) metalizada com titânia ou zircônia. As fases estacionárias foram avaliadas por testes químicos, físicos, cromatográficos e de estabilidade em fases móveis em condições agressivas. As melhores condições de preparo das fases estacionárias foram: sorção de 22 % de PMODS e 33 % de PDMS sobre sílica metalizada, mantendo períodos de 4 e 10 dias em repouso, respectivamente, após adição de cada polímero e depois imobilizados a 120 °C durante 16 horas. As fases estacionárias preparadas nas melhores condições apresentaram eficiências superiores a 45000 e 10000 pratos m-1, respectivamente, para os compostos naftaleno e N,N-dimetilanilina, além de picos simétricos para a maioria dos compostos. O estudo de caracterização através das misturas testes de Tanaka, Engelhardt, Neue e SRM 870 indicou a presença de silanóis residuais, mas os resultados dos parâmetros avaliados foram satisfatórias, principalmente comparados às fases PMODS e algumas comerciais. Quanto aos testes de estabilidade em meio básico as fases estacionárias mantiveram-se estáveis durante 550 e 800 volumes de coluna, respectivamente, SiTi(PMODS + PDMS) e SiZr(PMODS + PDMS), usando o acenafteno. Já no teste ácido as fases estacionárias mantiveram-se estáveis por 900 e 800 volumes de coluna, respectivamente, para SiTi(PMODS + PDMS), e SiZr(PMODS + PDMS). As fases estacionárias SiTi(PMODS + PDMS), e SiZr(PMODS + PDMS), sorvidas e imobilizadas por tratamento térmico, apresentam potencialidade na separação de diferentes classes de compostos, tais como, agrotóxicos e fármacos / Abstract: In this work the conditions for the preparation of stationary phases for use in reversed phase high performance liquid chromatography (RP-HPLC) with a mixture of poly(methyloctadecilsiloxane) (PMODS) and poly(dimethylsiloxane) (PDMS) sorbed and immobilized by thermal treatment (in an inert atmosphere) on metalized (titanium and zirconium) Kromasil silica (spherical, 5 µm) were studied. The stationary phases were evaluatied by chemical, physical and chromatographic tests and for stability in mobile phases having agressive conditions. The best conditions for preparation of the stationary phases were: sorption of 22 % PMODS and 33 % PDMS onto the metalized silica, storing for 14 days and then immobilizing at 120 °C for 16 hours. The stationary phases from these conditions showed higher efficiencies of 45000 and 10000 plates m-1 for naphthalene and N,N-dimethylaniline and symmetrical peaks for most compounds. Characterization studies using Tanaka¿s, Engelhardt¿s, Neue¿s and the SRM 870 test-mixtures indicated the presence of residual silanols, but evaluation parameters were still reasonable, compared to PMODS phases and to commercials phases. In the adverses stability tests the stationary phase was for stable 550 and 800 column volumes, respectively, for SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS), in the basic test, showing a decrease of efficiency (60 %) for N,N-dimethylaniline. In the acid test the stationary phases maintained efficiency for 900 and 800 column volumes, respectively, for SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS). The stationary phases SiTi(PMODS + PDMS) and SiZr(PMODS + PDMS) sorbed and immobilized by thermal treatment, showed potential for the separation of different compounds classes, such as, pesticides and pharmaceuticals / Doutorado / Quimica Analitica / Doutor em Ciências

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No description available.

Silicone polymers and network-materials have proven extremely useful in a variety of applications owing to their superb properties when compared to carbon-based polymers. Polysiloxanes containing functional groups other than simple alkyl moieties have allowed for further manipulations of pendant groups along the polymer backbone leading to a greater range of possible chemical transformations, as well as changes in physical/interfacial properties. One aspect of functional polymers that has yet to be explored with respect to primarily silicone-based systems is that of stimuli-responsive materials. In order for this unique application to work, silicones must be functionalized with a group or groups that can influence the polymer’s properties based on that group’s response to specific external stimuli. Boronic acids represent one such group, wherein the most common stimuli used to affect changes in ionization state and solubility are pH and diol-binding. Boronic acids are also capable of forming weak hydrogen-bonded dimers with other boronic acids, and dynamic covalent bonds with Lewis bases. It is proposed that the covalent attachment of boronic acids and their derivatives onto silicones could lead to stimuli-responsive silicone materials. Herein, the synthesis of silicone-boronic acids and their protected boronic esters is described. The simple two-step method involving boronic acid protection followed by hydrosilylation has led to a variety of molecules differing in molecular weight and three-dimensional geometry through the use of commercially available hydride-functional silicones. Initial results regarding saccharide binding selectivity and the impacts on silicone solubility are provided. The unique interfacial behaviour of silicone-boronic esters and their propensity to form self-assembled, crosslinked films at an air/water interface are also reported. Using several different diol protecting groups and a variety of aqueous sub-phases, the mechanism for changes in physical properties as well as crosslinking were revealed. Finally, the production of new thermoplastic silicone elastomers from silicone-boronic esters and amine-containing molecules is discussed. The Lewis acid/Lewis base complexation that occurs between nitrogen and boron can provide enough strength to produce robust, yet recyclable, silicone elastomers without the use of catalyst or solvent. Elastomers can be easily dissolved and reformed through the introduction and removal of a mono-functional Lewis base. The impact of crosslink density, controlled by the quantities and molecular weights of each polymer component used, on physical characteristics is reported. / Thesis / Doctor of Philosophy (PhD)

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The purpose of this work is to critically examine the Lauritzen-Hoffman (LH) secondary nucleation barrier model of polymer crystallization. One of the major criticisms of the LH theory was that it predicted divergence of the lamellar thickness and crystal growth rate at finite undercoolings - the so-called “δ𝑙 catastrophe." Within this work, it has been shown that the "δ𝑙 catastrophe" can be eliminated by considering all of the implications of the Hoffman-Miller reptation approach. Combination of this approach and the lattice-strain theory of Hoffman and Miller (which predicts curved face crystals) eliminates two of the major criticisms of the LH theory within a single theoretical framework. Through studies performed in this work, the LH theory has been modified in such a way as to extend its utility to higher undercoolings. Physically meaningful nucleation parameters can be obtained with the modified LH theory if the viscoelastic parameters characterizing the transport of chain segments to the growth front are known a priori. Crystal growth and melting behavior were studied in the case of linear and cyclic polydimethylsiloxanes. An equilibrium melting temperature (T_m) of 250K was determined by the Hoffman-Weeks extrapolation method for a linear PDMS fraction with <M_n>=62,700 g/mol. This value is 12°C higher than that previously cited in the literature. From the kinetic studies, a fold crystal/melt interfacial free energy of 10.2 erg/cm² was determined which corresponds to a work of chain folding of 2.5 kcal/mol. Studies performed on the cyclic PDMS fractions confirmed that the configuration entropy decreases with decreasing molecular weight. Additionally, the studies on the cyclic PDMS fractions have shown that the σ-C_∞ relationship of Hoffman and coworkers fails for cyclic systems. The crystal growth rates, T_m, and lamellar thicknesses of polytetrafluoroethylene have been determined in this work. T_m has been shown to be 331±2°C. By atomic force microscopy and theoretical arguments it has been shown that the lamellar thicknesses of polytetrafluoroethylene, over the temperature range studied, is on the order of 1000Å. These thicknesses correspond to quantization of the folds, from which it was shown that meaningful analysis of the growth rate data is impossible. / Ph. D.

Poliuretanas são materiais tradicionalmente obtidos por métodos não ambientalmente amigáveis e existe uma tendência para que novas rotas venham a ser utilizadas para que exista uma redução significativa dos danos causados à natureza e seres vivos. Esses novos materiais são chamados polihidroxiuretanas e podem ser obtidas através da abertura dos anéis de carbonatos cíclicos quando reagidos com aminas primárias ou secundárias. O ciclocarbonato foi obtido a partir da reação de PDMS e utilizou-se CO2 como matéria prima, o que o torna ainda mais ambientalmente amigável. Neste caso foi utilizado como finalizador de cadeia, 4-(2-aminoethyl)benzene-1,2-diol, conhecido comercialmente como Dopamina. Esta amina foi escolhida por conter em suas extremidades, grupos catecóis que apresentam boa adesão em diferentes substratos em diferentes condições. Os resultados mostraram que o material apresentava uma boa adesão em ligas de titânio e também apresentavam alto grau de hidrofobicidade. O material desenvolvido também foi aplicado em nanotubos de titanato, afim de hidrofobizar o material e melhorar a capacidade de adsorção de compostos orgânicos, como corantes e hidrocarbonetos aromáticos policíclicos. Através de resultados de espectroscopia UV-Vis e Fluorescência Molecular, foi possível constatar a eficácia do nanocompósito para adsorver hidrocarbonetos aromáticos policíclicos e também adsorver e fotodegradar corantes. O material também quando aplicado como revestimento em ligas utilizadas em implantes médicos e odontológicos, apresentou efeito antimicrobiano para a maioria dos micro-organismos testados e quando tratados com prata, apresenta resultados bastante satisfatórios tanto em testes colorimétricos com XTT quanto para halos de inibição de micro-organismos. Desta forma a polihidroxiuretana aqui proposta se mostrou versátil e eficaz para todas as aplicações às quais foram submetidas. / Polyurethanes are materials traditionally obtained by non-environmentally friendly methods and there is a tendency for new routes to be used to significantly reduce the damage to nature and living things. These new materials are called polyhydroxyurethanes and can be obtained by opening the cyclic carbonate rings when reacted with primary or secondary amines. The carbonate cycle was obtained from the PDMS reaction and CO2 was used as feedstock, which makes it even more environmentally friendly. In this case, 4- (2-aminoethyl) benzene-1,2-diol, known commercially as dopamine, was used as the chain terminator. This amine was chosen because it contains at its ends catechol groups that have good adhesion on different substrates under different conditions. The results showed that the material had a good adhesion in titanium alloys and also showed a high degree of hydrophobicity. The material developed was also applied to titanate nanotubes in order to hydrophobize the material and to improve the adsorption capacity of organic compounds, such as dyes and polycyclic aromatic hydrocarbons. Through the results of UV-Vis spectroscopy and Molecular Fluorescence, it was possible to verify the effectiveness of the nanocomposite to adsorb polycyclic aromatic hydrocarbons and also to adsorb and photodegradate dyes. The material also when applied as a coating in alloys used in medical and dental implants, presented antimicrobial effect for most of the microorganisms tested and when treated with silver, presents quite satisfactory results in both colorimetric tests with XTT and for micro-organisms inhibition halos. In this way the polyhydroxyurethane proposed here proved versatile and effective for all the applications to which they were submitted.

Orientador: Isabel Cristina Sales Fontes Jardim / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:12:26Z (GMT). No. of bitstreams: 1 Segato_MilenaPinotti_D.pdf: 2442383 bytes, checksum: e69a88b2ce9ec4c5ba2780755d0a6c2f (MD5) Previous issue date: 2011 / Resumo: Este trabalho descreve o desenvolvimento de novas fases estacionárias (FE) sorvidas e imobilizadas para cromatografia líquida de alta eficiência em fase reversa (CLAE-FR), utilizando-se suporte de sílica não modificada e metalizada com zircônia, recobertos com o polímero poli(dimetilsiloxano-co-metilfenilsiloxano) (PDMFS). O processo de imobilização do polímero foi feito por tratamento térmico e as condições que forneceram FE com o melhor desempenho cromatográfico foram 140 ºC e 6 h. As FE preparadas sob estas condições apresentaram porcentagens de carbono entre 10 e 11 % e espessura de camada entre 0,6 e 0,7 nm. Foi feito o capeamento das FE buscando-se um melhor recobrimento dos sítios ativos do suporte e, após este procedimento, houve um aumento de cerca de 2 % na porcentagem de carbono e redução do número de silanóis livres e vicinais nos suportes cromatográficos. A caracterização físico-química das FE sugere que o PDMFS está fisicamente adsorvido e quimicamente ligado aos suportes, sendo que as interações com o suporte metalizado são mais intensas. As FE foram avaliadas cromatograficamente por meio da separação de algumas misturas teste e seus desempenhos foram similares aos de colunas comerciais tradicionais, com eficiências superiores a 70000 pratos m para o acenafteno, nas FE não capeadas, e acima de 56000 pratos m nas FE capeadas. As características cromatográficas das FE preparadas foram similares no que diz respeito às seletividades hidrofóbica, estérica e aromática. As FE capeadas apresentaram maior hidrofobicidade e menor capacidade de formação de ligações de hidrogênio que as FE não capeadas. A zirconização aumentou a acidez dos sítios ativos e a capacidade de troca iônica das sílicas zirconizadas. Por outro lado, a combinação da zirconização do suporte com o capeamento é uma estratégia importante para a obtenção de FE com estabilidade elevada. As FE desenvolvidas neste trabalho apresentam potencial para serem aplicadas na separação de compostos aromáticos de diferentes polaridades, agrotóxicos e fármacos contendo grupos básicos / Abstract: This work describes the development of new stationary phases (SP) based on poly(dimethylsiloxane-co-methylphenylsiloxane) sorbed and immobilized onto silica and zirconized silica for reversed phase high performance liquid chromatography. The polymer was immobilized by thermal treatment at 140 °C during 6 h, which were the conditions that produced SP with the best chromatographic performance. The SP prepared using these conditions presented carbon loadings between 10 and 11 % and polymeric thicknesses between 0.6 and 0.7 nm. The SP were end-capped aiming at a better coverage of the active sites of the support. This procedure increased the carbon loadings by about 2 % and reduced the number of free and vicinal silanols on the chromatographic supports. Physico-chemical characterization of the SP suggests that PDMFS is physically absorbed and chemically bonded to the supports and that the interactions with the metalized support are stronger. The SP were chromatographically evaluated by the separation of some test mixtures and the performances were similar to those of traditional commercial columns, with column efficiencies higher than 70000 plates m for acenaphthene on the SP without endcapping, and above 56000 plates m with the end-capped SP. The chromatographic characteristics of the SP were similar with regard to hydrophobic, spatial and aromatic selectivities. The end-capped SP presented higher hydrophobicity and lower hydrogen bonding capacity than the not end-capped SP. The metallization procedure increased the acidity of active sites and the ion exchange capacity of zirconized silica. However, the combination of zirconization of the support and the end-capping procedure is an important strategy to obtain SP with high stability. The SP presented potential for the separations of aromatic compounds with different polarities, of pesticides and of pharmaceuticals having basic groups / Doutorado / Quimica Analitica / Doutor em Ciências

No description available.

<p>The analysis of low abundant biological molecules is often challenging due to their chemical properties, low concentration and limited sample volumes. Neuropeptides are one group of molecules that fits these criteria. Neuropeptides also play an important role in biological functions, which makes them extra interesting to analyze. A classic chemical analysis involves sampling, sample preparation, separation and detection. In this thesis, an enhanced solid supported microdialysis method was developed and used as a combined sampling- and preparation technique. In general, significantly increased extraction efficiency was obtained for all studied peptides. To be able to control the small sample volumes and to minimize the loss of neuropeptides because of unwanted adsorption onto surfaces, the subsequent analysis steps were miniaturized to a micro total analysis system (µ-TAS), which allowed sample pre-treatment, injection, separation, manipulation and detection. </p><p>In order to incorporate these analysis functions to a microchip, a novel microfabrication protocol was developed. This method facilitated three-dimensional structures to be fabricated without the need of clean room facilities. </p><p>The sample pre-treatment step was carried out by solid phase extraction from beads packed in the microchip. Femtomole levels of neuropeptides were detected from samples possessing the same properties as microdialysates. The developed injection system made it possible to conduct injections from a liquid chromatographic separation into a capillary electrophoresis channel, which facilitated for advanced multidimensional separations. An electrochemical sample manipulation system was also developed. In the last part, different electrospray emitter tip designs made directly from the edge of the microchip substrate were developed and evaluated. The emitters were proven to be comparable with conventional, capillary based emitters in stability, durability and dynamic flow range. Although additional developments remain, the analysis steps described in this thesis open a door to an integrated, on-line µ-TAS for neuropeptides analysis in complex biological samples.</p>