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No. of bitstreams: 2 Dissertação - Renata Cristina Duarte Marques - 2016.pdf: 8468280 bytes, checksum: 2c71316ea9d9e5c5e0c939c9c9f6b38e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Corn is a most produced and consumed cereal across the world the industrialization of the corn grains by wet milling is one of the methods for obtaining various types of byproducts. The FEBELA Agroindustrial Ltd. have wet milling system changes, which are generated through the process for obtaining starch two co-products, one with fibrous profile and the other with the protein/fat profile, specifically different from the conventional products obtained in this type of processing. The major concern with environmental impacts and the huge waste and loss lead to the need to evaluate the use of these co-products. This study aimed to evaluate the microbiological viability, nutrition and technology of the two co-products produced by the company, through the preparation of flour, physical-chemical study of prepared meals and the use of flour in the preparation of pasta. Microbiological analyzes of wet co-products where it was found the stability and suitability of co-products to the use in the preparation of meals. Flours were analyzed for proximate composition, technological, structural behavior, viscoamylographic and thermal properties. It was observed that the fibrous coproduct derived flour showed higher dietary fiber content, the higher starch concentration and a higher incidence of starch granules of increased size. The flour obtained from protein/fatty co-product showed higher content of proteins and lipids with low viscosity after the process of gelatinization and low gelatinization enthalpy when compared to fibrous flour. The sorption isotherms found for both flours presented the influence of the analysis temperature and can be represented by the mathematical model of Peleg. The combination of 60.05% of semolina, 23.3% of fibrous flour and 16.7% of protein/ fat meals provided an experimental pasta with better sensory acceptance and purchase intent, and desirable baking properties. The milled co-product of fibrous and protein/fat corn, can be an alternative to starch manufacturing industry because add value to waste, which after processing can be employed in the development of several products for human consumption. / O milho é um dos cereais mais produzidos e consumidos em todo o mundo, sendo a industrialização dos grãos de milho por via úmida um dos métodos de obtenção de diferentes tipos de coprodutos. A indústria FEBELA Agroindustrial Ltda apresenta o sistema de moagem úmida com modificações, onde são gerados através do processamento para obtenção de amido dois coprodutos, um com perfil fibroso e outro com perfil proteico/gorduroso, especificamente diferente aos coprodutos convencionais obtidos neste tipo de processamento. A grande preocupação com impactos ambientais e o grande desperdício e perdas, levam à necessidade de avaliação do aproveitamento destes coprodutos. Este estudo teve como objetivo avaliar a viabilidade microbiológica, nutricional e tecnológica dos dois coprodutos produzidos pela empresa, e reaproveitamento através da elaboração de farinhas, com estudo físico-químico e o aproveitamento na elaboração de massas alimentícias. Foram realizadas as análises microbiológicas dos coprodutos úmidos onde foi constatado a estabilidade e adequação dos coprodutos para aproveitamento na elaboração das farinhas. As farinhas foram analisadas quanto à composição proximal, comportamento tecnológico, estrutural, propriedades viscoamilográficas e térmicas. Foi observado que a farinha oriunda do coproduto fibroso apresentou maiores teores de fibra alimentar, maior concentração de amido, e maior incidência de grânulos de amido de maior tamanho. A farinha obtida do coproduto proteico/gorduroso apresentou maior teor de proteínas e lipídios, com baixa viscosidade após o processo de gelatinização e baixa entalpia de gelatinização quando comparada a farinha fibrosa. As isotermas de sorção encontradas para ambas as farinhas apresentaram influência da temperatura de análise e podem ser representadas pelo modelo matemático de Peleg. A combinação entre 60,05% de semolina, 23,3% de farinha fibrosa e 16,7% de farinha proteico/gordurosa proporcionou uma massa alimentícia experimental com melhor aceitação sensorial e intenção de compra, e propriedades de cozimento desejáveis. As farinhas de coproduto de milho fibrosa e proteico/gordurosa podem ser uma alternativa para a indústria de produção de amido, pois agregam valor aos resíduos sólidos, que após processados podem ser empregados no desenvolvimento de diversos produtos para alimentação humana.

Di-2-piridil cetona saliciloilhidrazona (DPKSH) é uma hidrazona que forma compostos de coordenação com diversos íons metálicos. As resinas Amberlite XAD-2 e XAD-7 são polímeros não-iônicos que podem ser usados para a pré-concentração de íons metálicos. A adsorção de DPKSH nessas matrizes poliméricas foi etudada utilizando a espectrofotometria. A quantidade de DPKSH adsorvida nessas resinas foi calculada a partir da diferença entre a concentração inicial a concentração remanescente na solução sobrenadante, após o contato com a fase sólida em diferentes intervalos de tempo. Modelos cinéticos de pseudo-primeira e pseudo-segunda ordens foram aplicados aos dados experimentais coletados no estudo cinético. Outros experimentos realizados com tempo constante, mas variando a concentração inicial de DPKSH, forneceram dados experimentais que foram aplicados a três modelos de isotermas (Langmuir, Freundlich and Dubinin-Radushkevich) e alguns parâmetros termodinâmicos foram calculados para descrever a adsorção. Para a XAD-7, um estudo cinético mais completo foi realizado incluindo concentrações iniciais de DPKSH. A resina XAD-7 modificada com DPKSH foi então utilizada para estudar a retenção de íons Cu(II) usando três sistemas diferentes: (a) espectrofotometria direta; (b) uma coluna de vidro parcialmente preenchida com a resina modificada e (c) usando a técnica de análise por injeção em fluxo (FIA) com uma mini-coluna preenchida com a fase sólida. Finalmente, Cu(II) foi determinado em amostras sintéticas e comerciais de aguardente. / Di-2-pyridyl ketone salicyloylhydrazone (DPKSH) is a hydrazone which forms coordination compounds with several metallic ions. Amberlite XAD-2 and XAD-7 resins are non-ionic polymers which can be used to pre-concentrate metallic ions. Adsorption of DPKSH onto these polymeric matrices was investigated using the spectrophotometry. The amount of DPKSH adsorbed onto the resins was calculated as the difference between the initial concentration and the remained concentration in the supernatant solution, after the contact with the solid phase at different intervals of time. Kinetic models of pseudo-first and -second orders and intra-particle diffusion model were applied on experimental data collected from the kinetic study. Other experiments carried out under a constant time, but changing the initial DPKSH concentration, led to experimental data which were applied to three different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) and some thermodynamic parameters were calculated and used to describe the adsorption. For XAD-7 a more complete kinetic study was carried out including different initial concentrations of DPKSH. The resin XAD-7 modified with DPKSH was then applied to study the retention of Cu(II) ions using three differents systems: (a) direct spetrophotometry; (b) a glass column filled with the modified resin and (c) using the flow injection analysis (FIA) with a mini-column partially filled with the solid phase. Finally, Cu(II) was determined in commercial and synthesized samples of sugar cane brandy.

Orientador: Miriam Gonçalves Miguel / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-19T16:01:32Z (GMT). No. of bitstreams: 1 Barreto_RodrigoPaiva_M.pdf: 3122702 bytes, checksum: 9ac60c09be2b124cf25015606b00e03b (MD5) Previous issue date: 2011 / Resumo: A primeira mina de extração de urânio do Brasil, atualmente em fase de descomissionamento, gerou vários impactos ambientais negativos em sua área, em decorrência dos processos de lavra, tratamento e beneficiamento. A geração de drenagem ácida na pilha de estéril número 4 (PE-4) é um dos impactos negativos gerados com a situação mais crítica. A água ácida, produto desta drenagem, apresenta metais pesados e elementos radioativos e pode estar sendo infiltrada pela base da bacia de captação, onde é feita a coleta desta água para tratamento. O objetivo deste trabalho foi selecionar um solo da área, visando a sua utilização como barreira impermeabilizante de base da bacia de captação desta água ácida, a fim de evitar a contaminação do ambiente. Dessa maneira, foram realizados ensaios geotécnicos e químico-mineralógicos para caracterização de seis solos coletados na área. Um dos solos estudados, coletado próximo à bacia, foi usado em um ensaio de coluna. O solo que obteve o melhor desempenho com relação aos ensaios geotécnicos e químico - mineralógicos com consideração aos limites recomendados pela literatura científica foi escolhido para ser submetido aos ensaios de adsorção em lote e difusão, que foram realizados com soluções de Al, Mn, Fe e F-. O primeiro tipo de ensaio foi realizado com e sem o ajuste de pH das soluções. Os resultados obtidos para o ensaio de adsorção em lote mostrou que, o comportamento de adsorção do solo com relação ao elemento Al não se mostrou diferenciado. No entanto, nos ensaios usando a solução de Mn, o comportamento do solo com e sem ajuste de pH foi distinto, assim como no ensaio com a solução de Fe, com valores de pH entre 3 e 3,5 mas com menor expressividade que o Mn. Para o F-, foi possível determinar a adsorção apenas no ensaio com ajuste de pH, cujo valor foi acima de 4,5. No ensaio de difusão ocorreu a diminuição da concentração dos elementos Al, Mn e F- no reservatório da célula de difusão e na solução retirada dos poros dos corpos-de-prova, em relação à sua profundidade. Já a concentração do elemento Fe apresentou comportamento inverso, aumentando a concentração tanto no reservatório como na solução dos poros do corpo-de-prova. No ensaio de coluna, no tempo de ensaio estudado, ocorreu a adsorção do F- e, possivelmente, do Al. No entanto em relação ao Mn e ao Fe, estes elementos foram dessorvidos, com maior expressividade do Fe. O solo submetido aos ensaios de adsorção em lote e difusão não apresentou características recomendáveis para sua utilização como barreira impermeabilizante, devido à baixa capacidade de adsorção dos elementos Al, Mn e Fe / Abstract: The first uranium extraction mine of Brazil, nowadays, found in decommissioning phase, has generated several negative environmental impacts in its area, as a result of mining, treatment and beneficiation processes. The generation of acid drainage in waste rock pile 4-(WR-4) is one of the negative impacts with the most critical situation. The acidic water, product of this drainage, presents heavy metals and radioactive elements and it may be infiltrated by the basis of the impoundment basin, where this water is collected for treatment. The objective of this research was to select a soil from the area, aiming at its use as a waterproofing barrier basis for the impoundment basin of this acidic water, as to prevent environmental contamination. In this way, geotechnical and chemo-mineralogical tests were conducted in order to characterize six soils collected in the area. One of the studied soils, collected close to the basin, was used in the column test. The soil that obtained the best performance in relation to the geotechnical and chemomineralogical tests, while considering the limits recommended by scientific literature, was selected for submission to batch adsorption tests and diffusion tests, which were conducted with solutions of Al, Mn, Fe and F-. The first test type was carried out with and without pH adjustment of the solutions. The results obtained in the batch adsorption tests indicated that, the adsorption behavior of the soil with relation to the element Al was not differentiated. However, for the pH interval utilized in the tests while using the Mn solution, the soil behavior with and without pH adjustment was distinct, as well as in the tests with the Fe solution, with pH values between 3 and 3.5 but with less expressive than the Mn. For the F-, it was possible to determine the adsorption only on the test done with pH adjustment, with values over 4.5. On the diffusion tests, the decrease on concentration of the elements Al, Mn and F- took place in the diffusion cell reservoir and in the specimen, in relation to its depth. The element Fe presented an inverse behavior, having its concentration increased as much in the reservoir as in the specimen. On the column test using the soil collected near the impoundment basin, the adsorption of F-, and possibly Al, took place during the studied period. Concerning to Mn and Fe, these elements are being transported, with more expressive leaching of Fe. Due to its low adsorption capacity of the Al, Mn and Fe, the soil submitted to batch adsorption and diffusion tests did not present recommendable characteristics to be used as a waterproofing barrier / Mestrado / Geotecnia / Mestre em Engenharia Civil

Alkaloid toxicities negatively impact livestock health and production and are of serious economic concern to animal industries. To date, few strategies have been developed to evaluate alkaloid levels in feed or to counteract alkaloid toxicities. The present research evaluated the applicability of imprinting technology to synthesize polymers that have potential to interact with ergot alkaloids and therefore reduce their bioavailability in the GIT. The studies also evaluated applicability of synthesized polymers for use in the ruminal environment using an in vitro ruminal fermentation model, and for the ability to ameliorate vasoconstriction using ex vivo myographic evaluations. In the first experiment, styrene-based molecularly imprinted polymer (MIP) was synthesized using ergotamine as the imprinting template and evaluated for specificity of adsorption to various ergot alkaloids. Cross reactivity with related alkaloids exists due to similarities in structure and functional groups. Both polymers (MIP and NIP) showed strong adsorption intensity and no difference was observed for estimated maximum adsorption capacity between MIP and NIP. Morphologically, MIP was highly porous with greater surface area than NIP. Solid phase extraction indicated stronger adsorption of MIP than NIP to ergot alkaloids suggesting the potential for MIP as a sorbent material for solid phase extraction (SPE) columns used for sample clean-up prior to HPLC or LC-MS/MS analysis of complex samples. In Experiment 2, methacrylic acid-based polymers were synthesized with ergotamine as a template. Among the 4 alkaloids evaluated for selectivity, adsorption difference between MIP and NIP interacted with alkaloid concentration, although differences were generally consistent across concentrations. Imprinting did not affect lysergol and bromocriptine adsorption, but resulted in higher adsorption to methylergonovine. However, there was no difference between MIP and NIP for adsorption of ergotamine. Hydrophobic interactions and H-bonding were the primary interactive forces between polymers and alkaloid adsorbents. Morphologically, MIP had greater surface area and porosity implying a larger surface for adsorption. In addition to its application as SPE sorbent, this MIP was a suitable candidate for application as a feed adsorbent to reduce the bioavailability of certain alkaloid in the gut. In experiment 3, methacrylic acid-based polymers were evaluated for their effect on in vitro ruminal fermentation. There were no interactions between polymer type and inclusion level, and no differences between polymer types for cumulative gas production or rate of gas production. Total gas production and rate of gas production were unaffected by inclusion level. Polymers did not affect total or individual VFA concentrations, ammonia-N or methane concentration at any inclusion level. However, a logarithmic increase in polymer dose level decreased the pH linearly with maximum depression of 0.24 units. This study indicated that, within the range of expected use levels, polymers were essentially inert and would not be expected to affect ruminal fermentation. In experiment 4, ex vivo myographic bioassays were used to determine the impact of polymers on ergotamine bioavailability. Responses measured in the ex vivo myographic studies had similar trend as the responses generated from in vitro isothermal adsorption studies. Results of that study also showed that ex vivo myographic responses could be predicted from in vitro isothermal adsorption studies with more than 80% accuracy. These studies indicate that synthetic polymers are potentially effective adsorbents to mitigate ergot toxicity with little evidence of substantial differences between MIP and NIP.

Quinones are natural or synthetic organic compounds and play important biological and physiological roles. Among the naphthoquinones, two of them appears as promising compounds: lapachol, found in large quantities in plants of the Bignoniaceae family, and its synthetic isomer, isolapachol. Lapachol and its derivative show several activities against the snail Biomphalaria glabrata, the intermediate host of the helminth Schistosoma mansoni, causative agent of schistosomiasis; against Trypanosoma cruzi, Chagas Disease causative agent and others. Isolapachol shows toxicity against fishes (Tilapia nilótica) and Artemia salina. A fact that can directly interfere in the activity of these substances is their lower solubility in aqueous media. It is necessary to employ of more water soluble derivatives, like their salts. Another substance in study is chitosan, a polisacaride from chitin found in great amounts at crustaceous, insects and fungi. It possesses a several of usefull things, like in treatment of wastewater, and in drug delivery systems. The interaction of lapachol and isolapachol sodium salts (LPS and IPS respectively) with chitosan has not found in literature. The aim of this work was to perform a detailed analysis of the interaction of chitosan, LPS and IPS, to obtain the physical-chemical parameters which influence the of adsorption processes of these substances. The first studies has shown that LPS and IPS undergo a chemical denaturation for a long period of storage time. Another results showed that the LPS and IPS solutions are also chemically instable. It was found that chitosan is fully protonated after 15 minutes of contact time, which was confirmed by the pH increasing to 7,0 after acid contact. The adsorption studies of LPS and IPS showed that both adsorb on chitosan, and those processes are more effective at lower pH solutions. The kinetic studies showed that the adsorptions are fast and the equilibria adsorption are reached after 60 minutes of contact time. Adsorption kinetics fit follows well the pseudo-second-order model. The adsorption isotherms of LPS and IPS exhibit higher amounts of IPS than LPS and both fit preferentially the model described by Langmuir, indicating adsorptions in monolayers on energetically homogeneous surfaces. LPS and IPS adsorptions were also influenced by the increase of ionic strength in solution indicating that the main interaction is of electrostatic nature. The thermodynamic parameters showed that the adsorption processes are spontaneous for the two quinones. In LPS the process is endothermic with positive entropy. In IPS, the adsorption is exothermic with negative entropy. These results shown the importance of the resonance of the naphtoquinonic group with the double bond at the side chain, in the adsorption of LPS and IPS. When the desorption was studied, the presence of a phosphate buffer media influence this process significantly, while the temperature does not affect the process and that the IPS is released in lower amounts that LPS. / Conselho Nacional de Desenvolvimento Científico e Tecnológico / As quinonas são compostos orgânicos sintéticos ou naturais e desempenham uma grande variedade de funções biológicas e fisiológicas. Na classe das naftoquinonas, duas aparecem como compostos promissores: o lapachol, encontrado em abundância em plantas da família Bignoniaceae, e seu isômero sintético, o isolapachol. Diversas atividades foram atribuidas ao lapachol e seu derivado, frente ao hospedeiro intermediário, o caramujo Biomphalaria glabrata e à cercária, forma larval do Schistosoma mansoni, agente causador da esquistossomose; ao Trypanosoma cruzi, causador da Doença de Chagas entre outras; possuindo também toxicidade frente a peixes (Tilapia nilotica) e a Artemia salina. Um fator que pode prejudicar diretamente a atividade destas substâncias são suas baixas solubilidades em meio aquoso, o que faz necessário a utilização de derivados mais solúveis como alguns seus sais. Outra substância estudada é a quitosana, um polissacarídeo derivado da quitina encontrada em grandes quantidades em diversos crustáceos, insetos e fungos. Ela apresenta uma série de aplicações, tais como sua utilização para a remoção de substâncias no tratamento de águas residuais, e em destaque na área de liberação controlada de fármacos. Não existem registros que mostrem a interação entre os sais de sódio do lapachol (LPS) e isolapachol (IPS) e a quitosana. Diante disso a pesquisa com estas substâncias se torna relevante. O objetivo do trabalho consistiu em realizar uma análise detalhada da interação entre a quitosana e o LPS e IPS, visando conhecer os parâmetros físico-químicos que podem influenciar no desenvolvimento da metodologia de adsorção de tais substâncias. Estudos prévios mostraram que o LPS e o IPS sofrem degradação quando estocados por longos períodos de tempo. Outros resultados também mostraram que as soluções destas quinonas também são instáveis, com a solução de IPS sofrendo modificações após 15 dias. Foi visto também que é necessário deixar a quitosana em meio ácido durante 15 minutos para a sua protonação, o que é confirmado pela elevação do pH para 7,0 após este procedimento. Os estudos de adsorção do LPS e do IPS em flocos de quitosana mostraram que ambos adsorvem na quitosana, e que este processo se mostrou mais efetivo em pH igual a 4,0, confirmando a influência da protonação da quitosana na adsorção. Os estudos cinéticos mostraram que a adsorção de ambas as quinonas ocorre de forma rápida, atingindo o equilíbrio em 60 minutos, seguindo o modelo de pseudosegunda- ordem. As isotermas de adsorção do LPS e IPS exibiram maiores quantidades de IPS adsorvido na quitosana e que as duas seguem preferencialmente o modelo descrito por Langmuir, indicando uma adsorção em monocamadas com uma superfície energeticamente homogênea. Esta adsorção também foi influenciada pelo aumento da força iônica indicando que o principal tipo de interação é de natureza eletrostática. Os parâmetros termodinâmicos químicos mostraram que o processo é espontâneo para as duas quinonas. Para o LPS, o processo de adsorção é endotérmico, com entropia positiva. Para o IPS, a adsorção é exotérmica, com diminuição da entropia. Estes resultados mostram a importância da ressonância do grupo naftoquinônico com a ligação dupla na cadeia lateral na adsorção do isolapachonato, em relação ao lapachonato. Quando se avalia a liberação, foi visto que a presença de um meio tamponado em pH 8,0 influencia de forma mais significativa, enquanto que a temperatura não afetou o processo e que o IPS é liberado em uma quantidade sensivelmente menor que o LPS.

Adsorption of radionuclides in granite pores and micropores ABSTRACT This graduation thesis deals with laboratory determination of adsorption isotherms parameters. Granite from the central moldanubian pluton, site Panské Dubenky, Czech Republic, was chosen to the experiment. The place is one of the candidate sites to build a deep nuclear waste disposal. A batch experiment was performed in two modes, differing in the way of addition of radioactive nuclide 90 Sr. From this experiment, distribution coefficients for a linear isotherm or parameters for Langmuir isotherm were obtained. Beside this, a through-diffusion experiment was performed. The objective of this experiment was to identify whether some of the radionuclides used (137 Cs, 90 Sr, 125 I) is able to penetrate through the pores of a granite slice barrier between two solutions of different concentrations. During the period of the experiment no radionuclide was detected reliably.

The sorption characteristics of hexavalent chromium [Cr(VI)] onto bone char and bio-char were evaluated as a function of pH, initial Cr(VI) concentration, and dosages of bone char and bio-char. Batch tests were conducted by using synthetic wastewater in this study. The effects of various initial Cr(VI) concentrations between 5 mg/L and 1000 mg/L were evaluated using bone char as a sorbent. A Cr(VI) removal efficiency of 100 % was achieved at pH 1 with 2 g of bone char in 50 mL of solution at 3 hours of reaction time using initial Cr(VI) concentration of 10 mg/L. About 100 % of Cr(VI) was removed at pH 2 with initial Cr(VI) concentrations of 10 mg/L using 4 g of bio-char in 200 mL of solution at 5 hours of reaction time. The initial Cr(VI) concentrations were varied between 10 mg/L and 500 mg/L when bio-char was used as the sorbent. The maximum sorption capacities of bone char and bio-char were determined to 6.46 mg Cr(VI)/g, and 1.717 mg Cr(VI)/g, respectively. Equilibrium, kinetics, and isotherms of the sorption process were also investigated. The sorption kinetics of Cr(VI) onto bone char and bio-char followed the second order kinetic model suggesting that the sorption reaction rate depends on two parameters, which might be the sorbate concentration and sorbent dosage. The Langmuir isotherm model was the best one for the description of sorption of Cr(VI) onto bone char and bio-char.

No description available.

Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In previous work, a triester (POSS-triester) and a triacid (POSS-triacid) were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl (POSS-OH) and Weisocyanate and fully characterized by surface pressure – area per molecule (Π-A) isotherm and Brewster angle microscopy (BAM) studies at the A/W interface. The results indicated that POSS-triester is surface active forming a liquid expanded (LE) monolayer, whereas POSS-triacid forms a liquid condensed (LC) monolayer that is only weakly affected by pH. A face-on conformation was proposed and examined to understand the packing of POSS-based amphiphilic molecules at the A/W interface. The face-on/vertex-on comparison is rarely discussed for Langmuir monolayers at the A/W interface. In this thesis, three other POSS-based esters were synthesized from POSS-OH and aminopropylisobutyl-POSS (POSS-NH₂) using Weisocyanate and a similar isocyanate containing two tert-butyl protected carboxylic acids. The synthesized materials are characterized by Π-A isotherm and BAM. For POSS-OH based diester (PAlDE) and POSS-NH2 based diester (PAmDE), LE/LC phase transitions were observed in Π-A isotherms over part of the experimentally accessible temperature range and were attributed to a change from a vertex-on to face-on conformation. Apparent BAM images confirmed LC islands coexisted with the LE phase. The experimentally observed dynamic estimates of the critical temperatures (Tc) were estimated from a two-dimensional Clausius-Clapeyron analysis and were consistent with the temperature dependence of the Π-A isotherms. These LE/LC phase transitions are the first observed for POSS amphiphiles. / Ph. D.

Polyhedral oligomeric silsesquioxanes (POSS) have attracted substantial academic interest for many years as hybrid materials and nanofillers for controlling thermal and mechanical properties, and for providing thermal and chemical resistance while retaining ease of processing. A natural extension of these studies has been working on POSS-based amphiphiles and thin film coatings. Studies at the air/water (A/W) interface have shown that trisilanol-POSS derivatives are amphiphilic and form uniform Langmuir films, whereas closed-cage POSS derivatives are hydrophobic and aggregate. In this study, two novel POSS derivatives were synthesized from PSS-(3-hydroxypropyl)-heptaisobutyl substituted (POSS-OH) and completely characterized. Weisocyanate reacted with POSS-OH, and a POSS-based triester (POSS-triester) was obtained. Trifluoroacidolysis of the POSS-triester at room temperature afforded the corresponding triacid (POSS-triacid). Purified POSS-OH, POSS-triester, and POSS-triacid were studied by using surface pressure - area per molecule (? -A) isotherms as well as Brewster angle microscopy (BAM) at the air/water (A/W) interface. Compared with previous work on trisilanol-POSS derivatives, the results indicated that POSS-triester was surface active and formed a liquid-expanded (LE) monolayer. In contrast, POSS-triacid monolayers were more condensed (LC) and were not dramatically affected by changes in pH. Results for the lift-off areas (Alift-off), limiting areas (A0), collapse areas (Ac), and collapse pressures (? c) of POSS-OH, POSS-triester, and POSS-triacid were compared to trisilanolisobutyl-POSS (TiBP) and were interpreted in terms of possible molecular conformations. Whereas, TiBP has been hypothesized to exist in a vertex-on conformation, POSS-OH and POSS-triacid packing at the A/W interface was consistent with face-on conformations. For POSS-triester, the isotherm was consistent with a vertex-on conformation at low ? , but a face-on conformation at high ? . / Master of Science