Made available in DSpace on 2016-03-15T19:36:55Z (GMT). No. of bitstreams: 1 Kelly Cristini Bertachini.pdf: 2103840 bytes, checksum: 660079f6465adb541730be86f9ddd866 (MD5) Previous issue date: 2016-01-21 / Fundo Mackenzie de Pesquisa / The pseudoboehmite is a nanomaterial of fine ceramics type, used in pharmaceutical synthesis and nanosystems to release molecules. It is a material that was obtained by the Mackenzie University materials engineering group by different methods, precipitation and inorganic polymerization. This study investigated the controlled release acyclovir using pseudoboehmite, with emphasis on the determination of acyclovir content in tests carried out by liquid chromatography High Performance (HPLC). Assays were performed "in vivo," demonstrating the effect of addition of pseudoboehmite in controlled drug release. Its controlled release was assessed by the results of analysis of the drug concentration of acyclovir in plasma of "wistar rats", determined by HPLC according to the administration time of the drug in the tests "in vivo". It was concluded that the pseudoboehmite has a role in the controlled release over time, showing that it has higher efficiency compared with the drug administration "wistar rats" without pseudoboehmite. The results showed that the concentration of acyclovir is lower in rats that were gavage with pseudoboehmite. / A pseudoboemita é um nanomaterial do tipo cerâmica fina, usada em sínteses farmacêuticas e nanosistemas para liberação de moléculas. É um material que foi obtido pelo grupo de engenharia de materiais da Universidade Presbiteriana Mackenzie por diferentes métodos, precipitação e polimerização inorgânica. Este trabalho pesquisou a liberação controlada de aciclovir com o uso de pseudoboemita, dando ênfase na determinação do teor de aciclovir em ensaios realizados pela técnica de Cromatografia Líquida de Alta Eficiência (CLAE). Foram realizados ensaios in vivo , demonstrando o efeito da adição da pseudoboemita na liberação controlada do fármaco. Sua liberação controlada foi avaliada pelos resultados da análise de concentração do fármaco aciclovir no plasma sanguíneo de wistar rats , determinada por CLAE em função do tempo de administração do fármaco nos ensaios in vivo . Concluiu-se que a pseudoboemita teve um papel importante na liberação controlada em relação ao tempo, demonstrando que teve maior eficiência comparando-se com a administração do fármaco em wistar rats sem a pseudoboemita. Os resultados mostraram que a concentração de aciclovir é menor nos ratos em que a gavagem foi com pseudoboemita.

Orientador: Marcos Akira D' Ávila / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T19:12:36Z (GMT). No. of bitstreams: 1 Almeida_RosemeiredosSantos_D.pdf: 3414008 bytes, checksum: 9f5516445d3c90d0f22d3a953197d6b7 (MD5) Previous issue date: 2014 / Resumo: O polímero Poli(caprolactona) (PCL) tem sido amplamente usado como biomaterial nas últimas décadas. Sua biocompatibilidade e boas propriedades termo-mecânicas são as principais características que levam à seleção desse material para aplicação nas áreas biotecnológica, farmacêutica e têxtil. Neste trabalho, montou-se um equipamento para realizar o processamento de eletrofiação e caracterização de mantas formadas por fibras de PCL puro e nanocompósitos de PCL/nanotubos de carbono (NTC). Recorreu-se à eletrofiação com a aplicação de um campo elétrico gerado por uma corrente alternada (CA) e por uma corrente contínua (CC) simultaneamente (CA/CC) visando o controle da estabilidade do escoamento do jato polimérico durante o processamento a fim de determinar os parâmetros de processo e comparar os efeitos das diferentes frequências durante o processamento. Foram obtidos também nanocompósitos de PCL/óxido de grafeno (GO) com aplicação de um potencial elétrico em corrente contínua (CC), a fim de determinar os parâmetros de processos em diferentes concentrações de óxido de grafeno. As soluções/suspensões utilizadas no processo foram caracterizadas através de medições de condutividade elétrica, tensão superficial e propriedades reológicas. As fibras obtidas na forma de mantas porosas não-tecidas (non woven) foram caracterizadas por Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR), Calorimetria Exploratória Diferencial (DSC), Análise Termogravimétrica (TGA), Resistividade, Ângulo de contato ensaios mecânicos de tração e ensaios biológicos in vitro com células tronco mesenquimais humanas (hMSCs). Observou-se que o diâmetro médio das fibras depende da frequência CA aplicada durante a eletrofiação. A análise por FT-IR mostrou que houve a interação entre o PCL e o NTC, e as análises biológicas indicaram que as mantas PCL/GO são promissoras para uso como biomaterial / Abstract: Poly (??caprolactone) (PCL) has been widely used as biomaterial in the last decades. Its biocompatibility and good thermomechanical properties are the main features that lead to the selection of this material for applications in biotechnological, pharmaceutical and textile areas. In this work, an equipment was set up to perform electrospinning; characterization of fibrous mats formed by pure PCL fibers and nanocomposites of PCL/carbon nanotubes (CNT). Electrospinning based on the application of an electric field generated by an alternating current (AC) and a direct current (DC) simultaneously (AC/DC) was performed aiming to control the stability of the jet flow of the polymer during processing in order to determine the process parameters and compare the effects of different frequencies during processing. Nanocomposites of PCL/graphene oxide (GO) with application of a DC electrical potential were also obtained in order to determine the process parameters at different concentrations of graphene oxide. Solutions/suspensions employed in the process were characterized by measurements of electrical conductivity, surface tension and rheological properties. The fibers obtained in the form of non- woven porous mats were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), Differential canning Calorimetry (DSC), Thermogravimetric Analysis (TGA), resistivity, contact angle and mechanical properties was measured, and in vitro biological assays with human mesenchymal stem cells (hMSCs) was evaluated. It was observed that the average diameter of the fibers depends on the AC frequency applied during electrospinning. The FT-IR analysis showed that there was interaction between the PCL and the CNTs, and biological analysis indicated that the blankets of PCL/CNT and PCL/GO are promising for use as a biomaterial / Doutorado / Materiais e Processos de Fabricação / Doutora em Engenharia Mecânica

Philosophiae Doctor - PhD / The fascinating optical properties of metallic nanostructures, dominated by collective oscillations of free electrons known as plasmons, open new opportunities for the development of devices fabrication based on noble metal nanoparticle composite materials. This thesis demonstrates a low-cost and versatile technique to produce stimuli-responsive ultrafast plasmonic nanostructures with reversible tunable optical properties. Albeit challenging, further control using thermal external stimuli to tune the local environment of gold nanoparticles embedded in VO2 host matrix would be ideal for the design of responsive functional nanocomposites. We prepared Au-VO2 nanocomposite thin films by the inverted cylindrical reactive magnetron sputtering (ICMS) known as hollow cathode magnetron sputtering for the first time and report the reversible tuning of surface plasmon resonance of Au nanoparticles by only adjusting the external temperature stimuli. The structural, morphological, interfacial analysis and optical properties of the optimized nanostructures have been studied. ICMS has been attracting much attention for its enclosed geometry and its ability to deposit on large area, uniform coating of smart nanocomposites at high deposition rate. Before achieving the aforementioned goals, a systematic study and optimization process of VO2 host matrix has been done by studying the influence of deposition parameters on the structural, morphological and optical switching properties of VO2 thin films. A reversible thermal tunability of the optical/dielectric constants of VO2 thin films by spectroscopic ellipsometry has been intensively also studied in order to bring more insights about the shift of the plasmon of gold nanoparticles imbedded in VO2 host matrix. / South Africa

Polypropylene (PP) has excellent mechanical and chemical properties. Thus, it is used in a wide range of applications. However, like for most polymers, the high flammability of PP limits its application in various fields requiring specific flame-retardant standards. Some of halogenated flame retardants are restricted by European Community directives ROHs, WEEE and REACH. Now metallic hydroxides flame retardants are widely used in industry, but the high loading (about 60 wt %) seriously destroys the mechanical properties of polymeric materials. To improve the performance of flame retardant polymers, an environment-friendly electron beam (EB) technology has been successfully used in modifying flame retardant and polymer matrix. In this work, high efficient functional intumescent flame retardants and functional surfactant are designed and prepared for EB technology. In-depth studies the thermal stability, fire behavior and mechanical properties of these flame retardant PP composites have been studied. The possible graft-linking and cross-linking mechanisms of such EB modified composites can be well established. Specially, it is shown that the novel surfactant has better thermal stability in comparison to traditionally used modifiers. Another part of this work deals with the exploration of novel allylamine polyphosphate (AAPP) as flame retardant crosslinker for PP by electron beam (EB) treatment. Multifunctional AAPP showed unique efficient intumescent flame retardant properties. The limiting oxygen index (LOI) value and the effective melt drop resistance in UL-94 test of multifunctional flame retardant PP composites is greatly enhanced. In the cone calorimeter test, a reduction of peak heat release rate, total heat release and smoke production is achieved. Moreover, EB treatment increased the thermal stability of these designed flame retardant PP composites. Furthermore, AAPP provided an excellent quality of char residue in the combustion stage due to P−N−C and P−O−C structure. In addition, synergistic mechanism of AAPP with montmorillonite (MMT) was explored. Finally, different EB parameters have been used to modify fire retardant polymer nanocomposites. The effects of EB treatment on thermal stability, fire behavior and mechanical properties of fire retardant PP nanocomposites have been discussed. The heat release, the production of toxic gases and the mass loss of EB modified fire retardant PP nanocomposites are delayed in accordance to the result of cone calorimeter test. Based on these results high performance fire retardant polymer nanocomposites can be developed for industrial applications such as insulated material of wire, cable, etc.

Philosophiae Doctor - PhD / The overall aim of this thesis was to prepare nanostructured more processable heteronuclear sulphonated polyanyline nanocomposites with electroconductive properties suitable for applications in biosensors. The sulphonated self-assembled polyaniline and derivatised polyaniline nanocomposites (SPAHs) were prepared by chemical oxidative polymerisation or electrical decomposition. The SPAHs prepared include those of polyaniline (PANi), poly-o-methoxyaniline (POMA) and poly-2.5 dimethoxyaniline (PDMA). Two types of sulphonic acids of heteronuclear aromatic hydrocarbons were used in the production of sulphonated SPAH composites. These were anthracene sulphonic acid (ASA) and naphthalene sulphonic acids (NSA) wich played both doping and surfactant roles. / South Africa

Hydrogen, nature’s simple and the most abundant element has been in the limelight for the past few decades from the stand point of the so-called hydrogen economy. With a high calorific value (142 MJ/kg) that is three times as large as the liquid hydrocarbons, hydrogen has emerged as a promising and environmentally friendly source of energy for the future generations. However, on-board hydrogen storage is one of the bottlenecks for its widespread usage for mobile applications. Storing hydrogen in liquid or compressed form is extremely difficult because of its low density. One of the best alternatives is to store hydrogen in a chemical form. Despite extensive work in this area, none of the materials seem to satisfy the essential criteria of reversible hydrogen storage with high gravimetric content. With regard to chemical hydrogen storage, apart from metal hydrides, ammonia borane (H3N•BH3, AB) is a promising prospect with a very high gravimetric storage of 19.6 wt% of hydrogen. Objectives 1) Develop cost-effective and active first-row transition metal based catalysts for the generation of hydrogen from AB in protic solvents 2) Study the dehydrogenation of AB in fluorinated alcohols and acids in order to realize compounds that are suitable for regeneration. 3) Study the interaction of Cu2+ with AB in non-aqueous medium using 11B NMR spectroscopy and powder XRD techniques. 4) Generation of highly pure hydrogen from ammonia borane in the solid state under mild conditions in the presence of late first row transition metal salts. 5) Synthesis of highly monodisperse ultrasmall colloidal Mg nanoparticles using the Solvated Metal Atom Dispersion (SMAD) method and digestive ripening technique; study the effect of size on the desorption temperature of MgH2. 6) Synthesize Cu/ZnO and Cu/MgO nanocomposites from the individual metal nanoparticles using co-digestive ripening technique and establish the structure of the composites using TEM, EF-TEM, and powder XRD techniques. Significant results Hydrogen generation from AB in protic solvents was realized using first-row transition metal catalysts. Initial studies were carried out using Cu nanocatalyst synthesized by the solvated metal atom dispersion method (SMAD). The activity order was found to be Cu2O > Cu@Cu2O > Cu. In addition, the late first-row transition metal ions, Co2+, Ni2+, and Cu2+ ions were also found to be highly active towards AB hydrolysis. These ions assisted AB hydrolysis via in-situ formation of metal atoms/clusters. Cu2+ assisted the hydrolysis of AB via the in-situ generation of both H+ and Cu clusters. At higher concentrations of AB, hydrolysis resulted in the evolution of NH3 in addition to H2 whereas, methanolysis afforded pure H2. In the case of methanolysis, for catalyst/AB = 0.2, three equiv of H2 were liberated in 2.5, 4.2, and 1.5 min when Co-Co2B, Ni-Ni3B, and Co-Ni-B nanopowders were used as catalysts, respectively. Dehydrogenation of ammonia borane (AB) was carried out in 2,2,2-trifluoroethanol and trifluoroacetic acid in order to realize compounds that are suitable for regeneration. The final byproduct obtained after the catalytic dehydrogenation of AB in 2,2,2-trifluoroethanol was NH4+B(OCH2CF3)4–. The FTIR data showed that the B-O bond in NH4+B(OCH2CF3)4 is slightly weaker compared to that in boric acid. Dehydrogenation of AB in trifluoroacetic acid in a controlled manner resulted in the formation of [CF3COO]–[BH2NH3]+ as the final by-product. Ammonia-borane was regenerated from [CF3COO]–[BH2NH3]+ by its reaction with LiAlH4, which served as the hydride source. Dehydrogenation of AB in non-aqueous medium and in the solid state were studied in hydrogen storage point of view. Cu2+ was found to activate the B–H bond in amine boranes in non-aqueous medium even at room temperature. As a result of the B–H bond cleavage in AB, [H3N•BH2]Cl species is formed. This compound reacts with unreacted AB via 3 separate pathways one involving hydrogen evolution, a second involving formation of a stable diammoniate of diborane cation [(NH3)2BH2]Cl without hydrogen evolution, and the third involving the formation of [H2NBH2]n and BNHx polymers accompanied by the generation of H2. Mechanisms of these pathways have been elaborated using 11B NMR spectroscopy and powder X-ray diffraction methods. These studies demonstrate that Cu(II) salts can be used as effective initiators for the dehydrogenation of amine boranes. Copper-induced hydrogen generation from AB in the solid state was also studied: for Cu2+/AB = 0.05, two equiv of H2 were liberated in 6.5 h at 333 K, which is equal to 9 wt% of the system. The 11B MAS NMR studies showed that the reaction proceeds through the intermediacy of [NH4]+[BCl4]– which eliminates the formation of borazine impurity, thereby affording pure H2. The cost effectiveness of CuCl2 makes this reaction scheme extremely attractive for real time applications. In the context of hydrogen storage in metal hydrides, highly monodisperse colloidal Mg nanoparticles with a size regime of 2–4 nm were synthesized by using the SMAD method followed by digestive ripening technique. The Mg-HDA nanopowder was fully hydrided at 33 bar and 391 K. Onset of hydrogen desorption from MgH2 nanoparticles was observed at a remarkably low temperature, 388 K compared to > 623 K in the case of bulk MgH2. The present study is a step towards realizing hydrogen storage materials that could operate close to ambient conditions. Colloids of Cu and Zn nanoparticles stabilized by 2-butanone have been prepared by the SMAD method. The as-prepared colloids which are polydisperse in nature have been transformed into highly monodisperse colloids by the digestive ripening process in the presence of hexadecylamine. Using this process, copper nanoparticles of 2.1 ± 0.3 nm and zinc nanoparticles of 3.91 ± 0.3 nm diameters have been obtained. Co-digestive ripening of Cu, Zn and Cu, Mg colloids resulted in the formation of Cu/ZnO and Cu/MgO nanocomposites, respectively. The structures of these nanocomposites were established using UV-visible spectroscopy, TEM, EF-TEM, and powder XRD techniques.

Orientadores: Florencia Cecilia Menegalli, Paulo José do Amaral Sobral / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-22T11:03:58Z (GMT). No. of bitstreams: 1 Molina_FrancieleMariaPelissari_D.pdf: 36133234 bytes, checksum: 708a6141c5f96de8a9fbf9b6d371fa0f (MD5) Previous issue date: 2013 / Resumo: Este trabalho de doutorado teve como objetivo estudar o potencial de uso do amido, farinha e nanofibras obtidos a partir de bananas verdes da variedade Terra (Musa paradisiaca) na elaboração de filmes biodegradáveis. Na primeira etapa do trabalho, o amido e a farinha de banana foram caracterizados quanto às propriedades físicoquímicas, funcionais e térmicas. Ambas as matérias-primas apresentaram considerável conteúdo de amido (94,8 e 83,2%, respectivamente) com alto teor de amilose (35,0 e 23,1%, respectivamente) e amido resistente (49,5 e 50,3%, respectivamente), além de fibras, proteínas e lipídios. Numa segunda etapa, filmes a partir de farinha de banana foram elaborados segundo um planejamento experimental. Os resultados obtidos foram analisados estatisticamente empregando a metodologia de superfície de resposta, que juntamente com a função de desejabilidade permitiu a obtenção da formulação e condições de processo ótimas (concentração de glicerol de 19%, temperatura de processo de 81 ºC, temperatura de secagem de 54 ºC e umidade relativa de 48%). Os filmes produzidos sob essas condições apresentaram tensão na ruptura de 9,2 MPa, elongação de 24,2%, módulo de Young de 583,4 MPa, permeabilidade ao vapor de água de 2,1 x 10-10 g/m.s.Pa e opacidade de 51,3%. Na terceira etapa do trabalho, foram elaborados filmes de farinha e amido de banana para determinar o efeito das fibras, proteínas e lipídios sobre as propriedades dos filmes. O filme de farinha de banana foi mais flexível, solúvel em água e opaco, e menos cristalino e resistente mecanicamente quando comparado com o filme de amido de banana. A partir da microestrutura, observou-se que o filme de farinha apresentou imperfeições na sua superfície e uma seção transversal menos densa com pequenas fissuras quando comparado com o filme de amido. Na quarta etapa, a casca da banana (subproduto do processamento da fruta) foi utilizada como matéria-prima para a obtenção de nanofibras de celulose, empregando tratamento químico e mecânico. A influência do número de passagens (0, 3, 5 e 7) das suspensões em um homogeneizador de alta pressão sobre a estrutura das nanofibras foi estudada. Os tratamentos foram efetivos no isolamento de fibras de banana na escala nanométrica (10,9 - 22,6 nm). Conforme o aumento do número de passagens no homogeneizador, nanofibras de celulose mais estáveis, cristalinas e de menor comprimento foram obtidas. Na última etapa, as nanofibras isoladas foram incorporadas na elaboração de nanocompósitos de amido da mesma fonte. As propriedades desses nanocompósitos foram comparadas com as de um filme de amido sem adição de nanofibras (controle), a fim de estudar o efeito deste reforço. Os nanocompósitos apresentaram uma melhora significativa nas propriedades tensão na ruptura, módulo de Young, resistência à água, opacidade e cristalinidade. Uma homogeneização mais drástica (7 passagens) promoveu a degradação das nanofibras, acarretando numa piora das propriedades do nanocompósito resultante, portanto, a condição de tratamento mecânico mais adequada foi de 5 passagens. As propriedades dos nanocompósitos foram relacionadas com as características físico-químicas das nanofibras incorporadas e também com a boa compatibilidade apresentada entre os biopolímeros amido e nanofibras, uma vez que estes foram obtidos da mesma fonte vegetal / Abstract: This doctor thesis aimed to study the potential use of the starch, flour, and nanofibers obtained from unripe bananas of the variety "Terra" (Musa paradisiaca) to develop biodegradable films. In the first stage of the work, banana starch and flour were characterized on the basis of their physicochemical, functional, and thermal properties. Both raw materials exhibited considerable starch content (94.8 and 83.2%, respectively) with high amylose (35.0 and 23.1%, respectively) and resistant starch (49.5 and 50.3%, respectively), besides fibers, proteins, and lipids. In the second stage, films based on the banana flour were prepared according to an experimental design. The results were statistically analyzed using the response surface methodology which, along with the desirability function, furnished the optimum formulation and process conditions (19% for glycerol concentration, 81 ºC for process temperature, 54 ºC for drying temperature, and 48% for relative humidity). Films produced under these conditions presented tensile strength of 9.2 MPa, elongation at break of 24.2%, Young's modulus of 583.4 MPa, water vapor permeability (WVP) of 2.1 x 10-10 g/m.s.Pa, and opacity of 51.3%. In the third stage of the work, films from banana flour and starch were produced and the effect of fibers, proteins, and lipids on the properties of the flour film was studied. The results showed that the flour film was more flexible, soluble in water and opaque as well as less crystalline and mechanically resistant than the starch film. Compared with the starch film, the microstructure of the flour film has flawed surface, less dense cross-section, and small cracks. In the fourth stage, the banana peel (byproduct from fruit processing) was treated chemically and mechanically, to obtain cellulose nanofibers. The influence of the number of passages (0, 3, 5, and 7) in a high-pressure homogenizer on the structure of the nanofibers was investigated. The treatments were able to isolate the banana fibers in the nanometer scale (10.9 - 22.6 nm). Increasing the number of passages in the homogenizer afforded more stable, more crystalline, and less long cellulose nanofibers. In the last stage, the cellulose nanofibers were incorporated into starch nanocomposites from the same source. The properties of these nanocomposites were compared with those of a starch film without nanofibers (control), in order to study the effect of this reinforcement. The nanocomposites exhibited significantly improved tensile strength, Young's modulus, water resistance, opacity, and crystallinity. A more drastic homogenization (seven passages) degraded the nanofibers, deteriorating the properties of the resulting nanocomposite. Thus, the most suitable mechanical treatment condition involved five passages. The properties of the nanocomposites are a function of the characteristics of the nanofibers, such as crystallinity, zeta potential, and aspect ratio; they also depend on the compatibility between the starch and the nanofibers, which were obtained from the same plant source / Doutorado / Engenharia de Alimentos / Doutora em Engenharia de Alimentos

Orientador: Ana Rita Morales / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T15:03:54Z (GMT). No. of bitstreams: 1 Coelho_PauloHenriquedaSilvaLeite_D.pdf: 3760291 bytes, checksum: 22f96d47dee695897cde8e5abc1fc578 (MD5) Previous issue date: 2014 / Resumo: A modificação de matrizes poliméricas isolantes em semicondutoras ou condutoras pela incorporação de cargas de carbono é amplamente difundida. O Negro de Fumo (NF) é a carga condutora mais utilizada e os Nanotubos de Carbono são considerados uma alternativa pelas suas propriedades diferenciadas. Neste trabalho estudou o comportamento destas cargas em nanocompósitos de PMMA obtidos por polimerização in situ. Para a análise da condutividade elétrica dos materiais resultantes foi considerada a teoria da percolação aplicando-se o modelo do volume excluído, que prevê a ocorrência de uma concentração crítica conhecida como o limiar de percolação. O trabalho foi dividido em etapas. Primeiramente foram estudadas as condições de dispersão e de polimerização para a obtenção dos nanocompósitos, obtendo-se as curvas de percolação da condutividade elétrica dos nanocompósitos e determinando o limiar de percolação para os sistemas com Nanotubos de carbono de paredes múltiplas (NTCPM) e NF de alta estrutura. Considerando-se a hipótese de que a combinação de cargas condutoras com diferentes geometrias pode apresentar efeitos diferentes da soma das cargas individuais, investigou-se o efeito da mistura NTCPM e NF em comparação com nanocompósitos das mesmas cargas individuais. Foram encontrados valores de condutividade próximos ao de semicondutores, e limiares de percolação de quase 8 vezes menor para NTCPM em relação ao NF. Para os sistemas híbridos, ou seja, sistemas de misturas das cargas, o limiar de percolação ocorreu para concentração total abaixo dos valores dos nanocompósitosos com as cargas unitárias, indicando o efeito de sinergismo. Por análise de microscopia eletrônica de transmissão observou-se que, morfologicamente, os NTCPM atuaram como filamentos ligando os agregados de NF, o que pode explicar o efeito observado para a menor concentração necessária para a percolação. A modelagem da condutividade elétrica de compósito polimérico com uma carga condutora é muito importante e pode prever o comportamento condutivo dos materiais. Para os sistemas híbridos pouco tem se avançado com relação à modelagem, e isto motivou a segunda parte deste trabalho, quando se levantou a hipótese de que é possível o desenvolvimento de um programa capaz de simular o limiar de percolação e o efeito de sinergismo, utilizando-se o método de Monte Carlo e programado em linguagem Fortran. A simulação foi feita levando-se em consideração a geometria das cargas condutoras para o sistema em duas dimensões. Este método mostrou-se eficaz na previsão do limiar de percolação dos sistemas híbridos e simples sendo uma importante contribuição para a previsão do comportamento de materiais o que permite a redução da quantidade de amostras a ser preparadas num estudo experimental / Abstract: The insulating polymer matrices modification with conductive carbon fillers is widely known. Carbon black is the most used conductive filler and Carbon Nanotubes are considered an important alternative because of its unique properties. The present work studied these fillers behavior in PMMA nanocomposites obtained by in situ polymerization. The electrical conductivity of the materials was analyzed considering the percolation theory by the excluded-volume model, which predicts the critical concentration known as the percolation threshold. The work was divided into steps. First, the nanocomposites dispersion and polymerization conditions were studied, obtaining the percolation curve of the electrical conductivity and determining the percolation threshold for carbon nanotube multi-walled (MWCNT) and high-structure carbon black (CB) nanocomposites. Aiming the hypothesis that conductive fillers combination with different geometries could provide different effect than the additive one, the present study analyzed the effect of the MWCNT and CB mixture on the electrical and dispersion properties of nanocomposites, comparing with individual fillers nanocomposites. The conductive value founded near the semiconductor and percolation threshold 8 times lower for NTCPM that for NF. Hybrid nanocomposites, the percolation threshold achieved total concentration below the singles fillers nanocomposites, showing the synergism effect. From the Transmission Electronic Microscopy, we could notice that, morphologically, the MWCNT acted as filaments linking clusters of the CB, what can explain the lower concentration required for the percolation threshold. Modeling of the electrical conductivity of carbon-filler-filled polymer composites is very important for predicting the conductive behavior of the materials and for material design. There are only few works related to modeling hybrid systems and this motivated the second part of this study considering the hypothesis that could be possible the prediction of the percolation threshold and the synergism effect by a simulator based on the Monte Carlo method programed in FORTRAN. This method demonstrated to be efficient in predicting the hybrid fillers and single fillers systems percolation, which can allow a decrease in the number of samples in an experimental study / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

Orientador: Oswaldo Luiz Alves / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T15:35:46Z (GMT). No. of bitstreams: 1 Moraes_AnaCarolinaMazarinde_D.pdf: 5504556 bytes, checksum: ff8566e313e82701925549e2ecd544ab (MD5) Previous issue date: 2015 / Resumo: O óxido de grafeno (GO) é uma forma quimicamente modificada de grafeno que possui grupos funcionais contendo oxigênio (epóxi, carboxila, carbonila, e hidroxila) distribuídos sobre a base e as bordas de suas folhas. Devido à abundância dos grupamentos oxigenados, o GO tem sido usado como uma plataforma para suportar e estabilizar nanoestruturas metálicas, tais como nanopartículas de prata (NPAgs), visando aplicações biológicas. Além disso, devido à sua excelente capacidade de dispersão e elevada área superficial, o GO tem sido considerado uma carga promissora para a construção de compósitos poliméricos. Neste trabalho, relatamos a síntese do GO e dos nanocompósitos de óxido de grafeno funcionalizado com NPAgs (GO-Ag) os quais podem ser utilizados como agentes antibacterianos de amplo espectro. O GO foi sintetizado por meio do método de Hummers modificado, e o GO-Ag foi preparado através da redução in situ dos íons de prata por citrato de sódio. As folhas de GO foram funcionalizadas com NPAgs esféricas de diâmetro médio de 9,4 nm. Estes nanocompósitos exibiram excelente atividade antimicrobiana contra as principais bactérias em ambiente hospitalar, tais como Escherichia coli, Enterococcus faecalis, Acinetobacter baumannii, e Staphylococcus aureus resistente à meticilina. Os nanocompósitos GO-Ag também foram aplicados como eficazes agentes antimicrobianos a fim de evitar a proliferação bacteriana em membranas de micro e ultrafiltração. Neste sentido, membranas antimicrobianas de acetato de celulose (CA) foram fabricadas a partir da incorporação de GO e GO-Ag na matriz polimérica (CA-GOAg). Após a funcionalização, as membranas permeáveis modificadas com GO-Ag foram capazes de inativar cerca de 90% das células de E. coli em comparação com as membranas de CA não modificadas. Os resultados sugerem que a incorporação de nanocompósitos GO-Ag é uma abordagem promissora para controlar o desenvolvimento da adesão bacteriana em membranas de purificação de água. Com relação à demanda de novos materiais com elevada estabilidade e com capacidade de proteção contra radiação ultravioleta (UV), foram fabricados filmes compósitos transparentes a partir de acetato de celulose e óxido de grafeno. A caracterização físico-química revelou que as folhas de GO estão bem dispersas por toda a matriz polimérica, proporcionando filmes compósitos lisos e homogêneos. Em comparação com os filmes pristinos de CA, os filmes compósitos exibiram melhor capacidade de proteção contra radiação UV combinado com transparência óptica à luz visível, o que reforça a sua aplicação como revestimentos transparentes com proteção UV para alimentos, produtos farmacêuticos, biomédicos, e produtos eletrônicos / Abstract: Graphene oxide (GO) is a chemically modified form of graphene that possesses oxygen-containing groups (epoxy, carboxyl, carbonyl, and hydroxyl) distributed on the plane and edges of the sheets. Owing to the abundance of oxygenated groups, GO has been used as a platform to support and stabilize metallic nanostructures such as silver nanoparticles (AgNPs), aiming biological applications. In addition, GO has been considered a promising material for building polymeric composites because of its excellent dispersibility and high surface area. In this work, we report the synthesis of GO and GO functionalized with AgNPs (GO-Ag) for use as a broad-spectrum antibacterial agent. GO was synthesized through the modified Hummers method, and the GO-Ag was prepared through the in situ reduction of silver ions by sodium citrate. Spherical AgNPs with average size of 9.4 nm were found well-dispersed throughout the GO sheets. This nanocomposite exhibited excellent antimicrobial activity against common nosocomial bacteria such as Escherichia coli, Enterococcus faecalis, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus. GO-Ag nanocomposites were also applied as an effective antimicrobial agent in order to prevent the bacterial proliferation on micro and ultrafiltration membranes. Cellulose acetate (CA) membranes were then fabricated from the incorporation of GO and GO-Ag into the polymeric matrix (CA-GOAg). After functionalization, the permeable CA membranes modified with GO-Ag were able to inactivate mostly 90% of E. coli cells compared to the non-modified CA membranes. The results suggest that the incorporation of GO-Ag nanocomposites is a promising approach to control biofouling development in water purification membranes. Concerning the demand for novel ultraviolet shielding materials with high stability, transparent and UV-shielding composite films were fabricated by casting a mixture of GO with cellulose acetate (CA). The physicochemical characterization revealed that GO sheets were well-dispersed throughout the polymeric matrix, providing smooth and homogeneous composite films. By comparison with pristine CA films, the composite films displayed an improved UV-shielding capacity combined with optical transparency under visible light, which underscores their application as transparent UV-protective coatings for food, pharmaceutical, biomedical, and electronic products / Doutorado / Quimica Inorganica / Doutora em Ciências

[EN] The current PhD thesis deals with the development and characterization of novel nanocomposites based on biodegradable poly(mannitol sebacate) (PMS) matrices with tailored properties and shape-memory capabilities for biomedical applications. Two types of fillers -cellulose nanocrystals (CNC) and electrospun poly(lactic acid) nanofibers (NF-PLA)- were used as reinforcement in order to induce and/or enhance the shape-memory properties of PMS matrices. Also, different crosslinking profiles and stoichiometric ratios between mannitol and sebacic acid (1:1 and 1:2) were studied and evaluated to obtain samples with low and high degrees of crosslinking. An appropriate combination of the crosslinking profile and the monomer ratio for PMS matrix, as well as the addition of low content of CNC, allowed the development of PMS/CNC nanocomposites with a wide range of mechanical properties and degradation profiles. On the other hand, highly oriented poly(lactic acid) (PLA) nanofiber mats obtained by electrospinning were embedded in the PMS matrices. An enhancement of up to 53-fold in the Young's modulus was observed for PMS/NF-PLA nanocomposites filled with 15 wt% of PLA nanofibers. The incorporation of fillers (CNC and NF-PLA) allowed the development of thermally active shape-memory nanocomposites with an enhancement of parameters such as recovery stress and shape fixity. The electrospun PLA-reinforced nanocomposites, offered the best balance of mechanical and thermal properties, as well as a greater control of the transition temperature for switching the change of shape, within a useful range of temperatures. Owing to that, these materials may be of interest as smart responsive systems in long-term biomedical applications. / [ES] La presente tesis doctoral, se centra en el desarrollo y caracterización de nuevos nanocompuestos biodegradables, a partir de matrices de poli(mannitol sebacato) (PMS) con propiedades a medida y capacidades de memoria de forma para aplicaciones biomédicas. Dos tipos de cargas -nanocristales de celulosa (CNC) y nanofibras de ácido poliláctico (NF-PLA) obtenidas mediante electrospinning- se han utilizado como refuerzo, con la finalidad de inducir y/o mejorar las propiedades de memoria de forma en matrices de PMS. Se han estudiado y evaluado diferentes tratamientos de curado y ratios de reacción entre el mannitol y ácido sebácico (1:1 y 1:2), con la finalidad de obtener muestras con bajo y alto grado de reticulación. Una combinación adecuada del tratamiento de curado y el ratio entre monómeros del PMS, así como la adición de bajos contenidos de CNC, permitió desarrollar nanocompuestos de PMS/CNC con un amplio rango de propiedades mecánicas y perfiles de degradación. Por otro lado, se han producido mats de nanofibras de ácido poliláctico (PLA) con alta orientación mediante la técnica de electrospinning, para embeberse en matrices de PMS, observándose una mejora de hasta 53 veces en el módulo de Young para nanocompuestos de PMS/NF-PLA con un 15% en peso de nanofibras. La incorporación de cargas (CNC y NF-PLA) permitió el desarrollo de nanocompuestos con memoria de forma activada térmicamente, con una mejora de parámetros tales como la fuerza de recuperación y la capacidad de fijación. Los nanocompuestos reforzados con NF-PLA obtenidas por electrospinning, ofrecieron el mejor balance de propiedades mecánicas y térmicas, así como un mayor control de la temperatura de transición para la activación del cambio de forma en un intervalo útil de temperaturas. Por todo ello, estos materiales pueden resultar de interés como sistemas activos en aplicaciones biomédicas de larga duración. / [CAT] La present tesi doctoral se centra en el desenvolupament i caracterització de nous nanocompostos biodegradables a partir de matrius de poli(mannitol sebacato) (PMS) amb propietats a mesura i capacitats de memòria de forma per a aplicacions biomèdiques. Dos tipus de càrregues -nanocristals de cel·lulosa (CNC) i nanofibres d'àcid polilàctic (NF-PLA) obtingudes mitjançant electrospinning- s'han utilitzat com a reforç amb la finalitat d'induir i/o millorar les propietats de memòria de forma en matrius de PMS. S'han estudiat i avaluat diferents tractaments de curat i ràtios de reacció entre el mannitol i àcid sebàcic (1:1 i 1:2) amb la finalitat d'obtenir mostres amb baix i alt grau de reticulació. Una combinació adequada del tractament de curat i el ràtio entre monòmers del PMS, així com l'addició de baixos continguts de CNC, va permetre desenvolupar nanocompostos de PMS/CNC amb un ampli rang de propietats mecàniques i perfils de degradació. D'altra banda, s'han produït mats de nanofibres d'àcid polilàctic (PLA) amb alta orientació mitjançant la tècnica de electrospinning, per embeure's en matrius de PMS, observant-se una millora de fins a 53 vegades en el mòdul de Young per nanocompostos de PMS/NF-PLA amb un 15% en pes de nanofibres. La incorporació de càrregues (CNC i NF-PLA) va permetre el desenvolupament de nanocompostos amb memòria de forma activada tèrmicament, amb una millora de paràmetres tals com la força de recuperació i la capacitat de fixació. Els nanocompostos reforçats amb NF-PLA obtingudes per electrospinning, van oferir el millor balanç de propietats mecàniques i tèrmiques, així com un major control de la temperatura de transició per a l'activació del canvi de forma en un interval útil de temperatures. Per tot això, aquests materials poden resultar d'interés com a sistemes actius en aplicacions biomèdiques de llarga durada. / Sonseca Olalla, A. (2015). DEVELOPMENT OF SHAPE-MEMORY COMPOSITES BASED ON A BIODEGRADABLE POLYESTER ELASTOMER [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54129 / TESIS