Titanium been used industrially for nearly a century. Ever since it was first reduced to its elemental form, concerted efforts have been made to improve the material and to reduce the cost of production. In this thesis, titanium is mechanically alloyed with cellulose nanocrystals followed by powder consolidation and sintering to form a solid titanium metal matrix composite. Cellulose nanocrystals (CNCs) were chosen as the particle reinforcement as they are a widely abundant and natural material. Additionally, the nanocrystals can be derived from waste materials such as pistachio shells. This offers a unique advantage to act as a green process to enhance the mechanical properties of the titanium as well as to reduce to cost of production. Vibrational milling using a SPEX 8000M mill was used to mechanically alloy titanium powder with varying concentrations of CNCs. Additionally, the milling time was varied. This process showed that varying the concentrations of CNCs between 0.5% - 2% by weight did not noticeably alter the microstructural or mechanical properties of the materials. Conversely, changing the milling time from 0.5 hours to 5 hours proved to greatly alter the microstructural and mechanical properties of the titanium matrix metal composites. Further increasing the milling time to 10 and 25 hours caused the materials to become exceedingly brittle thus, the majority of experiments focused on samples milled between 0.5 hours and 5 hours. The hardness values for the Ti-1%CNC materials increased from 325-450-600-800 for the samples milled for 0.5, 1, 2, and 5 hours respectively. The other concentrations used were found to yield similar values and trends. SEM micrographs showed that small precipitates had formed within the grains except materials milled at 5 hours, which showed the production of very coarse particles at the grain boundaries. Similarly, an attrition mill was used to mechanically alloy titanium with varying CNC concentrations. Milling time was also varied. The powders were consolidated, sintered and characterized. It was found that increasing CNC content at low milling times caused a reduction in hardness. The X-ray diffractograms also showed a trend in that the diffraction patterns shifted to the lower angle with increasing CNC concentration, thereby suggesting that the increase in CNC content facilitated the removal of oxygen atoms housed within the interstitial sites. The oxygen was observed to diffuse and precipitate platelet titanium dioxide particles. These particles were found to be located within the titanium grains and coarsened with milling time. Generally, increasing the milling time to 15 hours was found precipitate particles at the grain boundaries as well as to excessively dissolve oxygen into the titanium lattice leading to embrittlement. The materials milled for 5 hours showed the best increase in strength while maintaining good ductility. / Master of Science / Titanium has only been used industrially since the early 1940’s thanks in large to the modern advances to reduce titanium ore to its elemental state. Titanium gained much interest as a structural material because of its corrosion resistance and its exceptional strength for a lightweight metal, making the material ideal for medical and aerospace applications. Pure titanium was found to be soft and had poor wear resistance, therefore, efforts were made to create titanium alloys which mitigated these weaknesses. Often titanium is alloyed with costly and toxic elements to enhance its strength properties, making it dangerous to use in the medical field. One way to enhance the strength properties of titanium without the addition of these harmful alloying elements is to create a titanium composite by adding strong inert particles to a titanium matrix. One method to create titanium metal matrix composites is to violently mix titanium powder with the reinforcement material, through a process called mechanically alloying. Following the mixing process the powder is then compacted and heated to form a solid part through a process called sintering. While these powder processing methods are known and viable for forming titanium metal matrix composites, some of the reinforcement materials can be expensive. In this thesis, cellulose nanocrystals (CNCs) will be added as reinforcement to titanium by means of two mechanical alloying processes, vibratory milling (shaking) and attrition milling (stirring). CNCs can be derived from plant matter which is widely abundant and inexpensive. The viability of CNCs to be used as a reinforcement material, as well as the mechanical alloying processes were investigated to determine the effect on the titanium strength properties. The powder processing steps were found to cause the CNCs to react with the surrounding titanium matrix which caused beneficial oxides to form as the reinforcement materials. In general, it was found that vibratory milling caused the final titanium metal matrix composite to be hard and brittle. Attrition milling was found to be more favorable as some materials were observed to be strong yet ductile.

This thesis identifies a facile and versatile technique for creating multi-scale porous titania with tunable meso-scale morphology. Three templating approaches were simultaneously utilized in achieving this; namely, soft-templating by template-free self-assembly of an aligned macroporous structure, freeze-casting for the preservation of particle dispersion found in suspension, and hard-templating by the use of cellulose nanocrystals (CNCs) as sacrificial material. A systematic study was conducted wherein three synthesis parameters (water content, alcohol solvent content, and drying method) were varied in the hydrolysis of titanium tetra-isopropoxide (TTIP) by the sol-gel method to determine their contribution to the formation of multi-scale porous titania exhibiting aligned macrochannels and mesoporosity. The optimal synthesis settings for producing multi-scale porous titania were identified as H2O/TTIP molar ratio of 30, without any isopropanol (acting as solvent), and freeze-drying after freezing at -40°C. Subsequently, CNCs were added in various quantities (0-50vol%) to the hydrolysis of TTIP using these optimized settings to achieve more direct and precise control of the final titania meso-structure. Morphological studies revealed that the final titania bodies maintained the formation of macrochannels 1-3 μm in diameter as a result of hydrolysis in excess water in the absence of an organic solvent and exhibited successful templating mutually affected by CNC addition and freeze-casting. Freeze-drying preserved particle dispersion in the colloid suspension, hindering agglomeration otherwise found after oven-drying and enhanced the CNCs' role of disrupting titania aggregation and increasing interconnectivity. Thus, meso-structured multi-scale porous titania was prepared by a combined templating strategy using template-free self-assembly, freeze-casting, and CNC hard-templating. / MS / Titanium dioxide (TiO₂) has been shown to exhibit desirable properties including physical and chemical stability and biocompatibility making it a material of great interest in a variety of fields including pigments and biomedicine. Furthermore, the material’s photocatalytic activity (i.e. ability to absorb light energy to generate usable charge) has led to its implementation in solar cells, in the production of hydrogen as an eco-friendly fuel, and in decontaminating water from organic pollutants. While TiO₂ has shown great promise in these applications, there remains a need to identify a simple strategy to synthesize TiO₂ with a tunable multi-scale porous structure with pores of different sizes and shapes to improve its performance. To this end, a facile and versatile procedure was used to prepare multi-scale porous TiO₂ with tunable morphology. In investigating the effect of water content, alcohol content and drying method on the final morphology, a multi-scale structure was achieved by synthesizing TiO₂ in the absence of an alcohol solvent and within a new moderate range of water content that had not been previously explored. Lacking an effective and easy strategy to further manipulate the multi-scale morphology, this self-assembly technique was modified by incorporating cellulose nanocrystals (CNCs) into the synthesis procedures to further tune the structure on the nanometric scale by altering the final porosity and surface area. The final TiO₂ samples exhibited multi-scale porous structures that could be manipulated by combining the self-assembly and CNC-templating techniques in an adaptable strategy to tailor the TiO₂ morphology for its various uses in photocatalysis and biomedicine.

As celuloses nanocristalinas (CNC) são partículas de, pelo menos, uma dimensão nanométrica, possuem baixa densidade, alta resistência e área de superfície para realizar modificações químicas, podendo melhorar as propriedades de materiais compósitos. O método mais tradicional para isolar CNC é por hidrólise ácida com ácido sulfúrico, porém este procedimento apresenta desvantagens. Além disso, a ação não seletiva do ácido também ataca as regiões cristalinas levando a um baixo rendimento de produção, e a obtenção de uma suspensão muito diluída de açúcares solubilizados e outros compostos indesejáveis, o que inviabiliza a recuperação dos açúcares. Outra possibilidade para o isolamento de CNC envolve a utilização de preparos enzimáticos de celulases, uma alternativa promissora. Porém, a utilização de baixa carga de polpa celulósica e alta quantidade de enzima tipicamente utilizadas na rota enzimática para obter nanocristais são fatores limitantes. A fim de tentar superar estes problemas, este trabalho teve como objetivo avaliar um sistema de tratamento enzimático em duas etapas para possibilitar a condução do tratamento enzimático em alta concentração de polpa celulósica e baixa dose de enzimas e permitir a produção de CNC e recuperar os açúcares solubilizados em alta concentração. Os resultados mostraram que ao realizar uma hidrólise com baixa carga de sólidos e com suplementação de ?- glicosidade foi possível obter uma conversão de celulose 30% maior, mas uma significativa redução da eficiência enzimática foi observada quando a carga de sólidos foi aumentada, mesmo utilizando a suplementação.Por meio do sistema de duas etapas, foi possível obter uma conversão de celulose e uma concentração de açúcares relativamente alta, além de obter CNC com propriedades comparáveis as obtidas em situações tradicionais de hidrólises. No entanto, o diferencial da hidrólise aplicando o sistema de duas etapas se caracterizou pela utilização de, aproximadamente, metade da quantidade de enzimas utilizadas nas hidrólise tradicionais. Alem disso, o sistema em duas etapas possibilitou a reciclagem das enzimas não adsorvidas para reações de hidrólises subsequentes, se mostrando mais um fator de destaque para a área de conversão enzimática. Conclui-se, portanto, que este sistema se mostrou muito eficiente e promissor o que é interessante do ponto e vista econômico para processos subsequentes à hidrólise. / Nanocrystalline celluloses (CNC) are particles of at least one nanometric dimension, have low density, high strength and surface area to perform chemical modifications, and can improve the properties of composite materials. The most traditional method for isolating CNC is by hydrolysis with sulfuric acid, however this procedure has drawbacks. In addition, the non-selective action of the acid also attacks the crystalline regions leading to a low yield of production, and obtaining a very diluted suspension of solubilized sugars and other undesirable compounds, which impairs prevents the recovery of sugars. Another possibility for the isolation of CNC involves the use of enzymatic preparations of cellulases, a promising alternative. However, the use of low cellulosic pulp load and high amount of enzyme typically used in the enzymatic route to obtain nanocrystals are limiting factors. In order to overcome these problems, this work had as objective to evaluate a system of enzymatic treatment in two stages to enable the conduction of the enzymatic treatment in high concentration of cellulose pulp and low dose of enzymes and to allow the production of CNC and to recover the solubilized sugars in high concentration. The results showed that when hydrolysis was carried out with low solids loading and with ?-glycoside supplementation, 30% higher cellulose conversion was achieved, but a significant reduction of the enzymatic efficiency was observed when solids loading was increased, even using by means of the two-stage system, it was possible to obtain relatively high cellulose conversion and sugar concentration, in addition to obtaining CNCs with properties comparable to those obtained in traditional hydrolysis situations. However, the differential of the hydrolysis applying the two-stage system was characterized by the use of approximately half the amount of enzymes used in traditional hydrolysis. In addition, the two-step system allowed the recycling of the non-adsorbed enzymes to subsequent hydrolysis reactions, showing another important fator for the enzymatic conversion area. It is concluded, therefore, that this system proved very efficient and promising what is interesting from the economic point of view of processes subsequent to the hydrolysis.

Made available in DSpace on 2017-07-10T17:37:11Z (GMT). No. of bitstreams: 1 Jessica Cristina Urbanski Laureth.pdf: 1753789 bytes, checksum: 5516d92f3757c43a94720173f562bc89 (MD5) Previous issue date: 2016-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Edible coatings may assist improvement of quality and conservation of fruits. Polysaccharide polymers, such as starch, pectin and cellulose have been constantly used as base to form coatings, but their physical properties do not provide proper barrier to gas and water vapor diffusion. Cellulose nanocrystals, when incorporated to edible coatings may improve their barrier properties. The addition of a natural antioxidant to the coating may improve conservation capacity of fruit. Natural antioxidants have relative instability, which may limit its reducing properties. Nevertheless, including nanocrystals may aggregate higher stability to added antioxidant. Thus, the objective of this research was assessing the effect of polymeric coatings, along with cellulose nanocrystals and vegetable extract on the physiology of Persian lime. It consisted of two experiments, the first assessed the effect of pectin (PEC), starch (ST) and cellulose gum (CMC) polymers added to cellulose nanocrystals (CN). The second differed from the first due to the addition of peanut peel extract, chosen because it has higher rates of antioxidant activity by DPPH, ABTS and FRAP methods in comparison with extracts of Persian lime and Rangpur seeds. In both experiments the assessments occurred during nine storage days under 23 °C ± 2 °C. Ethylene, CO2, fresh mass loss, firmness and chlorophyll were assessed. In the second were included DPPH, ABTS and FRAP antioxidant activity analyses, as well as total phenolic composites and ascorbic acid. In the first experiment, coatings formed by CMC, PEC and ST pure polymers with their respective nanocomposites called NCMC, NPEC and NST were efficient to reduce ethylene production until first three storage days. Among tested treatments, NPEC nanocomposite (12.01 mg CO2 kg-1 h-1) was more efficient than PEC (14.93 mg CO2 kg-1 h-1) to inhibit CO2 diffusion. PEC polymer when reinforced by NC (NPEC) was the only coating to reduce fresh mass loss of Persian lime, and it was also more efficient than PEC pure polymer when it comes to retention of chlorophyll. All tested nanocomposites and pure polymers were similarly efficient to keep fruit s firmness. In the second experiment the combination of pectin, cellulose gum, nanocrystals and extract was responsible to present lower ethylene and CO2 production rates. All tested coatings slowed fresh mass and firmness loss of fruits, but pectin and cellulose gum active nanocomposite was the coating able to contribute to the lowest rate of fresh mass loss and to highest rate of fruit s firmness retention, but the addition of extract did not influence these results. The reinforcement with cellulose nanocrystals was able to retain antioxidant activity off added coatings, which consisted of peanut peel extract. This research showed that pectin coatings, based on nanocrystals and the coatings from polymeric combination of pectin and cellulose gum, along with peanut peel extract and nanocrystals, presented better barrier properties against gases and water vapor, based on physiologic and physicochemical indicators / Revestimentos comestíveis podem auxiliar na qualidade e conservação de frutos. Polímeros de polissacarídeos, como amido, pectina e celulose têm sido muito utilizados como base de formação de revestimentos, mas suas propriedades físicas não proporcionam barreira adequada à difusão de gases e vapor d´água. Nanocristais de celulose, quando incorporados a revestimentos comestíveis, podem melhorar suas propriedades de barreira. A adição de um antioxidante natural ao revestimento pode melhorar a capacidade de conservação do fruto. Antioxidantes naturais possuem relativa instabilidade que pode limitar suas propriedades redutoras. No entanto, a inclusão de nanocristais pode agregar maior estabilidade ao antioxidante adicionado. Assim, o objetivo deste trabalho foi avaliar o efeito de revestimentos poliméricos, adicionados com nanocristais de celulose e extrato vegetal na fisiologia e qualidade pós-colheita da lima ácida Tahiti. O trabalho foi dividido em dois experimentos. O primeiro consistiu na avaliação do efeito de polímeros de carboximetilcelulose (CMC), pectina (PEC) e amido (AM), adicionados de nanocristais de celulose (NC). O segundo diferiu do primeiro pela adição de extrato de película de amendoim, escolhido por possuir maiores valores de atividade antioxidante pelos métodos DPPH, ABTS e FRAP em comparação aos extratos de casca de lima ácida Tahiti e semente de limão Cravo. Em ambos experimentos as avaliações ocorreram durante 9 dias de armazenamento a 23 °C ± 2 °C. Etileno, CO2, perda de massa fresca, firmeza e clorofila foram avaliados nos dois experimentos. No segundo foram incluídas as análises de atividade antioxidante pelos métodos DPPH, ABTS e FRAP, compostos fenólicos totais e ácido ascórbico. No primeiro experimento, os revestimentos formados com os polímeros puros CMC, PEC e AM e com os seus respectivos nanocompósitos chamados NCMC, NPEC e NAM foram eficazes em reduzir a produção de etileno até os primeiros três dias de armazenamento. Entre os tratamentos testados, o nanocompósito NPEC (12,01 mg CO2 kg-1 h-1) foi mais eficiente em inibir a difusão de CO2 do que o polímero puro PEC (14,93 mg CO2 kg-1 h-1). O polímero PEC quando reforçado com NC (NPEC) foi o único revestimento que pôde reduzir a perda de peso fresco de lima ácida Tahiti, e também foi mais eficiente na retenção de clorofila do que o polímero puro PEC. Todos os nanocompósitos ou polímeros puros testados foram similarmente eficientes em reter a firmeza dos frutos. No segundo experimento a mistura de pectina e carboximetilcelulose, nanocristais e extrato foi responsável por apresentar as menores taxas de produção de etileno e CO2. Todos os revestimentos testados retardaram as perdas de massa fresca e de firmeza dos frutos, mas o nanocompósito ativo de pectina e carboximetilcelulose foi o revestimento capaz de influenciar a menor perda de massa fresca e reter a maior firmeza, mas a adição de extrato não influenciou esses resultados. O reforço com nanocristais de celulose foi capaz de reter atividade antioxidante dos revestimentos adicionados de extrato de película de amendoim. Este estudo mostrou que revestimentos de pectina, baseados em nanocristais e revestimentos da mistura polimérica de pectina e carboximetilcelulose, adicionais de extrato de película de amendoim e nanocristais, apresentaram melhores propriedades de barreira a gases e ao vapor de água, baseados nos indicadores fisiológicos e físico-químicos

Contrairement à leurs homologues animales, les cellules végétales sont entourées d’une fine enveloppe de polysaccharides appelée paroi primaire, dont la principale structure portante est un réseau de microfibrilles de cellulose reliées entre elles par des hémicelluloses. L’objectif de ce travail est de mettre au point des capsules biomimétiques de la paroi végétale qui puissent servir de système modèle dans l’étude des propriétés mécaniques de ce matériau naturel. Pour ce faire, des vésicules géantes unilamellaires d’un diamètre moyen de 20 µm ont été utilisées comme support de dépôts couche-par-couche de nanocristaux de cellulose (les sous-éléments des microfibrilles) et de xyloglucane (l’hémicellulose la plus répandue) jusqu’à une dizaine de bicouches, les capsules ainsi obtenues ayant été caractérisées par microscopie confocale. Leur comportement en déformation en réponse à une pression osmotique a pu être observé : leur dégonflement a donné lieu à l’apparition de diverses morphologies dont certaines sont similaires aux formes de coques minces de matériau isotrope dégonflées, tandis que leur comportement en gonflement est comparable à la réponse d’un matériau viscoélastique. Enfin, des expériences de nano-indentation par microscopie à force atomique ont été effectuées pour mesurer la rigidité de la paroi des capsules. Leur module d’Young a pu être déduit des courbes de force-déformation et s’avère être compris entre 6 et 18 MPa, ce qui est du même ordre de grandeur que les valeurs obtenues par des mesures similaires effectuées sur des parois végétales naturelles. / Unlike their animal counterparts, plant cells are surrounded by a thin polysaccharide-rich envelop called the primary wall, in which the main load-bearing structure is a network of cellulose microfibrils tethered by hemicellulose. This work aims at designing plant cell wall mimicking capsules that could be used as a model system in the mechanical characterization of this natural material. To do so, we used giant unilamellar vesicles with an average diameter of 20 µm as a template for the layer-by-layer deposition of cellulose nanocrystals (the microfibrils sub-elements) and xyloglucan (the most common hemicellulose) up to ten bilayers, the resulting capsules being characterized by confocal microscopy. Their deformation behaviour under osmotic stress could be observed : deflation of the capsules led to various morphologies, some of them similar to what is observed for thin deflated shells of isotropic material, while their response to swelling resembled that of a viscoelastic material. Nano-indentation experiments were eventually performed using an atomic force microscope to probe the stiffness of the capsules wall. Their Young’s modulus could be deduced from the force-depth curves and found to be in the 6-18 MPa range, which is in the same order of magnitude of values obtained with similar measurements done on natural plant cell walls.

L’originalité de ce projet consiste au développement et à l’étude de nouvelles structures hybrides à base de nanocelluloses et de polymères stimulables. En particulier, c’est le design d’hydrogels aux propriétés thermosensibles qui est visé. Les nanocelluloses - nanoparticules issues de la cellulose - sont de deux types : les nanocristaux de cellulose (CNCs) et les nanofibrilles de cellulose (CNFs) et possèdent des propriétés bien particulières. Cette étude s’est concentrée sur l’élaboration d’hydrogels de CNCs. Plusieurs polymères thermosensibles ont été utilisés pour leur biocompatibilité et leur température de solution critique (LCST) aux abords de la température du corps humain. Ce travail a consisté en (i) la préparation des systèmes sur les principes de la chimie verte, (ii) l’étude rhéologique de ces gels thermosensibles et (iii) l’élaboration d’applications à forte valeur ajoutée pour ces biomatériaux uniques. A travers l’utilisation de grands équipements (SANS, SAXS), les interactions physico-chimiques CNCs/polymères ont été étudiées. L’utilisation de block copolymères a permis l’obtention de suspension de CNCs aux propriétés rhéologiques spécifiques : de liquide a température ambiante à gel viscoélastique à température du corps. D’un point vue applicatif, les hydrogels ainsi réalisés ont permis le déploiement de systèmes injectables pour le biomédical ainsi que des surfaces thermosensibles.Mots clés : nanocristaux de cellulose, hydrogel, thermosensible, stimulable / This project consists to develop and study new hybrid structures based on nanocelluloses and stimuli-responsive polymers, in particular, thermo-responsive polymers. Nanocelluloses - nanoparticles extracted from cellulose - exist in two forms: cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). This study focused on the design of CNCs hydrogels with stimuli-responsive polymers. Several thermo-responsive polymers have been used for their biocompatibility and lower critical solution temperature (LCST) close to body temperature. This work consisted of (i) preparation of systems using the principles of green chemistry, (ii) the rheological study of these thermo-sensitive hydrogels, and (iii) the development of smart applications for these unique biomaterials. Through the use of state of the art technologies (SANS, SAXS), physicochemical interactions between the polymers and CNCs have been studied. The use of block copolymers made it possible to create CNCs-based hydrogels with specific rheological properties: liquid at ambient temperature to viscoelastic gel at body temperature. These hydrogels can be used in the creation of injectable systems for biomedical applications, as well as thermosensitive surfaces.Key-words: Cellulose nanocrystals, hydrogel, thermo-responsive, stimuli-responsive

La déformation des cellules végétales durant leur croissance génère des formes anisotropes variées. L'enveloppe des cellules en croissance, appelée paroi primaire végétales, est une couche fine, flexible et extensible, faite d'un réseau de microfibrilles de cellulose reliées entre elles par des hémicellulose qui ont une extension directionnelle. Le but de ce travail est d'élaborer des microcapsules biomimétiques possédant une structure similaire à la paroi primaire et d'étudier leur déformation sous une contrainte mécanique. Pour cela, nous avons utilisé les fortes interactions entre les nanocristaux de cellulose (sous-unités des microfibrilles) et les xyloglucanes (hémicellulose la plus répandue) déjà utilisée pour construire des multicouches plan [1]. Pour reproduire la géométrie des cellules, nous avons fabriqué des microcapsules multicouches à partir de nanocristaux de cellulose et de xyloglucanes, en combinant une émulsion d'huile dans l'eau, de dimension de 20µm environ, avec un dépôt couche par couche conduisant à des capsules biomimétiques. La régularité du dépôt de couche a été suivit par un marquage fluorescent sélectif, l'épaisseur et l'organisation de la paroi ont été caractérisées en microscopie électronique. Par séchage et évaporation du coeur d'huile, les capsules ainsi dégonflées présentent diverses formes révélées par des reconstructions 3D à partir de coupes de microscopie confocale. La relation entre les formes obtenus, les dimensions caractéristiques et les propriétés mécaniques de la paroi a été étudiée [2]. Le contrôle de la taille et de l'épaisseur de la capsule permet d'explorer diverses situations de déformations. [1] B. Jean*, L. Heux, F. Dubreuil, G. Chambat & F. Cousin, Non-electrostatic building of biomimetic cellulose-xyloglucan multilayers, Langmuir, 25(7), 3920-3923 (2009) [2] C. Quilliet, C. Zoldesi, C. Riera, A. van Blaaderen, and A. Imhof Anisotropic colloids through non-trivial buckling Eur. Phys. J. E, 27, 13{20} (2008) / The deformation of plant cells during their growth can generate various anisotropic shapes. The envelop of the growing cells, also called primary wall of plants, is a thin, flexible and extensible layer made of a network of cellulose microfibrils linked by hemicellulose tethers, that can have directional extension. The goal of this work is to elaborate biomimetic microcapsules with structures similar to the plant primary walls and explore their deformation under mechanical stress. For that purpose, we took advantage of the strong interaction of cellulose nanocrystals (the microfibrils sub-elements) with xyloglucan (the most common hemicellulose) already used to build planar multilayer systems [1]. In order to reproduce the cell geometry, we successfully build multilayered microcapsules from cellulose nanocrystals and xyloglucans, by combining oil in water emulsions with dimensions around 20 µm with layer-by-layer deposit, leading to biomimetic microcapsules. The regularity of the layer deposition has been followed by selective fluorescent tagging and the wall thickness and organization was characterized by electron microscopy. Upon drying and evaporation of the oily core, the deflated microcapsules exhibited various shapes as revealed by 3D reconstruction from confocal microscopy slices. We have investigate the relationships between the obtained shapes in relation to the characteristic dimensions and the mechanical properties of the wall [2]. The control of the capsule size and thickness allows exploring various situations in terms of deformation behavior. [1] B. Jean*, L. Heux, F. Dubreuil, G. Chambat & F. Cousin, Non-electrostatic building of biomimetic cellulose-xyloglucan multilayers, Langmuir, 25(7), 3920-3923 (2009) [2] C. Quilliet, C. Zoldesi, C. Riera, A. van Blaaderen, and A. Imhof Anisotropic colloids through non-trivial buckling Eur. Phys. J. E, 27, 13{20} (2008)

Orientador: José Antônio Malmonge / Resumo: Compósitos particulados de conectividade 0-3 obtidos a partir de cerâmicas ferroelétricas são objetos de inúmeros estudos científicos. Tal fato decorre da necessidade da indústria eletrônica de materiais com altas constantes dielétricas e densidade de energia, para fabricação de componentes passivos integrados em circuitos impressos e fabricação de dispositivos de armazenamento de energia. Por outro lado, a constante dielétrica dessa combinação se limita a baixos níveis para algumas aplicações. A fabricação de compósitos trifásicos vem ganhando atenção devido às elevadas constantes dielétricas obtidas com a inserção de uma terceira fase condutiva. A literatura apresenta tais compósitos com um perfil bem comportado baseado na regra das misturas e na teoria da percolação. Por outro lado, em alguns casos as interações das fases de preenchimento com a matriz, bem como a possível geração de cargas durante o processo de fabricação impedem um comportamento previsível considerando a distribuição não aleatória das fases. Este trabalho teve como objetivo a obtenção e caracterização de compósitos trifásicos empregando-se como matriz o poliuretano a base de água, como segunda fase Titanato Zirconato de Chumbo (PZT) e como terceira fase, para efeito de comparativo, negro de fumo (NF) ou nanocristais de celulose (CNC). Os compósitos trifásicos foram preparados a partir da mistura dos componentes em solução aquosa de PU, e suas propriedades comparadas àquelas obtidas para compósitos bifásic... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Particulate polymeric composite with connectivity 0-3 obtained using ferroelectric ceramics as a filler are objects of numerous scientific studies. This is due to the need of the electronics industry materials with high dielectric constants and high energy density, for the manufacture of integrated passive components in printed circuits and manufacturing energy storage devices. On the other hand, the dielectric constant of this combination is limited to low levels for some applications. The manufacture of three-phase composite has gained attention due to the high dielectric constant obtained by inserting a third conductive phase. The literature shows such composites with a well behaved profile based on the rule of mixtures and percolation theory. Moreover, in some cases the interactions of the filling phase with the matrix, as well as the possible generation of charges during the manufacturing process prevents a predictable behavior considering the non-random distribution of phases. This study aimed to obtain and characterize three-phase composites employing as matrix water-based polyurethane, and as a second phase Lead titanate zirconate (PZT) and as a third phase, for comparative purposes, carbon black (NF) or cellulose nanocrystals (CNC). The three-phase composites were prepared adding the fillers in aqueous PU, and their properties compared with those obtained for biphasic composites PU_PZT, PU_NF and PU_CNC. The characterizations were performed by Scanning Electron Micro... (Complete abstract click electronic access below) / Doutor

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / Atualmente à crescente o nÃmero de pesquisas sobre materiais biodegradÃveis e aproveitamento de resÃduos, devido à necessidade de preservaÃÃo dos recursos naturais e outras questÃes ligadas à sustentabilidade. O objetivo do trabalho foi desenvolver filmes biodegradÃveis a partir de gelatina obtida de resÃduos de tilÃpia adicionados de nanocristais de celulose (NC). A formulaÃÃo do filme foi feita com 9,6% de gelatina de peixe e 25% de glicerol (em base seca) variando a quantidade de nanocristais de celulose de lÃnter nas concentraÃÃes de 0, 5, 10 e 15% (em base seca) com uso ou nÃo de ultrassom (US) na preparaÃÃo do filme. A gelatina foi obtida de resÃduos de carne mecanicamente separada (CMS) de tilÃpia. Os filmes foram obtidos por casting e caracterizados quanto à permeabilidade a vapor de Ãgua, propriedades mecÃnicas de resistÃncia à traÃÃo, elongaÃÃo e mÃdulo elÃstico, propriedades tÃrmicas (DSC), Ãpticas, de estabilidade pela cor, morfolÃgicas (MEV) e de hidrofilicidade a partir do Ãngulo de contato. Os filmes obtidos se apresentaram com boa aparÃncia, homogÃneos e manuseÃveis, com boa transparÃncia e com umidade entre 12,5 e 20,7%, diminuÃda significativamente com a adiÃÃo de NC. Os nanocristais de celulose utilizados foram efetivos para reduzir a permeabilidade ao vapor de Ãgua (PVA), a qual foi reduzida significativamente com a utilizaÃÃo de 10% de NC e uso de ultrassom, e com 15% de NC com e sem US. A adiÃÃo de NC incrementou a resistÃncia à traÃÃo e mÃdulo a partir de 5% com um pequeno decrÃscimo na concentraÃÃo de 15%, e o aumentando o mÃdulo elÃstico a 15% de NC com ultrassom. NÃo houve efeito significativo com a adiÃÃo de NC e uso de US na elongaÃÃo dos filmes e nem na opacidade. O uso de ultrassom melhorou a barreira ao vapor de Ãgua, mÃdulo elÃstico e nÃo influenciou significativamente as propriedades de traÃÃo, elongaÃÃo e opacidade. As imagens obtidas por microscopia eletrÃnica de varredura apresentaram aglomerados, possivelmente pela presenÃa de minerais ou estruturas cristalinas de colÃgeno residuais do processo de hidrÃlise para obtenÃÃo da gelatina ou dos filmes, alÃm de processos com o tempo de armazenamento. As anÃlises de DSC mostraram possÃveis fenÃmenos de fusÃo da gelatina e outros processos tÃrmicos simultÃneos no primeiro ciclo, alÃm de processos tÃrmicos no segundo ciclo que podem estar associados à transiÃÃo vÃtrea, os quais nÃo foram influenciados expressivamente pelo teor de NC e pelo uso de US, porÃm foram bastante influenciados pelo tempo de armazenamento dos filmes. Estes apresentaram pequena intensidade de cor que foi mais intensificada com a quantidade de nanocelulose e nÃo variou de forma expressiva com o tempo, indicando que os filmes apresentaram cor estÃvel. O Ãngulo de contato revelou que a NC nÃo interferiu na hidrofilicidade dos filmes. O melhor filme obtido para aplicaÃÃo em alimentos foi o com 10% de nanocelulose e utilizaÃÃo de ultrassom por apresentar melhor barreira à Ãgua e melhores propriedades mecÃnicas, nÃo interferindo na transparÃncia dos filmes. / Currently the studies about biodegradable materials and waste recovery are increasing, due to need to preserve natural resources and other issues related to sustainability. The objective of this work is to develop biodegradable films from tilapia waste gelatin and cellulose nanocrystals (CN). The formulation of the film was made with 9.6% fish gelatin, glycerol 25% (on dry basis) and varying the amount of nanocrystals from linter pulp at concentrations of 0, 5, 10 and 15% (on a dry basis) and the use of ultrasonic treatment (US) in the preparation of films. The films were obtained by casting and characterized with respect to water vapor permeability (WVP), mechanical properties (tensile strength, elongation and elastic modulus), thermal properties (DSC), optical properties, color stability, morphology (SEM) and hydrophilicity by contact angle. The obtained films are presented in good shape, homogeneous and manageable, with good transparency and moisture content between 12.5 and 20.7%, which decreased significantly with adding CN. Cellulose nanocrystals were effective in reducing the permeability, substantially decreasing WVP with use of 10% CN and US, and 15% of NC with US and without US. The addition of CN increased tensile strength from 5% CN and with a small decrease in concentration of 15%. The elastic modulus increased at 15% with US. There was no significant effect with the addition of NC and use of US at elongation of films and no effects in opacity of films. The use of ultrasound has improved barrier to water vapor and elastic modulus, and it did not has significant influence on the properties of tensile strength, elongation and opacity. The images obtained by scanning electron microscopy showed structures originating from gelatin, possibly by presence of minerals or crystal structures of collagen in the process of obtaining gelatin or films, and processes with storage time. The DSC analysis showed possible phenomena of gelatin melting or other thermal processes simultaneously in the first cycle, and thermal processes in the second cycle, which can be associated with glass transition of gelatin. These events were not influenced significantly by CN content and use of US, but were heavily influenced by storage time of films. These showed little color intensity, which was further enhanced by the amount of CN and did not vary significantly with time, indicating that colors of the films were stable. Contact angle analysis have shown that CN did not decrease the hidrofilicity of films. The best film obtained for application to food products was 10% with NC and use of ultrasound due to better barrier to water, improved mechanical properties and the same transparency.

Orientador: Maria do Carmo Gonçalves / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T19:32:01Z (GMT). No. of bitstreams: 1 Brandao_LarissaReis_D.pdf: 4901816 bytes, checksum: e2662ff13e1db4f6ba5a090882ebef83 (MD5) Previous issue date: 2013 / Resumo: Neste trabalho foram preparados compósitos de acetato de celulose e polissiloxano, usando 3-isocianatopropiltrietoxissilano como agente de acoplamento em dois solventes distintos: tetrahidrofurano e N,N-dimetilformamida. A estrutura, os comportamentos térmico e dinâmico-mecânico, e a morfologia dos compósitos obtidos foram investigados. Inicialmente, o acetato de celulose foi modificado com o agente de acoplamento, por meio da reação entre os grupos hidroxila presentes na cadeia do acetato de celulose e os grupos isocianato presentes no agente de acoplamento. Os compósitos de acetato de celulose/polissiloxano foram então preparados usando duas etapas: (1) hidrólise seguida pela reação de condensação do acetato de celulose modificado na presença de água e (2) reação de condensação do acetato de celulose modificado na presença de polidimetilssiloxano com terminações silanol. Os compósitos, preparados em ambos solventes, apresentaram separação de fases que foi confirmada pela presença de micro e nanodomínios de siloxano dispersos na matriz de acetato de celulose, com boa adesão interfacial entre as fases. Os resultados demonstraram, para os compósitos preparados em tetrahidrofurano, que a incorporação da fase polissiloxano na matriz de acetato de celulose causou uma diminuição na temperatura de transição vítrea, módulo de armazenamento e dureza e um aumento do caráter hidrofóbico da superfície do acetato de celulose. Por outro lado, para os compósitos em N,N-dimetilformamida, a incorporação da fase polissiloxano causou um aumento na temperatura de transição vítrea, módulo de armazenamento e caráter hidrofóbico. Os compósitos apresentaram estabilidade térmica similar ao acetato de celulose puro, para os compósitos preparados em ambos os solventes. Foram preparados também nanocompósitos de acetato de celulose/nanocristais de celulose, pelo método casting, usando 3-isocianatopropiltrietoxissilano como agente de acoplamento. Os nanocristais de celulose foram obtidos a partir da hidrólise ácida com ácido clorídrico de fibras de algodão. Os nanocristais apresentaram formato de agulha. Os nanocompósitos preparados foram avaliados quanto às suas características estruturais, térmicas, dinâmico-mecânicas e morfológicas. Os nanocompósitos de acetato de celulose/nanocristais de celulose apresentaram uma diminuição na Tg e um aumento no módulo de armazenamento e no caráter hidrofóbico da superfície do acetato de celulose. Por outro lado, o nanocompósito de acetato de celulose modificado/nanocristais de celulose apresentou diminuição do caráter hidrofóbico quando comparado com o compósito acetato de celulose/polissilsesquioxano. Não foi observada variação na estabilidade térmica. Análises de microscopia eletrônica confirmaram a boa dispersão dos nanocristais de celulose na matriz de acetato de celulose, o que foi também confirmada pela transparência dos filmes obtidos. A metodologia proposta é, portanto, conveniente para a preparação de compósitos de acetato de celulose/polissiloxano, bem como nanocompósitos contendo nanocristais de celulose, o que permite obter materiais com propriedades úteis / Abstract: In this work, cellulose acetate and polisiloxane composites were prepared from 3-isocianatepropiltrietoxisilane as a coupling agent in two different solvents: tetrahidrofurane and N,N-dimethilformamide. The structure, thermal and dynamic-mechanical behavior, and morphology of the obtained composites were investigated. Initially, the cellulose acetate was modified with the coupling agent, by means of a reaction between the hydroxyl groups present in the cellulose acetate chain and the isocianate groups present in the coupling agent. The cellulose acetate/polisiloxane composites were prepared using two steps: (1) hydrolysis followed by condensation reaction of the cellulose acetate modified in the presence of water and (2) condensation reaction of the cellulose acetate modified in the presence of the polidimethilsiloxane with silanol endings. The composites prepared in both solvents presented phase separation which was confirmed by siloxane micro and nanodomains dispersed in the matrix of the cellulose acetate with good interfacial adhesion between the phases. The results demonstrated that for the composites prepared in THF, the incorporation of the polisiloxane phase in the cellulose acetate matrix caused a decreasing in the vitreous transition, storage and hardness moduli and an increasing of the hydrophobic character of the surface of the cellulose acetate. On the other hand, for the composites in DMF, the incorporation of the polisiloxane phase caused an increase in the vitreous transition, storage modulus and hydrophobic character. The composites presented thermal stability similar to the pure cellulose acetate for the composites prepared in both solvents. Nanocomposites of cellulose acetate/cellulose nanocrystals were also prepared of by the casting method using 3-isocianatepropiltrietoxisilane as a coupling agent. The cellulose nanocrystals were obtained from an acidic hydrolysis of cotton fibers. The nanocomposites prepared were investigated according to their structural, thermal, dynamic-mechanical and morphological characteristics. The nanocomposites of cellulose acetate/cellulose nanocrystals presented a decrease in the Tg and an increase in the storage modulus in relation to the CA matrix, but it was not observed a variation in the thermal stability. Microscopic analysis confirmed the good dispersion of the cellulose nanocrystals in the cellulose acetate matrix, which it was also confirmed by the transparency of the obtained films. Therefore, the proposed methodology is convenient for the preparation of the cellulose acetates/polisiloxane as well as nanocomposites containing cellulose nanocrystals, which allows to obtain materials with useful properties / Doutorado / Físico-Química / Doutora em Ciências