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The process of TEMPO-mediated oxidation has gained broad usage towards the preparation of highly charged, carboxyl-functionalized polysaccharides. TEMPO-oxidized nanocelluloses (TONc) of high surface charge and measuring 3 to 5 nm in width have been recently prepared from TEMPO-oxidized pulp. This study examines as-produced and surface-hydrophobized TONc as reinforcing additives in cellulosic polymer matrices. In the first part of the work, covalent (amidation) and non-covalent (ionic complexation) coupling were compared as treatment techniques for the hydrophobization of TONc surfaces with octadecylamine (ODA). Subsequently, TONc and its covalently coupled derivative were evaluated as nanofiber reinforcements in a cellulose acetate butyrate (CAB) matrix. The properties of the resulting nanocomposites were compared with those of similarly prepared ones reinforced with conventional microfibrillated cellulose (MFC). It was found that both ionic complexation and amidation resulted in complete conversion of carboxylate groups on TONc surfaces. As a result of surface modification, the net crystallinity of TONc was lowered by 15 to 25% but its thermal decomposition properties were not significantly altered. With respect to nanocomposite performance, the maximum TONc reinforcement of 5 vol % produced negligible changes to the optical transmittance behavior and a 22-fold increase in tensile storage modulus in the glass transition region of CAB. In contrast, hydrophobized TONc and MFC deteriorated the optical transmittance of CAB by ca 20% and increased its tensile storage modulus in the glass transition region by only 3.5 and 7 times respectively. These differences in nanocomposite properties were attributed to homogeneous dispersion of TONc compared to aggregation of both the hydrophobized derivative and the MFC reference in CAB matrix. A related study comparing TONc with MFC and cellulose nanocrystals (CNC) as reinforcements in hydroxypropylcellulose (HPC), showed TONc reinforcements as producing the most significant changes to HPC properties. The results of dynamic mechanical analysis and creep compliance measurements could be interpreted based on similar arguments as those made for the CAB-based nanocomposites. Overall, this work revealed that the use of TONc (without the need for surface hydrophobization) as additives in cellulosic polymer matrices leads to superior reinforcing capacity and preservation of matrix transparency compared to the use of conventional nanocelluloses. / Ph. D.

Les copolymères à blocs contenant une partie souple et une partie dure constituent aujourd'hui une classe de matériaux très attractifs en raison de leurs propriétés résultant de la combinaison de deux homopolymères de nature différente. Dans le cadre des copolymères à blocs à forte teneur en polydiméthylsiloxane (PDMS), une méthode de synthèse originale en deux étapes, compatibilisation puis extension, a été développée. Respectueuse de l'environnement grâce à l'utilisation du procédé d'extrusion réactive, cette approche ouvre une nouvelle voie vers le développement d'élastomères thermoplastiques. L'objectif de cette thèse est d'élaborer à l'état fondu des copolymères à blocs à base de PDMS silicone à partir de la réaction époxy-amine puis, par une réaction d'allongement d'obtenir un matériau avec une forte proportion en PDMS. Dans un premier temps, une étude de la réaction époxy-amine sur molécules modèles a été réalisée à partir d'oligodiméthylsiloxanes α,ω- fonctionnalisés époxy et d'une alkylamine. Indépendamment de la température et du ratio molaire, la réaction a permis d'obtenir des copolymères greffés de type (A2B2)n. Dans un deuxième temps, cette stratégie a ensuite été appliquée à des systèmes polymères tels que le polyéthylène et le polyamide. A cette échelle, la réaction s'est produite et conduit à des produits de type (A2B2)n. Dans un troisième temps, l'ensemble des copolymères synthétisés ont été étudiés lors de la réaction d'allongement, basée sur l'insertion de siloxanes cycliques à l'aide d'une superbase. Dépendante de la température et de la quantité de catalyseur, cette réaction a été étudiée sur molécules modèles et sur des systèmes polymères / Nowadays hard-soft block copolymers consist of a very attractive material class because of their properties resulting of the combination of two different homopolymers. In the case of block copolymers with on a high polydiméthylsiloxane (PDMS) content, an innovative 2-step synthesis method, compatibilization and extension, has been developed. Using an environmental friendly route such as a reactive extrusion process, this approach opens a new synthesis pathway towards the development of thermoplastic elastomers. The goal of this thesis is to develop mass block copolymers based on PDMS using the epoxy-amine reaction, followed by an extension reaction to reach a material with a high percent of silicone. Firstly, a study of the epoxy-amine reaction on model molecules was carried out between a low molecular weight PDMS and an alkylamine. Independently of the temperature and the molar ratio, the reaction allowed to obtain graft copolymers with an (A2B2)n type structures. Secondly, this strategy has then been applied in polymer systems such as polyethylene and polyamide. At this scale, the reaction occurred and lead to products with (A2B2)n type structures. Thirdly, all synthesized copolymers were studied during the extension reaction, based on the insertion of cyclic siloxanes using a catalysis system. Depending of the temperature and the catalyst quantity, this reaction was investigated on model molecules and polymer systems

Made available in DSpace on 2016-03-15T19:36:26Z (GMT). No. of bitstreams: 1 Renato Meneghetti Peres.pdf: 2481386 bytes, checksum: 4a0c9e9713ebe096dc1943b16d0149bd (MD5) Previous issue date: 2010-08-06 / Fundo Mackenzie de Pesquisa / Nanocomposites are nanometrical material particles embedded in a specific matrix. The degree of organization of the nanostructures and their properties depend on the nature of the organic and inorganic components of the structure that can generate synergic interactions. Polymeric nanocomposites are related to a class of hybrid materials where inorganic substances of nanometric dimensions are dispersed in a polymeric matrix. A small amount of inorganic material has a great effect on the structure performance. The nanoparticles of inorganic materials have high specific surface area that promotes the dispersion of the polymeric matrix and the properties depend on the homogeneity of the dispersion. The interaction reactions between the components can be observed on the material`s structure. The nanometrical material obtained by sol-gel process can be incorporated directly on the polymeric matrix. There is a tendency to a hard dispersion when a ceramic nanoscale particle is embedded in a polymeric matrix. This difficult can be attributed to a small spacement between the ceramic atomic planes to allow the passage of the polymeric chain between that. In this case, techniques can be used to the spacement to be enlarged with a organophilic agent action that enable a better addiction between the reinforcement and de matrix and make a influence in the mechanical, termical and rheological properties for the characterization by different techniques. In this work, the pseudoboehmite obtained by sol-gel process was treated by an octadecylamine solution to obtain a mix added to Nylon 6,12. After the mixing, the nanocomposite was dryed and processed to conformed the specimen used in the material caracterization. Mechanical, termical, reological, MEV and X-ray diffraction tests are done. The nanocomposite which contains pseudoboehmite and octadecylamine tests results were compared with the nanocomposite contained just pseduboehmite to compair and verify the octadecylamine treatment effect in the materials properties. / Nanocompósitos são materiais contendo partículas nanométricas dispersas em uma matriz específica. O grau de organização das nanoestruturas e suas propriedades dependem da natureza dos componentes orgânicos e inorgânicos de sua estrutura onde podem ocorrer interações sinérgicas. Os nanocompósitos poliméricos consistem em um grupo de materiais híbridos nos quais substâncias inorgânicas de dimensões nanométricas estão dispersas na matriz polimérica. Por possuírem alta área específica, uma pequena quantidade de nanocarga pode ocasionar um grande efeito no desempenho da estrutura, no entanto é importante observar que a dispersão do nanoreforço na matriz polimérica deve ocorrer da forma mais homogênea possível, promovendo as interações sinérgicas entre matriz e reforço ao longo de toda a estrutura do material. A obtenção de um reforço cerâmico por processo sol-gel, permite a obtenção de um produto com partículas de dimensões nanométricas, sendo que o mesmo pode ser incorporado à matriz polimérica. Ainda que em dimensões na escala nano, sempre que uma cerâmica é adicionada a um polímero, existe uma tendência à dificuldade na dispersão do material devido ao pequeno espaçamento entre os planos atômicos da cerâmica para que ocorra a passagem da cadeia polimérica entre estes planos. Neste caso, o emprego de técnicas de modificação da nanocarga, onde este espaçamento pode ser aumentado pela ação de um agente organofílico, possibilitando uma melhor acoplagem do reforço à matriz e influenciando diretamente nas propriedades mecânicas, térmicas e reológicas do material quando caracterizado pelas mais diversas técnicas. Neste trabalho, a pseudoboemita obtida por processo sol-gel foi tratada com uma solução de octadecilamina obtendo-se uma mistura adicionada ao Nylon 6,12. Após a mistura o nanocompósito foi seco e processado para conformação dos corpos-de-prova utilizados na caracterização do material. Realizou-se a caracterização por meio de ensaios mecânicos, térmicos, reológicos, MEV e Difração de Raios-X. Os resultados obtidos na caracterização do material contendo pseudoboemita e octadecilamina foram comparados aos resultados obtidos na adição apenas da pseudoboemita para comparação e verificação do efeito do tratamento com octadecilamina nas propriedades do material.