Poly(arylene ether sulfone)s (PAES) are important commercial polymers and have been extensively studied due to their excellent thermal and mechanical properties. However, some applications are still limited when good solvent resistance and low thermal expansion coefficient are required. There has been a continuous interest in developing new PAES based on new monomers or polymer modifications to obtain new properties or to enhance existing properties. In this dissertation, the synthesis, characterization and structure-property relationship of new 1,4-cyclohexylene ring containing PAESs were comprehensively studied. Different polymerization techniques were used to synthesize polymers with different segmental lengths. The monomer, 4,4'-[trans-1,4-cyclohexanebis(methylene)] bisphenol (CMB), was synthesized and fully characterized. Based on 4,4′-dihydroxy-p-terphenyl (DHTP), 4,4′-dihydroxybiphenyl (DHBP) and the CMB monomer, homopolymer and random copolymers of PAES were prepared with high molecular weights and high glass transition temperatures. Dynamic mechanical analysis (DMA) on these polymers showed multiple sub-Tg relaxations. A large increase in the ultimate elongation was obtained with the CMB and DHTP containing sample, which could be due to the strong sub-Tg relaxations observed from the DMA results. A series of four acid chloride monomers were synthesized and polymerized with phenol terminated PAES oligomers. Solution polymerization and pseudo-interfacial polymerization techniques were used to prepare both bisphenol-A (bis-A) based and DHBP based PAES oligomers. With the incorporation of the trans-1,4-cyclohexylene units, decreases in the glass transition temperatures were observed from both the bis-A based and the DHBP based polymers. However, melting transitions were only observed in the DHBP based trans-1,4-cyclohexylene containing PAESs. Crystallinity was confirmed by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). A mechanical property study of the high molecular weight trans-1,4-cyclohexylene containing polymer samples showed moderate ultimate elongation enhancements. A series of PAES-polyester multiblock copolymers were synthesized with both solution method and melt polymerization. In the solution method, phenol terminated PAES oligomers and the acid chloride terminated poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) oligomers were presynthesized and coupled in solution. The molecular weights of the polymer products obtained from the solution method were limited by solubility issues. Melt phase polymerization was employed to obtain high molecular weight polymers. Hydroxy ethoxy terminated PAES oligomers were synthesized and polymerized with 1,4-cyclohexanedimethanol (CHDM) and dimethyl terephthalate (DMT) in the melt. Polymers with high molecular weights were obtained. Tensile test results suggested that the mechanical properties of these polymers were dominated by the PAES components with polyester contents up to 20 wt%. Melting transitions were observed from polymers with higher polyester contents, and these polymers exhibited limited solubility in common organic solvents. / Ph. D.

Poly(arylene ether sulfone)s with dendritic terminal groups were synthesized by step-growth polymerization of two difunctional monomers in the presence of preformed dendritic end-cappers. These polymers were characterized by NMR, SEC, DSC, TGA, melt rheology and tensile tests. The melt viscosities of these polymers in the high frequency region were lower than the control while the stress-strain properties were comparable to those of the control, suggesting that it is possible to reduce the high shear melt viscosities of this type of polymers without affecting the stress-strain properties by introducing bulky dendritic terminal groups. Poly(arylene ether sulfone)s with hyperbranched terminal groups were also synthesized. These polymers were synthesized by reacting fluoro-terminated poly(arylene ether sulfone) chains with an arylene ether ketone AB2 monomer. The terminal groups of these polymers were capped by tert-butylphenol. The results from NMR and SEC showed that multiple tert-butyl units were successfully introduced onto the polymer chains, suggesting that this synthetic method could be useful for introducing multiple functional groups onto the polymer chain ends in fewer synthetic steps than an analogous method using preformed dendritic end-cappers. It was also demonstrated that multiple sulfonated phenols were attached to the terminal groups of polysulfones by this method. A novel cyclohexyl-containing difunctional monomer was prepared and successfully incorporated into poly(arylene ether sulfone) backbones. These polymers were characterized by NMR, SEC, DSC, TGA, DMA and tensile tests and compared to terephthaloyl analogs. Tensile tests and DMA showed the cyclohexyl units impart a higher magnitude of secondary relaxation than the terephthaloyl units while maintaining high modulus, suggesting that these polymers may have higher impact strength than the ones with no cyclohexyl units. / Ph. D.

Amorphous solid dispersion (ASD) is a popular method to increase drug solubility and consequently poor drug bioavailability. Cellulose ω-carboxyesters were designed and synthesized specifically for ASD preparations in Edgar lab that can meet the ASD expectations such as high Tg, recrystallization prevention and pH-triggered release due to the free -COOH groups. Rifampicin (Rif), Ritonavir (Rit), Efavirenz (Efa), Etravirine (Etra) and Quercetin (Que) cellulose ester ASDs were investigated in order to increase drug solubility, prevent release at low pH and controlled release of the drug at small intestine pH that can improve drug bioavailability, decrease needed drug content and medication price to make it affordable in third world countries, and extent pill efficiency period to improve patient quality of life and adherence to the treatment schedule. The studies were compared with cellulose based commercial polymers to prove the impact of the investigation and potential for the application. Furthermore, the in vitro results obtained were further supported by in vivo studies to prove the significant increase in bioavailability and show the extended release. The need of new cellulose derivatives for ASD applications extended the research area, the design and synthesis of a new class of polymers, alkyl cellulose ω-carboxyesters for ASD formulations investigated and the efficiency of the polymers were summarized to show that they have the anticipated properties. The polymers were synthesized by the reaction of commercial cellulose alkyl ethers with benzyl ester protected, monofunctional hydrocarbon chain acid chlorides, followed by removal of protecting group using palladium hydroxide catalyzed hydrogenolysis to form the alkyl cellulose wcarboxyalkanoate. Having been tested for ASD preparation, it was proven that the polymers were efficient in maintaining the drug in amorphous solid state, release the drug at neutral pH and prevent the recrystallization for hours, as predicted. / Ph. D.

Segmented copolymers are a commercially important class of materials that are utilized in a wide variety of applications. In these systems a relatively large number of variables such as backbone chemistry, segment molecular weight, and the overall molecular weight of the copolymer can be independently controlled to engineer materials with targeted properties. Such versatility also means that a large number of variables can influence the morphology and therefore, properties and performance of segmented copolymers. In this dissertation, the influence of selected variables on the solid state structure-property behavior of segmented poly(ether-block-amide), polyurethane, polyurethaneurea, and polyurea copolymers is explored. The specific variables which have been utilized singly or in conjunction with others are hard segment crystallizability, crystallization conditions, hard segment content, soft segment type and molecular weight, nature of hydrogen bonding, extent of inter-segmental hydrogen bonding, segment symmetry, and chain architecture. In poly(ether-block-amide)s, it was found that the morphology of both the crystalline and the amorphous phase depend upon the polyamide content of the sample and, as expected, the crystallization conditions. A comparison of polydimethylsiloxane based segmented polyurethanes with their polyurea counterparts demonstrated that for a constant hard segment content the soft segment molecular weight particularly governs the extent of microphase separation in these materials. The nature of hydrogen bonding, monodentate or bidentate, also strongly influences their mechanical response. Remarkably, the polyurea sample with a polydimethylsiloxane molecular weight of 7000 g/mol and a hard segment content of 25 wt % exhibited a remarkable service temperature window (for rubber-like behavior) of ca. 230°C (from -55°C to 175°C) whereas it was ca. 200°C wide (from -55°C to 145°C) for the equivalent polyurethane sample. The extremely high chemical incompatibility between the polydimethylsiloxane of sufficiently high molecular weight and urethane or urea segment is expected to generate a relatively sharp interface between the soft matrix and the dispersed hard domains. Therefore, a polyether co-soft segment was incorporated in a controlled manner along the chain backbone, which resulted in inter-segmental hydrogen bonding between the ether and the urea segments. The consequent segmental mixing gave rise to a gradient interphase, which led to a significant improvement in the tensile strength, and elongation at break in selected polydimethylsiloxane segmented polyurea copolymers. The importance of the hydrogen bonding network in model polyurethaneurea copolymers was also explored by utilizing LiCl as molecular probe. It has been demonstrated that hydrogen bonding plays an important role, over and above microphase separation, in promoting the long-range connectivity of the hard segments and the percolation of the hard phase through the soft matrix. The incorporation of hard segment branching in these polyurethaneurea also reduced the ability of the hard segments to pack effectively and establish long-range connectivity. The disruption of the percolated hard phase resulted in a systematic softening of the copolymers. The role of chain architecture in governing the structure/property/processing of segmented was also investigated by comparing highly branched segmented polyurethaneureas with their linear analogs. These copolymers were based on poly(propylene oxide) or poly(tetramethylene oxide) as the soft segments The highly branched copolymers utilized in this dissertation were able to develop a microphase morphology similar to their linear analogs. Particularly noteworthy, and surprising, was the observation of weak second order interference shoulder in the respective small angle X-ray scattering profiles of the highly branched samples based on poly(propylene oxide) of MW 8200 and 12200, indicating the presence of at least some level of long-range order of the hard domains in these samples. Tapping-mode atomic force microscopy phase images of these two samples clearly confirmed the small angle X-ray scattering results. In addition to the strain induced crystallization of the poly(tetramethylene oxide) MW 2000 g/mol based linear polyurethaneureas, the highly branched analog of this sample also exhibited similar behavior at ambient temperature and uniaxial deformation of ca. 400 % strain. Wide angle X-ray scattering confirmed the above observation. The reduced ability of the branched polymers to entangle resulted in slightly poorer mechanical properties, such as tensile strength, elongation at break, and stress relaxation as compared to their linear analogs. However, primarily due to their reduced entanglement density, the branched polyurethaneureas had significantly lower ambient temperature solution viscosity as compared to their linear polyurethaneurea analogs. Therefore, these highly branched polyurethaneureas can be more easily processed than the latter materials. Finally, it was demonstrated that non-chain extended segmented polyurethane and polyurea copolymers in which the hard segment is based on only a single diisocyanate molecule may well exhibit properties, such as the breadth of the service window, the average plateau modulus, stiffness, tensile strength, and elongation at break that are similar to chain extended segmented copolymers that possess distinctly higher hard segment content. A careful control of the hard segment symmetry and the nature of the hydrogen bonding is necessary to achieve such improved performance in the non-chain extended systems. Therefore, the results of this study provide new direction for the production of thermoplastic segmented copolymers with useful structural properties. / Ph. D.

Ce mémoire portant sur le développement de liquides ioniques protiques à l'état liquide à température ambiante en tant qu'électrolytes pour des supercapacités faradiques à base de dioxyde de ruthénium est divisé en trois études distinctes. La première permet d'évaluer quelles propriétés de ces sels fondus doivent être optimisées pour cette application en utilisant les données recueillies avec une série de nouveaux liquides ioniques protiques constitués de l'acide trifluoroacétique et différentes bases hétérocycliques azotées. La seconde discute de l'effet d'impuretés colorées sur les propriétés des liquides ioniques ainsi que sur des aspects pratiques devant être pris en considération lors des synthèses. La troisième traite d'importantes relations structure–propriétés pour une série de liquides ioniques protiques ayant des cations du type pyridinium et différents anions. Dans leur ensemble, les travaux présentés devraient permettre une recherche plus efficace de liquides ioniques avec des propriétés désirables en vue d'application comme électrolyte dans le futur. / This thesis on the development of room temperature protic ionic liquids as electrolytes in ruthenium-dioxide based faradaic superpacitors consists of three separate studies. The first one establishes which properties of molten salts need to be optimized for this application by using the data obtained from the analysis of a series of protic ionic liquids composed of trifluoroacetic acid and N-heterocyclic bases. The second study elaborates on the effect of colored impurities on the properties of ionic liquids and also reports practical aspects which need to be accounted for during their synthesis. The third study focuses on important structure–property relationships for a series of protic ionic liquids with pyridinium cations and various anions. Altogether, the results presented in here should allow a more efficient design of ionic liquids with desirable properties for application as electrolytes in the future.

Ce travail a consisté en la synthèse de nouveaux copolymères d’acétate de cellulose greffés par du poly(méthyl diéthylène glycol méthacrylate) avec un nombre et une longueur de greffons variables par une méthode de polymérisation radicalaire contrôlée : l’Atom Transfer Radical Polymerization (ATRP). Deux familles de matériaux ont été obtenues ayant mêmes compositions (entre 20 et 50% en masse de greffons) mais des architectures différentes : de nombreux greffons courts ou peu de greffons longs. Ces matériaux ont ensuite été étudiés pour la séparation par pervaporation de mélanges azéotropiques de type aprotique/protique : carbonate de diméthyle/méthanol et éthyl tert-butyl éther/éthanol. Pour la séparation du premier mélange, la réticulation des copolymères s’est avérée nécessaire, conduisant à des matériaux qui restent fragiles sous contrainte et qui présentent des flux élevés au détriment d’une très faible sélectivité. Pour cette séparation, ces matériaux permettent cependant de dépasser la limite thermodynamique imposée par l’azéotrope. Pour le mélange éthyl tert-butyl éther/éthanol, les copolymères montrent d’excellentes performances en extrayant l’éthanol de manière très sélective. L’introduction de greffons permet d’augmenter le flux de pervaporat tout en ne diminuant que faiblement la sélectivité par rapport à l’acétate de cellulose précurseur. L’analyse de la microstructure des copolymères montre que les copolymères avec peu de greffons longs sont beaucoup plus ségrégés que ceux avec de nombreux greffons courts. Les résultats de perméabilité montrent des comportements différents selon l’architecture du copolymère cohérents avec leur microstructure / This work deals with the synthesis of new copolymers of cellulose acetate grafted with poly(methyl diethylene glycol methacrylate) with different numbers and lengths of grafted chains by controlled radical polymerization (Atom Transfer Radical Polymerization ATRP). Two families of materials were obtained with the same compositions (between 20 and 50% in mass of grafted chains) but different architectures : a lot of short chains or a few long chains. These materials were then studied for the pervaporation separation of two aprotic/protic azeotropic mixtures : dimethyl carbonate/methanol and ethyl tert-butyl ether/ethanol. For the separation of the first mixture, copolymers had to be cross-linked but their mechanical withstanding was poor under stress and they showed high fluxes but very low selectivity. Nevertheless, the materials allowed to go over the thermodynamical azeotropic limit. For ethyl tert-butyl ether/ethanol separation, copolymers showed excellent performances with a very selective extraction of ethanol. The presence of grafted chains increased flux along with a slight decrease in selectivity compared with the cellulose acetate precursor. The analysis of the copolymer microstructure showed that copolymers with long grafted chains were more segregated than those with short grafted chains. The results of permeability showed different behaviours according to the copolymer architecture in good agreement with their microstructure

Este trabalho enquadra-se dentro dos objetivos da engenharia de cristais moleculares para a obtenção de novas formas sólidas que possam apresentar propriedades farmacêuticas aprimoradas, especificamente de um dos fármacos mais utilizados e comercializados na terapia antirretroviral, contra o HIV: lamivudina, β-L-2\',3\'-didesoxi-3\'-tiocitidina (3TC). As formas cristalinas apresentadas correspondem aos sais dos ácidos inorgânicos: bromidrato (3TCH+-Br-), difluoridrato de hidrogênio (3TCH+-F-HF) e nitrato de lamivudina (3TCH+-NO3-). Estes novos sais cristalizaram no grupo espacial não-centrossimétrico P21, com um par iônico por unidade assimétrica. Os sais halogenados (3TCH+-Br- e 3TCH+-F-HF) apresentaram arranjos supramoleculares isoestruturais inclusive com o sal anidro do cloridrato de lamivudina (3TCH+-Cl-), reportado em trabalhos anteriores no nosso grupo de pesquisa, e cuja solubilidade no equilíbrio apresentou um aumento em relação à forma farmacêutica da 3TC. A característica principal dos arranjos cristalinos destes sais está relacionada com o ordenamento supramolecular das unidades catiônicas 3TCH+, a qual é constante, observando-se a formação de vacâncias entre elas ao longo do eixo cristalino a, decorrente da simetria helicoidal característica do grupo espacial. Desta forma, os ânions se acomodam nos interstícios destas vacâncias estabilizando o arranjo cristalino. Entretanto, o sal 3TCH+NO3- apresentou um comportamento conformacional e supramolecular diferente do observado nos sais halogenados. Neste caso observaram-se a formação de fitas helicoidais ao longo do eixo b, as quais vão se acoplando por simetria translacional na direção horizontal no plano [10-1] por meio de ligações de hidrogênio clássicas do tipo N–H•••O entre os fragmentos citosinicos e O–H•••O dos grupos hidroxilas e os ânions nitrato correspondentemente. Portanto, há a formação de planos moleculares em ziguezague, que posteriormente vão se arquitetando paralelamente na direção [1 0 -1] através de interações de curto alcance. Tanto as características conformacionais e supramoleculares, quanto a pureza exibida pelos sais foram também corroboradas com a ajuda de outras técnicas de análise no estado sólido, como a difração de raios X por pó (DRXP), a análise vibracional no infravermelho (IV) e Raman, e a análise térmica: calorimetria exploratória diferencial (DSC), termogravimetria (TG) e microscopia termo-óptica (Hot-stage). Cálculos de single-point em nível da teoria do funcional da densidade (DFT) foram realizados com o intuito de auxiliar na compreensão de algumas interações intermoleculares. Comparações das propriedades estruturais dos sais sintetizados com algumas formas já reportadas da 3TC (por exemplo, a 3TCH-Cl) permitiram inferir possíveis propriedades farmacêuticas. / This work falls within the main goals of crystal engineering, the improvement of pharmaceutical properties, through the design of new solid forms of the lamivudine, β-L-2 ´, 3´-dideoxy-3´-tiocytidine (3TC), one of the most used and marketed drug in the antiretroviral therapy against HIV. The crystalline forms herein presented correspond to inorganic acid salts: Lamivudine hydrobromide (3TCH+-Br-), hydrogen difluoride (3TCH+-F-HF) and nitrate (3TCH+-NO3-). These new salts crystallized in non-centrossymetric space group P21, with an ionic pair per asymmetric unit. The halogenated salts (3TCH+-Br- and 3TCH+-F-HF) exhibited isostructural supramolecular assemblies, similar to the anhydrous salt of lamivudine hydrochloride (3TCH+-Cl-) reported in a previous studies performed in our research group, and whose equilibrium solubility showed an increase when compared with 3TC pharmaceutical form. The main feature of the salt crystalline assemblies is related to the supramolecular ordering of the 3TCH+ cationic units, which is constant, by observing the formation of vacancies between them along the a crystalline axis due to the helical symmetry, characteristic of their space group. In this way, the anions accommodate themselves into the interstices of these vacancies, stabilizing the crystalline assemblies. Meanwhile, the 3TCH+NO3- salt showed a conformational and supramolecular behavior different from that observed in the halogenated salts. In this case it was observed the formation of helical strands along the b axis, which will be engaging by translational symmetry in the horizontal direction in the [10-1] plane through N–H•••O e O–H•••O classical hydrogen bonds, between the cytosine and hydroxyl fragments and the nitrate anions. Therefore, they form molecular zigzag plans which will subsequently architect parallel with the [10-1] direction by short-contact interactions. Both conformational and supramolecular characteristics as well as the purity exhibited by these salts were also supported with the help of other solid state techniques such as X-ray powder diffraction (XRDP), vibrational analysis as Infrared (IR) and Raman spectroscopy and thermal analysis as differential scanning calorimetry (DSC), thermogravimetry (TG) and hot-stage microscopy. Single point theoretical calculations at the level of density functional theory (DFT) were performed in order to assist in the understanding of some intermolecular interactions. Comparison of the structural properties of the synthesized salts with some forms already reported (e.g. 3TCH+-Cl-) allowed to infer some possible pharmaceutical properties.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-08-27T20:28:46Z No. of bitstreams: 1 Uma perspectiva da modelagem QSPR para triagem-desenho de catalisadores para a s?ntese de carbona.pdf: 5038129 bytes, checksum: cd9bae4ba9eacd711c360bc304996732 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-08-28T12:42:24Z (GMT) No. of bitstreams: 1 Uma perspectiva da modelagem QSPR para triagem-desenho de catalisadores para a s?ntese de carbona.pdf: 5038129 bytes, checksum: cd9bae4ba9eacd711c360bc304996732 (MD5) / Made available in DSpace on 2018-08-28T13:11:11Z (GMT). No. of bitstreams: 1 Uma perspectiva da modelagem QSPR para triagem-desenho de catalisadores para a s?ntese de carbona.pdf: 5038129 bytes, checksum: cd9bae4ba9eacd711c360bc304996732 (MD5) Previous issue date: 2018-05-29 / To date, only a small number of organocatalysts have been applied to produce oleochemical carbonates, while the description of new catalysts system still limited. This work presents a preliminary perspective of Quantitative Structure-Property Relationship (QSPR) modeling to assist in the targeted choice/design of active organocatalysts to produce cyclic carbonates. The QSPR was developed by applying the molecular descriptors (2D) to model the structure-property relationship between the organocatalysts features and its activity to produce oleochemical carbonates. From the virtual screening, a total of 122 catalysts have their activity predicted and the best molecular targets are proposed. The principal molecular features (organic structure, molecular arrangement, carbon chain size and substituent type) were identified through data mining, while the principal component analysis (PCA) proved to be suitable to perform the exploratory analysis of the molecules set. In addition, is presented the first report of the application of cetyltrimethylammonium bromide (CTAB) as a new catalyst to produce oleochemical carbonate derived from soy, canola and rice oils. The reactions were performed in a 50 cm3 stainless steel autoclave at 120?C, for 48 hours, without stirring, 5 MPa (p, CO2), 2 g of epoxidized oil, 4 mL of butanol and 5 mol% of CTAB. From the proposed method, all reactions showed more than 98% of epoxide conversion to cyclic carbonate for all the vegetable oil. In this way, the QSPR modelling can be applied to reduce the costs and time in the organocatalysts screening/design for the cyclic carbonates synthesis from CO2 and epoxides. / At? o momento, apenas um pequeno n?mero de organocatalisadores foram aplicados para produ??o de carbonatos oleoqu?micos, enquanto a descri??o de novos sistemas de catalisadores ainda ? limitada. O presente trabalho apresenta uma perspectiva preliminar da modelagem por Rela??o Quantitativa Estrutura-Propriedade (QSPR) para auxiliar na escolha/desenho de novos organocatalisadores para produ??o de carbonatos c?clicos. O QSPR foi desenvolvido aplicando os descritores moleculares (2D) para modelar a rela??o estrutura-propriedade entre as caracter?sticas dos organocatalisadores e sua atividade para produ??o de carbonatos oleoqu?micos. A partir da triagem virtual, um total de 122 catalisadores tiveram sua atividade prevista e os melhores alvos moleculares s?o propostos. As principais caracter?sticas moleculares (estrutura org?nica, arranjo molecular, tamanho da cadeia de carbono e tipo de substituinte) foram identificadas atrav?s da minera??o de dados, enquanto a an?lise de componentes principais (PCA) mostrou-se adequada para realizar a an?lise explorat?ria do conjunto de mol?culas. Al?m disso, ? apresentado o primeiro relato da aplica??o do brometo de cetiltrimetilam?nio (CTAB) como um catalisador para a produ??o de carbonato oleoqu?mico derivados dos ?leos de soja, canola e arroz. As rea??es foram realizadas em uma autoclave de a?o inoxid?vel de 50 cm3 a 120 ? C, durante 48 horas, sem agita??o, 5 MPa (p, CO2), 2 g de ?leo epoxidado, 4 mL de butanol e 5% molar de CTAB. A partir do m?todo proposto, todas as rea??es apresentaram mais de 98% de convers?o de ep?xido em carbonato c?clico para todos os ?leos vegetais. Desta forma, a modelagem QSPR pode ser aplicada para reduzir os custos e tempo na sele??o/desenho de organocatalisadores para a s?ntese de carbonatos c?clicos a partir de CO2 e ep?xidos.

Establishing process-structure-property relationships is an important objective in the paradigm of materials design in order to reduce the time and cost needed to develop new materials. A method to link phase field (process-structure relations) and microstructure-sensitive finite element (structure-property relations) modeling is demonstrated for subsolvus polycrystalline IN100. A three-dimensional (3D) experimental dataset obtained by orientation imaging microscopy performed on serial sections is utilized to calibrate a phase field model and to calculate inputs for a finite element analysis. Simulated annealing of the dataset realized through phase field modeling results in a range of coarsened microstructures with varying grain size distributions that are each input into the finite element model. A rate dependent crystal plasticity constitutive model that captures the first order effects of grain size, precipitate size, and precipitate volume fraction on the mechanical response of IN100 at 650°C is used to simulate stress-strain behavior of the coarsened polycrystals. Model limitations and ideas for future work are discussed.

Electrically conductive polymer composites are suitable for use in the manufacture of antistatic products and components for electronic interconnects, fuel cells and electromagnetic shielding. The most widely used processing techniques for producing electrically conductive polymer composites place an inherent constraint on the geometry and architecture of the part that can be fabricated. Hence, this thesis investigates selective laser sintering (SLS), a rapid prototyping technique, to fabricate and characterize electrically conductive nanocomposites of Nylon-12 filled with 4% by weight of carbon black. The objective of the dissertation was to study the effects of the SLS process on the microstructure and properties of the nanocomposite. The effect of laser power and the scan speed on the flexural modulus and part density of the nanocomposite was studied. The set of parameters that yielded the maximum flexural modulus and part density were used to fabricate specimens to study the tensile, impact, rheological and viscoelastic properties. The electrical conductivity of the nanocomposite was also investigated. The thermo-mechanical properties and electrical conductivity of the nanocomposites produced by SLS were compared with those produced by extrusion-injection molding. The structure and morphology of the SLS-processed and extrusion-injection molded nanocomposites were characterized using gas pycnometry, gel permeation chromatography, differential scanning calorimetry, electron microscopy, polarized light microscopy and x-ray diffraction. Physical models were developed to explain the effects of the processing technique on the structure and properties of the nanocomposites. Finally, a one-dimensional heat transfer model of the SLS process that accounted for sintering-induced densification and thermal degradation of the polymer was implemented in order to study the variation in part density with respect to the energy density of the laser beam. This dissertation demonstrated that SLS can be successfully used to fabricate electrically conductive polymer nanocomposites with a relatively low percolation threshold. This capability combined with the ability of SLS to fabricate complicated three-dimensional objects without part-specific tooling could open up several new opportunities.