Les effets de la force magnétique orthogonale (MF) sur le processus d'électropolymérisation de l'aniline dans une solution d’acide chlorhydrique ont été étudiés.La voltammétrie cyclique (CV), la chronoampérométrie et la spectroscopie d'impédance électrochimique (EIS), ont été utilisées pour examiner le processus de transfert de masse et le processus de réaction électrochimique. Différentes techniques, telles que la microscopie électronique à balayage (MEB), la microscopie à force atomique (AFM) et la diffraction à rayons X (XRD) ont été utilisées pour caractériser les revêtements préparés.Les résultats montrent que la vitesse de dépôt augmente avec la force magnétique et la concentration du monomère d’aniline en raison de la convection magnétique et les propriétés magnétiques du radical.L’imagerie MEB et l'analyse topologique ont révélé que, sous MF les films sont essentiellement composés de gonflement des nanofibres et des ilots des polymères qui sont bien répartis sur la surface. Les études de diffraction à rayons X révèlent une amélioration de la cristallinité des couches, sans orientations préférentielles.Mots clés: polymère, polyaniline, aniline, champ magnétique, électropolymerisation, impédance électrochimique, DFT, susceptibilité magnétique. / The effects of static orthogonal magnetic force (MF) on the electropolymerization process of aniline from hydrochloric bath have been investigated. Cyclic voltammetry (CV), Chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques were used to examine the mass transfer process and electrochemical reaction process. Different techniques, such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) were employed to characterize the prepared coatings. The results show that deposit rate increased with increasing MF and aniline monomer concentration due to the magneto-convection involving the mass transport and radical magnetic properties. SEM imagery and topological analysis revealed that under MF the films are essentially composed of swelling of the nanofibers and ilots of polymers that are well distributed on the surface. The XRD studies reveal an enhancement of the crystallinity of the coatings without any preferential orientations.Keywords: Polymers, Polyaniline, aniline, Magnetic fiels, Electropolymerization, electrochemical impedance, DFT, magnetic susceptibility .

Nesse trabalho é apresentado o estudo de redes neurais artificiais (RNAs) como sistemas de aprendizado, simulação e otimização de processos de deposição de filmes finos poliméricos. Duas técnicas de deposição comumente utilizadas para a fabricação de dispositivos eletrônicos e sensores poliméricos foram escolhidas: i) spin coating ou centrifugação e ii) automontagem. Na primeira técnica, a espessura final dos filmes finos obtidos foi a característica avaliada em função da velocidade de rotação, do tempo de rotação e da concentração da solução polimérica. Como material de deposição, utilizou-se a poli(o-metoxianilina) (POMA). Com a segunda técnica analisou-se a influência sobre a espessura, sobre a condutância elétrica e sobre o espectro de absorção, do número de bicamadas, do tempo de exposição dos filmes a uma solução dopante de ácido clorídrico (HCl) e do pH das mesmas. Os poliíons utilizados nessa técnica foram a polianilina (PAni) e o poli(vinil sulfato de sódio) (PVS). Os filmes obtidos pela segunda técnica de deposição constituem uma classe de sensores capazes de detectar e quantificar concentrações baixas de HCl diluído em água. Os treinamentos e simulações com redes neurais artificiais foram realizados apenas para a espessura dos filmes de POMA e a absorção dos filmes de PAni/PVS. Foram construídas redes neurais artificiais do tipo multilayer perceptron (MLP) utilizando o software MATLAB e o componente Neural Networks Toolbox. A reprodutibilidade e o número de neurônios contidos na camada intermediária foram avaliados. Os resultados mostram que as redes neurais artificiais treinadas fornecem boas respostas simuladas interpolando e extrapolando os valores experimentais utilizados. Como conclusão mostra-se que é possível a utilização dessa ferramenta para auxiliar a engenharia de processos, as técnicas e análises de deposições de filmes finos poliméricos. / In this work it is shown a study of artificial neural networks used as learning and simulating systems to optimize polymeric thin films deposition processes. Two common layer deposition techniques to fabricate polymeric electronic devices and polymeric sensors were chosen: i) spin coating and ii) self-assembly. In the first technique the final thickness of obtained thin films was the analyzed characteristic as a function of spin speed, spin time and solution concentration. For the deposited layers we used poly(o-methoxyaniline) (POMA). In the second technique we analyzed the influence of the number of bilayers, the pH of deposition solutions and the dipping time in the final thickness, electrical resistance and UV-Vis absorption spectra. As polyions, we used polyaniline (PAni) and poly(vinyl sodium sulfate) (PVS). These films could be used as a sensor to detect low concentrations of HCl diluted in water. After obtaining the experimental data we constructed artificial neural networks using multilayer perceptrons (MLP) architecture with MATLAB and its component called Neural Networks Toolbox. The number of neurons in the hidden layer and the reproducibility were analyzed. The results show that the trained artificial neural networks used in this work provide good simulation responses interpolating and extrapolating the experimental data. As a conclusion we show that it is possible to utilize this tool to aid the process engineering and the polymeric thin film deposition techniques and analysis

Organic electronics is the study of organic materials with electronic functionality and the applications of such materials. In the 1970s, the discovery that polymers can be made electrically conductive led to an explosion within this field which has continued to grow year by year. One of the attractive features of organic electronic materials is their inherent mechanical flexibility, which has led to the development of numerous flexible electronics technologies such as organic light emitting diodes and solar cells on flexible substrates. The possibility to produce electronics on flexible substrates like plastic or paper has also had a large impact on the field of printed, electronics where inks with electronic functionality are used for large area fabrication of electronic devices using classical printing methods, such as screen printing, inkjet printing and flexography. Recently, there has been a growing interest in the use of cellulose in organic and printed electronics, not only as a paper substrate but also as a component in composite materials where the cellulose provides mechanical strength and favorable 3D-microstructures. Nanofibrillated cellulose is composed of cellulose fibers with high aspect-ratio and diameters in the nanometer range. Due to its remarkable mechanical strength, large area-to-volume ratio, optical transparency and solution processability it has been widely used as a scaffold or binder for electronically active materials in applications such as batteries, supercapacitors and optoelectronics. The focus of this thesis is on flexible devices based on conductive polymers and can be divided into two parts: (1) Composite materials of nanofibrillated cellulose and the conductive polymer PEDOT:PSS and (2) patterning of vapor phase polymerized conductive polymers. In the first part, it is demonstrated how the combination of cellulose and conductive polymers can be used to make electronic materials of various form factors and functionality. Thick, freestanding and flexible “papers” are used to realize electrochemical devices such as transistors and supercapacitors while lightweight, porous and elastic aerogels are used for sensor applications. The second focus of the thesis is on a novel method of patterning conductive polymers produced by vapor phase polymerization using UV-light. This method is used to realize flexible electrochromic smart windows with high-resolution images and tunable optical contrast.

Magister Scientiae - MSc (Chemistry) / The increasing cost of fossil fuel energy production and its implication in environmental pollution and climate change created high demand for alternative and renewable sources of energy. This has led to great interest in research in the field of photovoltaic or solar cells Due to the abundance of sunlight, the technology is sustainable, non-polluting and can be implemented at places where power demand is needed, for example in rural areas. Solar cell devices that have been commercialized are currently based on silicon technology, involving the use of monocrystalline, polycrystalline and amorphous silicon. Although they produce highly efficient solar cells, the cost of Si solar cells is too high. Second generation solar cell materials such as cadmium telluride and third generation materials such as perovskites and organic polymers have been receiving much attention recently. However, they lack the efficiency of Si solar cells. This research proposes the development of high energy conservation photovoltaic cells from novel low-cost organosilicon polymers. The aim was to develop novel highly branched organosilane polymers such as poly(3-hexythiophene), polydi(thien-2-yl)dimethylsilane, poly(3-hexyl- [2,2'] bithiophenyl-5-yl)-dimethyl-thiophen-2yl-silane) as electron donors along with zinc oxide nanorod as the electron acceptor which were able to bring the efficiency of the resultant photovoltaic cell close to that of current Si solar cell. / 2021-08-31

Le travail reporté dans ce manuscrit concerne l’élaboration de matériaux conducteurs protoniques et anioniques destinés à une application en tant que membrane ou liants d’électrodes. Tout d’abord, la première approche consiste en la formation de polymères pour la conception de membranes anioniques. Pour cela, 2 types de fonctions amine tertiaire ont été greffés le long de la chaîne des polysulfones, puis transformés en ammonium pour leur donner un caractère conducteur anionique. Les fonctions greffées sont de types diméthylamino et N,N diméthylaminométhyle. Différentes séries de polysulfones ont été élaborées en faisant varier le taux de fonctions amine greffées. Pour les polysulfones comportant les fonctions diméthyalmino, les résultats montrent que la stabilité thermique des fonctions ammonium est trop faible pour les utiliser pour la conception de membranes conductrices anioniques. Pour le deuxième type de fonctions amine, des membranes ayant une conductivité maximum de 40 mS.cm-1 pour un taux d’humidité de 95% et une température de 100°C ont été obtenu. Par ailleurs, pour la conception de liants d’électrodes, la synthèse de polyarylènes éthers fluorés conducteurs anioniques a été effectuée. Là encore, une série de polymères a été réalisée en faisant varier le taux de fonctions amine introduit. Les masses molaires ont été controlées pour permettre aux polymères d’être suffisamment soluble pour la mise en solution. Les valeurs de conductivités sont de l’ordre de 35 mS.cm-1. Enfin, pour la conception de membrane protonique, les polymères synthétisés précédemment avec les fonctions diméthylamino ont été utilisés. Ces polymères ont été par la suite dopés à l’aide d’acide phosphorique et la conductivité des membranes obtenues a été testée en condition anhydre. Les résultats obtenus pour ce genre de matériaux est de 160 mS.cm-1 pour un taux de dopage de 50%. En revanche, pour des forts taux de dopage, la conductivité obtenue était plus forte (260 mS.cm-1) mais les membranes perdaient de leurs propriétés mécaniques alors que pour de faibles taux de dopage (environ 18%), les conductivités obtenues étaient faibles. / The work reported in this thesis is the development of proton and anion conducting materials for applications such as membrane or binders electrodes. The first approach is the formation of polymers for the anionic membranes design. To perform it, two types of tertiary amine functions have been grafted along the polysulfones chain, then converted to ammonium rendering data anionic conductive. The grafted functions types are dimethylamino and N, N dimethylaminomethyl. Different series of polysulfones were prepared by varying the rate of amine functions grafted. For polysulfones with dimethyalmino functions, the results show that the thermal stability of ammonium functions is too low to be used in anion conductive membranes design. In the second type of amine, membranes having a maximum conductivity of 40 mS.cm-1 to a moisture content of 95% and a temperature of 100 °C have been obtained. In addition, for the electrodes binders design, the synthesis of fluorinated ethers polyarylenes anionic conductors has been completed. Then, a series of polymers was carried out by varying the rate of amine introduced. The molar masses were controlled to allow polymers to be sufficiently soluble for the dissolution. Conductivity values are around 35 mS.cm-1. Finally, the design of membrane proton polymers synthesized with previously dimethylamino functions has been chosen. These polymers were subsequently doped with phosphoric acid and the conductivity of the resulting membranes has been tested in anhydrous condition. The results obtained for this kind of material is 160 mS.cm-1 for a doping level of 50%. However, for high doping level, conductivity obtained was higher (260 mS.cm-1) but the membranes lost their mechanical properties, while for low doping levels (about 18%), the conductivities obtained were low.

Este trabalho descreve a preparação e caracterização de eletrodos modificados com azul da Prússia e materiais relacionados e a sua aplicação na construção de biossensores enzimáticos amperométricos para a detecção de oxalato e de glicose. Os materiais utilizados na modificação dos eletrodos foram azul da Prússia e compostos híbridos formados por hexacianoferrato de níquel e polipirrol ou hexacianoferrato de cobre e polipirrol. Os materiais lubridos mostraram-se capazes de mediar na eletroredução de peróxido de hidrogênio, mesmo em eletrólitos contendo Na+, apresentando melhor desempenho analítico quando comparados aos respectivos hexacianoferratos sem a presença do polímero condutor. Estes materiais foram utilizados com êxito na construção de biossensores para oxalato e para glicose, imobilizando as enzimas Oxalato Oxidase e Glicose Oxidase, respectivamente. Também foi estudada a preparação de um biossensor para a detecção de glicose utilizando a técnica de automontagem eletrostática camada por camada. Esta técnica permite otimizar o processo de immobilização da enzima, obtendo excelente desempenho analítico com pouca quantidade de enzima. Finalmente, são apresentadas a síntese, caracterização e aplicação de nanopartículas de azul da Prússia na determinação de peróxido de hidrogênio. Foi possível preparar nanopartículas com um diâmetro médio de 5 nm, as quais foram imobilizadas em eletrodos mediante a técnica de automontagem eletrostática camada por camada, a fim de estudar seu comportamento eletroquímico. / This work describes the preparation and characterization of modified electrodes with Prussian blue and some analogues and their application in the development of amperometric enzymatic biosensors for the detection of glucose and oxalate. The materials used in electrode modification were Prussian blue and hybrid compounds, formed by nickel hexacyanoferrate and polypyrrole or copper hexacyanoferrate and polypyrrole. These materials were able to mediate the hydrogen peroxide electroreduction even in electrolytes containing Na+, showing better analytical performance than the hexacyanyoferrates without polypyrrole. These materials were successfully used to build up oxalate and glucose biosensors. We also have studied the preparation of glucose biosensors using the layer by layer self assemble technique (LBL), which has optimized the enzyme immobilization process, obtaining good analytical performances even loading small amounts of enzyme. FinaIly, we have described the synthesis and characterization of Prussian blue nanoparticles by a sonochemical method. It was possible to synthesize nanoparticles with a diameter around 5 nrn, which were immobilized by the LBL technique, in order to study their electrochemical behavior.

O Nafion é um ionômero constituído por uma matriz de politetrafluoroetileno (PTFE) contendo ramificações laterais terminadas em grupos sulfônicos. Neste trabalho, a membrana na forma ácida e nas formas salinas (Li+, Na+, K+, Rb+ e Cs+) foram analisadas, via espectroscopia vibracional e análise térmica. Para proceder à análise vibracional, dividiu-se o ionômero em três grupos, cada qual pertencente a um grupo pontual distinto: o grupo sultanato (C3v) ; o grupo éter (C2v) e a matriz fluorocarbônica D(14π/15). O grupo sulfonato apresenta modos vibracionais de estiramento simétrico (1060 cm-1) e de estiramento degenerado (na região de 1300 cm-1). O Nafion apresenta dois grupos éter, os quais deram origem no espectro a duas bandas: uma em 984 e outra na região de 970 cm-1. Verificou-se que apenas a banda em 970 cm-1 sofre uma influência mais direta do ambiente iônico. A atribuição das bandas da matriz polimérica foi feita considerando-se que a cadeia de PTFE apresenta estrutura helicoidal (157) . Nesta estrutura são previstas a existência de quatro espécies de simetria que apresentam atividade nos espectro Raman e infravermelho. No Raman são ativos os modos de espécie A1, E1 e E2 e no infravermelho são ativos os modos de espécie A2 e E1. A análise térmica dividiu-se em: termogravimetria e calorimetria exploratória diferencial. A termogravimetria mostrou que a membrana na forma ácida apresenta um padrão de decomposição distinto das membranas nas formas salinas. A calorimetria exploratória diferencial mostrou que a membrana na forma ácida apresenta três eventos endotérmicos: em 134ºC, em 250ºC e o último em 325ºC. Na membrana nas formas salinas apenas o primeiro pico endotérmico é bastante evidente, o segundo pico é pouco pronunciado e o terceiro está completamente ausente. / Nafion is an ionomer that consists of a polytetrafluoroethylene (PTFE) backbone with side chains terminated with a sulfonate group. In this work, Nafion in acid and saline forms (Li+, Na+, K+, Rb+ e Cs+) forms were investigated by vibrational spectroscopy, thermogravimetry and differential scanning calorimetry. To proceed to the vibrational analysis the ionômero was splitted into three regions and which one has its own symmetry group. Sulfonate group (C3v), ether group (C2v) and the polymeric matrix D(14π/15). The sulfonate group presents two modes: the symmetric stretching (1060 cm-1) and the degenerated stretching (around 1300 cm-1). Nafion has two ether groups which originated two bands: one in 984 and the other in 970 cm-1. We verify that only the band in 970 cm-1 is affected by the ionic ambient. The assignment of the polymeric band was made considering that the PTFE has helicoidal structure (157). In this structure four symmetry species are predicted. In Raman spectra the following species are active: A1, E1 and E2 and the infrared are active the species: A2 and E1. Thermal analysis consisted of thermogravimetry and differential scanning calorimetry. Thermogravimetry shows that water content is dependent of cation change. Thermogravimetry also shows that the membrane in the acid and saline forms have different mechanisms of decomposition. Differential scanning calorimetry of Nafion-H shows three endothermic peaks: the first in 134ºC, the second in 250ºC and the last in 325ºC. Nafion saline forms shows only the first peak.

Neste trabalho sintetizamos o poli(2-hidrocloreto de 2-piridinium-2-piridilacetileno ), P2EPH, e o estudamos do ponto de vista vibracional. O produto obtido na síntese deste polímero possuía quantidade diferente de anéis piridínicos protonados e não protonados em relação àquela proposta na literatura, indicando a necessidade de uma revisão do mecanismo sugerido para esta polimerização. Para a obtenção dos espectros Raman do P2EPH, a interferência da fluorescência apresentada por este polímero na região visível foi eliminada pela utilização de superfícies de prata metálica ( eletrodo, pastilha e colóide) ou de radiação excitante no UV (244,0 nm). A obtenção dos espectros Raman deste polímero permitiu uma atribuição mais precisa de suas bandas através da comparação com os espectros Raman de outros polímeros similares. Esta, por sua vez, possibilitou a correção da atribuição corrente na literatura das bandas do estiramento C=C da cadeia polimérica e do anel piridínico. Variando a energia da radiação excitante percebemos que a frequência de algumas bandas Raman (em aproximadamente 1160, 1230, 1300 e 1500 cm-1) apresentavam deslocamento. Esta característica, denominada dispersão Raman ou fotosseletividade, também é notada para o poliacetileno e é atribuída à heterogeneidade da amostra polimérica. Outra variação observada nos espectros Raman com diferentes excitações foi a da intensidade relativa das bandas. Para radiações excitantes de menor energia as bandas mais proeminentes do espectro foram aquelas atribuídas, principalmente, a vibrações da cadeia poliacetilênica, enquanto que, para excitações de maior energia as bandas relativas aos anéis de piridina e piridinium se sobressaíram. Esta diferença é atribuída à ressonância das radiações excitantes com os diferentes cromóforos do polímero. Mesmo quando a excitação foi feita com radiação em 244 nm alguns modos da cadeia poliacetilênica puderam ser observados e quando utilizamos radiação excitante em 632,8 nm apareceram bandas dos anéis piridínicos, mostrando que existe acoplamento mecânico entre os cromóforos. Também estudamos o comportamento do monômero do P2EPH, a 2-etinilpiridina, em eletrodo de prata variando o potencial aplicado e o pH da solução, através do efeito SERS (Surface Enhanced Raman Scattering). As variações observadas na intensidade das bandas foram interpretadas considerando uma mudança de orientação da molécula em relação à superfície. Foi também observada a formação do íon 2-piridilacetileto (formado pela abstração do hidrogênio acetilênico da 2-etinilpiridina) em potenciais inferiores ou igual a −0,7 V na solução não acidulada. / In this work we synthesized and studied the vibrational spectra of poly(2-pyridinium hydrochloride-2-pyridylacetylene ), P2EPH. This polymer presents different amounts of pyridine and pyridinium rings when compared with previously reported data in literature. This difference points out the need of a review in the proposed mechanism. The fluorescence interference presented by this polymer was precluded using silver surfaces (electrode, pellet or colloid) or excitation in 244.0 nm. Raman spectra obtained through these techniques were useful to improve the assignment of P2EPH peaks. Toe assignment proposed in this work corrects the current one, showing that the peaks due to polyacetylenic backbone, pyridine and pyridinium ring C=C stretching appear, respectively, at 1532, 1588 and 1620 cm-1. When the energy of the excitation was changed we observed a shift in some Raman bands (close to 1160, 1230, 1300 and 1500 cm-1). This feature, called Raman dispersion or photoselectivity, has been observed in polyacetylene and was related to the polymeric sample inhomogeneity. Besides the frequency variation, the relative intensities have changed with different exciting radiation. When lower energy radiation was used, the Raman spectra obtained were similar to the polyacetylene spectrum, while, for higher energy the most intense peaks observed were pyridine and pyridinium ring vibrations. These changes in relative intensities are due to the resonance of the incident light with different chromophoric groups in the polymer. In spite of this, some peaks from backbone were observed in UV-Raman spectrum and a group of pyridine and pyridinium bands were still observed with excitation in 632.8 nm, showing the presence of mechanical coupling between the backbone and side groups vibrations. We also studied the SERS (Surface Enhanced Raman Scattering) behaviour of the P2EPH monomer, 2-ethynylpyridine, in silver electrode sweeping the potential and changing the solution pH. The changes in the band intensities were assigned to different molecule orientation on the surface. The ion 2-pyridylacetylide (2-ethynylpyridine without the acetylenic proton) was formed when the potential was − 0,7 V or more negative than that.

Os objetivos do trabalho consistem em síntese e caracterização de três polímeros: poli(2,1,3-benzotiadiazol-4,7-ilenovinileno) (PBTDV), poli(2,1,3-benzotiadiazol-4,7-ilenovinileno-co-2-bromo-5-hexilóxi-p-fenilenovinileno (PBTDV-co-BHPPV) e poli(2-bromo-5-hexilóxi-p-fenilenovinileno) (BHPPV), sendo os dois primeiros inéditos; aplicação de polímeros condutores no desenvolvimento de um nariz eletrônico capaz de identificar madeiras; e aplicação de polímeros condutores em um sensor de pressão. Os polímeros foram preparados de maneira satisfatória via redução catódica de seus precursores tetra-halogenados, que forneceu produtos com rendimentos apreciáveis. Para o projeto do nariz eletrônico que pretende identificar madeiras, dois conjuntos de espécies de madeira foram estudadas: (a) mogno e cedro e (b) imbuia e canela-preta. O nariz eletrônico desenvolvido apresenta um conjunto de quatro sensores de gás, que foram construídos por meio da deposição de finos filmes de polímeros dopados sobre a superfície de eletrodos interdigitados. Esse conjunto de sensores foi desenvolvido com sucesso, sendo capaz de diferenciar as espécies de madeira com taxa de acerto de 100%. Por fim, foi desenvolvido também com sucesso um sensor de gás capaz de atuar como sensor de pressão. Esse dispositivo mostrou-se sensível à variação de pressão, do vácuo a ambiente, e os ensaios apresentaram boa reprodutibilidade. A resposta do sensor, frente à variação de pressão, é produto de interação(ões) entre a camada ativa do polímero utilizado (PHBPE, poli(4\'-hexilóxi-2,5-bifenilenoetileno)) e algum(ns) componente(s) do ar atmosférico ou da atmosfera particular do laboratório. Esse sensor é de fácil fabricação e barato (~ R$ 1,00), sendo possível sua aplicação como sensor para pressões menores do que a ambiente / The syntheses of three polymers via electrochemical reduction of their precursors are described. Two out of the three generated polymers have never been described before. An electronic nose was developed capable of identifying two pairs of wood species: (a) mahogany and cedar and (b) Brazilian walnut and black-cinnamon. The electronic nose consisted of four gas sensors, fabricated by the deposition of thin doped polymer films onto the surface of interdigitated electrodes. The device presented a rate of hits of 100% in 80 assays of identification of the above cited species. Finally, a gas sensor based on a conductive polymer and capable of acting as a pressure sensor was fabricated. The sensor was suitable for measuring air pressures in the range of 100 mmHg to 700 mmHg due to its sensibility to one or more specific compounds present in the air. The device is cheap, easy to fabricate and lasts for several months

Les matériaux thermoélectriques (TE) permettent de convertir directement de la chaleur en électricité et vice-versa. Les objectifs de cette thèse étaient de tenter d'améliorer les performances TE de trois familles de matériaux et de mieux comprendre le lien entre les propriétés physiques (électriques, thermiques, magnétiques) généralement mesurées dans une large gamme de température (5–700 K) et les microstructures/compositions chimiques observées. Généralement, les matériaux ont été synthétisés par des techniques de métallurgie des poudres et densifiés par spark plasma sintering. La majeure partie de nos travaux a concerné la famille des matériaux tétraédrites, dérivés du minéral naturel (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13, présentant des propriétés TE prometteuses, récemment mises en évidence. D’abord, les propriétés TE de huit tétraédrites naturelles de provenance différente ont été étudiées. Nous avons montré que leurs propriétés physiques sont plutôt prévisibles selon leur composition chimique et finalement peu différentes selon leur origine. Les propriétés TE de mélanges de tétraédrites naturelles et synthétiques obtenus par broyage mécanique ont ensuite été déterminées. Ce procédé fortement énergétique produit des particules de taille nanométrique des deux phases qui forment une solution solide pendant le frittage. Par contre, un broyage manuel conserve la présence des deux phases, ce qui conduit à de plus faibles performances TE. Ensuite, nous avons montré que la substitution Sb <-> As, usuelle dans les spécimens naturels, n’influence que faiblement les propriétés TE. Enfin, les propriétés TE de manganites de calcium et de polymères conducteurs ont également été étudiées / Thermoelectric (TE) materials allow direct conversion between heat and electricity. The aim of this thesis was to try to improve the thermoelectric performance of three different families of materials and to better understand the link between the various physical properties (electrical, thermal, magnetic) generally measured in a broad temperature range (5–700 K) and the observed microstructure/chemical composition. In general, the materials were synthesized by powder metallurgy techniques and densified by spark plasma sintering (SPS). The major part of our studies concerns the tetrahedrite family of materials, derived from the mineral tetrahedrite, (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13, whose promising thermoelectric properties were only recently discovered. In a first approach, the TE properties of eight natural tetrahedrites of different geographic origin are studied. It is shown that they all behave rather predictably and uniformly. Next, the properties of ball milled mixtures of natural and synthetic tetrahedrites are investigated. This high-energy process yields nanoscale particles of the two phases, which form a solid solution during the sintering. Low-energy hand grinding preserves the two-phase nature and results in inferior TE performance. Because arsenic is a common substituent in natural specimens, several As-substituted tetrahedrites are synthesized and characterized. It is shown that the TE properties are only weakly influenced by the substitution of As for Sb. Besides tetrahedrites, calcium manganese oxides and conductive polymers are also studied