L’objectif de ce travail de thèse était de développer des encres organiques de polymères semi-conducteurs. Il s’est ainsi agi de synthétiser des latex de poly (3,4-éthylènedioxythiophène) (PEDOT) dispersibles en milieux organiques (cyclohexane ou toluène) par polymérisation oxydative de l’EDOT en présence de stabilisant stériques et/ou électrostatiques. Le stabilisant est un polymère fonctionnalisé par une unité ou plusieurs unités fonctionnelles qui peuvent réagir avec la chaîne de PEDOT en croissance assurant ainsi des liaisons covalentes ou électrostatiques entre celui-ci et le stabilisant. La taille des particules de PEDOT est contrôlée par la masse molaire, la concentration et par la fonctionnalité du stabilisant. Le PEDOT obtenu est caractérisé par diffusion de la lumière (DLS), par microscopie électronique à balayage (MEB) microscopie électronique à transmission (TEM) et par des mesures de conductivité. / Spherical poly(3,4-ethylenedioxythiophene) nano-particles with narrow size distribution were prepared in organic dispersant media in the presence of iron(III) chloride FeCl3 or iron(III) dodecylbenzenesulfonate {Fe(DBS)3} as oxidant and a functionalized polyisoprene (ω-R-PI) as a stabilizer. Two kinds of functionalized polyisoprene were used as stabilizers. Pyrrole, fluorene, Thiophene and methylthiophene end caped polyisoprenes were used as reactive stabilizers. Lithium sulfonate end caped polyisoprene was used as steric stabilizer. The effect of the nature of the solvent, the molar mass, the concentration, and the nature of the functional end unit of the stabilizer on the size and morphology of PEDOT particles were investigated. Polyisoprenes containing sulfonate groups were also used as steric/electrostatic stabilizers. By this way, the sulfonate groups act as counter ions for oxidized PEDOT leading to electrostatic attraction between it and the stabilizer, ensuring stabilization of the latex. Four kinds of polyisoprene-based steric electrostatic stabilizers having one or many sulfonate groups were prepared: sulfonate end-capped polyisoprene (PI-SO3Li), partially sulfonated polyisoprene (PIS), polyisoprene grafted to polystyrene sulfonate (PI-g-PSS) and polyisoprene grafted to polyisoprene sulfonate (PI-g-PIS). The effects of the molar mass of the stabilizer and the sulfonate group content on the PEDOT particle morphology were studied.PEDOT samples were characterized with transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), dynamic light scattering (DLS) analysis and conductivity measurements.

Poly(3,4-ethylendioxythiophen) (PEDOT) ist ein Kunststoff der zur Gruppe der intrinsisch leitfähigen Polymere (ILP) zählt. Aufgrund seiner chemischen und thermischen Stabilität findet er Verwendung in antistatischen Verkleidungen und als Elektrodenmaterial. PEDOT (und andere ILP) zeigen aufgrund ihrer Schaltbarkeit zwischen (reduzierten, ) neutralen und oxidierten Zuständen unterschiedliche Eigenschaften wie Leitfähigkeit, Farbe oder Viskoelastizität. Im Rahmen dieser Arbeit wurden die elektrochemischen und viskoelastischen Eigenschaften von PEDOT-Filmen untersucht. Dabei wurde die Quarzmikrowaage (QCM) in Verbindung mit potentiostatischen (Potentialsprung, PS) und potentiodynamischen (Cyclovoltammetrie, CV) elektrochemischen Methoden verwendet, so dass in situ elektrochemische und mechanische Eigenschaften der Filme zugänglich waren. Zur Bestimmung der viskoelastischen Eigenschaften wurde ein Auswertealgorithmus entwickelt, welcher auf ein mathematisches Modell zur Bestimmung des Schermoduls nach Efimov zurückgreift. Während der Herstellung wurden Parameter wie Lösungsmittel, Leitsalz, Vorpolarisations- und Abscheidungspotential variiert und die erhaltenen Filme bezüglich Schermodul und Morphologie charakterisiert. Es konnte gezeigt werden, dass die Elektrolytzusammensetzung einen entscheidenden Einfluss auf die viskoelastischen Eigenschaften der Filme besitzt, welche mit der Morphologie der Filme korrelieren. Des Weiteren wurden die Änderungen der viskoelastischen Eigenschaften dieser Filme untersucht, welche während dem elektronischen Schalten zwischen neutralem und oxidiertem Zustand aufgrund des Ionenaustausches erfolgen. CV- und PS-Experimente zeigten, dass die viskoelastischen Eigenschaften durch Konzentration und pH-Wert des Elektrolyten beeinflusst werden und in unterschiedlicher Weise auf die Potentialänderungen reagieren. Durch den Einbau von Magnetit-Partikeln in die Schichten konnten Hybridfilme erhalten werden, deren Eigenschaften durch das Anlegen eines äußeren Magnetfeldes beeinflusst werden können. Solche Filme zeigten in einem äußeren Magnetfeld (0,7T) höhere Schermodule und einen stark unterdrückten Ionenaustausch.

The subject of the present licentiate thesis is density functional theorybased electronic structure calculations of organic thermoelectric materials and novel organic molecules. We used the Car-Parrinello molecular dynamics method in order to investigate the electronic structure of “green energy” and “greenchemistry” compounds. First, we have investigated the electronic structure of the poly(3,4-ethylene-dioxythiophene) (PEDOT) and its derivatives - the best studied and successfully implemented by industry organic thermoelectric material. Its transparency, low toxicity and high stability in the oxidized state are combined withan ability to produce electrical current when applying a temperature gradient. This makes PEDOT a perfect “organic metal” and a first candidate for organic thermoelectrogenerators - devices that can produce “green energy” from a temperature difference. The average structures found in these quantum dynamical simulations agree well with earlier static electronic structure studies. The energy gap of two, four and six unit oligomers of PEDOT was calculated and was found to lie in the range of previous theoretical studies. We have also calculatedthe point-charge distributions along the polymer backbone in order to investigate the polaron formed by doping agents of PEDOT. Our analysis allowed us to predict possible localization of the charge in the center of the polymer chain. However, further calculations of the twelve unit PEDOT and its selenium and tellurium derivatives will provide more information. First-principles calculations for the tellurium derivative of PEDOT are here presented for the first time. The second part of our investigation concerns theoretical calculations of novel piperidine-containing acetylene glycols. These molecules were newly synthesized by our experimental collaborators and are expected to provideplant growth stimulation properties, the same as its diacetylene analogs. We performed quantum mechanical calculations of four compounds, presented ananalysis of the highest occupied and lowest unoccupied molecular orbitals and collected detailed information on point-charges for further parametrization of novel molecules for future computational studies. According to these results, the low production yield found in the experiments cannot be attributed to chemical instability in these novel compounds. / <p>QC 20150629</p> / ScalTEG SSF

Conductive polymers are also known as "organic metals" due to their semiconducting properties. They are found in a wide range of applications in the field of organic electronics. However, the growing number of experimental works is not widely supported with theoretical calculations. Hence, the field of conductive polymers is experiencing lack of understanding of mechanisms occurring in the polymers. In this PhD thesis, the aim is to increase understanding of conductive polymers by performing theoretical calculations.        The polymers poly(3,4-ethylenedioxythiophene) (PEDOT) together with its selenium (PEDOS) and tellurium (PEDOTe) derivatives, poly(p-phenylene) (PPP) and naphthobischalcogenadiazoles (NXz) were studied. Several computational methods were applied for analysis of mentioned structures, including density functional theory (DFT), tight-binding modelling (TB), and Car-Parrinello molecular dynamics (CPMD) calculations. The combination of CPMD and DFT calculations was applied to investigate the PEDOT, PEDOS and PEDOTe. The polymers were studied using four different functionals in order to investigate the full picture of structural changes, electronic and optical properties. Temperature effects were studied using molecular dynamics simulations. Wide statistics for structural and molecular orbitals analysis were collected.         The TB method was employed for PPP. The formation and motion of the excitations, polarons and bipolarons, along the polymer backbone was investigated in presence of electric and magnetic fields. The influence of non-magnetic and magnetic impurities was determined.        The extended π-conjugated structures of NXz were computed using B3LYP and ωB97XD functionals in combination with the 6-31+G(d) basis set. Here, the structural changes caused by polaron formation were analyzed. The combined analysis of densities of states and absorption spectra was used for understanding of the charge transition. / <p>QC 20170928</p>