The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe. The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction. The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads. / <p>QC 20170407</p>

Les nanoparticules (NPs) de métaux nobles ont de nombreuses applications grâce à leurs propriétés optiques, chimiques et électriques extraordinaires. Les propriétés optiques résultent de plasmons localisés de surface, exaltant l’absorption et la diffusion de la lumière aux longueurs d’onde de résonance dans le domaine du visible. Les propriétés optiques, dépendantes de la taille et de la forme exacte de la NP, sont mises à profit dans l’objectif de créer un absorbant parfait en couche mince. Les applications de ces couches minces concernent, parmi d’autres, les photodétecteurs, le solaire thermique et les applications de furtivité.Les récents progrès accomplis dans le domaine des synthèses colloïdales de NPs nous permettent de synthétiser des nanosphères, nanocubes et nanoprismes d’Ag de différentes tailles. Ces NPs sont déposées aléatoirement dans une matrice hôte non-absorbante afin d’être caractérisées optiquement. Les résultats expérimentaux sont validés à l’aide de calculs numériques, permettant en outre de visualiser les phénomènes physiques à l’échelle de la NP.Cette thèse décrit les synthèses chimiques et les caractérisations optiques. Des mesures de spectroscopie ellipsométriques sont effectuées sur différentes couches minces. Un modèle optique simple, constitué d’une loi de Cauchy et d’une ou plusieurs lois de Gauss, est dérivé afin d’obtenir les indices optiques complexes de nos échantillons. La comparaison des coefficients d’extinction des différentes couches montre que les propriétés optiques de chaque NP sont additionnées en mélange et en empilement. Les calculs numériques relient ce résultat à la faible densité de nanoparticules en couche. / Noble metal nanoparticles (NPs) have a broad range of applications thanks to their extraordinary optical, chemical and electrical properties. The optical properties are driven by their ability to support localized surface plasmon resonances, which induce enhanced absorption and scattering at their resonance wavelengths in the visible spectrum. These size and shape dependent optical properties are taken advantage of in the search for a thin film layer perfect absorber in the visible wavelength band. The application for such thin film layers with engineered optical properties ranges from photodetectors, over thermal solar cells to stealth applications.Recent progress in colloidal NP synthesis makes the chemical wet synthesis of silver nanospheres, nanocubes and nanoprisms of various sizes easily feasible. The different NPs are then randomly deposited in a transparent and non-absorbing host matrix for optical characterizations. Computer simulations validate the experimental results and allow a visualization of the phenomena occurring at the nanoparticle scale.This PhD thesis reports the chemical synthesis of the different nanoparticles and their optical characterizations. Spectroscopic ellipsometry measurements are performed on single shape NPs, blends and multilayer stacks. A simple diffusion model, composed of a single Cauchy law and one or several Gauss laws, is chosen to determine the complex optical indices. The comparison of the extinction coefficients of the different layers shows that the optical properties of each NP are simply added in the blend and multilayer samples. Computer simulations relate this to the low density of nanoparticles.

Este trabalho visou investigar as interações entre enzimas e polímeros em solução e a adsorção das mesmas sobre superfícies sólidas e para isto foi dividido em duas partes distintas. Na primeira parte a influência do poli(etileno glicol) (PEG), polímero considerado inerte e utilizado em muitos processosbiotecnológicos, na atividade enzimática e na conformação estrutural de enzimas foi estudada através de medidas de espectrofotometria- UV, calorimetria e espalhamento de raio-X de baixo ângulo (SAXS). Foram escolhidas neste estudo as enzimas glicose-6-fosfato desidrogenase (G-6-PDH) e hexoquinase (HK), que são enzimas largamente aplicadas em análises clínicas na determinação de glicose no sangue, e também a enzima álcool desidrogenase (AD), utilizada para determinação de concentração de álcool. Foram obtidos resultados quantitativos, numa faixa de baixa concentração de enzima, que indicam uma forte influência de PEG na atividade das enzimas estudadas. Medidas de calorimetria revelaram que PEG interage não só com a enzima em estudo mas também com a coenzima NADP+. Numa faixa de concentração maior, os resultados de SAXS mostraram que PEG exerce também um efeito significativo no processo de agregação das enzimas. Acima de tudo, foi evidenciado neste estudo que PEG não pode ser tratado como um polímero inerte, pois ele interfere na atividade e conformação de enzimas. As enzimas são macromoléculas complexas e PEG interage de forma diferenciada com cada enzima, merecendo atenção especial caso a caso. Na segunda parte do trabalho, o estudo da adsorção de hexoquinase (HK) e creatina fosfoquinase (CPK) sobre lâminas de silício foi realizado através de medidas de ângulo de contato, elipsometria in situ e microscopia de força atômica (AFM) em água. A CPK é uma enzima bastante utilizada em kits de determinação de creatina no sangue e no diagnóstico de desordens musculares. Este trabalho revelou que o mecanismo de adsorção de CPK sobre silício depende fortemente do pH. Em pH 4, 7 ou 9 CPK adsorveu mantendo a mesma conformação que tinha em solução. Medidas de espectrofotometria UV-Vis revelaram uma mudança no pH ótimo para atividade enzimática de CPK de 6,8 para 9 após adsorção. A HK imobilizada em esferas de vidro mostrou atividade maior do que HK imobilizada nas placas. A reutilização das esferas e placas recobertas com HK foi testada e observou-se que as atividades das enzimas adsorvidas no substrato esférico foram mantidas. Entretanto, nas placas revestidas a atividade foi perdida. As enzimas imobilizadas sobre esferas puderam ser reutilizadas pelo menos 3 vezes, mantendo a atividade por um período de até 3 semanas. / This work aimed to investigate the interactions between enzymes and polymers in solution and also the adsorption behavior of these enzymes on solid surfaces. For that reason it was divided into two parts. In the first part, the influence of poly(ethylene glycol) (PEG), a polymer considered inert and utilized in several biotechnological processes, on the enzymatic activity and structure of the enzyme was studied by means of UV spectrophotometry, calorimetric titration, circular dichroism (CD) and small angle X-ray scattering (SAXS). Glucose-6-phosphate dehydrogenase (G-6-PDH) and hexokinase (HK) were chosen because of their large application in clinical analysis for determination of glucose in the blood strain. Alcohol dehydrogenase (AD), which is widely used to determine alcohol concentration in various samples, was also used. Quantitative results, in a low enzyme concentration range, indicated a strong influence of PEG on the enzymes activity. The calorimetric measurements revealed no favorable interactions between enzyme and polymer, but indicated favorable interactions between PEG and co-enzyme NADP+. In a higher concentration range, SAXS results showed that PEG also exerts a significant effect on the enzyme aggregation process. This work showed that PEG shall no longer be treated as an inert polymer since it interferes in the enzyme activity and structure. The enzymes are complex macromolecules and PEG interacts differently with each one, deserving special attention in each case. In the second part of the work, the adsorption behavior of creatine phosphokinase (CPK) and hexokinase (HK) onto silicon wafers was studied by means of contact angle measurements, in situ ellipsometry and atomic force microscopy (AFM) in water. CPK was chosen due to its large application on the diagnosis of several muscle disorders. This work revealed that the adsorption mechanism of CPK on silicon surfaces is strongly dependent on pH. At pH 4, 6.8 or 9, CPK adsorbed keeping the same conformation as in solution. pectrophotometric measurements revealed a shift on the optimum pH from 6,8 to 9 upon CPK adsorption. HK adsorbed onto glass beads showed higher activity than HK immobilized on silicon wafers. HK covered glass beads could also be reused three times and for a period of at least three weeks. In the contrary, HK covered silicon wafers could not be reused. For practical purposes, HK covered glass beads showed to be a better “biosensor" than HK covered silicon wafers.

Ce travail porte sur l’exaltation de l’effet magnéto-optique (MO) Kerr transverse induite par des «résonances extraordinaires» dans un réseau d’or périodique 1D déposé sur un oxyde de grenat magnéto-optique. La structure complète incluant le réseau métallique 1D a été conçue, simulée numériquement, dimensionnée, fabriquée puis caractérisée. Un algorithme de type RCWA (Rigorous Coupled Wave Algorithm) adapté au calcul parallèle a été développé et utilisé d’une part pour l’étude théorique des modes résonants dans les réseaux magnétoplasmoniques et d’autre part pour l’analyse des données de mesures optiques et magnéto-optiques d’ellipsométrie à base de matrices de Mueller. L’impact sur la réflectivité angulo-spectrale du couplage entre les modes Fabry-Pérot des fentes du réseau et les plasmons de surface à l’interface entre l’or et la couche de grenat MO est ainsi étudié, en utilisant les paramètres optiques et magnéto-optiques réels des matériaux. Pour cela, les caractéristiques optiques du substrat en sGGG (grenat de gallium et gadolinium dopé CaMgZr) et du matériau Bi:GIG (grenat de fer et de gadolinium substitué bismuth) sont au préalable déterminés dans la gamme spectrale 0,73 – 6,42 eV (193 nm-1,7 μm) par ellipsométrie à base de matrices de Mueller. Puis de même la dispersion des composantes magnéto-optiques du tenseur diélectrique est obtenue en appliquant un champ magnétique externe dans le plan, en configuration longitudinale ou transverse. Ces données mesurées sont alors utilisées dans les simulations. Il est ainsi démontré numériquement que grâce à l’interaction des résonances de surface et de cavité dans le réseau 1D l’effet Kerr transverse peut être exalté, éteint ou même de signe inversé, et cela sans renverser ou modifier l’aimantation de la couche magnéto-optique. Pour confirmer les résultats théoriques, une série d’échantillons comportant des réseaux de fentes différentes a été fabriquée par lithographie électronique et procédé de lift-off. Afin de reproduire les données des matrices de Mueller mesurées, les modèles ont été adaptés et optimisés pour tenir compte des imperfections des structures réelles. Les mesures expérimentales confirment l’exaltation de l’effet Kerr magnéto-optique transverse due aux effets magnéto-plasmoniques et prouvent la validité des modèles. / This work studies the enhancement of the transverse magneto-optical Kerr effect by exploiting extraordinary resonances occurring in 1D periodic grating. The 1D periodic gold grating structure was designed, described, numerically simulated, and fabricated. A rigorous Coupled Wave Algorithm (RCWA) developed for parallel computing is used for the theoretical study of resonant modes in magnetoplasmonic gratings and for analysis of optical and magneto-optical data measured by Mueller matrix ellipsometry. The impact of coupling between Fabry-Perot modes inside grating air-gaps and surface plasmon mode at the interface between gold and MO garnet layer is studied via spectra of specular reflectivity and for the various angles of incidence. In a first step, the optical functions of the (CaMgZr)-doped gallium-gadolinium garnet (sGGG) substrate and the Bi-substituted gadolinium iron garnet (Bi:GIG) are obtained in the spectral range from 0.73 eV to 6.42 eV (wavelength range 193 nm – 1.7 μm). Subsequently, the spectra of the magneto-optical tensor components are obtained by applying an external in-plane magnetic field in longitudinal and transverse geometry. The obtained functions are then used for numerical simulations demonstrating that by hybridization of surface and cavity resonances in this 1D plasmonic grating, the transverse Kerr effect can be further enhanced, extinguished or even switched in sign and that without inverting or modifying the film's magnetization. To confirm theoretical results a set of samples, gratings with a different width of an air-gap, was fabricated using electron beam lithography and liftoff technique. To be able to reproduce Mueller matrix data from the samples, the models describing realistic structures were further developed and optimized. Experimental measurements of real structures confirm transverse MO effect enhancement using magnetoplasmonic effects and prove applicability of numerical models.

Le but de ce travail de thèse est d’étudier les propriétés d’un plasma réactif ainsi que les caractéristiques structurales, optiques et électriques de couches minces d’oxynitrure de tantale (TaOxNy) élaborées par pulvérisation cathodique radiofréquence. L’élaboration de ce matériau ternaire par pulvérisation d’une cible de tantale au moyen d’un plasma contenant à la fois de l’argon, de l’oxygène et de l’azote est complexe en raison de phénomènes d’empoisonnement de la cible. L’analyse de la composition du plasma par spectroscopie d’émission optique et le suivi de l’évolution de certaines raies représentatives d’espèces excitées dans le milieu, nous ont permis de déterminer les conditions optimales au dépôt de films de types TaOxNy sur une large gamme de compositions. Grâce à une étude par diffraction des rayons X et spectroscopie de photoélectrons X, nous avons suivi les évolutions structurales de couches ayant subi ou non un recuit thermique. Nous avons montré de quoi étaient constituées les parties amorphes et cristallisées de ces films et déterminé la taille des domaines de cohérence. Enfin, les propriétés optiques (indice de réfraction, gap optique, paramètre d’Urbach) et diélectriques ont été corrélées à la structure des matériaux. / The aim of this thesis is to study the properties of a reactive plasma as well as the structural, optical and electrical properties of tantalum oxynitride thin films (TaOxNy) prepared by radiofrequency sputtering. The elaboration of this ternary material by sputtering a pure tantalum target using plasma containing both of argon, oxygen and nitrogen is complex due to the target-poisoning phenomenon. The analysis of the composition of the plasma by optical emission spectroscopy and monitoring the evolution of some representative line of excited species in this environment, allow us to determine the optimal conditions to deposit TaOxNy films over a wide range of composition. Thanks to a study by X-ray diffraction and X-ray photoelectron spectroscopy, we followed the structural evolution of the films subjected or not to a rapid thermal annealing. We showed by what were constituted the amorphous and crystalline parts of the films and determined the size of the crystalline domains. Finally, the optical properties (refractive index, optical gap, Urbach parameter) and dielectric behavior have been correlated with the structure of materials.

Dans les dernières 15 ans, la recherche biomédicale a exploré en profondeur l’utilisation de nanoparticules pour la délivrance ciblée de médicaments. Parmi plusieurs matériaux étudiés, la silice mésoporeuse représente une plateforme exceptionnelle pour ce type d’applications puisque elle est biocompatible et capable d’être chargé avec une quantité élevée de médicament, tout en étant facile à synthétiser et à fonctionnaliser. La connaissance des interactions entre nanoparticules de silice et environnement biologique est nécessaire pour concevoir des vecteurs thérapeutiques efficaces et pas toxiques. Cet étude a développé une nouvelle méthode d’analyse in situ pour suivre les interactions entre silice mésoporeuse et fluides biologiques réels (sérum et sang), employant une cellule d’analyse microfluidique et l’ellipsométrie en réflexion totale interne. Nous avons ainsi réalisé le suivi dynamique de la dégradation de vecteurs models à base de silice poreuse structuré dans une solution tampon à pH physiologique et une solution concentré de protéines. Ces analyses ont permis d’évaluer l’influence de la structure poreuse, de l’adsorption de protéines sur la surface et de la vitesse du flux sur la dissolution de la silice mésoporeuse. / Dans les dernières 15 ans, la recherche biomédicale a exploré en profondeur l’utilisation de nanoparticules pour la délivrance ciblée de médicaments. Parmi plusieurs matériaux étudiés, la silice mesoporeuse représente une plateforme exceptionnelle pour ce type d’applications puisque elle est biocompatible et capable d’être chargé avec une quantité élevée de médicament, tout en étant facile à synthétiser et à fonctionnaliser .La connaissance des interactions entre nanoparticules de silice et environnement biologique est nécessaire pour concevoir des vecteurs thérapeutiques efficaces et pas toxiques. Cet étude a développé une nouvelle méthode d’analyse in situ pour suivre les interactions entre silice mesoporeuse et fluides biologiques réels (serum et sang), employant une cellule d’analyse microfluidique et l’ellipsometrie en réflexion totale interne. Nous avons ainsi réalisé le suivi dynamique de la dégradation de vecteurs models à base de silice poreuse structuré dans une solution tampon à pH physiologique et une solution concentré de protéines. Ces analyses ont permis d’évaluer l’influence de la structure poreuse, de l’adsorption de protéines sur la surface et de la vitesse du flux sur la dissolution de la silice mesoporeuse.

Les métamatériaux sont des matériaux artificiels présentant des propriétés que l’on neretrouve pas dans les matériaux naturels. Il s’agit en général de matériaux compositesconstitués de résonateurs dont la réponse intense permet l’obtention de propriétés uniques.Cette thèse est consacrée à la fabrication et à l’étude de métamatériaux électromagnétiquespour une utilisation dans la gamme de fréquences du spectre visible. Nos matériaux sont desassemblages denses de nanoparticules coeur écorce. Le coeur métallique d’or présente unerésonance plasmon dans le visible et l’écorce de silice permet de contrôler les couplagesinterparticulaires. Les matériaux sont réalisés par une méthode dérivée de la technique deLangmuir-Blodgett et par microévaporation. Les propriétés optiques des matériaux sontétudiées par ellipsométrie spectroscopique. Nous avons mis en évidence la présence d’uncouplage fort avec le substrat de silicium permettant l’obtention d’indice réfraction n < 0,5dans le cas du système le plus fortement couplé. Nous avons décrit un phénomèned’extinction topologique pouvant être mis à profit pour la fabrication de capteurs ultrasensibles.Nous avons également synthétisé des nanoparticules présentant un coeur de silicechargé de molécules fluorescentes encapsulé d’une écorce d’or dont l’étude a permis unemeilleure compréhension du phénomène de compensation de perte. / Metamaterials are artificial materials exhibiting novel properties that are not found in naturalmaterials. Metamaterials are usually composite materials which contain artificial resonatorswhose intense response generates unique properties. This thesis is dedicated to the fabricationand characterization of electromagnetic metamaterials which are designed to be used atoptical frequency. Our materials are dense assemblies of core-shell nanoparticles. Corenanoparticles exhibit a plasmon resonance in the visible and the silica shell is used to controlthe interparticle coupling. The materials are made by a method derived from the Langmuir-Blodgett technique and by microevaporation. The optical properties of the materials werestudied by spectroscopic ellipsometry. We have demonstrated the presence of a strongcoupling with the silicon substrate which allows for a refractive index value of n <0.5, in thecase of the most coupled system. We have also described a topological extinctionphenomenon that can be exploited for the production of ultra-sensitive sensors. Finally, wesynthesized silica nanoparticles containing fluorescent molecules that are encapsulated with agold shell whose study has allowed for a better understanding of loss compensationphenomenon.

<p>In this study the formation of supported membranes onto planar solid supports has been investigated. The stability and activity of reconstituted membrane receptors has been studied. The potential use of such preparations in biosensor applications is discussed.</p><p>The lipid films were made by the Langmuir Blodgett and by the liposome fusion techniques. These supported films were characterised by ellipsometry, atomic force microscopy, surface plasmon resonance (SPR) and resonant mirror techniques. The thickness of the films was in agreement with that of a cell membrane. The kinetics of formation of the lipid films was studied and discussed.</p><p>The proteins, bacteriorhodopsin, cytochrome oxidase, acetylcholinesterase and the nicotinic acetylcholine receptor were reconstituted into the supported membrane. The subsequent analysis showed that the proteins were individually distributed and that the activity was retained, in some cases for several weeks after immobilisation.</p><p>The glycolipids, GM1, GM2, GD1b, asialo-GM1, globotriaosylceramide, lactosylceramide and galactosylceramide, were also reconstituted into the supported membranes. Their specific interaction with the toxin ricin or with its B-chain was examined using SPR. The affinity of intact toxin and of its B-chain differed markedly and was pH dependent. The carbohydrate chain length and charge density of the glycolipids also influenced the affinity.</p>

<p>The study and understanding of molecular interactions is fundamentally important in today's field of life sciences and there is a demand for well designed surfaces for biosensor applications. The biosensor has to be able to detect specific molecular interactions, while non-specific binding of other substances to the sensor surface should be kept to a minimum.                                                                                                                                                                                The objective of this master´s thesis was to design sensor surfaces based on self-assembled monolayers (SAMs) and evaluate their structural characteristics as well as their performance in Biacore systems. By mixing different oligo (ethylene glycol) terminated thiol compounds in the SAMs, the density of functional groups for bimolecular attachment could be controlled.  Structural characteristics of the SAMs were studied using Ellipsometry, Contact Angle Goniometry, IRAS and XPS. Surfaces showing promising results were examined further with Surface Plasmon Resonance in Biacore instruments.<p>Mixed SAM surfaces with a tailored degree of functional COOH groups could be prepared. The surfaces showed promising characteristics in terms of stability, immobilization capacity of biomolecules, non-specific binding and kinetic assay performance, while further work needs to be dedicated to the improvement of their storage stability. In conclusion, the SAM based sensor surfaces studied in this thesis are interesting candidates for Biacore applications.</p></p>

Eine Nutzung der optischen Anisotropie dünner Schichten ist vor allem für die Displaytechnologie, die optische Datenspeicherung und für optische Sicherheitselemente von hoher Bedeutung. Diese Doktorarbeit befasst sich mit theoretischen und experimentellen Untersuchung von dreidimensionaler Anisotropie und dabei insbesondere mit der Untersuchung von lichtinduzierter dreidimensionaler Anisotropie in organischen dünnen Polymer-Schichten. Die gewonnenen Erkentnisse und entwickelten Methoden können wertvolle Beiträge für Optimierungsprozesse, wie bei der Kompensation der Blickwinkelabhängigkeit von Flüssigkristall-Displays, liefern.<br><br> Die neue Methode der Immersions-Transmissions-Ellipsometrie (ITE) zur Untersuchung von dünneren Schichten wurde im Rahmen dieser Dissertation entwickelt. Diese Methode gestattet es, in Kombination mit konventioneller Reflexions- und Transmissionsellipsometrie, die absoluten dreidimensionalen Brechungsindices einer biaxialen Schicht zu bestimmen. Erstmals gelang es damit, das dreidimensionale Brechungsindexellipsoid von transparenten, dünneren (150 nm) Filmen hochgenau (drei Stellen hinter dem Komma) zu bestimmen. Die ITE-Methode hat demzufolge das Potential, auch bei noch dünneren Schichten mit Gewinn eingesetzt werden zu können.<br><br> Die lichtinduzierte Generierung von dreidimensionaler Anisotropie wurde in dünnen Schichten von azobenzenhaltigen und zimtsäurehaltigen, amorphen und flüssig-kristallinen Homo- und Copolymeren untersucht. Erstmals wurden quantitative Untersuchungen zur Änderung von lichtinduzierten, dreidimensionalen Anisotropien in dünnen Schichten von azobenzenhaltigen und zimtsäurehaltigen Polymeren bei Tempern oberhalb der Glastemperatur durchgeführt.<br><br> Bei vielen der untersuchten Polymere war die dreidimensionale Ordnung nach dem Bestrahlen mit polarisiertem Licht und anschließendem Tempern oberhalb der Glastemperatur scheinbar von der Schichtdicke abhängig. Die Ursache liegt wohl in der, mit der neuentwickelten ITE-Methode detektierten, planaren Ausgangsorientierung der aufgeschleuderten dünneren Schichten.<br><br> Um Verkippungs-Gradienten in dickeren Polymerschichten in ihrem Verlauf zu bestimmen, wurde eine spezielle Methode unter Benutzung der Wellenleitermoden-Spektroskopie entwickelt.<br> Quantenchemisch bestimmte, maximal induzierbare Doppelbrechungen in flüssig-kristallinen Polymeren wurden mit den experimentell gefundenen Ordnungen verglichen. / The optical anisotropy of thin films is of great interest mainly in the display technology, the optical data storage and for optical security elements. The topic of this thesis was the theoretical and experimental investigation of three-dimensional anisotropy and especially the investigation of light-induced three-dimensional anisotropy in thin organic polymer films. The results and newly developed methods can contribute significantly to technical optimisation processes, e. g. for the compensation of the viewing angle dependence of liquid crystal displays.<br><br> The new method of immersion-transmission-ellipsometry (ITE) for the investigation of thinner layers was developed in the course of this PhD. The new method allows to determine the absolute three-dimensional refractive indices of a biaxial film. For the first time it has been possible to determine the three-dimensional indicatrix of transparent, 150 nm thin films with an accuracy of three digits after the decimal point. The ITE-method therefore has the potential to be used for the investigation of even thinner films.<br><br> The light-induced generation of three-dimensional anisotropy was investigated in thin films of azobenzene-containing and cinnamate containing, amorphous and liquid crystalline homo- and copolymers. For the first time, quantitative investigations of the changes of light-induced, three-dimensional anisotropies in thin films of azobenzene containing and cinnamate containing polymers, that were brought about by annealing above the glass transition temperatures, were carried out.<br><br> For many of the investigated polymers the three-dimensional order after irradiation with polarised light and subsequent annealing above the glass transition temperature seemed to be dependent on the film thickness. The reason could be the planar initial order of the spin-coated thinner films, which was detected with the new ITE-method.<br><br> For the characterisation of tilt gradients in thicker polymer films a special method using waveguide spectroscopy was developed. <br> Quantum chemically determined maximal values of inducible birefringence were compared with the experimentally determined values.