The present work is devoted to establishing of a new generation of self-healing anti-corrosion coatings for protection of metals. The concept of self-healing anticorrosion coatings is based on the combination of the passive part, represented by the matrix of conventional coating, and the active part, represented by micron-sized capsules loaded with corrosion inhibitor. Polymers were chosen as the class of compounds most suitable for the capsule preparation. The morphology of capsules made of crosslinked polymers, however, was found to be dependent on the nature of the encapsulated liquid. Therefore, a systematic analysis of the morphology of capsules consisting of a crosslinked polymer and a solvent was performed. Three classes of polymers such as polyurethane, polyurea and polyamide were chosen. Capsules made of these polymers and eight solvents of different polarity were synthesized via interfacial polymerization. It was shown that the morphology of the resulting capsules is specific for every polymer-solvent pair. Formation of capsules with three general types of morphology, such as core-shell, compact and multicompartment, was demonstrated by means of Scanning Electron Microscopy. Compact morphology was assumed to be a result of the specific polymer-solvent interactions and be analogues to the process of swelling. In order to verify the hypothesis, pure polyurethane, polyurea and polyamide were synthesized; their swelling behavior in the solvents used as the encapsulated material was investigated. It was shown that the swelling behavior of the polymers in most cases correlates with the capsules morphology. Different morphologies (compact, core-shell and multicompartment) were therefore attributed to the specific polymer-solvent interactions and discussed in terms of “good” and “poor” solvent. Capsules with core-shell morphology are formed when the encapsulated liquid is a “poor” solvent for the chosen polymer while compact morphologies are formed when the solvent is “good”. Multicompartment morphology is explained by the formation of infinite networks or gelation of crosslinked polymers. If gelation occurs after the phase separation in the system is achieved, core-shell morphology is present. If gelation of the polymer occurs far before crosslinking is accomplished, further condensation of the polymer due to the crosslinking may lead to the formation of porous or multicompartment morphologies. It was concluded that in general, the morphology of capsules consisting of certain polymer-solvent pairs can be predicted on the basis of polymer-solvent behavior. In some cases, the swelling behavior and morphology may not match. The reasons for that are discussed in detail in the thesis. The discussed approach is only capable of predicting capsule morphology for certain polymer-solvent pairs. In practice, the design of the capsules assumes the trial of a great number of polymer-solvent combinations; more complex systems consisting of three, four or even more components are often used. Evaluation of the swelling behavior of each component pair of such systems becomes unreasonable. Therefore, exploitation of the solubility parameter approach was found to be more useful. The latter allows consideration of the properties of each single component instead of the pair of components. In such a manner, the Hansen Solubility Parameter (HSP) approach was used for further analysis. Solubility spheres were constructed for polyurethane, polyurea and polyamide. For this a three-dimensional graph is plotted with dispersion, polar and hydrogen bonding components of solubility parameter, obtained from literature, as the orthogonal axes. The HSP of the solvents are used as the coordinates for the points on the HSP graph. Then a sphere with a certain radius is located on a graph, and the “good” solvents would be located inside the sphere, while the “poor” ones are located outside. Both the location of the sphere center and the sphere radius should be fitted according to the information on polymer swelling behavior in a number of solvents. According to the existing correlation between the capsule morphology and swelling behavior of polymers, the solvents located inside the solubility sphere of a polymer give capsules with compact morphologies. The solvents located outside the solubility sphere of the solvent give either core-shell or multicompartment capsules in combination with the chosen polymer. Once the solubility sphere of a polymer is found, the solubility/swelling behavior is approximated to all possible substances. HSP theory allows therefore prediction of polymer solubility/swelling behavior and consequently the capsule morphology for any given substance with known HSP parameters on the basis of limited data. The latter makes the theory so attractive for application in chemistry and technology, since the choice of the system components is usually performed on the basis of a large number of different parameters that should mutually match. Even slight change of the technology sometimes leads to the necessity to find the analogue of this or that solvent in a sense of solvency but carrying different chemistry. Usage of the HSP approach in this case is indispensable. In the second part of the work examples of the HSP application for the fabrication of capsules with on-demand-morphology are presented. Capsules with compact or core-shell morphology containing corrosion inhibitors were synthesized. Thus, alkoxysilanes possessing long hydrophobic tail, combining passivating and water-repelling properties, were encapsulated in polyurethane shell. The mechanism of action of the active material required core-shell morphology of the capsules. The new hybrid corrosion inhibitor, cerium diethylhexyl phosphate, was encapsulated in polyamide shells in order to facilitate the dispersion of the substance and improve its adhesion to the coating matrix. The encapsulation of commercially available antifouling agents in polyurethane shells was carried out in order to control its release behavior and colloidal stability. Capsules with compact morphology made of polyurea containing the liquid corrosion inhibitor 2-methyl benzothiazole were synthesized in order to improve the colloidal stability of the substance. Capsules with compact morphology allow slower release of the liquid encapsulated material compared to the core-shell ones. If the “in-situ” encapsulation is not possible due to the reaction of the oil-soluble monomer with the encapsulated material, a solution was proposed: loading of the capsules should be performed after monomer deactivation due to the accomplishment of the polymerization reaction. Capsules of desired morphologies should be preformed followed by the loading step. In this way, compact polyurea capsules containing the highly effective but chemically active corrosion inhibitors 8-hydroxyquinoline and benzotriazole were fabricated. All the resulting capsules were successfully introduced into model coatings. The efficiency of the resulting “smart” self-healing anticorrosion coatings on steel and aluminium alloy of the AA-2024 series was evaluated using characterization techniques such as Scanning Vibrating Electron Spectroscopy, Electrochemical Impedance Spectroscopy and salt-spray chamber tests. / In Anlehnung an den Selbstheilungsmechanismus der menschlichen Haut entwickeln wir ein innovatives Verfahren zur Funktionalisierung von Korrosionsschutzbeschichtungen, um auch diese in die Lage zu versetzen Beschädigungen selbstständig „auszuheilen“. Dazu werden winzige Mikro- und Nanobehälter mit aktiven Substanzen (z. B. Korrosionshemmstoffen, Versiegelungsmitteln, Bioziden etc.) befüllt und anschließend in eine Korrosionsschutzbeschichtung eingebettet. Kommt es nun im Zeitablauf zu korrosionsauslösenden Beschädigungen der Schutzbeschichtung (z. B. durch Kratzer oder Risse) werden an der Defektstelle die eingebetteten Behälter zerstört und aktiv wirkende Gegensubstanzen freigesetzt. Dadurch wird die verletzte Stelle sofort wieder verschlossen und die Korrosionsgefahr eliminiert. Der entscheidende Vorteil derart funktionalisierter Schutzbeschichtungen ist ihre aktive Rückkopplung mit dem Korrosionsauslöser: Die aktive Schutzsubstanz wird nur an der Defektstelle und nur in der zur Korrosionsvermeidung erforderlichen Menge freigegeben. Somit werden eine länger anhaltende Wirkdauer sowie eine deutlich höhere Nachhaltigkeit der Beschichtungen ermöglicht. Dieses „intelligente Verhalten“ der neuen aktiven Korrosionsschutzbeschichtungen ist nur dank ihrer innovativen Mikrostruktur möglich. Die winzigen Mikro- und Nanobehälter beinhalten nicht nur aktive Substanzen in ihrem Inneren sondern besitzen auch eine intelligent konstruierte Hüllenstruktur, deren Durchlässigkeit sich je nach Art des Korrosionsauslösers ändert. Wird die eingekapselte aktive Substanz freigesetzt, fängt diese sofort an gegen die korrosionsverursachenden Einflüsse zu wirken. Ist die Gefahr beseitigt verringert sich die Durchlässigkeit der Behälterhülle wieder. Diese bedingte Reversibilität zwischen geschlossenem und geöffnetem Zustand des Behälters sorgt für einen sehr sparsamen Verbrauch der aktiven Substanz und für die stark verbesserte Schutzwirkung darauf basierender Antikorrosionsbeschichtungen. Diese Arbeit befasst sich mit dem Aufbau polymerer Kern-Schale-Mikrokapseln, die entsprechende Korrosionsinhibitoren und Biocide enthalten. Der Morphologie wird für zahlreiche Lösungsmittel und Polymere mit Hilfe der Hansen-Löslichkeitsparameter in guter Übereinstimmung mit elektronenmikroskopischen Experimenten beschrieben. Die Wirkungsweise in technischen Beschichtungen wird quantifiziert anhand von elektrochemischer Impedanzspektroskopie, Rastervibrationssondenmessungen und industrienahen Testverfahren.

Nanomaterials have attracted considerable attention during the past decades due to their unique and fascinating properties. However, this class of materials is not an invention of modern age. People have been using nanomaterials for centuries, although unwittingly. Probably the most famous example for the usage of nanomaterials in ancient times is the Lycurgus Cup, a Roman glass cage cup created in the 4th century which changes the colour of its glass from green to ruby depending on the illumination conditions. The foundation for the development of the field of nanotechnology was laid by the speech of Feynman “There is plenty of room at the bottom” in 1959, in which he spoke about the principles of miniaturisation as low as to the atomic level. Today, modern nanotechnology made it its business to purposefully develop and synthesise nanomaterials as well as to face their applications in various fields, such as microelectronics, catalysis or biomedicine. However, the term “nanomaterials” does not solely involve the nanoparticulate units itself, but also their arrangement into two- or three-dimensional structures. Thereby, the maintenance of the nanoscale properties is one of the main challenges. This task was focussed by this work implied the preparation and macroscale arrangement of fluorescent QDs while preserving their optical properties. The main achievement of this work was the development of a novel aerogel material with non-quenching PL behaviour by using silica coated QDs as nanoparticulate building units. In comparison to other monolithic silica-QD structures or aerogels from pure QDs, a defined and controllable distance between the fluorescent QDs is provided in these structures by the silica shell. The spacing was shown to efficiently disable energy transfers so that no spectral shifts, lifetime shortening or PL QY losses are observed during the colloid to gel transition. The silica shell, established by a standard reverse microemulsion approach, was found to exhibit a certain porosity, which was proven by gas adsorption measurements. Existing cavities in the micro- and mesoporous range were found to allow small species such as metal ions to pass through the shell and interact with the QD core causing a detectable change of the PL intensity, which makes these materials suitable for future sensing applications. The gel preparation was based on a metal ion assisted complexation approach, which requires tetrazole functionalisation of the nanoparticulate building units. A major development in this work that permitted this gelation approach for silica-QDs was the development of a novel tetrazole-silane ligand. TMSPAMTz was specifically designed to bind to the silica surface of silica-QDs in aqueous solution and was prepared by a covalent coupling of an alkyl chained silane with a 5-subsituted tetrazole ring. Network formation is subsequently achieved by the interconnection of negatively charged tetrazole rings with metal ions, which allows for a broad spectrum of aerogel materials from different NP species as well as their mixtures as long as tetrazole capping is provided. Considering this diversity and the disabling of energy transfers, straightforward colour tuning was demonstrated herein by mixing differently emitting silica-QD species which gives great prospects for lighting applications. Furthermore, the possibility of plasmon enhanced emission was presented for mixed Au NP/silica-QD gels. With respect to future sensing applications, thin porous films from silica-QDs gels were prepared, which showed a promising concentration dependant PL quenching for the model analyst hydrogen peroxide. However, the film reproducibility of the applied drop-cast coating method was insufficient. As a suggestion to this, a LbL method was presented, wherein a gel is subsequently grown with the metal ion assisted complexation approach. In addition to the tetrazole ligands on the NP surface, tetrazole-silane ligands were used in this approach to functionalise the glass substrate surface. By this, homogeneous gel films of distinct thickness can be grown while the use of organic polymers can be completely avoided. Besides the preparation of NP assemblies, standard Cd-based QD materials as well as Au NPs of different sizes and shape, recent progresses in the synthesis of InP-based QDs were presented in this work. A thorough investigation and understanding of the growth influencing parameters allowed for the establishment of preparation routes for In(Zn)P/GaP/ZnS core/shell/shell QDs with emission wavelengths tuneable within a large range from 500 to 650 nm, narrow peak widths of 45 to 70 nm and PL QYs up to 60%. Successful incorporation of these QDs into salt matrices was further demonstrated. The resulting composite materials are very photostable and suitable as colour conversion materials for solid state lighting, as was clearly pointed out by a self-prepared WLED that met the standard commercial LEDs.

Nanomaterials have attracted considerable attention during the past decades due to their unique and fascinating properties. However, this class of materials is not an invention of modern age. People have been using nanomaterials for centuries, although unwittingly. Probably the most famous example for the usage of nanomaterials in ancient times is the Lycurgus Cup, a Roman glass cage cup created in the 4th century which changes the colour of its glass from green to ruby depending on the illumination conditions. The foundation for the development of the field of nanotechnology was laid by the speech of Feynman “There is plenty of room at the bottom” in 1959, in which he spoke about the principles of miniaturisation as low as to the atomic level. Today, modern nanotechnology made it its business to purposefully develop and synthesise nanomaterials as well as to face their applications in various fields, such as microelectronics, catalysis or biomedicine. However, the term “nanomaterials” does not solely involve the nanoparticulate units itself, but also their arrangement into two- or three-dimensional structures. Thereby, the maintenance of the nanoscale properties is one of the main challenges. This task was focussed by this work implied the preparation and macroscale arrangement of fluorescent QDs while preserving their optical properties. The main achievement of this work was the development of a novel aerogel material with non-quenching PL behaviour by using silica coated QDs as nanoparticulate building units. In comparison to other monolithic silica-QD structures or aerogels from pure QDs, a defined and controllable distance between the fluorescent QDs is provided in these structures by the silica shell. The spacing was shown to efficiently disable energy transfers so that no spectral shifts, lifetime shortening or PL QY losses are observed during the colloid to gel transition. The silica shell, established by a standard reverse microemulsion approach, was found to exhibit a certain porosity, which was proven by gas adsorption measurements. Existing cavities in the micro- and mesoporous range were found to allow small species such as metal ions to pass through the shell and interact with the QD core causing a detectable change of the PL intensity, which makes these materials suitable for future sensing applications. The gel preparation was based on a metal ion assisted complexation approach, which requires tetrazole functionalisation of the nanoparticulate building units. A major development in this work that permitted this gelation approach for silica-QDs was the development of a novel tetrazole-silane ligand. TMSPAMTz was specifically designed to bind to the silica surface of silica-QDs in aqueous solution and was prepared by a covalent coupling of an alkyl chained silane with a 5-subsituted tetrazole ring. Network formation is subsequently achieved by the interconnection of negatively charged tetrazole rings with metal ions, which allows for a broad spectrum of aerogel materials from different NP species as well as their mixtures as long as tetrazole capping is provided. Considering this diversity and the disabling of energy transfers, straightforward colour tuning was demonstrated herein by mixing differently emitting silica-QD species which gives great prospects for lighting applications. Furthermore, the possibility of plasmon enhanced emission was presented for mixed Au NP/silica-QD gels. With respect to future sensing applications, thin porous films from silica-QDs gels were prepared, which showed a promising concentration dependant PL quenching for the model analyst hydrogen peroxide. However, the film reproducibility of the applied drop-cast coating method was insufficient. As a suggestion to this, a LbL method was presented, wherein a gel is subsequently grown with the metal ion assisted complexation approach. In addition to the tetrazole ligands on the NP surface, tetrazole-silane ligands were used in this approach to functionalise the glass substrate surface. By this, homogeneous gel films of distinct thickness can be grown while the use of organic polymers can be completely avoided. Besides the preparation of NP assemblies, standard Cd-based QD materials as well as Au NPs of different sizes and shape, recent progresses in the synthesis of InP-based QDs were presented in this work. A thorough investigation and understanding of the growth influencing parameters allowed for the establishment of preparation routes for In(Zn)P/GaP/ZnS core/shell/shell QDs with emission wavelengths tuneable within a large range from 500 to 650 nm, narrow peak widths of 45 to 70 nm and PL QYs up to 60%. Successful incorporation of these QDs into salt matrices was further demonstrated. The resulting composite materials are very photostable and suitable as colour conversion materials for solid state lighting, as was clearly pointed out by a self-prepared WLED that met the standard commercial LEDs.