Professional nurses comprise the largest number of health care professionals in South Africa. High turnover rates contribute to shortages of nurses in South Africa, aggravated by the emigration of nurses, inadequate recruitment of student nurses, and the expected retirement of many baby boomer nurses by 2016. This study addressed factors influencing the retention of professional nurses in the Gauteng Province of South Africa. In phase 1, postal questionnaires were completed by 101 registered nurses while semi-structured interviews were conducted with 21 nurse managers in phase 2. Personal, organisational and managerial factors influenced the retention potential of the professional nurses. In terms of Maslow' Hierarchy of Needs Theory, most factors influencing nurses' retention operated on the lowest (physiological) level and concerned remuneration. Safety needs were compromised by the lack of equipment and supplies, the shortage of nurses and unsafe working places. Esteem needs included respect from doctors, managers and colleagues as well as recognition for outstanding performance. In terms of Vogt et al's Theory of Nurse Retention Theory, the constrictions caused by inadequate remuneration and safety aspects should be addressed. Lewin's Force-Field Analysis Theory recommends that the factors that influence nurses' retention negatively should be unfrozen, changed and refrozen, including communication. Based on these results guidelines were compiled for enhancing the retention rates of professional nurses (Annexure G). / Health Studies / D.Litt. et Phil. (Health Studies)

Die Arbeit untersucht die Position der Öffentlichen Bibliotheken im Bibliotheksfeld der Bundesrepublik Deutschland. Den theoretischen Rahmen bildet die Theorie der sozialen Felder von Pierre Bourdieu. Dargestellt werden zunächst die Außengrenzen des Bibliotheksfeldes sowie seine administrative Verortung. Es folgen professionssoziologische Aspekte, insbesondere die Verbands- und Ausbildungsstruktur. Der Schwerpunkt liegt dabei auf der Binnengliederung des Feldes und seiner historischen Spartentrennung in „wissenschaftliche“ und „Öffentliche“ Bibliotheken. Dazu gehören eine Untersuchung der technisch-administrativen Infrastruktur und der ideologischen Verortung der Öffentlichen Bibliotheken. Die Kapitalbinnenstruktur des Feldes wird anhand von Daten der Deutschen Bibliotheksstatistik analysiert. Den Hauptteil der Arbeit bildet eine empirische Untersuchung der Diskursstruktur anhand einer quantitativen Analyse von 7.159 Aufsätzen, Vorträgen und Beiträgen zu Mailinglisten, die den allgemeinen bibliothekarischen Fachdiskurs in den Jahren 1964 bis 2016 abbilden. Aus dieser Untersuchung werden Schlüsse auf die informelle Feldstruktur unterhalb der Institutionenebene gezogen. Weitere Ergebnisse betreffen die genderspezifische Arbeitsteilung und die ideologische und kapitalbezogene Position der Öffentlichen Bibliotheken im Bibliotheksfeld. / The dissertation examines the position of public libraries in the library “field” (as described by Pierre Bourdieu) of the Federal Republic of Germany. This includes the outer borders of the field and the administrative position of libraries as well as sociological aspects such as the structure of professional associations and formal qualifications. A focus lies on the historical division between “research” and “public” libraries. This includes an analysis of technical and administrative infrastructure as well as different ideologies. An analysis of the German Library Statistics investigates the capital-based substructure of the field. The main empirical work consists of an analysis of the structure of the professional discourse between 1964 and 2016, i.e. a quantitative analysis of 7.159 articles, conference papers and e-mail-posts that cover the main part of the national professional discourse. This allows conclusions about the informal structure of the field underneath the institutional level. Further results refer to the gender-specific division of labour and the ideological and resource-based position of public libraries in the library field.

Ziel der vorliegenden Arbeit war es, die Zusammenhänge zwischen der molekularen Architektur, Morphologie und den mechanischen bzw. bruchmechanischen Eigenschaften in S-SB-S-Triblockcopolymeren und deren Blends und in PI-PS-Multipfropfcopolymeren herauszuarbeiten und damit einerseits einen Beitrag für das Verständnis der Struktur-Eigenschaftsbeziehungen in Block- und Pfropfcopolymeren zu leisten und andererseits Möglichkeiten zur Entwicklung neuer Materialien aufzuzeigen, welche besondere Eigenschaftskombinationen aufweisen und damit ein bedeutendes Interesse für industrielle Anwendungen hervorrufen. Für die Untersuchungen wurde dabei der PS-Außenblockanteil und das S/B-Verhältnis im SB-Mittelblock in S-SB-S-Triblockcopolymeren, die Thermoplast/Thermoplastisches Elastomer (TP/TPE) -Zusammensetzung in S-SB-S-Triblockcopolymer-Blends sowie die Funktionalität und die Anzahl der Verknüpfungspunkte in PI-PS-Multipfropfcopolymeren variiert. Zur Charakterisierung der Phasenmischbarkeit und der Morphologie wurden die dynamisch mechanische Analyse (DMA), die Transmissionselektronenmikroskopie (TEM) und die Röntgenkleinwinkelstreuung (SAXS) angewandt. Die mechanischen Eigenschaften wurden mit dem einachsigen Zugversuch untersucht. Bruchmechanische Untersuchungen erfolgten unter Anwendung der „Essential Work of Fracture“- (EWF-) Methode, welche als Konzept der „Post-Yield“-Bruchmechanik innerhalb der Fließbruchmechanik für duktile nanostrukturierte polymere Materialien sehr gut anwendbar ist und Aussagen zur Bruchzähigkeit der Materialien liefert. Zur näheren Charakterisierung des zeitaufgelösten Deformationsverhaltens sowie der Rissausbreitungskinetik wurden die Dehnungsfeldanalyse, eine Bruchflächenanalyse mittels Rasterelektronenmikroskopie (REM) sowie das Risswiderstandskurven-Konzept angewandt. Die Untersuchungen der S-SB-S-Triblockcopolymersysteme und der PI-PS-Multipfropfcopolymere konnten den signifikanten Einfluss der molekularen Architektur, der Blockzusammensetzung und des PS-Gehaltes auf das Phasenverhalten, die Morphologie und die Eigenschaften klar herausstellen. Durch die Variation dieser Parameter kann das Eigenschaftsspektrum von thermoplastisch zu elastomer eingestellt und somit sowohl TPs oder TPEs mit hoher Steifigkeit und Zähigkeit als auch TPEs mit superelastischem Charakter erzeugt werden. Daraus eröffnet sich ein breiter Anwendungsbereich dieser Materialien, welche aufgrund ihrer Transparenz und physiologischen Verträglichkeit auch interessante optische und gesundheitliche Vorteile mitbringen. Es konnte gezeigt werden, dass durch die systematische Variation der Architektur die gezielte Einstellung gewünschter Eigenschaftsprofile möglich ist. Die Arbeit leistet somit einen Beitrag zur Entwicklung anwendungsorientierter Materialkonzepte, welche ingenieurwissenschaftlich interessant sind. / The aim of this thesis was to study the relation between molecular architecture, morphology and (fracture) mechanical properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. Hence, this work should contribute to the understanding of structure-property-relationship in block and multigraft copolymers and thus offer possibilities for the development of novel materials with special properties interesting for industrial application. Within this study in the case of S-SB-S triblock copolymers the PS outer block content and the S/B ratio of the middle block, in the case of S-SB-S triblock copolymer blends the thermoplast/thermoplastic elastomer (TP/TPE) composition and in case of PI-PS multigraft copolymers the functionality and number of branch points were varied. For the characterisation of morphology and phase miscibility dynamic mechanical analysis (DMA), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were applied. Uniaxial tensile tests were carried out to investigate the mechanical properties. The fracture mechanical behaviour was studied using essential work of fracture (EWF) concept based on the post yield fracture mechanic principles, which is suitable to characterise fracture toughness of ductile nanostructured materials. The time resolved analysis of deformation and fracture behaviour was characterised qualitatively by strain field analysis, scanning electron microscopy (SEM) of the fractured surfaces and quantitatively by evaluation of the crack propagation kinetics and construction of R-curves. This study clearly highlights the significant influence of molecular architecture block composition and PS content on the phase behaviour, morphology and properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. By varying these parameters the property profile can be adjusted diversifying from thermoplastic to elastomeric and both TP or TPE materials with high stiffness and toughness and TPEs with super-elastic characteristics can be designed. Hence, fundamentally it offers a broad scope of application of these materials, in which physiological compatibility and transparency are added advantages. Thus, conceptually it could be shown, that by systematic variation of the architecture desired property profiles can be adjusted. Therefore the present work contributes to the development of application-oriented material concepts, which are interesting in engineering terms.

Professional nurses comprise the largest number of health care professionals in South Africa. High turnover rates contribute to shortages of nurses in South Africa, aggravated by the emigration of nurses, inadequate recruitment of student nurses, and the expected retirement of many baby boomer nurses by 2016. This study addressed factors influencing the retention of professional nurses in the Gauteng Province of South Africa. In phase 1, postal questionnaires were completed by 101 registered nurses while semi-structured interviews were conducted with 21 nurse managers in phase 2. Personal, organisational and managerial factors influenced the retention potential of the professional nurses. In terms of Maslow' Hierarchy of Needs Theory, most factors influencing nurses' retention operated on the lowest (physiological) level and concerned remuneration. Safety needs were compromised by the lack of equipment and supplies, the shortage of nurses and unsafe working places. Esteem needs included respect from doctors, managers and colleagues as well as recognition for outstanding performance. In terms of Vogt et al's Theory of Nurse Retention Theory, the constrictions caused by inadequate remuneration and safety aspects should be addressed. Lewin's Force-Field Analysis Theory recommends that the factors that influence nurses' retention negatively should be unfrozen, changed and refrozen, including communication. Based on these results guidelines were compiled for enhancing the retention rates of professional nurses (Annexure G). / Health Studies / D.Litt. et Phil. (Health Studies)

Plug nozzle, a passive altitude adaptive nozzle, for futuristic SSTO applications, exhibits greater efficiency as compared to conventional nozzles over a wide range of altitudes. The plug nozzle comprises of a primary nozzle and a contoured plug; an under–expanded jet exiting the primary nozzle is allowed to further expand over the plug surface for altitude adaptation. At design condition the flow expands correctly to the ambient conditions on the full length plug surface, while at off design conditions the flow adapts to the ambient conditions through wave interactions within the nozzle core jet. Based on thrust to weight considerations, the full length plug is truncated and this results in a base flow rich in flow physics. In addition, the base flow exhibits an interesting transitional behaviour from open wake to a closed wake because of the wave interactions within the nozzle core jet. The plug surface flow can further exhibit flow complexities because of wave interactions resulting from the shear layer emanating from the splitter plates, in case of clustered plug flows. Considering these flow complexities, the design of the plug nozzles and analysing the associated flows can be a challenge to the aerodynamic community. An attempt has been made in understanding this class of flows in this thesis. This objective has been accomplished using both experimental and computational tools. In the present work, both the linear and annular plug nozzle geometries have been analysed for a wide range of pressure ratios spanning from 5to 80. The linear and annular nozzles have been designed for similar flow conditions and their respective design pressure ratios are 60and 66. From the experimental and computational results, it has been shown that the computational solver performs well in predicting the wave interactions on the plug surface. In addition the limitations of the computational solver in predicting the plug base flows in general has been brought out. This limitation in itself need not be considered as a serious handicap in the design and analysis of plug nozzle flows; this is because the plug base contribution to the thrust is very minimal, as has been brought out in this thesis. Apart from this the high quality experimental data generated is also of immense value to the CFD community as this also serves as a valuable data base for CFD code validation. For analysis, the plug flow field has been categorized into three different regimes based on the primary nozzle lip expansion fan extent. The flow field is categorised based on the reflection of the primary nozzle lip expansion fan from plug surface, base region shear layer and symmetry line downstream of the base region recirculation bubble. This flow division is particularly helpful in understanding the base wake characteristics with increasing pressure ratio. The base lip pressure and the base pressure variation have been discussed with respect to the primary nozzle lip expansion fan extent. In the open wake regime (or for low pressure ratios) the wave interactions within the core jet flow impinge on the base region shear layer. Because of these interactions it is difficult to propose an empirical model for open wake base pressure. In the closed wake regime (for higher pressure ratios), the base region recirculation bubble is completely under the shower of primary nozzle lip expansion fan. Hence the base lip pressure and base pressure are frozen with respect to stagnation conditions. Based on these insights it was possible to propose empirical models for linear and annular closed wake base pressure. Along with these, a mathematical model defining a reference pressure ratio PR∗, beyond which the closed wake base pressure is expected to be more than the ambient pressure has also been proposed. This is expected to serve as a good design parameter. In case of linear plug flows, this also serves the purpose of base wake transition, for the cases considered in this thesis. The flow expansion process or the primary nozzle lip expansion fan extent was also useful in understanding the differences between the linear and annular plug nozzle flow fields. In a linear plug nozzle, the flow expands only in the streamwise direction while in an annular plug nozzle the flow expands both along the streamwise and azimuthal directions. The flow expands at a faster rate in case of annular nozzle as against linear nozzle. Hence differences are observed between the linear and annular nozzle on plug and base surfaces. On the annular plug surface more wave interactions are observed because of faster expansion. With regard to base characteristics, faster expansion in annular plug nozzle, with respect to linear nozzle, results in a lower base lip pressure, lower base pressure and higher wake transition pressure ratio. The realistic cluster plug configurations have also been considered for the present studies. The effects of clustering on the plug nozzle flow field have been brought out by considering two different linear cluster nozzles and one annular cluster nozzle. The differences in the flow field of a simple and cluster plug nozzle has been discussed. In case of simple plug nozzle wave interactions are observed only in the stream wise direction, while in case of cluster plug nozzle three dimensional wave interactions are observed because of the splitter plates. Along the splitter plate differential end conditions introduce a curved recompression shock on the plug surface. This recompression shock in turn induces a streamwise vortex and also a secondary shock. It has been observed that differences between the simple and cluster plug surface pressure field are because of three dimensional wave interactions. Regarding the base pressure, differences between the simple and cluster geometries were observed for shorter truncation plug lengths (20% length plug). While for longer plug lengths (more than 34% length) the effects of clustering were reduced on the base pressure. Regarding the transition pressure ratio, differences were observed between simple and clustered plug nozzles for all the plug lengths considered. In addition, the performance of the plug nozzles has been carried out. From the analysis it was found that the primary nozzle and plug surface are major contributors towards thrust. The base surface contributes only about 2– 3% of the thrust at design condition. Hence, from a design point of view, a computational solver can be a useful tool considering its efficacy on the plug surface and in the primary nozzle.

Plug nozzle, a passive altitude adaptive nozzle, for futuristic SSTO applications, exhibits greater efficiency as compared to conventional nozzles over a wide range of altitudes. The plug nozzle comprises of a primary nozzle and a contoured plug; an under–expanded jet exiting the primary nozzle is allowed to further expand over the plug surface for altitude adaptation. At design condition the flow expands correctly to the ambient conditions on the full length plug surface, while at off design conditions the flow adapts to the ambient conditions through wave interactions within the nozzle core jet. Based on thrust to weight considerations, the full length plug is truncated and this results in a base flow rich in flow physics. In addition, the base flow exhibits an interesting transitional behaviour from open wake to a closed wake because of the wave interactions within the nozzle core jet. The plug surface flow can further exhibit flow complexities because of wave interactions resulting from the shear layer emanating from the splitter plates, in case of clustered plug flows. Considering these flow complexities, the design of the plug nozzles and analysing the associated flows can be a challenge to the aerodynamic community. An attempt has been made in understanding this class of flows in this thesis. This objective has been accomplished using both experimental and computational tools. In the present work, both the linear and annular plug nozzle geometries have been analysed for a wide range of pressure ratios spanning from 5to 80. The linear and annular nozzles have been designed for similar flow conditions and their respective design pressure ratios are 60and 66. From the experimental and computational results, it has been shown that the computational solver performs well in predicting the wave interactions on the plug surface. In addition the limitations of the computational solver in predicting the plug base flows in general has been brought out. This limitation in itself need not be considered as a serious handicap in the design and analysis of plug nozzle flows; this is because the plug base contribution to the thrust is very minimal, as has been brought out in this thesis. Apart from this the high quality experimental data generated is also of immense value to the CFD community as this also serves as a valuable data base for CFD code validation. For analysis, the plug flow field has been categorized into three different regimes based on the primary nozzle lip expansion fan extent. The flow field is categorised based on the reflection of the primary nozzle lip expansion fan from plug surface, base region shear layer and symmetry line downstream of the base region recirculation bubble. This flow division is particularly helpful in understanding the base wake characteristics with increasing pressure ratio. The base lip pressure and the base pressure variation have been discussed with respect to the primary nozzle lip expansion fan extent. In the open wake regime (or for low pressure ratios) the wave interactions within the core jet flow impinge on the base region shear layer. Because of these interactions it is difficult to propose an empirical model for open wake base pressure. In the closed wake regime (for higher pressure ratios), the base region recirculation bubble is completely under the shower of primary nozzle lip expansion fan. Hence the base lip pressure and base pressure are frozen with respect to stagnation conditions. Based on these insights it was possible to propose empirical models for linear and annular closed wake base pressure. Along with these, a mathematical model defining a reference pressure ratio PR∗, beyond which the closed wake base pressure is expected to be more than the ambient pressure has also been proposed. This is expected to serve as a good design parameter. In case of linear plug flows, this also serves the purpose of base wake transition, for the cases considered in this thesis. The flow expansion process or the primary nozzle lip expansion fan extent was also useful in understanding the differences between the linear and annular plug nozzle flow fields. In a linear plug nozzle, the flow expands only in the streamwise direction while in an annular plug nozzle the flow expands both along the streamwise and azimuthal directions. The flow expands at a faster rate in case of annular nozzle as against linear nozzle. Hence differences are observed between the linear and annular nozzle on plug and base surfaces. On the annular plug surface more wave interactions are observed because of faster expansion. With regard to base characteristics, faster expansion in annular plug nozzle, with respect to linear nozzle, results in a lower base lip pressure, lower base pressure and higher wake transition pressure ratio. The realistic cluster plug configurations have also been considered for the present studies. The effects of clustering on the plug nozzle flow field have been brought out by considering two different linear cluster nozzles and one annular cluster nozzle. The differences in the flow field of a simple and cluster plug nozzle has been discussed. In case of simple plug nozzle wave interactions are observed only in the stream wise direction, while in case of cluster plug nozzle three dimensional wave interactions are observed because of the splitter plates. Along the splitter plate differential end conditions introduce a curved recompression shock on the plug surface. This recompression shock in turn induces a streamwise vortex and also a secondary shock. It has been observed that differences between the simple and cluster plug surface pressure field are because of three dimensional wave interactions. Regarding the base pressure, differences between the simple and cluster geometries were observed for shorter truncation plug lengths (20% length plug). While for longer plug lengths (more than 34% length) the effects of clustering were reduced on the base pressure. Regarding the transition pressure ratio, differences were observed between simple and clustered plug nozzles for all the plug lengths considered. In addition, the performance of the plug nozzles has been carried out. From the analysis it was found that the primary nozzle and plug surface are major contributors towards thrust. The base surface contributes only about 2– 3% of the thrust at design condition. Hence, from a design point of view, a computational solver can be a useful tool considering its efficacy on the plug surface and in the primary nozzle.

La quantité de données disponibles n'a jamais été aussi grande. Se poser les bonnes questions, c'est-à-dire des questions qui soient à la fois pertinentes et dont la réponse est accessible est difficile. L'analyse topologique de données tente de contourner le problème en ne posant pas une question trop précise mais en recherchant une structure sous-jacente aux données. Une telle structure est intéressante en soi mais elle peut également guider le questionnement de l'analyste et le diriger vers des questions pertinentes. Un des outils les plus utilisés dans ce domaine est l'homologie persistante. Analysant les données à toutes les échelles simultanément, la persistance permet d'éviter le choix d'une échelle particulière. De plus, ses propriétés de stabilité fournissent une manière naturelle pour passer de données discrètes à des objets continus. Cependant, l'homologie persistante se heurte à deux obstacles. Sa construction se heurte généralement à une trop large taille des structures de données pour le travail en grandes dimensions et sa robustesse ne s'étend pas au bruit aberrant, c'est-à-dire à la présence de points non corrélés avec la structure sous-jacente.Dans cette thèse, je pars de ces deux constatations et m'applique tout d'abord à rendre le calcul de l'homologie persistante robuste au bruit aberrant par l'utilisation de la distance à la mesure. Utilisant une approximation du calcul de l'homologie persistante pour la distance à la mesure, je fournis un algorithme complet permettant d'utiliser l'homologie persistante pour l'analyse topologique de données de petite dimension intrinsèque mais pouvant être plongées dans des espaces de grande dimension. Précédemment, l'homologie persistante a également été utilisée pour analyser des champs scalaires. Ici encore, le problème du bruit aberrant limitait son utilisation et je propose une méthode dérivée de l'utilisation de la distance à la mesure afin d'obtenir une robustesse au bruit aberrant. Cela passe par l'introduction de nouvelles conditions de bruit et l'utilisation d'un nouvel opérateur de régression. Ces deux objets font l'objet d'une étude spécifique. Le travail réalisé au cours de cette thèse permet maintenant d'utiliser l'homologie persistante dans des cas d'applications réelles en grandes dimensions, que ce soit pour l'inférence topologique ou l'analyse de champs scalaires. / Massive amounts of data are now available for study. Asking questions that are both relevant and possible to answer is a difficult task. One can look for something different than the answer to a precise question. Topological data analysis looks for structure in point cloud data, which can be informative by itself but can also provide directions for further questioning. A common challenge faced in this area is the choice of the right scale at which to process the data.One widely used tool in this domain is persistent homology. By processing the data at all scales, it does not rely on a particular choice of scale. Moreover, its stability properties provide a natural way to go from discrete data to an underlying continuous structure. Finally, it can be combined with other tools, like the distance to a measure, which allows to handle noise that are unbounded. The main caveat of this approach is its high complexity.In this thesis, we will introduce topological data analysis and persistent homology, then show how to use approximation to reduce the computational complexity. We provide an approximation scheme to the distance to a measure and a sparsifying method of weighted Vietoris-Rips complexes in order to approximate persistence diagrams with practical complexity. We detail the specific properties of these constructions.Persistent homology was previously shown to be of use for scalar field analysis. We provide a way to combine it with the distance to a measure in order to handle a wider class of noise, especially data with unbounded errors. Finally, we discuss interesting opportunities opened by these results to study data where parts are missing or erroneous.

Ziel der vorliegenden Arbeit war es, die Zusammenhänge zwischen der molekularen Architektur, Morphologie und den mechanischen bzw. bruchmechanischen Eigenschaften in S-SB-S-Triblockcopolymeren und deren Blends und in PI-PS-Multipfropfcopolymeren herauszuarbeiten und damit einerseits einen Beitrag für das Verständnis der Struktur-Eigenschaftsbeziehungen in Block- und Pfropfcopolymeren zu leisten und andererseits Möglichkeiten zur Entwicklung neuer Materialien aufzuzeigen, welche besondere Eigenschaftskombinationen aufweisen und damit ein bedeutendes Interesse für industrielle Anwendungen hervorrufen. Für die Untersuchungen wurde dabei der PS-Außenblockanteil und das S/B-Verhältnis im SB-Mittelblock in S-SB-S-Triblockcopolymeren, die Thermoplast/Thermoplastisches Elastomer (TP/TPE) -Zusammensetzung in S-SB-S-Triblockcopolymer-Blends sowie die Funktionalität und die Anzahl der Verknüpfungspunkte in PI-PS-Multipfropfcopolymeren variiert. Zur Charakterisierung der Phasenmischbarkeit und der Morphologie wurden die dynamisch mechanische Analyse (DMA), die Transmissionselektronenmikroskopie (TEM) und die Röntgenkleinwinkelstreuung (SAXS) angewandt. Die mechanischen Eigenschaften wurden mit dem einachsigen Zugversuch untersucht. Bruchmechanische Untersuchungen erfolgten unter Anwendung der „Essential Work of Fracture“- (EWF-) Methode, welche als Konzept der „Post-Yield“-Bruchmechanik innerhalb der Fließbruchmechanik für duktile nanostrukturierte polymere Materialien sehr gut anwendbar ist und Aussagen zur Bruchzähigkeit der Materialien liefert. Zur näheren Charakterisierung des zeitaufgelösten Deformationsverhaltens sowie der Rissausbreitungskinetik wurden die Dehnungsfeldanalyse, eine Bruchflächenanalyse mittels Rasterelektronenmikroskopie (REM) sowie das Risswiderstandskurven-Konzept angewandt. Die Untersuchungen der S-SB-S-Triblockcopolymersysteme und der PI-PS-Multipfropfcopolymere konnten den signifikanten Einfluss der molekularen Architektur, der Blockzusammensetzung und des PS-Gehaltes auf das Phasenverhalten, die Morphologie und die Eigenschaften klar herausstellen. Durch die Variation dieser Parameter kann das Eigenschaftsspektrum von thermoplastisch zu elastomer eingestellt und somit sowohl TPs oder TPEs mit hoher Steifigkeit und Zähigkeit als auch TPEs mit superelastischem Charakter erzeugt werden. Daraus eröffnet sich ein breiter Anwendungsbereich dieser Materialien, welche aufgrund ihrer Transparenz und physiologischen Verträglichkeit auch interessante optische und gesundheitliche Vorteile mitbringen. Es konnte gezeigt werden, dass durch die systematische Variation der Architektur die gezielte Einstellung gewünschter Eigenschaftsprofile möglich ist. Die Arbeit leistet somit einen Beitrag zur Entwicklung anwendungsorientierter Materialkonzepte, welche ingenieurwissenschaftlich interessant sind. / The aim of this thesis was to study the relation between molecular architecture, morphology and (fracture) mechanical properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. Hence, this work should contribute to the understanding of structure-property-relationship in block and multigraft copolymers and thus offer possibilities for the development of novel materials with special properties interesting for industrial application. Within this study in the case of S-SB-S triblock copolymers the PS outer block content and the S/B ratio of the middle block, in the case of S-SB-S triblock copolymer blends the thermoplast/thermoplastic elastomer (TP/TPE) composition and in case of PI-PS multigraft copolymers the functionality and number of branch points were varied. For the characterisation of morphology and phase miscibility dynamic mechanical analysis (DMA), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were applied. Uniaxial tensile tests were carried out to investigate the mechanical properties. The fracture mechanical behaviour was studied using essential work of fracture (EWF) concept based on the post yield fracture mechanic principles, which is suitable to characterise fracture toughness of ductile nanostructured materials. The time resolved analysis of deformation and fracture behaviour was characterised qualitatively by strain field analysis, scanning electron microscopy (SEM) of the fractured surfaces and quantitatively by evaluation of the crack propagation kinetics and construction of R-curves. This study clearly highlights the significant influence of molecular architecture block composition and PS content on the phase behaviour, morphology and properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. By varying these parameters the property profile can be adjusted diversifying from thermoplastic to elastomeric and both TP or TPE materials with high stiffness and toughness and TPEs with super-elastic characteristics can be designed. Hence, fundamentally it offers a broad scope of application of these materials, in which physiological compatibility and transparency are added advantages. Thus, conceptually it could be shown, that by systematic variation of the architecture desired property profiles can be adjusted. Therefore the present work contributes to the development of application-oriented material concepts, which are interesting in engineering terms.

No description available.

No description available.