Universität Stuttgart

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Open Access
Chemical design and probing of novel molecular 2-qubit systems
(2023) Schäfter, Dennis; Slageren, Joris van (Prof. Dr.)
Open Access
Molekulardynamische Simulation zu Fragen der smektischen Translationsordnung in thermotropen Flüssigkristallen
(2021) Häge, Christian; Gießelmann, Frank (Prof. Dr.)
Es wurden zwei Fragestellungen zur smektischen Translationsordnung von Flüssigkristallen bearbeitet. Der erste Teil der Arbeit befasst sich mit dem Einfluss der molekularen Ladungsanordnung von ionischen Flüssigkristallen auf deren Phasenverhalten. Der zweite Teil der Arbeit untersucht unter welchen Voraussetzungen die Gleichungen zur Bestimmung von Translationsordnungsparametern angewendet werden können und welche Rolle die molekulare Elektronendichteverteilung des Mesogens dabei spielt.
Open Access
Probing molecular quantum bits
(2021) Lenz, Samuel; Slageren, Joris van (Prof. Dr.)
Open Access
Micellar lyotropic gels : the interplay between gel network and liquid-crystalline order
(2021) Dieterich, Sonja; Gießelmann, Frank (Prof. Dr.)
Surfactant based lyotropic liquid-crystalline (LLC) gels in the sense that genuine micellar LLC phases are immobilized by an interpenetrating gel network were practically unknown until 2016. This “blind spot” in the landscape of anisotropic gels has now been filled to a certain extent by the results of this dissertation. Following the rational design strategy to gel surfactant based LLC phases with the help of low molecular mass gelators (LMWGs), not only lamellar and hexagonal LLC gels, but also the very first example of micellar nematic gels were obtained. Furthermore, this work has led to first important insights into how the self assembly of the gel is directed and how the gel network and the LLC phase mutually influence each other in terms of structure and morphology
Open Access
The electronic and geometric structure of chemically immobilised catalysts in mesopores
(2023) Winkler, Mario; van Slageren, Joris (Prof. Dr.)
Open Access
Chemically active micromotors
(2021) Yu, Tingting; Fischer, Peer (Prof. Dr.)
Open Access
Preparation and characterization of mesoscale confined materials for asymmetric catalysis
(2024) Abitaev, Karina; Sottmann, Thomas (Apl. Prof. Dr.)
Open Access
Tailor-made methacrylate-based polymer foams via emulsion and foamed emulsion templating
(2020) Dabrowski, Miriam Lucia; Stubenrauch, Cosima (Prof. Dr.)
Inspired by studies on tissue engineering, this PhD thesis aims at synthesizing and characterizing methacrylate-based polymer foams with tunable pore structures. To reach this goal, two templating routes, namely emulsion templating and foamed emulsion templating, were combined with microfluidics. Two different templating routes were chosen to get access to different pore sizes without changing the monomer. The monomer used was 1,4-butanediol dimethacrylate (1,4-BDDMA). The liquid templates and the solid polymer foams were characterized via light microscopy and scanning electron microscopy (SEM) to prove the “templating effect”.
Open Access
Particle size-dependent phenomena of lyotropic colloidal graphene oxide liquid crystals
(2024) Abele, Christina D.; Gießelmann, Frank (Prof. Dr.)
Open Access
Emulsion templating: unexpected morphology of monodisperse macroporous polymers
(2021) Koch, Lukas; Stubenrauch, Cosima (Prof. Dr.)
The polymerization and drying of monodisperse water-in-styrene/divinylbenzene (DVB) high internal phase emulsions (HIPEs) leads to monodisperse macroporous polystyrene (PS)/polydivinylbenzene (polyDVB). When the monomer-soluble azobisisobutyronitrile (AIBN) is used as initiator, spherical and interconnected pores and porous pore walls are obtained. In contrast, when the water-soluble potassium peroxodisulfate (KPS) is used, polyhedral and closed pores are obtained and the pore walls are comprised of two similar looking outer layers and one different inner layer. The aim of this work was to identify the mechanism (1) that transforms spherical droplets into polyhedral pores and (2) that creates a three-layered pore wall when the polymerization is initiated from the water/monomer interface with KPS. The styrene/DVB mass ratio and the KPS mass fraction were varied to test the existing hypothesis, i.e. an osmotic transport of DVB. Scanning electron microscopy (SEM) pictures revealed that the morphology of the samples does not change in the way it is expected if osmotic transport of DVB was the acting mechanism. Therefore, the existing hypothesis was rejected and a new explanation had to be found. Experiments in which the surfactant mass fraction βsurfactant was varied revealed that the relative size of the inner layer increases and the relative size of the outer layers decreases when βsurfactant is increased. Moreover, it was found that the outer layers are non-porous and that the inner layer is porous. With the help of a model ternary phase diagram consisting of styrene, surfactant, and PS, it was shown that the surfactant is not soluble in partially polymerized styrene/PS mixtures. The experimental results allow suggesting a mechanism that is based on surfactant diffusion. Since the polymerization starts at the water/monomer interface with KPS, a partially polymerized layer forms close to the interface. From this layer, surfactant molecules that are dissolved in the continuous phase diffuse either (1) to the water/monomer interface or (2) to the interior of the continuous phase. (1) Surfactant diffusion to the interface induces an overpopulation of surfactant. This enables the interface to increase its area, which, in turn, transforms the spherical droplets to polyhedral pores. (2) Surfactant diffusion to the interior of the continuous phase leads to an accumulation of surfactant, while the regions close to the interface become surfactant-free. When the surfactant is washed out during purification, a porous inner and two non-porous outer layers are obtained. Additionally, the mechanical properties of monodisperse macroporous PS/polyDVB were investigated. It was found that the samples are only elastomeric when the amount of DVB is low, while they are elastic-brittle for all other monomer compositions.

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