Current Topics for Research Internships or Bachelor Thesis


Synthese von Terpyridin–Derivaten zum Aufbau sequenz-kontrollierter Polymere
Assoziierende Polymere enthalten funktionelle Einheiten, die in der Lage sind durch nicht-kovalente Wechselwirkungen transiente Bindungen einzugehen und ein supramolekulares Polymernetzwerk zu bilden. Für systematische Studien an solchen Netzwerken eignen sich Vernetzungsmotive mit definierter Stöchiometrie und bekannter, variierbarer Bindungsstärke, wie beispielsweise die Bis-Terpyridin Komplexe verschiedener Übergangsmetalle. Um Struktur-Eigenschafts-Beziehungen solcher Gele systematisch untersuchen zu können, werden Terpyridin-funktionalisierte Polymere mit definierter Primärstruktur benötigt. Die in unserer Gruppe angewendeten Synthesestrategien zum Aufbau solch sequenz-kontrollierter Architekturen erfordern Terpyridin-funktionalisierte Aminosäuren und Diole.
Im Rahmen eines Forschungsmoduls oder einer Bachelorarbeit können etablierte Syntheserouten zur Herstellung von Terpyridine Aminosäure-Derivaten reproduziert, optimiert und anschließend in der Festphasensynthese eingesetzt werden. Alternativ ist auch die Mitarbeit bei der Synthese oligomerer Terpyridin-Diole möglich.

Betreuung: Katharina Breul (kabreul[a]
Stand: Januar 2019; Starttermin: jederzeit


Structure and Dynamics of Inhomogeneous Model Double Network Hydrogels
Polymer hydrogels are present in our daily life, in food, cosmetics, drugs, and even sophisticated areas like tissue engineering and batteries. Polymer gels can be either chemical, with permanent network junctions, or physical, with reversible bonds. This offers diverse network properties, like high mechanical strength versus self-healing. Double network hydrogels are a new class of polymer gels that contain both chemical and physical network junctions. They can impart stimuli-responsiveness to the chemical gels, but specifically, they deliver high toughness. This is realized by repetitive reversible breakage of physical bonds and dissipation of the applied force.
Hydrogels are often illustrated as a perfect mesh structure with a uniform stand length. However, depending on the preparation method, they instead contain several types of inhomogeneities at different length scales, which significantly amplify at the swollen state and affect their properties like clarity and permeability. We deliberately add such inhomogeneities into the structure and chemical constitutes of a model double network hydrogel and study the consequences using light scattering, Fluorescence Recovery after Photobleaching (FRAP), and rheology. The ideally homogeneous network is already synthesized in our group and under similar investigations. This means that the polymer precursors are available, and we are know looking for candidates who are interested in preparing the inhomogeneous gels and performing the aforementioned studies in the context of a research module or bachelor thesis.

Supervisor: Mostafa Ahmadi (ahmadi[a]
Time of posting: January 2019; possible start date: anytime


Stimuli-Responsive Supramolecular Hydrogels
Hydrogels are 3D network materials made of crosslinked hydrophilic polymer chains. Charged hydrogels have a high capacity for water uptake, up to 1000 times of their own weight; these materials are called superabsorbers and are commercially utilized in hygiene applications. Another class of hydrogels are supramolecular hydrogels in which hydrophilic polymer building blocks self-organize into a network by non-covalent bonds such as hydrogen bonding or ionic interactions. Due to the dynamic nature of these physical bonds, the sol–gel transition of supramolecular hydrogels can occur dependent on the environment such as temperature or pH. Therefore, different applications such as drug delivery, tissue engineering, and 3D printing can profit from them. This research project, which can be a Bachelor thesis or a research module, targets at combining the utility of both these types of hydrogels. Prototype samples will be fabricated by droplet-based microfluidics, and their water swelling capacity as well as their swelling/deswelling temperature range will be tuned by physical bonds and network architecture parameters.  The project involves both preparative polymer-chemistry aspects, for example, preparation of hydrophilic polymer backbones with non-covalent cross-linking motifs as side groups, and analytical polymer-physics work, for example, assessment of the gel-sample mechanics by rheology.

Supervisor: Amir Jangizehi (amir.jangizehi[a]
Time of posting: May 2019; possible start date: anytime


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