Projects
Project description
I develop new crosslinker molecules based on diazo groups that can be activated by photochemical or thermal energy. Thus it is possible to form free-standing or surface-bound networks. The advantage here is that the crosslinkers are already built into the polymer and are not introduced subsequently. By modifying the crosslinker molecules, the required photochemical energy (excitation wavelength) or thermal energy (temperature) can be adjusted.
Project outcomes
The interaction between a material and its environment depends on the materials surface chemistry. To tune the surface properties and therefore the interaction, polymeric coatings can be applied. Polymer coatings can either change the surface properties to a desired outcome or shield the material from damage. In order to achieve such resilient properties, the coatings have to be mechanical and chemical stable, and the interaction between the coating and the surface must be highly adhesive. The approach taken here was to study the crosslinking behavior of functionalized Rx-phenyl diazo ester based crosslinkers to improve the photochemical and thermal crosslinking reaction and to expand the toolbox of crosslinker systems that can be used. The activation leads to a loss of nitrogen, forming a carbene that serves as the reactive intermediate to carry out the C-H insertion based crosslinking (CHic) reaction. This crosslink technique is universally applicable in polymers since the reaction partner is a C-H group, which is abundant in a polymer chain. If any C-H bonds are available, it can simultaneously react to the surface as well, forming chemically surface-attached polymer networks.
Utilizing this approach, I synthesized and copolymerized a variety of different donor and acceptor substituted phenyl diazo ester (Rx-PEDAz) crosslinker molecules and studied their thermal and photochemical crosslinking behavior. The higher thermal and photochemical reactivity of the new crosslinkers opens the path to gentler activation parameters and therefore more delicate polymers and substrates can be used in applications. Crosslinking below 100 °C, using 365 nm UV- or even sunlight can all be achieved in seconds and the reactivity can be adjusted depending on the needs using the acceptor/donor strength of substituents.
Supervisor and dissertation
Prof. Dr. Jürgen Rühe
Dennis Rusitov successfully defended his dissertation in September 2023.
Dissertation: Tunable phenyl diazo ester containing polymers for C-H insertion crosslinking (CHic)
Moved on to
Postdoctoral researcher in the Electrochemical Energy Systems (EES) Junior Research Group at the technical faculty in Freiburg. The research is about investigating and improving fluor-free Ion exchange membranes for the use in electrolysis and fuel cells ex- and in-situ.