Light-triggered metal-ligand coordination in polymers – from fundamental studies to photoresponsive polymer networks

• Applicants: Professor Dr. Benjamin Dietzek-Ivansic; Professor Dr. Ulrich S. Schubert
• Subject Area: Preparatory and Physical Chemistry of Polymers ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549386640

Stimuli-responsive polymers have gained much interest over the last years due to their switchable properties, which can be changed upon a certain stimulus. Different stimuli, like heat or change in pH-value have been applied to trigger the responsive behavior of these smart materials. Light is a special trigger of interest, since different wavelengths can be utilized and the stimulus can also be applied locally with temporal control. Hence, different classes of photo-responsive polymers, like polymers with azodyes or metallopolymers, have been studied. Metallopolymers as polymers featuring supramolecular interactions represent promising materials. There are some examples of photoresponsive metallopolymers featuring photolabile Ru(II) complexes. However, there is a gap in the current literature that relates to systematic mechanistic studies of the complexes’ photocleavage and binding interaction in polymers as a function of complexes’ architectures and the local environment of the photoactive units in polymer networks. The latter aspect includes several parameters like the glass transition temperature of the polymer, the polarity of the polymer as well as the additional presence of solvent in gels. This project will strive to address this question by combining the synthesis of photoactive Ru(II)-complexes with a range of photolabile ligands of different coordination strength and embed them into different polymer structures. Thereby, we will investigate the role of local environment, e.g., solvent accessibility, polymer polarity on the light-driven ligand labilization. The set of the polymeric structures being utilized to tune the properties will range from polymer gels to polymer networks. Semi-IPNs with “oligomeric solvent” will be used to have a smooth transition of the gels (with solvent) to the polymer network (no solvent). Besides the molecular process upon light irradiation, we will investigate the impact of the ligand labilization on the macroscopic properties of the polymeric materials, in particular the mechanical properties. The stimuli-responsiveness of the polymer materials will be utilized in the context of shape-memory polymers as well as self-healing polymers. The photo-induced reversibility of the Ru(II)-complexes will allow the restoration of the permanent shape and the closure of scratches, respectively.

• DFG Programme: Research Grants