Cationic Ring-Opening Polymerisation-Induced Chiral Self-Assembly of 2-Oxazolines Yielding Covalently Cross-linked Nanostructures with Chiral Core

• Applicant: Professorin Dr. Meike Leiske
• Subject Area: Polymer Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563027621

Since their discovery, poly(2-oxazoline)s (POx) have received significant attention for applications in the life-science sector. The interest in this polymer class specifically derives from the low-fouling or “stealth” properties of hydrophilic POx. However, due to the synthetic route via the cationic ring-opening polymerisation (CROP), mostly linear POx were synthesised in the past. These suffer from low molar mass and, consequently, fast renal clearance in a biological setting. Hence, research has focused on the preparation of non-linear, high molar mass POx by different techniques, ranging from multifunctional initiators and termination agents to post-polymerisation cross-linking and the preparation of nanostructures (e.g., bottle-brush polymers) via combination with other polymerisation techniques (e.g., controlled radical polymerisation techniques). One mostly unexplored strategy to develop high molar mass POx with defined morphology (e.g., spherical or worm-like) is the application of polymerisationinduced self-assembly (PISA), which has previously been established for controlled radical polymerisation techniques such as the reversible addition-fragmentation chain-transfer (RAFT) polymerisation and ringopening metathesis polymerisation (ROMP). Via these techniques, PISA has been demonstrated to yield defined macromolecular architectures in a reproducible manner, however, it has not been reported for the CROP of 2-oxazolines. For this reason, this project aims to establish the preparation of non-linear POx via cationic ringopening polymerisation-induced chiral self-assembly (CROPICSA) to yield core cross-linked nanostructures with chiral cationic cores. We will synthesise 2-oxazoline monomers featuring a tert-butyloxy (Boc)-protection group from chiral aliphatic α-amino-acids and will study their polymerisability and the solubility of the resulting polymers in relevant solvents. We will then apply these conditions to a chainextension reaction of a soluble reactive block and study the assembly of the resulting polymers during CROPICSA. Eventually we will further expand the reaction conditions established within the project to a cross-linked system by feeding in a bifunctional monomer during the chain-extension reaction to eventually create cross-linked nanostructures, which are responsive to a redox-stimuli and hence could be cleaved by the addition of a reducing agent.

• DFG Programme: Research Grants