Molecular Regulation of Vinylogous Urethane Networks by Zn2+ Coordination: Balancing Stress Relaxation, Creep Response, and Reprocessability

Abstract Dynamic covalent polymer networks based on vinylogous urethane (VU) bonds are attractive reprocessable materials, but their service stability is strongly affected by residual amines, network mobility, and bond-exchange kinetics. Herein, we report a Zn2+-regulated VU network constructed from trifunctional acetoacetate oligomers and mixed amine curing agents. A slight excess of acetoacetate functionality was used to minimize residual primary amines and suppress uncontrolled low-temperature exchange. Zn2+ ions were further introduced as reversible coordination sites that interact with nitrogen- and oxygen-containing groups in the network. The resulting materials show matrix-dependent mechanical behavior: moderate Zn2+ contents improve strength and energy dissipation in flexible D400-based networks, whereas Zn2+ mainly increases stiffness in rigid IPDA-based networks. Stress relaxation and creep tests reveal a concentration-dependent trade-off between network stability and dynamic rearrangement. Temperature-dependent stress relaxation further reveals a reduced apparent activation energy after Zn2+ incorporation. This work provides a molecular strategy for regulating the relaxation, creep response, and reprocessability of VU-based dynamic polymer networks.