Synergistic Integration of Covalent and Supramolecular Cross-Linking among Aromatic-Hydrazone Macrocyclic Polymer Networks with Enhanced Mechanical Properties

Polymer networks have gained great attention due to their unique structural arrangement and characteristic properties. The interconnection of polymer chains can be achieved through covalent or noncovalent interactions. However, it remains a challenge to explore a strategy for the precise integration of covalent and noncovalent cross-linking within polymer network architectures. In this work, we designed and synthesized hydrogen-bonding preorganized arylhydrazone dual-arm monomer <b>1</b> (<b>M1</b>) and triarm monomer <b>2</b> (<b>M2</b>), which were used to fabricate covalent polymer networks (<b>CPN</b>s), <b>CPN1</b> and <b>CPN2</b>, via acid-catalyzed macrocyclization. The resulting <b>CPN1</b> and <b>CPN2</b> exhibited well-defined electron-rich macrocyclic cavities, enabling subsequent supramolecular cross-linking with bipyridinium guest (<b>BP</b>) to generate supramolecular/covalent polymer networks (<b>SCPN</b>s), <b>SCPN1</b> and <b>SCPN2</b>. <b>CPN1</b> formed denser, more flexible films compared to the brittle <b>CPN2</b>, highlighting the importance of appropriate covalent cross-linking density. Importantly, incorporation of <b>BP</b> significantly improved the mechanical properties of the networks, including Young's modulus, tensile strength, and toughness, demonstrating the effectiveness of host-guest interactions in reinforcing polymer network structures and the potential of macrocycle-driven supramolecular engineering for advanced material design.