Tuning the Multinetwork Structures of Acetoacetylated Poly(vinyl alcohol) Adhesives for Polarizers with Zn ²⁺ : Achieving Synergistic Improvements in Cohesion and Interfacial Bonding

Eco-friendly waterborne optical adhesives suffer from simultaneously achieving high interfacial adhesion and high bulk cohesion, alongside poor hydrothermal resistance. Here, we address this challenge by introducing Zn 2+ coordination into a covalently cross-linked acetoacetylated poly(vinyl alcohol) (AAPVA) network. This synergistic multinetwork─comprising dynamic metal–ligand bonds, PVA crystallites, and covalent cross-links─dissipates energy to alleviate cohesive brittleness while providing new interaction sites at the adhesive–substrate interface. Consequently, the average peel strength is remarkably enhanced from 2.68 × 10 –2 to 9.32 × 10 –2 N mm –1, achieving optimal hydrothermal aging resistance at 0.22 wt % Zn 2+ . Furthermore, quantitative topological analysis via time-resolved low-field NMR, DSC, and FT-IR reveals that Zn 2+ accelerates the initial cross-linking kinetics. Notably, the network constraint sites peak at 0.10 wt % Zn 2+, while crystallization is completely suppressed above 0.64 wt %. This work provides a robust physical paradigm for utilizing dynamic metal coordination to decouple the adhesion–cohesion conflict in soft materials for demanding environments.