Vanillin-Based Poly(Phenoxy-Imine) Networks with Zn <b> ²⁺ </b> Coordination for Enhanced Mechanical Strength and Recyclability

Vanillin-based dynamic polymer networks are extensively studied, while their mechanical performance is generally determined by the cross-linking components. Here, we synthesized a dialdehyde compound from vanillin (DAV) to create poly(phenoxy-imine) networks with coordination interactions with Zn 2+ . Increasing ratios of Zn 2+ lead to higher tensile strength and Young’s modulus. The synergistic effect of DAV’s phenol and imine groups for the coordination was validated through comparative model studies. Chemical and coordination dual-dynamic networks not only exhibited enhanced mechanical performance, but also improved moldability, as the activation energy ( E a ) for dynamic exchanges decreased from 71 to 52 kJ/mol after introducing coordination, even though the stress relaxation became slower. Moreover, Zn 2+ coordinated poly(phenoxy-imine) networks would dissolve into HCl aqueous solution within 10 min under sonication, and DAV will then quantitatively crystallize out from the solution with high purity for recyclable usage. The current work represents a new strategy to generate Zn 2+ coordination-enhanced dynamic networks from vanillin through molecular engineering.