Cation‐π Dynamic Cross‐Linking Enabled High‐Performance PVA Films With Synchronous Strength‐Toughness Enhancement, Self‐Healing, and Recyclability

Abstract

Poly (vinyl alcohol) (PVA), a representative biodegradable and water‐soluble polymer, suffers from high crystallinity, a strength‑toughness trade‑off, and poor thermal stability arising from strong interchain hydrogen bonding. Conventional modification strategies fail to simultaneously achieve synergistic enhancement of strength‐toughness and functionalization, severely restricting its engineering applications. Herein, inspired by the robust yet dynamic nature of cation‐π interactions, we present a universal design strategy for high‐performance water‐soluble polymers based on indole‐Mg2+ cation‐π dynamic cross‐linking. Molecular simulations and spectroscopic characterization demonstrate that Mg2+ forms strong cation‐π interactions with indole moieties, exhibiting a binding energy of −113 kJ mol−1. Mechanical testing reveals that the optimally formulated PVAI‐7.5%Mg2+ film achieves a tensile strength of 51 MPa (a 130% increase from 22 MPa) and an elongation at break of 400% (enhanced from 320%), thereby realizing synchronous improvement of strength and toughness. Benefiting from the dynamic reversibility of cation‐π interactions, the film exhibits autonomous scratch healing within 12 h at room temperature without external stimuli, while retaining excellent water solubility that enables multiple recovery and reprocessing cycles via solvent‐based methods without performance degradation. This study overcomes the dual bottlenecks of the strength‐toughness trade‐off and the performance‐functionalization incompatibility inherent to PVA modification, offering new avenues for the high‐performance and multifunctional design of water‐soluble polymers and providing experimental and theoretical insights into the application of cation‐π interactions in polymeric materials.