Polyoxometalates-Driven Oxidative Polymerization of Thioctic Acid and Synchronized Noncovalent Cross-Linking to Generate High-Strength and Colorimetric Adhesives.

Abstract

Polythioctic acid (PTA) and its derivatives carrying disulfide bonds within the polymer backbone have emerged as leading candidates for yielding degradable and recyclable polymers. However, their development has been impeded by the persistent trade-off between degradability and mechanical strength, as well as the lack of effective polymerization strategies that can be used under mild conditions. Herein, we report a polyoxometalate (POM)-mediated "one-stone-three-birds" strategy, in which rapid ring-opening polymerization (ROP) of TA is synchronously coupled with noncovalent crosslinking under mild ambient conditions. Combined experimental and theoretical investigations reveal that POM nanoclusters act as multifunctional "stones": oxidizing TA to generate cationic radical species that initiate ROP, engaging in strong electrostatic interactions with the sulfonium termini of the resulting PTA chains to form robust polymer networks with high adhesion strength (>11 MPa), and imparting a redox-responsive colorimetric signal. This synergistic integration of mechanical reinforcement and chromic response provides a new strategy for designing adhesives with coupled structural integrity and optical feedback, which enables in situ visual indication of material changes during leakage of oxidizing species in confined environments.