Closed-Loop Recyclable and Multifunctional Supramolecular Hydrogel from Reversible Ring-Opening Polymerization of Guanidine-Modified Thioctic Acid in Water

The development of multifunctional hydrogels that seamlessly integrate antibacterial activity, self-healing, and closed-loop recyclability is crucial for advanced sustainable functional materials. Herein, we present a supramolecular hydrogel prepared exclusively via an evaporation-induced ring-opening polymerization (ROP) of a guanidine-modified thioctic acid (GTA) monomer in water. Remarkably, the resulting supramolecular hydrogel, i.e., poly(GTA), can be fully depolymerized into a monomer through a catalyst-free ring-closing depolymerization (RCD) process in water, enabling efficient closed-loop recycling. The cationic, dynamic, and hygroscopic properties of the guanidine motif endow the poly(GTA) hydrogel with unique features, including intrinsic antibacterial activity against both Escherichia coli and Staphylococcus aureus, humidity-sensitive morphology transitions, rapid self-healing, and closed-loop recyclability. Notably, the poly(GTA) hydrogel exhibits exceptional ductility (up to 15000% strain) and high adhesion to biological tissue surfaces (>15 KPa), highlighting its potential for various interface applications, including biomedical fields. As a proof-of-concept study, this work demonstrates a sustainable and straightforward strategy for constructing recyclable, multifunctional supramolecular hydrogels from a single small molecule in water, offering a promising platform for sustainable antibacterial materials and future interface applications.