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 <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>, 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.