Tough, Multifunctional, and Biodegradable Polyurethanes Enabled by Structure–Property Tuning for Versatile Applications

The development of next-generation sustainable polymers presents a promising strategy for addressing the global plastic waste crisis. However, many designs focus solely on degradability and recyclability while neglecting mechanical properties and functionalities, ultimately limiting their potential, as they often fall short of conventional plastics. Herein, we designed various tough, multifunctional, and biodegradable polyurethanes (PUs) through structure–property tuning for versatile applications. By tailoring their chemical and polymer structures, the mechanical properties, enzymatic degradability, and functionalities of PUs can be finely tuned. Notably, PUs incorporating a low content of triacetylated γ-cyclodextrin (TAcγCD)-based movable cross-links (γCD-PUs) exhibited enhanced mechanical properties and excellent recyclability. Furthermore, selective enzymatic degradation of γCD-PUs was achieved with specific enzymes and reaction conditions. By adjusting their chemical structures, biodegradable γCD-PUs can function as hydrophobic materials, shape-memory materials, adhesives or strain sensors. After applying a novel enzymatic reinforcement strategy, the reinforced γCD-PUs exhibited either exceptional rigidity with a fracture stress of 45.3 MPa and a toughness of 450 MJ m–3 or outstanding stretchability with a fracture strain of 2,943% and a toughness of 381 MJ m–3. This work offers fundamental insight for designing tough and biodegradable polymers with tailored functionalities, thereby advancing the development of the circular plastics economy.