Synergistic enzyme/acid-degradable PCL-based polyurethanes with enhanced biocompatibility and shape memory properties

Addressing conventional polyurethane (PU) challenges including non-renewable resource reliance, recycling difficulties, and demands for functionalization, this study designed an enzymatic and acidic-synergistically degradable PU material with biocompatibility and shape-memory behavior. By incorporating acid-hydrolyzable hexahydrotriazine (HT) units and bio-based isosorbide (ISO) into polycaprolactone (PCL)-based PU chains, crosslinked PCL-PU films with dual degradability were synthesized. By regulating the ratio of ISO units and HT chain extender, the PCL-PU films exhibited superior mechanical properties, with a tensile strength of ∼31.1 MPa and elongation at break of ∼963 %, while maintaining high thermal stability. Thanks to their unique chemical structure, PCL-PU films exhibited superior synergistic degradation properties in both acidic and enzymatic environments. Specifically, they achieved rapid and full breakdown in a phosphoric acid/ethanol solution at room temperature, while exhibiting partial enzymatic degradation (∼28.7 % weight loss after 6 weeks in lipase solution). Furthermore, the PCL-PU films also demonstrated good biocompatibility, and possessed shape-memory functionality, enabling spontaneous recovery to their original shape above 37 °C. This study not only provides a new direction for the sustainable development of PU materials but also lays the foundation for medical materials, flexible sensors, smart wearable devices, adaptive structures, and environmentally friendly biomedical applications.