Designing enzyme-CNC brick-and-concrete structured PLA film for photothermal regulation and agricultural protection applications with stage-dependent degradation

Solar-enabled thermal regulation is important for agricultural protection applications, yet it remains challenging to simultaneously achieve mechanical robustness, environmental stability, and degradability in biodegradable polymers. Here, a novel bioinspired brick-mortar-reinforcement architecture was designed to construct a multifunctional PLA-based film. In this design, the PLA matrix serves as the load-bearing 'bricks', the polydopamine-calcium carbonate stabilized enzymes act as the functional 'mortar', and the hydrophobically modified cellulose nanocrystals (DPC) function as the 'reinforcing bars', collectively forming a hierarchically integrated structure. Benefiting from this multiscale architecture, PCPM7% exhibits significantly enhanced mechanical performance, with a tensile strength of 32.5 MPa and an elongation at break of 186.9%. The engineered structure also imparts excellent UV shielding (UPF 2000), improved hydrophobicity (water contact angle of 101.2°), and effective solar-to-thermal conversion, enabling stable heat retention under fluctuating environments. The embedded enzyme system enables stage-dependent biodegradation after service, achieving a mass loss of 78.3% within 180 days. This work provides a comparative design strategy for developing high-performance photothermal agricultural films.