Pore-filling engineering of all-biomass cellulose/thymol films via solvent-induced phase inversion for moisture-barrier and antibacterial fruit preservation

Plastic pollution and postharvest food loss have intensified the demand for high-performance biodegradable packaging, yet regenerated cellulose films are limited by a porous Cellulose II architecture and high moisture sensitivity. Here, a robust all-biomass film is developed by incorporating thymol into a bamboo-derived cellulose matrix via solvent-induced phase inversion. During solvent exchange, thymol crystallizes in situ and fills the inherent micropores, stabilized by interfacial hydrogen bonding, transforming the porous network into a dense, high-barrier interface. This pore-filling selectively suppresses the polar surface-energy component, raising the water contact angle from 43° to 68° (61° for the optimized CT-0.3) and lowering the water vapor permeability by around 53%, thereby resolving the trade-off between breathability and moisture barrier without sacrificing mechanical integrity (tensile strength around 46 MPa at around 12 μm). Molecular dynamics simulations show thymol to be dynamically anchored, undergoing humidity-dependent, chain-selective redistribution without bulk desorption. The optimized film exhibits potent antibacterial activity against Staphylococcus aureus and Escherichia coli , reducing viable bacteria by around 60–90%, with sustained, near-zero-order thymol release. Applied to strawberries and bananas, it inhibits weight loss and delays senescence, extending shelf life to seven days (over double the pristine-cellulose control), offering a promising platform for all-biomass active packaging.