Supramolecular reconstruction of rice straw lignocellulosic microfibrils into high-performance food packaging films

Petrochemical plastic films dominate food packaging yet impose persistent environmental burdens through carbon-intensive production and end-of-life pollution. Here, we present an efficient, additive-free method that converts rice straw into high-strength, humidity-resistant, high-barrier biodegradable films through structural reorganization of native lignocellulose. Subcritical water treatment promotes the redistribution of native lignin and increases phenolic hydroxyl groups, while mechanical defibrillation and roll-to-roll densification generate highly aligned and compact lignocellulosic microfibril networks. The resulting compact lamellar architecture suppresses free volume and creates highly tortuous diffusion pathways across the film thickness. The film achieves a tensile strength of 192 MPa and a strain of 5.7%, and maintains 112 MPa at 90% relative humidity of refrigeration storage. Its oxygen and water vapor transmission rates are 0.097 mL·mm/(m²·day·atm) and 3.04 g·mm/(m²·day), respectively, both of which are lower than those of commercial polyethylene films. Confocal microscopy together with molecular interaction analysis suggests that redistributed lignin contributes to enhanced interfacial cohesion between adjacent microfibrils while simultaneously imparting intrinsic antioxidant activity without detectable cytotoxicity. Cradle-to-gate life-cycle assessment further reveals substantially lower global warming potential and fossil resource depletion than polyethylene and polypropylene. These results demonstrate that synergistic lignin redistribution, microfibril alignment, and structural densification provide an effective strategy for developing sustainable lignocellulosic packaging materials with balanced mechanical and barrier performance.