All-water-based fabrication of biodegradable mulch films from dead leaves via complex hydrogen-bonded networks

Abstract

The escalating accumulation of plastic waste in agricultural soils underscores the urgent need for sustainable alternatives to conventional polyethylene (PE) mulch films. Here, we report the fabrication of high-strength, biodegradable mulch films derived from lignocellulose nanofibers (LCNFs) extracted from a biomass of abundant, non-edible dead leaves. LCNFs were isolated using a hydrated multi-carboxylic acid deep eutectic solvent (DES) coupled with high-intensity ultrasonication. The resulting LCNFs were then blended with cellulose nanocrystals (CNCs), polyvinyl alcohol (PVA), and glycerol (Gly) at varying ratios, using water as the only processing medium to construct lignin-containing all-nanocellulose-combined PVA (LANC/PVA) films through evaporation-induced self-assembly. The incorporation of CNCs and PVA into the LCNF matrix reduced film porosity, yielding denser, smoother, and mechanically stronger structures. Moreover, the high compatibility of LCNFs, CNCs, Gly, and PVA facilitated the formation of an extensive and stable hydrogen bonding network, which contributed to excellent performance characteristics, including improved hydrophobicity (WCA = 77.8–118.6°), low water vapor permeability (WVP = 1.93–5.7 g µm (m² day Pa)⁻¹), complete UV radiation blocking (∼100% for both UVA and UVB), and effective soil moisture retention (∼5% loss over 14 days). Notably, the soil biodegradation test employing a respirometer revealed that the LANC/PVA films degraded by approximately 34.4 ± 0.9% within 115 days, while ecotoxicity assessments confirmed negligible adverse effects on the germination and growth of monocotyledonous (ryegrass) and dicotyledonous (tatsoi) plants. These findings highlight the potential of dead leaf-derived LANC/PVA films as high-performance, biodegradable mulch films for environmentally responsible plasticulture.