Multifunctional composite polyvinyl alcohol film reinforced with polymeric ionic liquid-modified cellulose nanocrystals for multimodal bacteriostatic food packaging

Multifunctional food packaging remains challenging due to complex processes requiring multiple additives. This study presents a simplified fabrication of polyvinyl alcohol (PVA) composite films using a multifunctional nanofiller. An ionic liquid monomer (ILFe III ) bearing quaternary ammonium salt (QAS) cations for antibacterial activity and tetrachloroferrate(III) anions (FeCl₄ − ) for photothermal conversion was grafted onto cellulose nanocrystals (CNCs) to producing CNC@PILFe III nanofiller, which was incorporated into PVA by one-pot blending and casting. Owing to the rationally designed ionic liquid structure, incorporating QAS cations, hydrophobic phenyl/alkyl groups, and FeCl₄ − anions, this nanofiller endowed the PVA/CNC@PILFe III composite films with multimodal antibacterial activity, mechanical reinforcement, and enhanced water resistance. The optimized film exhibited mechanical strength (tensile strength 11.92 ± 0.21 MPa and elongation at break 202.1 ± 2.7 %), stiffness (66.40 ± 0.71 MPa), water resistance (water contact angle 98.8 ± 3.0°), and reduced oxygen and water vapor permeability, along with >99 % antibacterial efficacy against E. coli and S. aureus and > 90 % cytocompatibility. Preservation tests on cherry tomatoes showed significantly inhibited microbial growth, reduced weight loss, and sustained texture and acidity over 14 days, demonstrating effectively extended shelf life. This approach offers a promising strategy for sustainable, high-performance food packaging materials.