Citric-acid-crosslinked starch/polyvinyl alcohol composite films reinforced with sodium lignosulfonate for sustainable packaging applications

Plastic pollution remains a critical global environmental challenge. Although biodegradable polymers offer a sustainable alternative to petroleum-based plastics, their industrial uptake is limited by high moisture sensitivity and insufficient mechanical and functional performance. This study develops multifunctional starch/poly(vinyl alcohol) (PVA) films reinforced with sodium lignosulfonate (LS) and crosslinked with citric acid to address these limitations. A systematic variation of LS content was employed to clarify its role in tailoring interfacial interactions and film performance. Spectroscopic and morphological analyses revealed strong hydrogen bonding and aromatic-polar interactions between LS and the hydroxyl-rich polymer network, modifying surface chemistry and microstructure without disrupting the polysaccharide backbone. These synergistic interactions yielded films with tunable mechanical behavior (modulus 60-218 MPa; elongation up to 0.76), improved barrier performance, such as WVTR reduced to 174 g·m -2 ·day -1 , markedly enhanced antioxidant activity up to 90% DPPH scavenging, and nearly complete UV blocking (∼99.99%). The findings elucidate the molecular mechanisms underlying LS’s simultaneous enhancement of reinforcement, moisture resistance, UV shielding, and antioxidant capacity. Overall, LS-reinforced starch/PVA-citric-acid films demonstrate strong potential as sustainable, high-performance materials for food packaging applications, particularly for protecting photosensitive and oxidation-sensitive products. • Citric-acid-crosslinked starch/PVA films were reinforced with sodium lignosulfonate • Lignosulfonate formed strong interactions within the starch/PVA polymer network • Films showed reduced WVTR and nearly complete UV blocking (∼99.99%) • Antioxidant activity increased up to 90% due to lignosulfonate incorporation • Multifunctional films are promising for sustainable active food packaging