Multifunctional Performance Lignin-Crosslinked-PVA Composite Film Based on a Dual Crosslinking Network

The development of high-performance biocomposites based on poly vinyl alcohol (PVA) and lignin is often hindered by the limited interfacial compatibility. Herein, we reporte a synchronized crosslinking strategy to seamlessly integrate lignin and PVA into a uniform and robust composite film. The vinyl groups were introduced into both lignin and PVA molecular chains, which enable the formation of dense covalent bonds through reactions between these unsaturated carbon-carbon double bonds. This dual network structure combining covalent crosslinking with hydrogen bonding effectively strengthened the interfacial compatibility between lignin and PVA, which substantially enhanced film toughness, exhibiting an elongation at break of up to 4300%. Furthermore, the prepared composite film also demonstrated outstanding UV-blocking efficiency (>90%), strong antioxidant activity (82% DPPH scavenging), enhanced hydrophobicity (water contact angle of 97.9°), and improved thermal stability. The dramatic enhancements were attributed to the homogeneous dispersion of modified lignin within the covalently bonded network, which ensured efficient stress transfer and reduced the availability of hydrophilic groups. This synchronized crosslinking approach presents a versatile and effective route for fabricating high-value lignin-based composite materials.