Thermal, antioxidant and swelling behaviour of transparent polyvinyl (alcohol) films in presence of hydrophobic citric acid-modified lignin nanoparticles.

Lignin nanoparticles (LNP) have been esterified and etherified by citric acid and then blended with poly (vinyl alcohol) (PVA) at various loading levels (up to 10 wt%). Poly(vinyl alcohol) nanocomposite films containing unmodified and modified lignin nanoparticles (LNP and MLNP) were prepared through solvent casting approach. Microscopic investigation of films fractured surfaces confirmed that MLNP could be evenly dispersed in PVA matrix, and no macroscopic phase separation was generated in the nanocomposite films. Water contact angle, swelling efficiency and moisture adsorption properties of LNP and MLNP based films were measured and compared, revealing an overall increase of dimensional stability and reduced moisture adsorption for MLNP nanocomposites. MLNP based nanocomposite films outperformed the films containing LNP in antioxidant property and transparency, slight sacrificing in UV-absorbing, confirming these materials as promising candidates for applications requiring high antioxidant potential and improved performance towards light absorbance.