Comparative Performance of Poly(Vinyl Alcohol)/Chitosan Hydrogels Reinforced With Kraft Lignin and Kraft Lignin Nanoparticles

ABSTRACT The development of multifunctional hydrogels combining mechanical stability with environmental responsiveness remains challenging. This study examines poly(vinyl alcohol) (PVA)/chitosan (CS) hydrogels containing kraft lignin (KL) or kraft lignin nanoparticles (KL‐NP) at loadings of 2–10 wt.%. Lignin morphology and loading significantly influenced the mechanical, swelling, UV‐shielding, and antibacterial properties of the hydrogels. Among the tested formulations, KL‐6 and KL‐NP‐8 exhibited the highest measured mechanical performance within their respective series, with KL‐NP‐8 reaching a tensile strength of 0.235 MPa and an elongation at break of 137%. At pH 9, KL‐NP‐8 achieved approximately 1700% swelling. SEM revealed a finer and more uniform matrix‐level void morphology in the freeze‐dried KL‐NP specimens, while nitrogen‐sorption analysis showed higher N 2 ‐accessible dry‐state BET specific surface areas than those of the PVA‐CS and KL specimens. All lignin‐containing hydrogels provided essentially complete shielding across the measured UV range. Quantitative CFU analysis showed bacterial reductions of 94%–99% for E. coli and 99%–100% for S. aureus with the KL‐NP formulations. Following 12 h of accelerated UVC–ozone exposure, the KL‐NP specimens exhibited loading‐dependent reductions in elongation. Overall, the findings identify lignin morphology and loading as coupled design variables for balancing mechanical performance, swelling, and multifunctionality.