Lignin- and Silver-Modified Multifunctional Cotton Fabrics: Influence of α- and β-Chitosan Pretreatment on Structure–Property Relationships

This study investigates lignin as a renewable functional dye capable of simultaneously imparting coloration and multifunctional performance to cotton textiles, with particular emphasis on how chitosan polymorphs influence lignin-mediated silver nanoparticle (AgNP) systems. Cotton fabrics were pretreated with α- or β-chitosan crosslinked with glyoxal and subsequently dyed with lignin in the presence of silver ions to generate lignin-mediated AgNPs. Inductively coupled plasma optical emission spectrometry (ICP–OES) analysis showed that α-chitosan retained a higher silver content (40.7 mg/kg) than β-chitosan (14.7 mg/kg). Transmission electron microscopy (TEM) revealed that α-chitosan produced larger AgNPs (≈13.6 nm), whereas β-chitosan was associated with smaller measurable nanoparticles (≈4.3 nm). Despite lower silver loading, β-chitosan–modified fabrics exhibited higher antibacterial activity against Staphylococcus aureus (82.6%) than α-chitosan-modified fabrics (68.7%). These results suggest that antibacterial performance in lignin–silver coating systems may depend not only on silver loading, but also on the distribution and accessibility of active components within the coating layer. In addition, the coatings improved UV protection, tensile properties, and color strength. Overall, the findings demonstrate that chitosan polymorphism plays an important role in controlling nanoparticle characteristics and multifunctional performance in lignin-based textile systems.