Laccase-catalyzed polymerization of syringic acid for eco-friendly cotton dyeing: Mechanism, optimization, and multifunctional performance

초록

With the growing emphasis on environmental sustainability, the development of eco-friendly dyeing and finishing processes has become a focal point of research worldwide. In this study, cotton fabric was selected as the substrate, chitosan was employed as a modifier, and laccase was utilized to catalyze the polymerization of syringic acid, leading to the formation of colored polymers. This approach innovatively integrated monomer polymerization, fabric dyeing, and functional finishing into a single process. The structural characteristics of the polymerized products were analyzed using UV-Visible spectroscopy, Fourier transform infrared spectroscopy, and mass spectrometry, and the polymerization mechanism was systematically elucidated. The dyeing performance of the fabrics was evaluated based on K/S values, color fastness, and fiber surface morphology, while different dyeing methods were compared and optimized reaction conditions were determined. Additionally, the mechanical and functional properties of the dyed fabrics were investigated. Molecular dynamics simulations were employed to analyze the affinity and interaction modes between chitosan and the colored polymers. The results revealed that under laccase catalysis, syringic acid monomers underwent dehydrogenation, forming phenoxy (Ph-O) and phenyl (Ph-Ph) linkages, leading to the synthesis of polysyringic acid (PSA) with distinct coloration. Notably, Ph-Ph-linked PSA exhibited a stronger affinity with chitosan, primarily via C--N bonding. Furthermore, the one-step dyeing process proved superior performance compared to the two-step process, yielding fabrics with uniform coloration, high color depth (K/S = 11.57), excellent color fastness (grade 4-5), and enhanced mechanical properties relative to undyed cotton fabrics. Moreover, the dyed fabrics demonstrated outstanding antioxidant, ultraviolet resistance, and antibacterial properties. This study provides a theoretical foundation and technical support for the advancement of green and sustainable dyeing and finishing technologies.

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