Highly elastic lignin-based waterborne polyurethane with light color and its application in functional fabric coatings.

The increasing emphasis on green and sustainable development has propelled the integration of lignin into polymer matrices as a promising trend. Lignin, a highly reactive biomass material endowed with hydrophilic functional groups, presents significant potential in polymer applications. However, its intrinsic dark coloration poses a considerable challenge to its polyurethanes (PU) use. In this study, lignin was chemically modified through sulfonation, introducing an abundance of sulfonic acid groups that not only enhanced its hydrophilicity but also markedly reduced its color intensity. Additionally, 2-methacryloyloxyethyl phosphorylcholine diol (MPC-diol) was employed as a chain extender in conjunction with sulfonated lignin (SL) to further augment the hydrophilicity of the resulting PU. The incorporation of both anionic and cationic species within the polymer side chains facilitated improved polymer chain interactions. The synergistic combination of polycaprolactone (PCL) soft segments and SL end-capped segments enabled the formation of multiple hydrogen bonds and disulfide linkages, culminating in waterborne polyurethanes (WPU) characterized by superior mechanical properties and self-healing capabilities. The application of these light-colored, SL-based polycarbonate waterborne polyurethane (PCPUSL) coatings to fabrics significantly enhanced their biocompatibility and antimicrobial properties. This development represents a green, sustainable, and highly flexible WPU coating with exceptional self-healing properties and promising potential for diverse applications.