Bioinspired Catechol-Functionalized Zwitterionic Waterborne Polyurethane for Enhanced Wet Rubbing Fastness and Color Fixation of Denim Fabrics

Inspired by the adhesive chemistry of mussel foot proteins, two catechol-functionalized polyamine chain extenders (NCA1 and NCA2) were synthesized via reductive amination and incorporated into zwitterionic waterborne polyurethane (WPUIP) systems for enhancing the wet rubbing fastness of denim fabrics. Structural characterization confirmed the successful synthesis of the chain extenders and their incorporation into the polyurethane backbone. The resulting emulsions exhibited excellent colloidal stability, maintaining stability over a pH range of 3–9, with particle sizes ranging from 73.37 to 278.36 nm and zeta potentials up to 42.17 mV. The introduction of catechol moieties improved thermal stability and surface hydrophobicity, while the enhanced wet rubbing performance was consistent with stronger catechol-mediated interfacial interactions. Denim fabrics treated with WPUIP displayed significantly enhanced wet rubbing fastness, increasing from < Grade 1 for untreated fabric to Grade 3–4, while maintaining dry rubbing fastness at Grade 4–5. Moreover, a maximum water contact angle of 152.5° was achieved, indicating excellent hydrophobicity. The synergistic integration of catechol-inspired adhesion and zwitterionic stabilization provides an effective strategy for developing high-performance textile fixing agents with broad process adaptability.