Dynamic Diels–Alder-Crosslinked Zwitterionic Polyurethane Coatings with Self-Healing, Antibacterial, and Antifouling Properties

Abstract Coatings used in marine and humid environments are simultaneously exposed to biofouling and mechanical damage, which progressively compromise their interfacial functionality and service stability. In this study, polyurethane resins bearing terminal maleimide groups and sulfobetaine moieties (ZPU-X) were synthesized and subsequently crosslinked with a tetrafunctional furan-terminated compound (TF) through reversible Diels–Alder (DA) reactions to produce dynamically DA-crosslinked zwitterionic polyurethane coatings (SA-X). The sulfobetaine groups promoted the formation of hydrated interfaces that reduced microorganism-coating interactions, achieving maximum antibacterial and antialgal rates of 96.7 and 99.7%, respectively, while effectively suppressing surface colonization by Aspergillus niger (A. niger). The reversible furan-maleimide crosslinks endowed the system with the capacity for segmental rearrangement and network reconstruction. After self-healing, the tensile strength and elongation at break of the coatings reached up to 25.69 ± 0.17 MPa and 1645.13 ± 54.27%, respectively. After 1000 Taber abrasion cycles, the coatings retained liquid-repellent behavior, demonstrating good surface functionality under wear. This work provides an effective strategy for developing functional polyurethane coatings that integrate antibacterial, antifouling, and self-healing properties.