Tannic acid-mediated covalent adaptable networks in chitosan-collagen coatings: Toward on-demand peelable superhydrophobic textiles with enhanced durability

Superhydrophobic coatings present several challenges, including the reliance on organic solvents and fluorine chemicals, vulnerability to mechanical abrasion of hierarchical structures, poor durability and environmental concerns of coated textiles when discarded. This study introduces a bio-based, fluorine-free superhydrophobic coating on cotton fabrics via a layer-by-layer (LBL) self-assembly of chitosan and collagen, followed by tannic acid (TA)-mediated crosslinking and grafting octadecylamine (ODA) through Schiff-base and 1,4-Michael addition reactions. The resulting coating exhibits a water contact angle (WCA) of 158.6°, achieving robust superhydrophobicity with only ~10 % weight gain and a pencil hardness of 8H. The covalent adaptable networks (CANs) formed between chitosan/collagen layers and TA endows the coating exceptional washability and resistance to sand abrasion. Acid-triggered dissociation of imine bonds in CANs weakens interfacial adhesion, enabling on-demand coating peelability from the fabric surface under mild acidic conditions. This work innovatively integrates CANs into bio-based superhydrophobic coatings, overcoming the historically conflicting issues of durability and recyclability in functional textiles. TA-mediated CANs offer the dual advantages of mechanical robustness and acid-triggered peelability. This work establishes a sustainable framework for next-generation functional textile coatings that align with the principles of the circular economy.