Intrinsically flame-retardant and biodegradable DDP-based adhesives for wet environments

Adhesives have been increasingly utilized in multifaceted applications, such as furniture, electrical appliances, and buildings. Currently, in addition to fundamental requirements for high adhesiveness, there are increasing demands for environmental sustainability, flame retardancy, and high-performance in extreme conditions. (6H-dibenz[c,e][1,2]oxaphosphorin-6-ylmethyl)-p-oxide-butanedioic acid (DDP) is selected to be incorporated into the Poly(butylene adipate-co-terephthalate) (PBAT) backbone, enabling the synthesis of a novel adhesive (poly(butylene adipate-co-terephthalate-co-phosphaphenanthrene) (PBATDn). Due to the π-π stacking of DDP, PBATD 20 exhibits an extremely high adhesion strength of 11 N/cm. Owing to the hydrophobicity of the aromatic ring and the insensitivity of π-π stacking to water, PBATD 20 maintains a high adhesion even after being immersed in water for 15 days, thus meeting the requirements for wet-environment applications. In addition to meeting the demand for adhesives, PBATD 20 has been shown to reduce the potential fire risk. DDP releases phosphorus-oxygen free radicals to capture the ·H or ·OH radicals generated by polymer burning, effectively inhibiting the burning process. PBATD 20 leaves some compact char residues that act as barriers to slow down the transfer of heat, oxygen, and combustible gases, showing excellent flame retardancy. Furthermore, PBATD 20 exhibits a superior biodegradation capacity in Candida antarctica lipase B (CALB) at 37 ℃ compared with PBAT, thus reducing environmental pollution. PBATD 20 is considered highly suitable for diverse applications in daily production and consumer use, including degradable packaging adhesion, electronics assembly, and the bonding of environmentally friendly building materials.