Photo-curing preparation of biobased underwater adhesives with hydrophobic chain-ring interlace structure for protecting adhesion

Adhesives with long-lasting and reversible adhesion to various underwater surfaces have a wide range of potential applications. However, the development of adhesives for underwater applications is challenging because the surface hydration layer weakens the intermolecular interactions such as hydrogen bonds (H-bonds). Herein, a simple and effective UV-curing strategy was proposed for the preparation of a strong, reusable, and durable biobased underwater adhesive with the combination of fatty acid chains and isobornyl rings as hydrophobic protection for H-bonds interactions. Specifically, a palm oil (PO)-derived monomer, PO fatty acid-ethyl acrylamide (POFA-EA), was chosen owing to its unique amphipathic structure, wherein the amide groups formed strong H-bonds with substrates and the long fatty acid chains served as hydrophobic protection layers. The ring structure of isobornyl acrylate (IBOA) which was used as a comonomer further enhanced the hydrophobic protection. The hydrophobic protection mechanism was confirmed by molecular dynamic simulation combined with experimental verification. The prepared poly(POFA-EA–IBOA) underwater adhesives exhibited a good energy dissipation efficiency (66.4%), and thus, it could reduce the damage caused by adhesive deformation. The adhesives can adhere to a metal surface underwater for up to 15 days and be reused for more than 50 times. This study provides a new hydrophobic protection strategy for the preparation of inexpensive, tough, reusable, and long-lasting underwater adhesives from renewable feedstocks.