Multivalent Interactions Enable the Natural Alkaline Amino Acids to Transmute into Macroscopic Adhesive Materials

Natural alkaline amino acids (aAAs) have been found to interact with tannic acid (TA) in aqueous solution via multiple noncovalent interactions, giving rise to the formation of water-immiscible supramolecular copolymers (aAAs/TA). The driving forces and the internal structures of the supramolecular copolymers were characterized by nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), ζ-potential, elemental analysis (EA), and scanning electron microscopy (SEM). Rheological and lap shear adhesion measurements identify that the aAAs/TA soft materials exhibit wet and underwater adhesion, shear thinning, and self-healing behavior. This supramolecular adhesive can be utilized as both injectable materials and self-gelling powder. Another feature of the aAAs/TA adhesives is the acceptable cellular compatibility with L-929 cells, which enables the supramolecular copolymers to be potential soft materials for health care and bio-related applications. The work highlights that the cross-linked supramolecular polymerization strategy enables minimalistic biomolecules to emulate the functions of complicated proteins secreted by aquatic organisms.