Tough Polymeric Hydrogels Based on Amino Acid Derivative Mediated Dynamic Metal Coordination Bonds

Abstract

The development of physically crosslinked hydrogels with excellent mechanical and sensing properties is of importance for expanding the practical applications of intelligent soft hydrogel materials. Herein, after copolymerization of hydroxyl-containing amino acid derivative N-acryloyl serine (ASer) with acrylamide (AM), we introduce Zr⁴⁺ through an immersion strategy to construct metal ion-toughened non-covalent crosslinked hydrogels (with tensile strength of up to 5.73 MPa). It is found that the synergistic coordination of hydroxyl and carboxyl groups with Zr⁴⁺ substantially increases the crosslinking density of the hydrogels, thereby imparting markedly superior mechanical properties compared to hydroxyl-free Zr⁴⁺-crosslinked hydrogels, such as N-acryloyl alanine (AAla) copolymerized with AM hydrogels (with tensile strength of 2.98 MPa). Through the adjustment of the composition of the copolymer and the density of coordination bonds, the mechanical properties of the hydrogels can be modulated over a wide range. Additionally, due to the introduction of metal ions and the dynamic nature of coordination bonds, the hydrogels also exhibit excellent sensing performance and good self-recovery properties, paving the way for the development of flexible electronic substrates with outstanding comprehensive performances.