Transient Polymer Hydrogels Based on Dynamic Covalent Borate Ester Bonds

Comprehensive Summary In nature, biological systems maintain their unique structures and functions by using nonequilibrium processes driven by chemical fuels. Inspired by natural systems, transient hydrogel systems based on chemical reaction networks have been developed that are in thermodynamically nonequilibrium states. The formation of dynamic covalent bonds is an effective tool for designing analogous systems. Herein, we design a transient polymer hydrogel based on fuel‐mediated covalent borate ester bonds. The pH‐sensitive covalent borate ester bond is formed by the reaction between polyvinyl alcohol (PVA) and boric acid (B(OH) 3 ). Sodium hydroxide (NaOH) and 1,3‐propanesulfonate (PrS) are used together as the chemical fuels to temporally control the pH of the system. Meanwhile, the lifetime of the transient hydrogel can be simply controlled by adjusting the composition of the chemical fuel, and the cyclic phase transitions can also be achieved. These programmable transient hydrogels have potential applications in the fields of information transmission and fluid guidance.