An Off-the-Shelf Shape Memory Hydrogel Based on the Dynamic Borax-Diol Ester Bonds

An off-the-shelf hydrogel with high-efficiency shape memory property is designed on the basis of the dynamic borax-diol chemistry. The system is facilely prepared from only several unmodified commercially available components: acrylamide (AAm), bis-acrylamide (Bis), poly(vinyl alcohol) (PVA), and borax. The chemically crosslinked poly(acrylamide) network works to fix the permanent shapes of the hydrogel, while the dynamic PVA-borax boronate ester bonds serve as the reversible crosslinks to memorize the deformed temporary shapes. Retreatment of the hydrogel in acid/glucose solutions dissipates the PVA-borax ester bonds to recover its permanent shape. Because of the highly invertible nature of borax-diol chemistry, the developed hydrogel system is characterized by high shape memory/recovery ratios, continuously adjusted shape memory/recovery rates, thus having a wealth of potential applications.