Room temperature shape self-adjustable tough hydrogel based on multi-physical crosslinking

Abstract

Room temperature shape adjustable hydrogels (rtSAH) can be (re)processed into different stable shapes at ambient conditions, making them appealing for various applications. However, elastomer-like and mechanically tough rtSAH is hard to obtain because of the elastic recovery force that prevents a deformed new shape from being fixed. Herein, we demonstrate a supramolecular elastic rtSAH having high tensile strength (2.6 MPa) and large strain at break (1770 %), whose network structure is designed to rely on a combination of strong and weak non-covalent interactions through three types of physical crosslinking: host–guest interaction, hydrogen bonding and coordination interaction. When deformed at room temperature and held in that state for sufficient time, the hydrogel adapts to a stable new shape while remaining elastic. The reconstruction of the dynamic Fe3+-carboxylate coordination interaction in the deformed hydrogel is the key to self-locking the new shape with stored elastic energy and enabling the shape memory function. Exposure the rtSAH to UV light or an acid solution disrupts the coordination crosslinking and allows the hydrogel to recover its initial shape. The demonstrated structural design represents an effective strategy to develop all-physically crosslinked shape memory hydrogels whose shapes can be reprocessed and self-locked at room-temperature.