Shape Memory Networks With Tunable Self‐Stiffening Kinetics Enabled by Polymer Melting‐Recrystallization

Abstract Shape memory polymers (SMPs) are deformable materials capable of recovering from a programmed temporary shape to a permanent shape under specific stimuli. However, shape recovery of SMPs is often accompanied by the evolution of materials from a stiff to soft state, leading to a significant decrease in strength/modulus and thereby impacting their practical applications. Although some attempts are made to pursue the SMPs with self‐stiffening capability after shape recovery, the modulus increase ratio is much limited. Inspired by the recrystallization process of CaCO 3 during crab molting, a novel and universal strategy is developed to construct water‐free self‐stiffening SMPs by using a single thermal stimulus through harnessing the polymer melting‐recrystallization. The shape recovery is achieved through the melting of polymer primary crystals, followed by the self‐stiffening via polymer recrystallization at the same recovery temperature, in which the modulus increase rate and ratio can be programmed in a wide range. Additionally, conceptual applications of these self‐stiffening SMPs as artificial stents with self‐enhancing supporting function are successfully demonstrated. This work is believed to provide new insights for developing the advanced shape memory devices.