Shape memory polyimides with large strain and high temperature resistance based on covalent-noncovalent dual-crosslinked networks

Abstract

High-temperature shape memory polymers (SMPs) often face inherent trade-offs between strain capacity and thermal stability. To address this challenge, we develop a novel shape memory polyimide (SMPI) that concurrently achieves record-breaking high temperature resistance and shape memory performance with a glass transition temperature ( T g ) exceeding 230°C, recoverable strain capabilities surpassing 450%, and shape recovery higher than 99.5%. This optimal performance balance stems from the synergistic interplay of molecular chain flexibility, dynamic hydrogen bonds, and covalent cross-linking networks. Molecular simulations and experimental analyses reveal the cooperative mechanisms between dynamic hydrogen bonds and covalent networks. Specifically, upon thermal activation, temperature-dependent dynamic hydrogen bonds dissociate, facilitating large-strain deformability. Conversely, upon cooling, their recombination restricts polymer chain mobility, enhancing shape fixity. Concurrently, the covalent cross-linking network suppresses plastic deformation during shape programming and accelerates shape recovery. Furthermore, we engineered polyimide fiber-reinforced SMPI composites that exhibited two-way shape memory behavior with 100% cyclic retention over 10 cycles, demonstrating their potential to be applied in aerospace actuators and intelligent robots in extreme environments. Covalent/noncovalent dual-network polyimides achieve 450% recyclable strain at >230°C with 100% recovery over 10 cycles, reducing polymer waste in smart shape-shifting devices. • SMPI show transformative T g exceeding 230°C with remarkable 450% strain. • Temperature-dependent hydrogen bonds enable large-strain deformability and high shape fixity by modulating dissociation and recombination. • The covalent crosslinking network suppresses plastic deformation during programming and drives entropy-driven shape recovery. • Two-way shape memory SMPI composites achieve 100% recovery rate over 10 cycles.