Dual-functional polymer blends with rapid thermo-responsive shape memory and repeatable self-healing properties

Abstract

Although dynamic chemical interaction plays a crucial role for designing sustainable materials with extended lifespans and functionality, the preparation complexity and lack of acceptable mechanical strength limit their practical application. Herein, tunable thermo-responsive shape memory and self-healing bifunctional blends are fabricated by melt blending of poly(ethylene-co-methacrylic acid sodium salt) (EMNa) and poly(ethylene-co-methyl acrylate) (EMA) copolymers. To realize the complementary advantages, the ionic interactions in the EMNa ensure the structural integrity and self-healing repeatability of the blends, meanwhile the highly elastic EMA as the dispersed phase is capable to provide the main driving force during the shape recovery process. The shape recovery behavior can be well controlled by varying the EMA content. The shape recovery time shortens with increasing EMA content, and a U-shaped EMNa with 30 wt% of EMA (EMNa/EMA-30) specimen could recover to a plate shape within 8 s. Interestingly, the EMNa/EMA-30 exhibits repeatable self-healing capability, and its tensile strength can reach 19.4 and 15.9 MPa after one and three healing cycles, respectively. The self-healed EMNa/EMA-30 still exhibits excellent reusability and endurance, and the shape fixity and shape recovery ratios are both above 95% after 15 shape memory cycles. The rapid thermo-responsive shape memory effect, superior self-healing property, and prominent programmability make the EMNa/EMA blends promising in various cutting-edge applications, such as self-deployable structures, artificial muscles, and wearable devices.