Triple-Network Biopolyester Elastomer Composites for Tailorable Shape-Shifting Performances in Response to Multiple Stimulus

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For shape-memory polymers (SMPs), there are two main types of polymer networks: amorphous and crystallizable. However, amorphous cross-linked polymers cannot have too low cross-linking density in order to ensure that the shape-memory transition temperature ( T trans ) is above room temperature, thus sacrificing their stretchability. Crystallizable cross-linked polymers with fewer cross-links have a large stretchability, but their mechanical strength is usually very low above the T trans . Also, the intrinsic properties of polymers limit their response to external stimuli to heat only. In this work, a crystallizable polymer network with fewer cross-links is designed to fabricate multistimuli-responsive SMPs with large stretchability, high strength, and tunable T trans . (1) The introduction of a long-chain PCL combined ensured the material’s high stretchability and the contribution of the crystalline network to the material’s strength. (2) The chain entanglement of a cross-linked network with a long-chain PCL enhanced the mechanical strength of the material above its T trans . (3) The carbon nanofiber network was further introduced into the system as both a reinforcing component and an energy conversion mediator. The design of network structures not only significantly enhanced the mechanical properties of the material but also endowed the material with laser-/sunlight-/electricity-induced shape-shifting capacity. Furthermore, precise control of the response threshold and shape-shifting speed of the material was realized by regulating the content of CNF and the intensity of external stimuli. This work provides a universal solution for large stretchability, good mechanical strength, and multistimuli response, expanding the scenarios of engineering application and practicality of SMPs.