Engineering bioinspired rigid-soft architecture for enhanced stiffness and toughness in liquid-free stretchable ionic conductors

In recent years, liquid-free stretchable ionic conductors have emerged as a promising alternative to gel-based stretchable conductive materials owing to their excellent performance stability and ability to circumvent solvent-related defects. Nevertheless, the intrinsic compromise between stiffness and toughness in these materials restricts their utility as load-bearing materials. To overcome this challenge, we propose a solvent exchange-assisted polymerization strategy inspired by the structure–property relationships observed in biological tissues and develop a stiff yet tough liquid-free stretchable ionic conductor. This approach involves using solvent exchange to homogenize the polymer network and improve polymer crystallization. Additionally, the incorporation of flexible polymer chains through spontaneous solvent polymerization stabilizes the network. As a result, a rigid-soft polymer network characterized by high-density rigid crystalline domains embedded in a homogeneous soft matrix was engineered. This strategically designed architecture endows the material with relatively stable ionic conductivity (1.9 mS m −1 ) and unprecedented mechanical properties, including coordinatively enhanced stiffness (128.6 MPa) and toughness (134.7 MJ m −3 ), as well as remarkable mechanical strength (37.5 MPa) and resistance to tearing and crack propagation. Furthermore, this strategy can be directly applied to fabricate liquid-free ionic conductive fiber, which has great potential for use as wearable sensors and electronic tendons. This research not only reconciles the challenging trade-off between stiffness and toughness, but also offers a practical avenue for designing robust liquid-free stretchable ionic conductors, contributing to the advancements of soft electronics and engineering materials.