Ionic Polyimine Nanocomposite Membranes with Bidirectionally Tunable Mechanics for Flexible Electronics

In flexible wearable electronics, the mechanical demands on substrate materials such as polyimine (PI) membranes vary significantly with the application. Adding toughening fillers to adjust the mechanical properties is effective. However, such approaches typically enable only unidirectional enhancement, lacking the capacity for controllable, bidirectional regulation. Inspired by mixed matrix membrane design, this work introduces iCONs into ionic polyimine network (IPIN). By modulating hydrogen bond cross-linking density and molecular chain entanglement through iCONs loading, the mechanical behavior of the composite membranes can be tuned from flexible (76.10% elongation at break) to rigid (8.56 MPa tensile strength). Notably, the IPIN-TpPaSO₃-30% based flexible wearable sensor shows rapid, accurate, and stable electrochemical response to volatile iodine, promising for real-time detection. This work demostrates iCONs' potential in controllably regulating the mechanical properties of membrane materials, offering a novel approach for creating flexible membranes tailored to different applications.