Confined-interphase bridging-constraint synergy regulating filler motion and chain dynamics in conductive elastomer composites.

Conductive elastic composites (CECs) show significant potential for flexible sensing applications owing to their inherent flexibility and stretchability. However, their practical performance is often constrained by a limited sensing range, insufficient sensitivity, and pronounced shoulder effects during unloading, which lead to signal instability and poor repeatability. To overcome these limitations, this study developed an interphase-confined conductive elastomer (PP₇-S₃) by integrating polyvinylpyrrolidone (PVP)-modified graphene (GR) conductive fillers with a confined interphase domain constructed between silicone rubber (SR) and a terpolymer (PEV). PVP functionalization markedly improves the dispersion stability of graphene and enhances interfacial interactions within the composite matrix. Meanwhile, the SR/PEV interphase acts as a finite-thickness, three-dimensional interfacial domain that effectively regulates filler distribution, interfacial interactions, and interphase bonding. Through the combined effects of interfacial reinforcement and spatial confinement, a stable bridging-constraint conductive network is established. As a result, PP₇-S₃ exhibits excellent mechanical performance, achieving a tensile strength of 17.64 MPa and an elongation at break of 1207.52%, corresponding to improvements of approximately 80.3% and 68.9%, respectively, compared with the unmodified system. In addition, PP₇-S₃ demonstrates an ultrahigh sensitivity (GF = 2.50 × 105) and a broad sensing range of 494%, while maintaining a smooth and shoulder-free electromechanical response. These results indicate that interphase-engineered conductive elastomers provide an effective strategy for achieving highly sensitive and stable flexible sensors, highlighting the strong potential of PP₇-S₃ for applications in flexible electronics, aerospace devices, and wearable sensing technologies.