Scalable, high-performance EMI shielding nanocomposites with outstanding folding reliability enabled by a generalizable and cost-effective molecular motif

Developing scalable, high-performance electromagnetic interference shielding (EMIS) materials requires a transition from empirical optimization to rational design. This study introduces a chemistry-guided design framework that establishes fundamental molecular principles—specifically, a well-defined balance of basicity and steric hindrance—for stabilizing heterogeneous interfaces while preserving intrinsic filler properties. These principles were rigorously validated through a model system approach. This approach identified the characteristic molecular features of triethylamine as a prototypical molecular motif that embodies the required physicochemical balance. Implementing this validated motif strengthened multiple cooperative interfacial interactions, enabling the fabrication of a hierarchical, nacre-mimetic nanocomposite film exhibiting excellent thickness-normalized EMIS performance (489.1 dB mm^{− 1}), high electrical conductivity (12,115 S m^{− 1}), and exceptional folding reliability (> 400,000 cycles without performance degradation). Furthermore, the nanocomposite film exhibited robust environmental stability under severe conditions, including damp-heat, artificial perspiration, and thermal cycling. In a device-level proof-of-concept, the optimized film suppressed EMI-induced signal distortion in a commercial flexible pressure and strain sensor, restoring stable, state-resolved voltage outputs under EMI exposure and thereby validating its practical applicability. Overall, this work provides a generalizable and cost-effective platform for the rational design of high-performance materials for next-generation flexible electronics. Furthermore, the validated interfacial motif can be extended to other nanomaterial-based systems beyond EMI shielding, enabling broader applicability in scalable, multifunctional composite technologies.