Hierarchical Carbon–Metal Architectures in Flexible Polymer Multilayers Enabling High-Performance Electromagnetic Interference Shielding

Leveraging the inherent flexibility, durability, and filler compatibility of hydroxyl-terminated polybutadiene (HTPB)-based polyurethane (PU), we present a lightweight and mechanically robust (flexible, twistable) multilayered composite for advanced electromagnetic interference (EMI) shielding, ideally suited for wearable electronics. This unique P-M–C–P architecture strategically integrates conductive multiwalled carbon nanotubes (MWCNTs) and microflower-like carbon-encapsulated Ni/Co alloy (NCC) within the PU matrix to create conductive (P) and magnetic (M) layers, respectively. Critically, an electrostatically functionalized interpenetrating network (IPN) ‘paper’ (C) is seamlessly incorporated to further enhance absorption. The resultant composite exhibits exceptional EMI shielding attenuation (SET ∼ 35 dB) in the high frequency K-band (18–26.5 GHz), characterized by a significantly high absorption-to-reflection ratio (A/R ∼ 3.0) and a green shielding index (gs ∼ 2.64), unequivocally demonstrating an absorption-dominated shielding mechanism. The inherent flexibility and demonstrated mechanical robustness (bendability, twistability, and foldability) of this lightweight arrangement provide effective and conformable solutions to shield electromagnetic interference in emerging 5G and IoT applications, particularly within the demanding context of wearable electronic devices.