Dynamically Cross-Linked Polyurethane Urea Elastomers with Amino-Modified T-ZnO@Ag for Highly Stretchable and Self-Healable EMI Shielding

Abstract The rapid growth of modern electronics and 5G communication has created a strong demand for flexible electromagnetic interference (EMI) shielding materials; however, achieving high shielding effectiveness in polymer composites typically requires large amounts of conductive fillers, often at the severe cost of mechanical performance. To address this trade-off, a highly stretchable and self-healable polyurethane urea (PUU) composite film was developed by introducing amino-modified, silver-plated tetrapod zinc oxide whiskers (T-ZnO@Ag-NH2) as conductive fillers. The PUU matrix was deliberately constructed with dynamic disulfide bonds, reversible imine bonds, and multiple hydrogen-bonding interactions, which together imparted excellent toughness and intrinsic self-healing ability. Meanwhile, the T-ZnO fillers were modified through electroless silver plating followed by amino functionalization, thereby improving their electrical conductivity, dispersibility, and interfacial compatibility with the polymer matrix. The optimized composite containing 25 wt % T-ZnO@Ag-NH2 exhibited stable tensile performance, with a tensile strength of 8.7 MPa, while still maintaining effective self-healing behavior, reaching a healing efficiency of up to 70% at 60 °C. In addition, the composite film delivered an outstanding EMI shielding effectiveness of 49.57 dB in the X-band at a thickness of only 0.5 mm. Overall, this work provides an effective route for designing flexible, durable, and multifunctional EMI shielding materials, and also highlights their considerable potential in flexible electronics and wearable sensing devices.