Multi-hierarchically Structural Polycaprolactone Composites with Tunable Electromagnetic Gradients for Absorption-Dominated Electromagnetic Interference Shielding.

Achieving absorption-dominated electromagnetic interference (EMI) shielding composites with high shielding effectiveness (SE) remains a great challenge due to their minimization of secondary EM radiation pollution, which is highly desired for next-generation electronic devices. Herein, an ingenious approach is proposed to develop asymmetric hierarchical polycaprolactone (PCL) composites composed of an impedance matching layer and a conductive layer through the combination of alternate casting and electroless plating methods, while the polarization loss caused by the difference in conductivity between the two layers would further attenuate the EM waves. The gradient distribution of the shielding fillers creates a positive conductive gradient and a negative magnetic gradient; the higher the gradient, the more it induces magnetic and dielectric losses, which results in an enhanced absorption mechanism that could overcome the restrictions of the nonadjustable reflective properties. The obtained Fe3O4@rGO/Ni/Ag/PCL composite possesses a remarkable EMI SE of 47.6 dB, while the power coefficient of reflectivity (R) could be significantly reduced to 0.27. This research provides a feasible strategy for developing absorption-dominated shielding materials with tunable EM performance that are appropriate for the next generation of electronic devices.