Compressible thermoplastic polyurethane/silver nanorod foams for absorption dominant electromagnetic interference shielding

Conductive polymer composites (CPCs) have attracted significant interest in the field of flexible electromagnetic protection, but the challenge of balancing high electromagnetic interference shielding effectiveness (EMI SE) and low reflection losses still exists. Herein, thermoplastic polyurethane/silver nanorod (TPU/AgNR) composite foams have been successfully prepared using both the salt template and vacuum-assisted thermal compression methods. By varying the AgNRs content and employing a layer-by-layer bonding approach, a gradient structure with optimized impedance matching is achieved. The "absorb-reflect-reabsorb" EM attenuation mechanism of the asymmetric gradient EMI shielding in the internal structure is exploited, resulting in TPU/AgNR foam (TAF) with high EMI SE and significantly reduced EM reflection. Notably, the three-layer foams exhibit an average shielding efficacy of 35.5 dB and a reflected power coefficient (R) of 0.085 in the X-band, thereby substantially mitigating secondary EM wave reflections. Furthermore, these foams demonstrate exemplary compressive resilience, with the sample maintaining excellent EMI shielding stability even after undergoing 100 compression cycles at 50 % strain. Consequently, a straightforward approach is employed to fabricate materials with high EMI SE and low reflectivity, offering the potential for use in EM shielding applications of next-generation flexible electronic devices.