Facile synthesis of polypyrrole nanoparticles with tunable conductivity for efficient electromagnetic wave absorption and shielding performance

The exploitation of highly efficient electromagnetic (EM) wave absorbing and shielding materials is deemed as a valid strategy to eliminate EM radiation/interference. However, it is arduous for a material to achieve satisfactory EM absorption and shielding performance simultaneously. Here, by tailoring the molar ratio of the monomer and oxidant, we have utilized a straightforward procedure to synthesize polypyrrole (PPy) nanoparticles with tunable conductivity and blended them with a flexible thermoplastic polyurethane (TPU) matrix to obtain integrated EM absorption and shielding properties. PPy with medium conductivity is suitable as an absorbent, while PPy with higher conductivity tends to be used as a shielding material. When the molar ratio of the monomer/oxidant reaches 1 : 2, the PPy1 : 2/TPU composite achieves excellent wave attenuation capacity with a minimum reflection loss value of -46.1 dB with a filler amount of 20 wt% at 3.2 mm. Moreover, the effective absorption bandwidth almost covers the entire X band at 2.8 mm. Meanwhile, when the molar ratio becomes 1 : 1, the prepared PPy1 : 1/TPU composite exhibits the optimal EMI shielding performance with the maximum shielding effectiveness (SE) of 35.9 dB at 12.4 GHz. This work reports that conductivity can serve as a switch to modulate the EM absorption and shielding performance.