Flexible, conductive, porous, fibrillar polymer–gold nanocomposites with enhanced electromagnetic interference shielding and mechanical properties

Abstract

Porous polymer nanocomposites with a density of only <0.26 g cm⁻³ and robust flexibility have been prepared by ionic self-assembly of gold nanoparticles (NPs) on the charged polymer skeleton made of poly(pyridobisimidazole)-grafted-poly(dimethyl diallyl ammonium chloride) (PIPD-g-PDDA) composite nanofibers. Toward electromagnetic interference (EMI) shielding, a shielding effectiveness of over −64.9 dB in the frequency range of 250 MHz–1.5 GHz was demonstrated in the as-obtained nanocomposites with a thickness of only 20 μm. The equivalent gold thickness of these films was 10–50 times thinner than the skin depth of 6–12 μm for the bulk gold in the same frequency range. The electrical conductivity of these composites was around 15 890 S cm⁻¹ with the volume fraction of gold nanoparticles at 40.5%. The added nanoparticles enhanced the tensile strength by 12.4% as compared to the pure polymer films. No obvious degradation in electrical conductivity was observed even after repeatedly bending 1000 times with a bending radius of 1 cm. The shielding mechanism was disclosed by comparatively analyzing the reflection from the material surface (SE_R), the absorption of electromagnetic energy (SE_A), and the multiple internal reflection of electromagnetic radiation (SE_M).