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

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).