Thin polyaniline films in EMI shielding

Electromagnetic interference shielding efficiency has been measured for highly electrically conducting Polyaniline-Camphor Sulfonic Acid. The polymer is spin coated from m-cresol solution on an electrically insulating substrate as a 1–30 μm thick layer having a conductivity of 10–100 S/cm. The shielding efficiencies (SE) for these electrically thin polyaniline films have been measured in the near-field with a dual-chamber box and in the far-field with a transmission line method in the frequency range 0.1–1000 MHz. The measurements show that SE depends primarily on the surface resistance both in the far-field and the near-field. An additional effect >10 dB is seen when the two layer structure is measured in the near field. By using layer structures, the SE is >40 dB up to ca. 100 MHz in the near-field and 39 dB at 1 GHz in the far-field.