ABSTRACT
Conjugated polymers and their composites have attracted much attention due to their unique electrical properties. They have wide use in a number of applications, such as in solar cells, lightweight batteries, light-emitting diodes, polymer actuators, corrosion protection agents, sensors, molecular electronic devices, and stealth and electromagnetic interference (EMI) shields1-3. Among these polymers, the members of the polyaniline (PANI) family show much expectation due to their simple routes of synthesis, environmental stability, and ability to be doped for altering electrical conductivity, either by protonic acids or by oxidants/reductants. In the self-doped state, they show high electrical conductivity over a wide range of pH3,4. Typically, metals have good mechanical and shielding properties, but their heavy weight, easy corrosion, and poor processibility are disadvantages when used as a shielding material. Conducting polymers are attractive because of their light weight, corrosion resistance, good processibility, low processing cost, and simple control of conductivity. PANI is an environmentally stable conducting polymer with excellent electrical, magnetic, and optical properties, so it remains one of the most intensely studied polymer5-9. It has been generally regarded as one of the conducting polymer with very high potential in commercial applications, such as batteries, electromagnetic shielding, and gas sensors10-13. Duan and coworkers14 reported a PANI composite with an EMI shielding
performance as high as –19.3 dB in the frequency range of 3-1500 MHz. Wang15 and Wu16 discovered the excellent microwave absorption capability of PANI nanocomposites. Doped PANI and its composites have been widely investigated and applied. The emeraldine base (EB) form of PANI is electrically insulating and doping can made it change from insulator into conductor and the doping process can be described as Fig. 4.1. The stable forms of PANI are leucoemeraldine base (LEB, y = 1), EB (y = 0.5), and pernigraniline base (PNB, y = 0)14,17.
