Polymers by virtue of their light weight and ease of fabrication have replaced metals in several areas of application; as often remarked “from buckets to rockets”. Until about 30 years ago all carbon based polymers were rigidly regarded as insulators. The idea that plastics could be made to conduct electricity would have been considered to be absurd. Indeed, plastics have been extensively used by electronic industry because of this very good insulating property. They were utilized as inactive packaging and insulating materials. This narrow perspective is rapidly changing as new class of polymers known as conductive polymers or electro active polymers are being discovered. Although this class is in its infancy much like the plastic industry was in the 30‟s and 50‟s, the potential uses of these are quite significant.
For more than a decade now, researchers have shown that certain class of polymers which are conjugated (those possess extended π – conjugation along polymer backbone), exhibit semi-conducting behavior. The discovery of doping in polymers has led to further dramatic increase in the conductivity of such conjugated polymers to values as high as 105 Scm-1. The discovery of these conducting polymers has opened up new frontiers in material Chemistry and Physics. This new generation of polymers, combines the mechanical properties and processability of traditional polymers with electrical and optical properties which are unknown earlier. The enormous technological potential that, this rare combination offers is beginning to be trapped.
The interest of these materials has been recognized by awarding of Nobel Prize in Chemistry in 2000 to Heeger, MacDiarmid and Shirakawa, for their contribution to conducting polymers.
Among various conducting polymers, polyaniline family of polymers finds extensive technologies applications in plastic batteries, LED‟s, micro motors transducers, optical storage lithography, solid state sensors, conductive surfaces for EMI shielding, magnetic recording, display devices, harmonic generators, membranes for separation of gases, super capacitors and corrosion inhibitors etc, because of their processibility and stability. Polyaniline, probably the oldest known synthetic organic polymer, consisted of an ill-defined class of materials obtained by the chemical or electrochemical oxidative polymerization of aniline. PANI is a typical conducting polymer resulting from oxidative polymerization of aniline, whose resistivity can be affected by doping concentration, dopant, morphology and degree of crystallization.