Protonation of Emeraldine: Formation of a Granular Polaronic Polymeric Metal

A summary is presented of our recent work in the study of the physical properties of the emeraldine form of polyaniline as a function of protonation level. These studies show that upon protonation, the insulating emeraldine base becomes a conducting emeraldine salt polymer. The fully protonated form has been proposed to be a metallic polymer with an energy band formed from a lattice of polarons. Phase segregation of the partly protonated polymer into conducting and nonconducting regions leads to a conductivity dominated by charging energy limited tunneling among the “metallic” emeraldine salt regions.