Metal-insulator transition in doped polymerized polyaniline

In this paper, the metal-insulator transition is studied in polyaniline (PANI) as the doping increases. The study incorporates a polymerization process that produces a cross-linking of the PANI chains, yielding an extended disordered branched lattice. The presence of the phenazine structure is fundamental and allows the polymer to acquire extra dimensions, which permits a transition to the metallic phase when doping is increased as the Fermi level goes through the mobility edge into a region of extended states. This PANI system is described assuming that the polymerization process gives rise to a structure that could be represented by a Bethe lattice. It is observed, as indicated by the experiments, that the conductivity increases as a function of the pH of the acid solution when agents like bipolarons are introduced.