Defect Generation and Charge Transport in Polyaniline

Through analogy with the behavior of polyaniline aimers in solution, it is suggested that the doping of polyaniline by protonic acids is an equilibrium process. The expected equilibrium relation for this reaction successfully predicts the variation of composition of polyaniline as a function of the pH of the doping solution. It is further proposed that in the latter stage of doping the equilibrium population of the insulating undoped chain segments are randomly distributed along chains of the conductive salt form of polyaniline. A model for the conductivity of polyaniline based on these assumptions successfully predicts the temperature dependence of conductivity for both the polymer and the octomer. The model also successfully predicts the variation of conductivity with doping level and fixes a lower limit on the molecular weight of conventionally prepared polyaniline (6,000).