Doping process conducting polymers

In an attempt to illustrate in a simple way the general concept of the doping process in polymers, let us consider the p-doping (oxidation) process of polypyrrole. In the undoped state, polypyrrole is a poor electronic conductor with an energy gap of 3.2 eV between the conduction band (CB) and the valence band (VB) ... 

One of the major problems associated with utilization of conducting polymers is processibility. Since these polymers are unsaturated, they tend to be insoluble and also infusible which makes shaping difficult. Moreover, air stability of conducting polymers after doping is a problem.2 Thus, there is a need to develop air stable, processible conducting polymers. 

Processibility still remains a concern, since processibility appears to be much easier to obtain for undoped conducting polymers than for the same polymers in doped forms. If the polymer must be doped after fabrication of a shaped article, the problem of introducing the dopant uniformly is serieous, especially when it is required that the same dopant which easily diffuses into the article must eventually be thermally stable. What is needed here appears to be new methods for processing conducting polymers. One attractive possibility would be a process analogous to conventional RIM (reaction injection molding) in which polymer articles are directly fabricated from a mixture of monomer and dopant. 

---