VAPOR-PHASE SECONDARY DOPING OF POLYANILINE

A dramatic change occurs in the electronic spectrum of a thin (solid) film of polyaniline doped with the ''primary dopant,'' d,l-camphorsulfonic acid (spun from its solution in chloroform on to a quartz plate) when it is exposed to the vapor of the ''secondary dopant,'' m-cresol, at room temperature. The resistance decreases by a factor of > 10(2) and it becomes insoluble in chloroform due to an increase in its crystallinity. The localized polaron absorption at 780 nm is replaced by a very intense free carrier tail commencing at approximate to 1000 nm and increasing steadily in intensity to approximate to 2600 nm, which is consistent with delocalized electrons in the polaron band. ''Secondary doping'' with a variety of substituted phenols and a number of different ''primary'' protonic acid dopants is observed.