Conformational changes in sulfonated polyaniline caused by metal salts and OH-

The fully sulfonated, water soluble polyaniline, poly(2-methoxyaniline-5-sulfonic acid), has been shown to be remarkably inert to alkaline dedoping, remaining in the conducting emeraldine salt form even in 2.0 M NaOH. Instead, its polyaniline chains undergo a conformational change from an extended coil to a compact coil structure. The same conformational change is caused, but more slowly, by the presence of added alkali and alkaline earth metal salts (1.0 M). These unprecedented rearrangements proceed via two steps, the speeds of which are sensitive to the nature of the metal ions and the associated anions. The processes are reversed by acid.