Deprotonation and dehydration of pristine PPy/DS films during open-circuit relaxation:: an ignored factor in determining the properties of conducting polymers

The relaxation process of pristine polypyrrole/dodecyl sulfate (PPy/DS) films at open circuit, immediately after electropolymerization, was studied by in situ spectroelectrochemical, alternating-current conductance, electrochemical quartz crystal microbalance, and pH-metric techniques. A new phenomenon, called irregular reduction, involving apparent redoping and resulting in a polymer with a lower conjugation length is observed, which may occur if the pristine film is reduced without a waiting period. During this waiting period at open circuit, the film is deprotonated and partially desolvated with concurrent stacking of the polymer chains. The length of the waiting period allowed for the newly made polymer is of utmost importance, and ignorance of the relaxation of the film may explain the well-known irreproducibility in the fabrication of conducting polymers.