Structure and degradation behavior of polypyrrole doped with sulfonate anions of different sizes subjected to undoping-redoping cycles

The effects of cyclic base/acid treatment on electrochemically synthesized polypyrrole-toluenesulfonate (PPY-TSA) and polypyrrole-poly(styrenesulfonate) (PPY-PSSA) films are investigated. The structural modification of the films during the undoping-redoping process is monitored using spectroscopic techniques and elemental analysis, and the changes occurring at the pyrrole nitrogen are quantified. For both types of films, the undoping-redoping process cannot return the films to the conductivity and doping level of the pristine state, with the PPY-TSA film showing a higher degree of degradation. The degradation results from the loss of effective conjugation in the polymer due to reactions of the pyrrole rings with oxygen or oxygen containing groups. The differences in the degradation behavior of the two types of films are attributed to the differences in the manner in which the anions are incorporated into the polymer matrix and the mobility of the anions during the undoping-redoping process.