Multiple electrochemical doping-induced insulator-to-conductor transitionsobserved in the conjugated ladder polymer polybenzimidazobenzophenanthroline (BBL)

Spectroelectrochemical techniques have been used to study doping-induced re actions in conjugated polymers. Here, we report results on reduction reacti ons (n-doping) of the conjugated ladder polymer polybenzimidazobenzophenant hroline (BBL). The spectra are recorded in situ during applied potential in a three-electrode spectroelectrochemical cell. The spectral and thus the s tructural changes during the reduction (n-doping) of the polymer film at di fferent electrode potentials are discussed. In contrast to most of the othe r conjugated polymers, this polymer shows four reversible redox reactions d uring n-doping, corresponding to various insulating and conducting forms of BBL.