Chronoamperometric Study of Conformational Relaxation in PPy(DBS)
West, Bryan Jason
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In conjugated polymer devices that switch from one oxidation level to another, such as artificial muscles, it is important to understand memory effects that stem from conformational relaxation movements of the polymer chains. Chronoamperometry during electrochemical switching of polypyrrole doped with dodecylbenzenesulfonate, PPy(DBS), is used to gain insight into the conformational relaxation kinetics. During oxidation and reduction (stepping to the anodic and cathodic voltages, respectively), an exponentially decaying current is observed, but a shoulder appears during reduction when the cathodic voltage is high enough. Subtracting an exponential curve fit from the reduction current yields a small current peak at the shoulder position. The position of this peak depends logarithmically on the applied cathodic potential, the anodic potential that was applied just prior to the reduction step, and on the time that the prior anodic voltage was held. These results are consistent with the electrochemically stimulated conformational relaxation (ESCR) model.