| Abstract
| - The electronic conductivity of the electroactive polymer polypyrrole−dodecyl benzene sulfonate (PPy−DBS)has been characterized as function of the redox level. The polymer was synthesized with different isomers ofthe dopant anions: the common mixed DBS tenside and three well-defined synthetic dodecyl isomers (withthe benzene group at positions 1, 2 and 6). The conductivity was measured both by van der Pauw measurementson PPy−DBS in the oxidized, dry state as function of temperature, and by electrochemical impedancespectroscopy as function of potential in 0.1 M NaCl aqueous electrolyte. These investigations demonstratethat even minor differences in the dopant anion can cause significant changes in the physical properties ofthe electroactive polymer. The highest conductivities (σ25 = 39 Scm-1) are obtained by the (6D)BS isomer,perhaps because the branching leads to denser packing and therefore smaller hopping distances. This wassupported by X-ray measurements. Synthesis at lower temperatures generally leads to higher conductivity.The conductivity is strongly dependent on the potential, being more than four magnitudes smaller for thereduced state where the number of electronic carriers is at a minimum. The conductivity is further reducedbecause of the uptake of water at low potentials, creating electrolytic domains that separate the electronicdomains and inhibit hopping. There is a pronounced hysteresis in the conductivity as a function of potential.However, the major part of this hysteresis can be accounted for by the composition hysteresis implying thatthat the conductivity mainly depends on the number of charge carriers, but not on the history of the sample.
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