Charge transport in mesoscopic conducting polymer wires

In an attempt to reconcile transport in aniline oligomers with that observed in bulk polyaniline, we constructed meso-scale (60nm) molecular junctions bridged by polyanion-stabilized polyaniline (PANI) strands. Junctions were characterized by their conductance versus electrochemical potential (G-E) and current versus voltage (I-V) characteristics, In contrast to bulk polyaniline, sharp peaks were seen in the G-E data, and these gave rise to negative differential resistance in the I-V curves, behavior much like that observed in aniline oligomers. The width of the conductance peaks increased with the amount of polymer deposited in the junction. In contrast to oligomers, the peaks in the meso-scale devices displayed a large hysteresis. The absolute conductance of the junctions is far too high to be consistent with transport along isolated chains, suggesting that a fundamental charge carrying unit is something morphologically more complex than a single polymer molecule.