Magnetoresistance studies of polymer nanotube/wire pellets and single polymer nanotubes/wires

Conductivity and magnetoresistance (MR) measurements on pellets of conducting polyaniline and polypyrrole nanotubes/wires are presented. A transition from small negative MR to large positive MR was measured below 60 K. The positive and negative MR has been discussed in terms of a wavefunction shrinkage effect and a quantum interference effect on hopping conduction. In addition, further studies show that the MR of single polymer nanotubes/wires is very small even at 2 K (MR < 5% at 10 T) compared with that of the pellets (40%-100% at 10 T), and no evident and stable negative MR is observed above 50 K. The results indicate that the MR in the bulk pellet samples made of polymer nanotubes/wires is dominated by a random network of inter-fibril contacts.