Aggregation and molecular conformation of doped polyaniline in chloroform solution

The UV/Vis spectrum of a freshly made chloroform solution of polyaniline (emeraldine base) doped by d,l-camphorsulfonic acid after filtration through a 0.22 mu m filter has a localized polaron peak at similar to 730 nm. After stirring for similar to 72 hours at room temperature, this localized polaron peak shifts to similar to 810 nm. A change in color from ''blue-green'' to green can be observed visually. The GPC chromatogram of the freshly made solution in CHCl3 shows a small high molecular weight peak (retention time, similar to 31 min), in addition to the major polyaniline peak (retention time, similar to 33 min). After similar to 72 hours stirring, this small peak disappears. It is postulated that both the freshly-made and aged solutions are comprised of doped polyaniline, the former containing aggregates (due to H-bonding) of single molecules having larger hydrodynamic volumes than the polyaniline comprising the major peak. The polymer represented by the smaller ''high molecular weight'' peak slowly becomes disentangled in solution.