Double-strand Polyaniline as a Molecular Quasi-Memory to Chemical Stimuli

We report the apparent hysteresis cycles in the protonation/deprotonation induced conductor-insulator transition for a water-soluble double-strand polyaniline. Experimental evidences show that the polymeric complexes of polyaniline and poly(styrene sulfonic acid) are soluble in water as non-aggregated single molecules. Although the hysteresis loop becomes narrower within 40 hours and the bistability is not permanent, the rate of collapse of the hysteresis loop is extremely slow for a solvated polymer in water. The water soluble polyaniline was compared with solid state samples of PAN:HCl. It was found that, under thermodynamically identical conditions, the memory effect is stronger for the water-soluble polyaniline than the water-insoluble solid of PAN:HCI.