Two doping structures and structural anisotropy revealed by the mass loss and shrinkage of polypyrrole films on alkali treatment

Alkali solution and distilled water immersing treatments were performed for the polypyrrole (PPy) films, PPy(TsO−), PPy(ClO4−) and PPy(No3−). Volume shrinkage and mass loss of the PPy films were observed after the treatment. The shrinkage of the thickness is more than that of the length or width, which revealed that a structural anisotropy existed in PPy, especially in PPy(NO3−) films. The mass loss supports the assumption that two kinds of doping structures exist in PPy. The degrees of counter-anion exchange with OH− at structure I and that of the counter-anions dedoped with deprotonation at structure II were calculated from the mass change after alkali treatment. Film extension of the alkali-treated PPy was observed after 1 M HNO3 re-treatment.