Gas sorption in polyaniline powders and gas permeation in polyaniline films

Abstract

Comparison of gas sorptions by microgravimetry and differential calorimetry on polyaniline (PANi) powders with gas permeation on polyaniline films are described. Polyaniline powders and films were in the following forms: as-synthesized in polyemeraldine base, doped PANi (with 4M HCl), undoped PANi (with 1M ammonia) and redoped PANi (with 10 −2 M HCl solutions). Gases included for this study included nitrogen, oxygen, methane and carbon dioxide. CO 2 is about ten time more sorbed than O 2 and N 2 for the as-synthesized and undoped PANi while the ratio was close to 20 for the doped and redoped powders. For any powders the ratio of sorption between CO 2 and CH 4 was equal to five. The gain in weight of methane was twice that of of oxygen and nitrogen for the as-synthesized powders and four times larger for the doped and redoped powders. Let's note that neither of these powders present a significant difference in the gain in weight of oxygen and nitrogen. The measured energies were very different from one gas to another. ΔH of gases for doped powder was in the order: N 2 < O 2 < CH 4 < CO 2. ΔH of as-synthesized was close to ΔH of undoped ≤ ΔH of redoped < ΔH of doped powders. Mechanism of sorption for nitrogen follows only Henry's law and for the other gases, it needs to also involve a Langmuir contribution. Then values of solubilities of gases were compared with that of permeation experiments on PANi films.