Sorption and interactions of gases in polyaniline powders of different doping levels

Sorption of different gases (N 2 , O 2 , CH 4 , and CO 2 ) were performed on as-synthesized polyemeraldine base, on HCl 4M doped, on NH 4 OH 1M undoped, and on HCl 10 -2 M redoped powders. In the pressure range examined (100-700 torr), linear sorption isotherms were observed for N 2 and correspond to an ordinary dissolution in Henry's law state. Concerning O 2 , CH 4 , and CO 2 , nonlinear isotherms were evidenced and could be described by the dual-mode sorption mechanism proposed for glassy polymers, which consists of the combination of a Henry's type dissolution with a Langmuir sorption in unrelaxed gaps between macromolecular chains. Specific interactions between polyaniline (PANi) and O 2 , CH 4 , and CO 2 were studied. Gas permeation experiments were performed by using different upstream pressures, P 1 , and have confirmed the dissolution of Henry's type for N 2 and the dual-mode mechanism for O 2 and CO 2 . From the fits of the sorption isotherms, gas solubilities of N 2 , O 2 , CH 4 , and CO 2 were calculated for three different gas pressures and analyzed in terms of gas separation for permeation experiments. © 1995 John Wiley & Sons, Inc.