SORPTION AND INTERACTIONS OF GASES IN POLYANILINE POWDERS OF DIFFERENT DOPING LEVELS

Sorption of different gases (N-2, O-2, CH4, and CO2) were performed on as-synthesized polyemeraldine base, on HCl 4M doped, on NH4OH 1M undo ped, and on HCl 10(-2) M redoped powders. In the pressure range examin ed (100-700 torr), linear sorption isotherms were observed for N-2 and correspond to an ordinary dissolution in Henry's law state. Concernin g O-2, CH4, and CO2, nonlinear isotherms were evidenced and could be d escribed by the dual-mode sorption mechanism proposed for glassy polym ers, which consists of the combination of a Henry's type dissolution w ith a Langmuir sorption in unrelaxed gaps between macromolecular chain s. Specific interactions between polyaniline (PANi) and O-2, CH4, and CO2 were studied. Gas permeation experiments were performed by using d ifferent upstream pressures, P-1, and have confirmed the dissolution o f Henry's type for N-2 and the dual-mode mechanism for O-2 and CO2. Fr om the fits of the sorption isotherms, gas solubilities of N-2, O-2, C H4, and CO2 were calculated for three different gas pressures and anal yzed in terms of gas separation for permeation experiments. (C) 1995 J ohn Wiley & Sons, Inc.