Polyaniline: evidence of oxygen–polarons interactions to explain the high selectivity values in oxygen/nitrogen gas permeation experiments

High selectivity between oxygen and nitrogen has been found by gas permeation with doped polyaniline. Because of the small difference in kinetic diameters, solubility rather than diffusion may explain the preferential oxygen permeation. Electron spin resonance (ESR) measurements have been performed to check whether interactions of oxygen with polarons in polyaniline exist. A tenfold decrease in the spin number was observed when the polymer was in the presence of oxygen rather than nitrogen. This result was interpreted as being due to interactions between oxygen triplet states and polarons of polyaniline.