GAS SORPTION IN POLYANILINE .1. EMERALDINE BASE

Measurements of the sorption isotherms (at 298 K) for Ar, O-2, and N-2 in several polyaniline emeraldine base (PANi-EB) forms were made (as- cast film, powder, and fully undoped film) over the pressure range 100 -1300 kPa. Model fits of the sorption isotherms were made using a modi fied Flory-Huggins equation (MFHE) and a dual mode sorption equation. In general, the variation of parameters for the MFHE was consistent wi th morphological interpretations from prior X-ray scattering studies. The ordering of gas sorption with respect to a particular PANi-EB form correlates with the relative sizes and condensabilities of the gas mo lecules. We see evidence that the morphological variations between dif ferent PANi-EB forms, as indicated by their He densities and X-ray sca ttering data, affects the ratio of O-2/N-2 solubilities primarily thro ugh restricted access to available free volume. From our current measu rements of solubilities and prior results for the O-2 and N-2 permeabi lities, we conclude that the O-2/N-2 ideal separation factor is due to diffusivity selectivity in an as-cast PANi-EB him and solubility sele ctivity in a fully undoped one.