Polypyrrolones for membrane gas separations. II. Activation energies and heats of sorption

The temperature dependence of the gas permeability and sorption coefficient s of a series of ladder-type polypyrrolones, 6FDA-TAB and 6FDA/PMDA-TAB cop olymers, is reported at temperatures up to 80 degrees C. Knowledge of gas t ransport and sorption behavior at higher temperatures provides insights int o these unusual systematically varied high-performance polymers. Activation energies for permeation and diffusion as well as heats of sorption for He, CO2, O-2, N-2, and CH4 are reported for the four polypyrrolones. These gas transport properties are interpreted in terms of the polypyrrolone structu res, which possess different average interchain spacings. In addition, the activation energy for diffusion is shown to be dominant in influencing the activation energy for permeation. The so-called "dual mode" sorption behavi or, especially of highly sorbing gases like CO2, is shown to affect the cal culation of the apparent heat of sorption. The individual heats of sorption associated with the Henry's law and Langmuir environments provide a more c omplete description of the temperature dependence of sorption in these glas sy materials. (C) 1999 John Wiley & Sons, Inc.