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

Abstract

The temperature dependence of the gas permeability and sorption coefficients of a series of ladder-type polypyrrolones, 6FDA–TAB and 6FDA/PMDA–TAB copolymers, is reported at temperatures up to 80°C. Knowledge of gas transport and sorption behavior at higher temperatures provides insights into these unusual systematically varied high-performance polymers. Activation energies for permeation and diffusion as well as heats of sorption for He, CO2, O2, N2, and CH4 are reported for the four polypyrrolones. These gas transport properties are interpreted in terms of the polypyrrolone structures, 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 behavior, especially of highly sorbing gases like CO2, is shown to affect the calculation of the apparent heat of sorption. The individual heats of sorption associated with the Henry's law and Langmuir environments provide a more complete description of the temperature dependence of sorption in these glassy materials. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1251–1265, 1999