The role of competitive sorption and plasticization in microporous polymers

Early-stage research in evaluating polymeric materials for membrane-based gas separations frequently relies on pure-gas permeation testing. However, properties predicted from pure-gas measurements rarely match those from measurements of mixtures, precluding simple tests from providing relevant data for many application-specific targets. Differences between pure- and mixed-gas performance are frequently reported for emerging classes of microporous polymers, which often exhibit strong competitive sorption and plasticization effects when materials are tested under complex mixtures. This presentation will introduce several classes of emerging microporous polymers and demonstrate examples of how mixture testing results in separation properties that are significantly different from pure-gas predictions. A detailed discussion will be presented on the role of competitive sorption, and how this phenomenon can be leveraged in certain cases to engineer materials that have mixture property sets that exceed those of pure-gas estimates. In particular, the role of amine functionality will be discussed in emerging microporous polymers, and examples will be presented on how these materials behave in the presence of mixtures containing CO₂, H₂S, CH₄, and other gases common in commercial applications. The role of competitive sorption will then be compared with respect to plasticization to demonstrate how microporous polymers can be designed to achieve stable and enhanced performance under relevant gas-phase compositions.