Integrating Troger's Base (TB) into Commercially Available Polyimide Membranes with Tailored Microporosity

Owing to its peculiar structural architecture, a rigid, V-shaped and bridged bicyclic amine, Tröger’s Base (TB) has been explored over 130 years especially in applications of stereochemistry and organocatalysis. In particular, since McKeown et al., assessed theoretical feasibility in gas separation applications via introducing the TB units into polymers of intrinsic microporosity (PIMs) [1], there have been noticeable research papers exploiting TB chemistry with tunable polymer rigidity and microporosity.

In this study, rigid TB moieties were integrated into commercially available polyimides (PI-TBs) [2-5], which is different from general approaches including rational monomer design containing the TB units. TB used in this study can be readily introduced into the polyimide backbones using imide-containing diamine building blocks and dimethoxymethane (DMM). The proposed approach only requires commercial monomers with two preparation steps, thus it can accommodate scalable and practical productions. Five different kinds of imide-containing diamines were synthesized to investigate the effect of the number of methyl substituents and isomerism on molecular packing and gas transport characteristics in the corresponding PI-TBs.

All PI-TBs prepared in this work presented good processability and thermal and chemical stabilities. They exhibited enhancement in BET surface area and gas sorption and transport properties, indicating that the TB units endowed polyimides with improved microporosity. In addition, PI-TB membranes retained or even improved CO₂-induced plasticization resistances in comparison to the benchmark polyimide membranes.

References

1. M. Carta et al., Science 339 303-307 (2013)
2. Y. Zhuang et al., Macromolecules 47 3254-3262 (2014)
3. J. G. Seong et al., J. Membr. Sci 480 104–114 (2015)
4. Y. Zhuang et al., J. Membr. Sci 504 55-65 (2016)
5. Y. Zhuang et al., Chem. Commun 52 3817-3820 (2016)