Mechanically robust thermally rearranged (TR) polymer membranes with spirobisindane for gas separation

Novel spirobisindane-containing thermally rearranged (TR) benzoxazole(spiroTR-PBO) membranes were prepared by thermal treatment of four newly synthesized spirobisindane-containing hydroxyl-polyimides (spiroHPIs). Transport properties of spirobisindane-containing polymers were investigated along with fractional free volume and density measurements, as well as molecular simulation analysis. The resulting spiroTR-PBOs exhibited high free volumes and superior mechanical properties in terms of elongation and tensile strength, and these findings were supported by molecular dynamic simulations. SpiroTR-PBO membranes containing hexafluoroisopropylidene moiety in the polymer backbone showed a six-fold increase in CO2 permeability, compared to that of the spiroHPI precursor. SpiroTR-PBO membranes showed strong potential to be applied in carbon capture and separation of gases because of their high gas permeability coupled with robust mechanical properties.

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► Novel spirobisindane-containing thermally rearranged (TR) benzoxazole membranes.
► Robust mechanical properties with large fractional free volume elements.
► Six-fold increase in CO2 permeability of spiroTR-PBO compared with that of spiroHPIs.
► Strong potential to apply in gas separation including carbon capture.