Highly permeable polyimide membranes with a structural pyrene containing tert-butyl groups: Synthesis, characterization and gas transport

Three new polyimides with high gas permeability based on a new dianhydride 3,8-di(4-tertbutylphenyl)pyrene-1,2,6,7-tetracarboxylic DPt, containing tert-butyl moieties are reported. Chemical structures of the resulting dianhydride monomer and polyimides were confirmed by FTIR and 1H-NMR. All polyimides show high thermal stability with onset decomposition temperatures above 490 °C, and glass transition temperatures above 340 °C. The incorporation of a pendant tert-butyl group into the polymer provided high gas permeability with moderated selectivity. The polyimide formed from DPt and 2,4,6-trimethyl-m-phenylenediamine, DPt-TMPD, showed 2035 Barrer CO2 permeability which could be attributed to its inefficient chain packing from the incorporation of tert-butyl groups that increased the polymer FFV. The obtained gas permeability coefficients and gas selectivities are similar to those reported for PIM-PI polymers.