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 degrees C, and glass transition temperatures above 340 degrees 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 tertbutyl groups that increased the polymer FFV. The obtained gas permeability coefficients and gas selectivities are similar to those reported for PIM-PI polymers.