Intrinsically microporous co-polyimides derived from ortho-substituted Tröger's Base diamine with a pendant tert-butyl-phenyl group and their gas separation performance

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Title: Intrinsically microporous co-polyimides derived from ortho-substituted Tröger's Base diamine with a pendant tert-butyl-phenyl group and their gas separation performance Authors: Xiaofan Hua,b, Yabing Hec, Zhen Wanga,∗, Jingling Yana,d,∗∗ Year/Journal: Polymer 153 (2018) 173–182 DOI: https://doi.org/10.1016/j.polymer.2018.08.013 Polymer Name & Family: TB-containing intrinsically microporous co-polyimides (TB-PIMPIs)... The one-step polymerization of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), TTBDA, and 3,9-diamino-4,10dimethyl-6,12-dihydro-5,11-methanodibenzo[b,f][1,5]diazocine (TBDA2) afforded TB-containing intrinsically microporous co-polyimides (TB-PIMPIs). Film Type: First, a polymer solution in CHCl3 (3 wt%) was filtered through 0.45 μm PTFE filters, and poured into a Teflon mold. CHCl3 was slowly evaporated at 23 °C for 72 h. Functional Group: ortho-substituted Tröger's Base (TB) diamine with a pendant tert-butyl-phenyl group... hexafluoroisopropylidene)diphthalic anhydride (6FDA)... 3,9-diamino-4,10dimethyl-6,12-dihydro-5,11-methanodibenzo[b,f][1,5]diazocine (TBDA2) Ladder or Linear: Molecular modeling results revealed that compared with 6FDA/TBDA2, 6FDA/TTBDA exhibited a more contorted chain conformation and higher chain stiffness. Fabrication Method: TB-PIMPIs were prepared by the polymerization of TBDA2, TTBDA and 6FDA... The resultant polymer solution was precipitated into ethanol... Film formation: First, a polymer solution in CHCl3 (3 wt%) was filtered through 0.45 μm PTFE filters, and poured into a Teflon mold. Casting Solvent: First, a polymer solution in CHCl3 (3 wt%) was filtered... m-cresol (7.08 g) were combined... for polymerization. Pretreatment: Next, the membrane was immersed in methanol for one day and dried at 130 °C under vacuum for one day before subjected to gas permeability test [73]. Annealing Condition: The membrane was subsequently dried at 120 °C for 12 h under vacuum to evaporate residual solvent. Gas Pair: All copolyimides showed better gas separation performance in terms of the permeability/selectivity trade-off of O2/N2, CO2/CH4, and CO2/N2. Measurement Type & Pure/Mixed: Pure gas permeability (P) was measured using a PERME VAC-2 permeation system (Labthink Inst... Notes: Compared with 6FDA/TBDA2, 6FDA/TTBDA exhibited a more contorted chain conformation and higher chain stiffness. As a result, with a TTBDA percentage of > 50%, the copolymers exhibited a higher Brunauer-Emmet-Teller surface area, fractional free volume, total pore volume, and interchain distance compared with 6FDA/TBDA2. On the other hand, the ultra-micropores width (0.8–0.9 nm) of the copolyimides was less than that of 6FDA/TBDA2 because of the space-filling and pore-partitioning effects of the tert-butyl-phenyl groups. The combination of higher pore volumes and smaller ultra-micropores in the copolymers induced a more efficient molecular gas-sieving effect and thus higher diffusion selectivity.