Molecular design of Tröger's base-based polymers with intrinsic microporosity for gas separation

High performance polymers with intrinsic microporosity have been prepared via introducing sites of contortion and chain stiffness with the incorporation of Tröger's base (TB). An experimental investigation coupling with computational simulation was executed to study the effects of polymers’ chemical structures on their gas separation performance. A general acid-catalyzed and low-temperature synthetic route was adopted to achieve the polymerization between 1, 5-diaminonaphathelen (1,5-DAN) and 4,4′-(Hexafluoroisopropylidene) dianiline (4,4′-HFD) via condensation and cyclization. It is found that the resultant 1, 5-diaminonaphathelen Tröger's base-based polymer (1,5-DTBP), 4,4′-(Hexafluoroisopropylidene) dianiline Tröger's base-based polymer (4,4′-HTBP) and their copolymers are readily soluble in the N-methyl-2-pyrrolidone (NMP) solvent, cast as free standing films and exhibit good gas separation performance. The TB-based polymer containing 10% 4,4′-HFD has both the highest permeability and acceptable selectivity even exceeding the Robeson upper bound for H₂/CH₄. Molecularly designed ineffective chain packing via the enhancement of backbone rigidity and introduction of bulky side groups is proved to be the main mechanism that achieves the high separation performance. Since the newly synthesized TB-based polymers display desirable H₂/CH₄ and H_2/N₂ gas separation performance approaching the Robeson upper bounds, this work proves the feasibility of designing advanced polymeric materials with Tröger's base as the sole constituent.