Synthesis And Permeation Properties Of Swelling-resistant Triptycene-based PIMs For Gas Separation Membrane

Polymers of intrinsic microporosity (PIMs) are emerging classes of high-performance materials, which possess a rigid fused-ring structure that promote permeability and selectivity at the same time. In spite of the superiority, the selectivity of PIMs materials is also dramatically affected by the swelling-induced plasticization, which led to an increase in permeability and a decrease in separation efficiency of the membrane.Studies shows that cross-linking is a feasible way to obtain the ability to resist the swelling-induced plasticization, and feeds the purpose of maintain a fine permeability and selectivity at the same time after the cross-linking.PIMs that consist of a bridged bicyclic structure called Troger’s base demonstrate extraordinary properties in both gas permeability and selectivity with a more rigid polymer chains and higher free volume than others, and we present the synthesis and properties of triptycene-based Troger’s base (TB) polymers of intrinsic microporosity (PIMs) that possess carboxyl attached to the side of aromatic ring, which allowed chemical cross-linking after glycidol modification that retain a favorable property to resist swelling-induced plasticization. Three kinds of TB-PIMs membrane were prepared and those polymers with free carboxylic acid groups were cross-linked with ethylene glycol for gas separation test which we modified with glycidol by cross-linking at 120 ℃ .The order of several common pure gas permeability is CO2>H2>He>02>CH4>N2 (measured at 25 ℃ in standard atmosphere).The permeability of all these gases is lower with the increasing percentage of carboxyl groups but a gain in selectivity. The permeabilites in CH4/CO2 mixed-gas were measured at different pressure up to 40 bar,and an increase of permeability was found in CH4 only for the membrane without carboxyl groups, but a decrease for others, and the CH4/CO2 selectivity of PIM-Trip-TB was dramatically dropped under high pressure mix-gas condition, whereas cross-linked materials was much less, thus making it a promising membrane material for resisting natural gas sweetening.