Design and Synthesis of Polyimides Based on Carbocyclic Pseudo-Troger's Base-Derived Dianhydrides for Membrane Gas Separation Applications

Two novel carbocyclic pseudo-Troger's base-derived dianhydrides, 5,6,11,12-tetrahydro-5,11-methanodibenzo [a,e][8]annulene-2,3,8,9-tetracarboxylic anhydride (CTB1) and its dione-substituted analogue 6,12-dioxo-5,6,11,12-tetrahydro-5,11-methanodibenzo [a,e][8]annulene-2,3,8,9-tetracarboxylic dianhydride (CTB2), were made and used for the synthesis of soluble polyimides of intrinsic microporosity with 3,3'-dimethylnaphthidine (DMN). The polyimides CTB1-DMN and CTB2-DMN exhibited excellent thermal stability of similar to 500 degrees C and high BET surface areas of 580 and 469 m(2) g(-1), respectively. A freshly made dione-substituted CTB2-DMN membrane demonstrated promising gas separation performance with O-2 permeability of 206 barrer and, O-2/N-2 selectivity of 5.2. A higher O-2 permeability of 320 barter and lower O-2/N-2 selectivity of 4.2 were observed for a fresh CTB1-DMN film due to its higher surface area and less tightly packed structure as indicated by weaker charge-transfer complex interactions. Physical aging over 60 days resulted in reduction in gas permeability and moderately enhanced selectivity. CTB2-DMN exhibited notable performance with gas permeation data located between the 2008 and 2015 permeability/selectivity upper bounds for O-2/N-2 and H-2/CH4.