Abstract
Two intrinsically microporous polyimides (PIM-PIs) were synthesized by the polycondensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,3,3',3'-tetramethylspirobisindane-6,7,6',7'-tetracarboxylic dianhydride (SBI) with a newly designed o-hydroxyl-functionalized Troger's base diamine, 1,7-diamino-6H,12H-5,11-methanodibenzo [1,5] diazocine-2,8-diol (HTB). Both amorphous PIM-Pis were soluble in aprotic solvents and showed excellent thermal stability with onset decomposition temperature of similar to 380 degrees C. SBI-HTB displayed a higher CO2 permeability (466 vs 67 barrer) than 6FDA-HTB but a significantly lower selectivity for CO2/CH4 (29 vs 73), H-2/CH4 (29 vs 181), O-2/N-2 (4.6 vs 6.0), and N-2/CH4 (1 vs 2.5). 6FDA-HTB displayed the highest gas-pair permselectivity values of all reported OH-functionalized PIM-PIs to date. The high permselectivity of 6FDA-HTB resulted primarily from exceptional diffusion selectivity due to strong size-sieving properties caused by hydrogen bonding between the proton of the hydroxyl group and the nitrogen atoms in the tertiary amine of the Troger's base (O-H center dot center dot center dot N).