Polymers of Intrinsic Microporosity Postmodified by Vinyl Groups for Membrane Applications

The synthesis of a new series of polymers of intrinsic microporosity (PIM) containing vinyl groups and its performance as gas separation membranes are reported. The incorporation of the vinyl group on the spirobisindane backbone was based on the postmodification of the methylated spirobisindane polymers. Generally, the prepared polymers display good solubility and easy processability to form robust films. Characterization of the new polymers was performed by 1 H and 13 C nuclear magnetic resonance spectroscopy, gel permeation chromatography, infrared spectroscopy, thermal gravimetric analysis, and density measurements. The gas permeability of the CO 2, N 2, O 2, and CH 4 was measured, and selectivities for the CO 2 /N 2 and CO 2 /CH 4 gas pairs were calculated for the prepared polymers and compared to the values obtained from PIM-1. The two vinyl groups per repeating units enabled the modified homopolymers to engage in π-orbital overlap and conjugation with the π-orbitals of the aromatic backbone, thus leading to a reduction in CO 2 permeability but surpassing the Robeson’s upper bound with CO 2 /N 2 selectivity. The attractive CO 2 /N 2 gas separation characteristics of the newly synthesized vinylated PIMs might be useful for postcombustion application in the capture of CO 2 from power plant flue gases. The chemical versatility of the vinyl groups has been tested in two successful addition reactions (bromination and thiol–ene click).