Tuning the Free Volume of Polyimide Membranes for Efficient Gas Separation

摘要

Robust polymer membranes that are both highly permeable and highly selective are essential to make membrane separation competitive to conventional gas separation technologies. Over the years, substantial research efforts have been devoted to expanding the polymeric membrane performance envelope via designing and synthesizing sophisticated macromolecular structures. The key structural variables that determine the gas transport properties of glassy polymers are the fractional free volume and the size distribution of those free volume elements ("microcavities") in the membranes. While high fractional free volume is desired for high throughput, a narrow size distribution of these microcavities is required for approaching molecular sieving characteristics.