The Use of Iptycenes in Rational Macromolecular Design for Gas Separation Membrane Applications

Iptycene molecules, featuring three-dimensional [2,2,2]-ring configurations with 120° contortion sites and unique internal free volume (IFV) elements, have recently been identified for their great potential in the design of polymers for gas separation membranes. Some of these novel iptycene-containing polymers have already displayed unprecedented separation performance. This review summarizes the progression of the gas separation membranes, utilizing iptycene structures over the past five years by dividing the polymers into three categories: nonladder polymers, semiladder polymers, and ladder polymers. The focus lies on examining macromolecular design strategies of these novel polymers and consequential effects on chain packing, free volume architecture, and gas transport properties to provide useful guidance on the design of new membrane materials. Finally, we provide some perspectives and future research directions for designing and utilizing iptycene-containing polymers for gas separation membranes.