(531f) Ultra-Permeable and Selective Crosslinked Polymer Membranes for Energy Efficient Gas Separation

Si Li, Greg Kline, Ruilan Guo

Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN

Most glassy polymers used for gas separation membranes suffer from physical aging as well as plasticization induced by sorption of condensable gases like CO₂. Additionally they often are not chemically and thermally stable under complex feed conditions. Chemical crosslinking has been demonstrated as an effective approach to improve membrane resistance and durability. However, the much improved membrane stability upon crosslinking is inevitably accompanied with significant loss of gas permeability with little to no gain in selectivity due to great reduction in the free volume. Here we report a new approach of end-linking process to prepare crosslinked polymer membranes from telechelic oligomers with well-controlled molecular weight. This new curing process introduces bulky pendent groups at crosslink junctions, which effectively disrupts chain packing counteracting the undesired densification effect frequently observed in conventional random crosslinking processes. As a result, even the most densely crosslinked membranes (e.g., average inter-crosslink chain length of 3000 g/mol) prepared using this new approach showed similarly high permeability compared to their linear counterparts along with expectedly improved selectivity and excellent membrane stability. Several crosslinked membranes with controlled crosslink density in this work show separation performance well beyond the 2008 upper bounds for H₂ separations, CO₂/CH₄ and O₂/N₂ separations. For example, a crosslinked membrane with 10,000 g/mol inter-crosslink chain length has an ultrahigh CO₂ permeability of 128 barrer along with an excellent ideal CO₂/CH₄ selectivity of 47. In this talk, preparation and characterization of these new crosslinked polymer membranes will be presented. Discussions will focus on elucidating the fundamental relationship between microscopic structures and macroscopic transport properties for these innovative crosslinked polymer membranes.