(343h) Highly Permeable Supported PDMS Ultrathin Films As a Gutter Layer for Gas Separation Composite Membranes

Engineering useful membrane materials into ultrathin selective layers is the key to maximize membrane gas permeance for energy-efficient separations. The fabrication of a defect-free ultrathin selective layer usually requires a porous substrate to provide mechanical strength and a gutter layer to offer smooth coating surface and prevent pore penetration, forming a multilayer thin film composite (TFC) membrane. Polydimethylsiloxane (PDMS) is the most commonly used gutter layer material due to its high permeability and non-aging property. To minimize gas transport resistance introduced, the supported gutter layer should be 10-fold or more as permeable as the thin selective layer. However, current PDMS gutter layers can hardly provide more than 10,000 GPU CO₂ permeance, which are insufficient to support high-permeance TFC membranes, especially those for CO₂ capture from flue gas. The low permeance is most likely caused by the PDMS material intrusion into the porous substrate with limited porosity. To address this issue, we report a supported 100 nm-thick PDMS gutter layer with a record CO₂ permeance of 12,600 GPU and CO₂/N₂ selectivity of 11.5 at 25 °C. This extremely permeable yet defect-free gutter layer was achieved on a high-porosity (~20%), nanoporous (pore diameter of ~40 nm), and chemical-resistant polymer substrate that was developed through a traditional phase-inversion method. This presentation will discuss the formation of the high-performance porous substrate as well as the subsequent fabrication of the ultrathin PDMS gutter layer with minimal material intrusion. The sought-after performance and good scalability make this supported PDMS thin film a promising gutter layer for high-performance and large-scale TFC membranes for gas separation.