Layer-by-layer Polymer Assemblies as Size-Selective Gas Separation Membranes-
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The proposed research effort addresses the need for low-cost membrane materials for gas purification by investigating polymer coatings capable of combining high rates of gas separation with high purity. The researchers propose growing polymer films one layer at a time by alternately dipping the membrane substrate into a water bath containing positively- and negatively-charged polymers. This results in the growth of a Layer-by-Layer (LbL) thin film. Recently the PIs have confirmed that order-of-magnitude improvements in hydrogen-carbon dioxide and hydrogen-nitrogen selectivity may be achieved using LbL films assembled from polyacrylic acid (PAA) and branched polyethylemine (PEI) solutions. The proposed work leverages these recent results to identify breakthrough polymeric materials capable of size-selective gas separations to meet multiple sustainable energy needs. The PIs propose to use the LbL assembly technique to manipulate membrane structure, in turn tuning both transport properties and membrane durability. Increased transport properties and membrane durability will be achieved through a combination of (i) fundamental materials analysis aimed at characterizing the extent of polyanion and polycation bonding and relating it to mechanical and nanostructural properties, and (ii) transient gas permeation measurements for obtaining precise measurements of individual gas permeabilities through the LbL membrane. The research efforts are focused not only upon proven hydrogen-carbon dioxide separation capability of LbL films, but also applying fundamental concepts to tailored membranes for biofuel (ethanol) dehydration and natural gas processing. Therefore, materials developed may have significant and immediate impact upon the energy industry. The PI''s team has ongoing engagement of underrepresented groups at the graduate and undergraduate levels in socially relevant research topics. Aspects of this work will also be incorporated into multiple ongoing K-12 outreach programs present at Texas A&M University. The PI team plan to also develop online learning exercises utilizing the popular line of HexBug Nano toys, which will be disseminated online. These outreach efforts will be leveraged as a platform for developing teaching tools for illustrating diffusion and related transport phenomena concepts to non-STEM audiences.