Microporous mixed matrix (ZeoTIPS) membranes
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Recent work in the areas of zeolite membranes and mixed matrix membranes have inspired the development of isotropic microporous mixed matrix (ZeoTIPS) membranes, consisting of high-selectivity zeolite particles suspended in a cellular, microporous polymer matrix formed by thermally induced phase separation (TIPS). The particles form nanoporous connections between the cellular voids in the matrix, and can carry out separations independent of the choice of polymer matrix. Existing water purification and gas separation membranes have a variety of drawbacks, including durability, chemical instabilities, cost, flux, and formation difficulty. ZeoTIPS membranes address each of these drawbacks while yielding high selectivity. Included in this work are theoretical predictions of ZeoTIPS membrane performance along with models and experiments designed to gain fundamental knowledge that can be used to develop these membranes. This dissertation discusses how zeolite particles influence the processes of droplet coarsening and pore formation in thermally induced phase separation by disrupting flow fields as well as changing local compositions and viscosities. Additionally, a mathematical model is presented, leading to understanding of the ZeoTIPS formation process. Polymers used in these membranes must have acceptable interactions with the zeolite particles and desired mechanical properties, but must also be able to undergo thermally induced phase separation with a non-hazardous diluent under reasonable processing conditions. Furthermore, processing conditions such as cooling rate are of vast importance in forming ZeoTIPS membranes, but the required conditions can be difficult to obtain. Thus, development of these membranes has required extensive experimental research to determine feasible polymer--diluent systems for forming the microporous matrix and to develop methods of formation.