Factors controlling successful formation of mixed-matrix gas separation materials

Prior work has suggested simple guidelines for matching transport character istics of materials to form high-performance mixed-matrix materials for gas separation. Such materials comprise a dispersion of molecular sieving part icles in a properly selected matrix polymer phase. Recent work has shown th at these simple criteria are necessary but not sufficient to achieve the de sired properties. The analysis presented here shows the need to optimize th e transport properties of the interfacial region, i.e., the region between the bulk polymer and dispersed sieve phases. Guided by the need to optimize both the transport properties of the interfacial region and the matrix mat erial selection criteria noted above, a new paradigm is recommended for mat rix phase selection. The practicality of the paradigm is validated by the f ormation of mixed-matrix membranes with an appropriate polymer and sieve. T hese materials lead to the attractive predicted performances at low loading . For success at higher loading a zeolite "priming" protocol based on polym er-solvent sieve interactions is shown to be necessary. This modified proto col leads to success at intermediate and high dispersed-phase loading.