Formation, characterization and modeling of mixed matrix membrane materials

This work presents the first successful comprehensive study of novel hybrid membrane materials called mixed matrices. Such materials comprise molecular sieve entities embedded in a polymer matrix. Mixed matrix materials have the potential to combine the processability of polymers with the superior gas separation properties of rigid molecular sieving materials. Truly broad applications of membranes have been limited by shortcomings in performance determined by the economically achievable selectivity and productivity of current membranes. Mixed matrix materials offer the most viable approach around the current limitations on continued economical membrane materials development.; Prior work suggested simple guidelines (matching transport characteristics of the continuous and dispersed components) to form high performance mixed matrix materials for gas separation. These criteria guided the experimental incorporation of appropriate sieves in a well-suited polymer matrix. This work shows that these simple criteria are necessary but not sufficient to achieve the desired properties. The analysis presented here shows the need to also optimize the transport properties of the interfacial region, i.e., the region between the bulk polymer and dispersed sieve phases.; Guided by the need to satisfy the matrix material selection criteria noted above, as well as to optimize transport through the interfacial region, a new paradigm is recommended for matrix phase selection (flexible matrix phase with an affinity for the sieve phase and suitable transport characteristics). The practicality of the paradigm is validated by the formation of mixed matrix membranes with an appropriate flexible polymer and sieve. These materials display the attractive expected performance enhancements suggested by theory at low loading. For success at higher loading a sieve 'priming' protocol based on polymer-solvent-sieve interactions has been found to be necessary.; The insights provided by this work were then used to guide successful mixed matrix material formation with more practical rigid commercial gas separation polymers. The promising results achieved in this work now set the stage for the next level of development to make mixed matrix membranes a commercial success.