Preparation and characterization of a glassy fluorinated polyimide zeolite-mixed matrix membrane

Mixed matrix membranes of 6FDA-6FpDA-DABA, a glassy polyimide, and modified zeolites (ZSM-2) were successfully fabricated using the procedure outlined in this paper. The membranes were cast from solution and then exposed to different gases for the purpose of determining and comparing the diffusivity coefficients, the solubility coefficients, and the permeation rates of He, O-2, N-2, CH4, and CO2 of the pure polyimide and the composite membrane. FTIR spectra were collected from the pure polyimide, the polyimide and untethered zeolite solutions, and the mixed matrix membrane (MMM) solution. Comparison of the spectra revealed the presence of hydrogen bonding in the MMM solution not present in the other samples. FESEM images and TEM images did not reveal the presence of voids between the polymer and the zeolite. These images also revealed that when given ample time for the solvent to evaporate, the zeolites sediment to one side of the membrane. This develops a polymer-rich phase and a zeolite-rich phase, and many of the ZSM-2 zeolites appear to adopt an orientation with their largest face orthogonal to the direction of the gas flow.