Perfluorinated Membranes for Pharmaceutical Processing

Perfluoro-2,2-dimethyl-1,3-dioxole-tetrafluoroethylene (PDD-TFE) is an amorphous, glassy, perfluorinated copolymer with a high fractional free volume, 0.342, and glass transition temperature, 240 °C. As with similar materials, it exhibits considerable thermal and chemical stability. Previous studies show this copolymer having an oxygen permeance of 1500 x10^-6 cm³/cm²*sec*cm Hg, and a selectivity of 2.6 (oxygen/nitrogen). Due to its ability to separate gaseous mixtures, coupled with its chemical stability, separating organic solvent mixtures through pervaporation (PV) seems highly favorable. Furthermore, the pharmaceutical industry would greatly benefit from an athermal and economic means to separate common solvents used in processing. Reported maximum free volume dimensions of perfluorinated copolymers are on the order of 5.9-6.4 Å. Solvents whose molecular dimensions are larger than these pores are typically rejected. This is an attempt to utilize such free volume dimensions of this particular PDD-TFE formulation as we determine its performance as a membrane in PV. Common pharmaceutically relevant of varying sizes and boiling points have been selected : toluene, ethyl acetate, tetrahydrofuran, methanol, n-dimethylsulfoxide, n-dimethylformamide, and n-dimethylacetamide. Testing for pure component permeation of all organic solvents was implemented to create a baseline of performance. The effects of temperature and composition in mixtures were explored to properly gauge the behavior of the membrane. By analyzing separation/permeation data and molecular dimensions of each solvent, a permeance profile can be generated for a variety of solvents that are expected to permeate through the membrane.