Abstract: Reverse osmosis (RO) separation of organic solvent mixtures where solvent molecular weights <100 Da is challenging especially for powerful solvents that swell most uncrosslinked polymers. To avoid polymer swelling by solvents, a particular perfluoropolymer, perfluoro-2,2-dimethyl-1,3-dioxole copolymerized with tetrafluoroethylene, (PDD-TFE), designated CMS-7, was studied. This amorphous glassy extremely hydrophobic copolymer has a very high free volume (FV) fraction. The maximum radial dimension of FV regions is less than ˜0.65 nm allowing only single solvent molecule permeation. Further, interactions between polarity, dimensions and shapes of solvent molecules with those of polymer FV elements can lead to extraordinarily selective permeation. Permeation behaviors of other solvent mixtures, toluene-n-heptane, NMP-tetrahydrofuran, methanol-water, ethanol-water as well as individual phases of the immiscible mixture of NMP and the nonpolar solvent n-heptane were also studied.

Abstract: Reverse osmosis (RO) separation of organic solvent mixtures where solvent molecular weights <100 Da is challenging especially for powerful solvents that swell most uncrosslinked polymers. To avoid polymer swelling by solvents, a particular perfluoropolymer, perfluoro-2,2-dimethyl-1,3-dioxole copolymerized with tetrafluoroethylene, (PDD-TFE), designated CMS-7, was studied. This amorphous glassy extremely hydrophobic copolymer has a very high free volume (FV) fraction. The maximum radial dimension of FV regions is less than ˜0.65 nm allowing only single solvent molecule permeation. Further, interactions between polarity, dimensions and shapes of solvent molecules with those of polymer FV elements can lead to extraordinarily selective permeation. Permeation behaviors of other solvent mixtures, toluene-n-heptane, NMP-tetrahydrofuran, methanol-water, ethanol-water as well as individual phases of the immiscible mixture of NMP and the nonpolar solvent n-heptane were also studied.