Sorption of Gases and Vapors in an Amorphous Glassy Perfluorodioxole Copolymer

Abstract

Gas and vapor sorption properties of a random copolymer of 87 mol % 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole and 13% tetrafluoroethylene (AF2400) are reported. Using both pressure decay and inverse gas chromatography (IGC) methods, a wide range of solutes was studied: He, N2, O2, CO2, C1−C13 n-alkanes, CF4, C2F6, C6F6, and C6F5CF3. These solutes have critical temperatures ranging from 5 to 677 K. AF2400 has very large solubility coefficients, S, relative to other glassy and rubbery polymers. Only poly(1-trimethylsilyl-1-propyne), the most permeable polymer known, exhibits higher solubility coefficients. The large solubility coefficients in AF2400 are mainly due to high Henry's law solubility coefficients. Fluorocarbon solutes exhibit higher solubility than their hydrocarbon analogues. A novel linear correlation between the logarithm of S and Tc2, where Tc is the solute critical temperature, was observed. On the basis of IGC results, the microcavity size in this perfluoropolymer is larger than in conventional hydrocarbon-based glassy polymers.