Thermodynamics of Sorption in an Amorphous Perfluorinated Rubber Studied by Inverse Gas Chromatography

Abstract

The work is aimed to further investigate thermodynamics of sorption of organic vapors in perfluorinated polymers. Amorphous perfluorinated random copolymer of 50.7 mol % tetrafluoroethylene and 49.3 mol % perfluoromethylvinyl ether, poly(TFE−PMVE), was studied using the inverse gas chromatography method. As solutes, several hydrocarbons and fluorocarbons of different classes were studied, namely, n-alkanes C7−C10, benzene and toluene, methylcyclohexane, n-perfluoroalkanes C6 and C8, perfluoromethylcyclohexane, perfluorinated benzene, and toluene. In addition, partially fluorinated toluene derivatives were investigated. It was shown that solubility coefficients S of fluorocarbons in this rubbery polymer are significantly higher than those of their hydrocarbon analogues. Correlations of the type ln S = A + BTc2, where Tc is the critical temperature of the solutes, were demonstrated for both hydrocarbons and fluorocarbons; however, the curve for fluorocarbons is located above that of hydrocarbons. Therefore, in this regard, the behavior of perfluorinated rubber is analogous to the amorphous glassy perfluorinated polymers studied earlier. Hydrocarbons and fluorocarbons also reveal significant differences in other thermodynamic parameters of sorption in poly(TFE−PMVE): enthalpies of sorption, activity coefficients, partial molar enthalpies of mixing, and Flory−Huggins parameters.