Hydrocarbon and Perfluorocarbon Gas Sorption in Poly(dimethylsiloxane), Poly(1-trimethylsilyl-1-propyne), and Copolymers of Tetrafluoroethylene and 2,2-Bis(trifluoromethyl)-4,5- difluoro-1,3-dioxole

Abstract

Sorption of a series of gases, perfluorocarbon vapors (CF4, C2F6, and C3F8) and their hydrocarbon analogues in poly(dimethylsiloxane) [PDMS], poly(1-trimethylsilyl-1-propyne) [PTMSP], and two random copolymers of tetrafluoroethylene [TFE] and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole [BDD] are reported as a function of penetrant pressure at 35 °C. Sorption isotherms for all penetrants in rubbery PDMS are linear or slightly convex to the pressure axis, while those in the glassy polymers are concave and are well described by the dual mode model. Fluorocarbon sorption levels are lower than sorption levels of their hydrocarbon analogues in the hydrocarbon-based PDMS and PTMSP matrixes, while the reverse is true in the fluorinated TFE/BDD copolymers. Exceptionally low fluorocarbon solubilities in PDMS are ascribed to poor penetrant/polymer energetic interactions.