Direct C−C Bond Breaking in the Reaction of O(³P) with Flouropolymers in Low Earth Orbit

Spacecraft flying in low Earth orbit (LEO) are exposed to a harsh environment which includes frequent bombardment by fast atomic oxygen (AO) and ultraviolet (UV) radiation. As a result, many spacecraft surface materials are severely eroded. In the case of fluoropolymers, a controversy exists whether AO or UV or AO/UV synergy is responsible for the degradation. In this study, with the use of ab initio calculations, we address the question whether the most abundant species in LEO, viz., atomic oxygen in its ground state, O( 3 P), alone can cause the degradation in fluoropolymer materials. The smallest fluorocarbons C N F 2 N +2 ( N = 2, 3, 5) serve as models of fluoropolymers. Since electronegativity of fluorine seems to preclude F-abstraction by O( 3 P), we concentrate on direct O( 3 P) attacks on carbon−carbon bonds. For the case of fluoroethane ( N = 2), we explore the triplet potential energy surface of the following reaction: O( 3 P) + CF 3 −CF 3 → • O−CF 3 + • CF 3 . Analogous reactions, where O( 3 P) attacks a central carbon atom, are studied for the higher fluorocarbons. Results obtained using the Hartree−Fock method and density functional theory are reported. We conclude that O( 3 P) species in LEO possesses enough translational energy to degrade fluorocarbon materials.