The Photodissociation of Perfluoropolyethers by Ultraviolet Light

AbstactThe 172 nm ultraviolet (UV) photodissociation of perfluoropolyether (PFPE) boundary lubricants is examined experimentally and theoretically. Carbonyl fluoride, COF2, is the major gas phase product that results from the UV irradiation of non-functionalized perfluoropolyethers containing the perfluoromethylene oxide, perfluoroethylene oxide, and the perfluoro-n-propylene oxide monomer units. The energetics for COF2 evolution from the carbon centered radicals R-OCF2OCF2·, R-CF2CF2OCF2·; and from the oxygen centered radicals R-CF2OCF2O·, R-CF2CF2O· are quantified via ab initio calculations. The electronic structure of the transition state geometries leading to COF2 dissociation is characterized. COF2 originating from oxygen-centered radicals, leaving behind a carbon-centered radical on the PFPE main chain, appears to be the most energetically favorable dissociation pathway.