New routes to highly fluorinated ethers

Abstract

The aim of this research project was to devise a viable synthetic route to perfluoropolyethers. Current commercial processes are elaborate but inefficient and hence are limited in application by cost. The approach undertaken in this project consisted of essentially two steps; (1) the free radical addition of a polyether to a fluorinated olefin and (2) the direct fluorination of the polyadducts derived from the addition process (scheme i) (Rf = polyfluoroalkyl, Rf(^1) = perfluoroalkyl) The research work was carried out in two phases. The initial investigation examined the free radical addition of simple mono-, di-, and poly-ethers to various fluorinated olefins. The participation of a 1, 5 hydrogen transfer process was found to have a major influence onthe production of poly-adducts. The second phase of the process involved the development of techniques for the further fluorination of the simple adduct systems. Fluorination was achieved using cobalt trifluoride for volatile systemsbut the approach was limited by fragmentation of the substrate as the molecular weight of the adduct increased.Techniques for direct fluorination have been developed and a range of simple ether adducts were successfully fluorinated producing the corresponding perfluoroetherso The findings from the model compound studies were applied to polyethylene glycol diethyl ether (avo molecular weight 456). Addition of the polyether to hexafluoropropene followed by fluorination of the resulting polyadduct with elemental fluorine~ produced a perfluoroether with the following structural featurasin good yield: