Synthesis of fluorinated polyethers

Abstract

The addition of ethers and polyethers to fluoroalkenes (especially hexafluoropropene, but also chlorotrifluoroethene, decafluoro-3,4-bis(trifluoromethyl)- hex-3-ene, 1,1-difluoroethene, hexafluorocyclobutene, octafluorocyclopentene and pentafluoropropene) and hexafluoroacetone was investigated. Studies involving model compounds, such as diethyl ether and oxolane, indicated that this general reaction proceeded with ease when initiated by UV light, using acetone as both solvent and photosensitiser. High field NMR studies allowed a high degree of structural and also mechanistic information to be derived. It was established that the diadducts of HFP with diethyl ether and with oxolane form by two different processes, the former with a surprising degree of stereocontrol. Additions of polyethers to fluoroalkenes were performed and, using the information gained from the model compounds, approximate structures for the new materials were derived. These materials have interesting properties and were shown to migrate to the air interface in acetone solutions of poly(methyl methacrylate) and also in paint by ESCA. Cyclic analogues of these materials (derived from crown ethers) were also synthesised, and evidence for the formation of corresponding alkali metal complexes was obtained by mass spectrometry, though the complexes could not be isolated. Both the cyclic and acyclic materials were successfully fluorinated, using elemental fluorine at room temperature, in an unusual solvent system. NMR and other analysis were performed on these perfluoropolyethers.