Abstract: Amorphous, highly viscous high molecular weight copolyethers containing in excess of 200 total repeating units and formed of --CF.sub.2 --CF.sub.2 --O-- and --CF.sub.2 --O-- repeating units randomly distributed along the chain and linked to each other either directly or through an oxygen atom, in which latter case a peroxy group is present along the chain. These copolyethers, which are useful for preparing bifunctional telomers, high molecular weight fluoropolymers, and highly stable lubricants and heat exchange materials, are prepared by reacting molecular oxygen with tetrafluoroethylene dissolved in a fluorinated or chlorofluorinated solvent selected from the group consisting of dichlorodifluoromethane, perfluorocyclobutane, perfluorodimethylcyclobutane, 1,2-dichloro-hexafluoropropane and 1,2-dichloro-tetrafluoroethane in the presence of ultraviolet radiation and under such conditions that the molar ratio of the tetrafluoroethylene to the oxygen in the reactant feed is between about 0.

Abstract: Perfluoropolyether oils containing traces of H.sub.2 O molecularly dissolved therein are rendered anhydrous and hyperpure by treatment with chlorine trifluoride or monofluoride at a pressure of 1-5 atm. and a temperature of 0.degree.-50.degree. C. after which the treated oil is selectively fractionated.