Copolymers of tetrafluoroethylene oxide and hexafluoropropylene oxide useful as lubricants

The copolymer comprises from 20 mol% to 80 mol% of-CF2CF2O-units, from 20 mol% to 80 mol% of-CF( CF3) CF2O-units, and from 0 mol% to 45 mol% of one or more additional perfluoroalkylene oxide units. The copolymer has a number average molecular weight of 1,500 to 20,000, a viscosity index of 100 to 220, and an average tetrafluoroethylene oxide (TFEO) run length of less than 6. A method of forming a perfluoroalkyl polyether copolymer includes feeding a gas stream containing TFEO and hexafluoropropylene oxide (HFPO) to a reactor containing a fluorinated solvent, a fluoride salt, an ether, and an acyl fluoride to form an acyl fluoride-containing polymer. The method further includes hydrolyzing the acyl fluorine-containing polymer to form a perfluoroalkyl polyether carboxylic acid or carboxylate. The method further includes distilling off the fluorinated solvent and treating the perfluoroalkyl polyether carboxylic acid or carboxylate with elemental fluorine to obtain the perfluoroalkyl polyether copolymer. 共聚物包含20摩