The invention provides a fluorinated surfactant having the general formula: [Rf-(O)t-CHF-(CF2)n-COO-]iX (I) wherein Rf represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, t is 0 or 1 and n is 0 or 1, X represents a cation having a valence i and i is 1, 2 or 3. The surfactant can be used in emulsion polymerization of fluoromonomers to prepare fluoropolymers.