The invention relates to an aqueous emulsion polymerization of fluorinated monomers using perfluoropolyethers of the following formula (I) or (II). In particular, the perfluoropolyether surfactants correspond to formula (I) or (II)
CF3—(OCF2)m—O—CF2—X (I)
wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof,
CF3—O—(CF2)3—(OCF(CF3)—CF2)z—O-L-Y (II)
wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from —CF(CF3)—, —CF2— and —CF2CF2— and Y represents a carboxylic acid group or salt thereof. The invention further relates to an aqueous dispersion of a fluoropolymer having the aforementioned perfluoropolyether surfactant(s).