The radical co- and terpolymerization of fluorinated monomers bearing an SF5 group, XYC= CZSF(5) (where X, Y, and Z represent either H or F atoms) with 1,1-difluoroethylene (vinylidene fluoride, VDF or VF2) and hexafluoropropene (HFP), is presented. Although these SF5 monomers do not homopolymerize under radical initiation, they do copolymerize (and terpolymerize) in solution, in the presence of radical initiators with VDF (and with VDF and hexafluoropropylene (HFP)), hence leading to original copolymers bearing SF5 side groups. NMR characterizations and yields enabled one to compare the relative reactivities of F2C=CFSF5, HFP, perfluoromethyl vinyl ether, and perfluoropropyl vinyl ether in the copolymerization of VDF with these fluoroolefins. The degree of fluorine substitution on the ethylenic unit of the SF5 monomers had an influence on their reactivity, on their relative incorporation in the copolymers, and on the molar masses of the resulting terpolymers-the higher the fluorine in the SF5 monomer, the higher molecular weight. Interestingly, the greater the degree of fluorine substitution of the SF5-containing monomer, the greater the yield of the reaction. The yield also increased as the amount of initiator was increased. The relative concentrations of the comonomers in each copolymer were assessed by F-19 and H-1 NMR spectroscopy. The thermal properties (thermal stability and glass transition temperature) of these resulting SF5-containing fluoropolymers were also examined.