Described herein is a composition comprising: a polymer derived from (a) a fluorinated olefin monomer; (b) a highly fluorinated sulfur-containing monomer of the formula: CX1X2═CX3[(CX4X5)w—O—R1—SO2Y] where X1, X2, X3, X4, and X5 are independently selected from H, Cl, or F; w is 0 or 1; R1 is a non-fluorinated or fluorinated alkylene group; and Y is selected from F, Cl, Br, I, or OM, where M is a cation; and (c) a polyfunctional monomer comprising at least two functional groups, wherein the functional groups are selected from the group consisting of: (i) a fluorovinyl ether group, (ii) a fluoroallyl ether group, (iii) a fluorinated olefinic group, and (iv) combinations thereof; articles thereof; and a method of making such polymers.