Described herein are fluoropolymer compositions comprising a compound of Formula I wherein X1 is selected from O or S; L is a divalent linking group comprising at least one aromatic ring; and X2 is selected from the group consisting of a hydroxyl group, an amino group, a thiol group, and a nitrile group. In one embodiment, the phthalonitrile-containing compound is used to crosslink a dehydrohalogenated polymer, and optionally with a polyhydroxy curative. In another embodiment, the phthalonitrile-containing compound is added to a composition comprising (i) a fluorinated elastomeric gum, wherein the fluorinated elastomeric gum comprises a fluoropolymer having a cure-site and (ii) a peroxide curing system.