Allylic halide displacement from brominated poly (isobutylene-co-isoprene) (BUR) by carboxylate nucleophiles is used to prepare elastomer derivatives containing pendant polymerizable functionality. These solvent-borne substitutions are conducted under homogeneous and phase-transfer catalyzed reaction conditions to synthesize acrylate and vinylbenzoate esters in high yield. The resulting macro-monomer derivatives are shown to crosslink efficiently with peroxide initiation to give high modulus, thermoset products that cannot otherwise be accessed from isobutylene-rich elastomers. The extent of cure, as measured by the storage modulus of the vulcanizate, scales with RCH=CH2 content, and can be extended by co-oligomerization of pendant unsaturation with that contained within multifunctional coagents. An alternate approach involving the introduction of pendant sulfonyl azide functionality is described, wherein thermal decomposition to nitrene intermediates supports an efficient crosslinking process. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4691-4696, 2010