Halide displacement from brominated polyisobutylene-co-isoprene) (MIR) under homogeneous and phase-transfer catalyzed reaction conditions is used to prepare acrylate, styrenic and maleimide functionalized elastomers in high yield. These macro-monomer derivatives cross-link efficiently under peroxide initiation to give high modulus, thermoset products that cannot otherwise be accessed from isobutylene-rich elastomers. The extent of cure scales with content of activated C═C, and can extended by co-oligomerization of pendant unsaturation with that contained within multi-functional co-agents.