Block copolymers consisting of polyisobutylene (PLB) and either poly(methyl methacrylate) (PMMA) or polystyrene (PS) block segments were synthesized by a site transformation approach combining living cationic and reversible addition-fragmentation transfer (RAFT) polymerizations. The initial PIB block was synthesized via quasi-living cationic polymerization using the TMPCl/TiCl4 initiation system and Subsequently converted into a hydroxyl-terminated PIB. Site transformation of the hydroxyl-terminated PIB into a macro-chain-transfer agent (PIB-CTA) was accomplished by N,N'-dicyclohexylcarbodiimide/dimethylaminopyridine-catalyzed esterification with 4-cyano-4-(dodecylsulfanylthiocarbonylsulfanyl) pentanoic acid. Structure of the PIB-CTA was confirmed by both H-1 and C-13 NMR spectroscopy. The PIB-CTA was then employed in a RAFT polymerization of either methyl methacrylate or styrene, resulting in PIB block copolymers with narrow polydispersity index and predetermined molecular weights confirmed by both H-1 NMR and GPC.