Metal-free initiating systems for living cationic polymerizations are desirable from the viewpoint of environmentally benign polymer synthesis. We describe here the development of a halogen-bonding-mediated and controlled cationic polymerization of isobutyl vinyl ether (IBVE) using 2-iodoimidazolium salts as an organocatalyst. Due to the ionic nature of the catalysts, the polymerization should be performed in CH2 Cl2 . The HCl-adduct of IBVE was the most suitable initiator, and the polymerization was carried out at -10 °C under the catalyst concentration of 10 mm to suppress alcohol elimination from the polymer chain. The addition of a small amount of nBu4 NCl (0.02 equivalent) was effective to accomplish the controlled cationic polymerization and obtain polyIBVE, having the molecular weight distribution below 1.3.