AbstractAddition of hydrogen iodide to isobutyl vinyl ether (1) yields 1‐(1‐iodoethoxy)‐2‐methylpropane (2). The cationic polymerization of1initiated by2/tetraalkylammonium salts (R4N+A−) shows the characterstics of a living polymerization. Different tetraalkylammonium salts were investigated. The coinitiator R4N+A−has no effect on the molar mass and the molar mass distribution of the resulting polymers. However, the rate of polymerization depends heavily on the nature and concentration of the coinitiator. The effect of the coinitiator is discussed on the basis of a special