Our recent extensive research on Lewis acid catalysts with a weak base for the cationic polymerization of vinyl ethers led to unprecedented living reaction systems: fast living polymerization within 1-3 s; a wide choice of metal halides containing Al, Sn, Fe, Ti, Zr, Hf, Zn, Ga, In, Si, Ge, and Bi; and heterogeneously catalyzed living polymerization with Fe2O3. The use of added bases for the stabilization of the propagating carbocation and the appropriate selection of Lewis acid catalysts were crucial to the success of such new types of living polymerizations. In addition, the base-stabilized living polymerization allowed the quantitative synthesis of star-shaped polymers with a narrow molecular weight distribution via polymer-linking reactions and the precision synthesis and self-assembly of stimuli-responsive block copolymers. (c) 2007 Wiley Periodicals, Inc.