A near 100% initiation efficiency and 100% regioselectivity at the methylacrylic C=C bond was realized by bulky Lewis pairs-mediated polymerization of polar divinyl monomers such as 4-vinylbenzyl methacrylate at mild conditions, affording soluble polymers bearing pendant active vinyl groups with narrow dispersities. A delicate combination of Lewis acid and base with suitable steric hindrance is necessary for achieving high initiation efficiency and activity. The livingness and robustness of the bulky Lewis pair polymerization systems provide a simple and convenient route to produce various di- or tri-block copolymers by the stepwise addition of the different monomers, as well as the copolymer in random distribution by the use of the mixed monomers.