A methodology is described for the synthesis of polyolefin containing block-copolymers using a catalytic postpolymerization modification strategy. Common polyolefin grades may be converted into macroinitiators using a cross-metathesis reaction. The functionalized polyolefins may then be used to initiate living: coordinative ring opening polymerization of cyclic ester monomer, anionic ring opening polymerization of epoxide monomer, and radical polymerization of vinylic monomer, to yield the corresponding block copolymers.