A novel strategy for the synthesis of fully conjugated donor-acceptor block copolymers, in a single reaction step employing Stille coupling polymerization of end-functional polythiophene and AA + BB monomers, is presented. The unique donor-acceptor structure of these block copolymers provides a rich self-assembly behavior, with the first example of a fully conjugated donor-acceptor block copolymer having two separate crystalline domains being obtained.