A series of functionalized oligophenylenevinylene (OPV) molecules have been synthesized via an orthogonal approach for the purpose of preparing diblock copolymers. The coupling reaction between the aldehyde-terminated OPVs and a "living" polyisoprene (PI) species leads to the formation of OPV-PI diblock copolymers. TEM results on thin films of four copolymers with the same OPV block but different lengths of the PI blocks clearly show nanophase separation. Alternating strips of OPV- and PI-rich lamella domains were observed under TEM, confirmed by the SAXS experiments on bulk samples. Temperature-dependent SAXS studies also revealed an order-disorder transition at around 128 degrees C for copolymer 1, which is consistent with the TEM results.