Novel pi-corjugated polymers (7) consisting of both poly(phenylenevinylene) (PPV) and poly(phenyleneethynylene) (PPE) blocks are synthesized by using a combination of Heck-type coupling and Horner-Wadsworth-Emmons condensation reactions. These polymers have well-defined chemical structure (-Ph-Cequivalent toC-Ph-Cequivalent toC-Ph-C=C-Ph-C=C-)(n), in which phenyl rings are linked alternately at meta and para positions. C-13 NMR spectroscopy further confirms the structural regularity of the polymers. The degree of polymerization (DP) is in the range 27-76. Resulting from efficient energy transfer from PPE block to PPV block, the PPV/PPE hybrid polymer emits light with the same color as poly[(m-phenylenevinylene)-alt-(p-phenylenevinylene)], 1. LED devices of ITO/PPV/7/Ca and ITO/PEDOT/7/Ca configurations have been fabricated, which give green EL emission with external quantum efficiency of 0.15% for the former and 0.32% for the latter.