A Sonogashira polycondensation reaction has been used to synthesize copolymers consisting of alternating oligo(p-phenyleneethynylene) with a precise block length as an electron-rich component and 1,4-bis(2-phenylene-2-cyanovinylene)benzene or 2,6-bis(2-pyridinylene-ethynylene)pyridine as an electron-poor component. The copolymers differ in the length of the phenyleneethynylene block (trimer or pentamer) and the content of the electron-poor component. The length of the phenyleneethynylene block has no influence on the maximum wavelength. The electron-poor cyano-block component lowers the optical band-gap energy of the copolymers. The value is equivalent to that of poly(cyano-phenylenevinylene) (CN-PPV) (2.3-2.4 eV). (c) 2005 Wiley Periodicals, Inc.