Alkyne metathesis of mixtures of 2,5-didodecyl-1,4-dipropynylbenzene and {1,3-bis[2',5'-didodecyl-4'-propynyl(phenylethynyl)]-2,4-bis(trimethylsilyl)cyclobutadiene}cyclopentadienylcobalt in the presence of Mo(CO)(6) and 4-trifluoromethylphenol at 150 degreesC furnishes a series of organometallic PPE copolymers in which CpCo-ligated (cyclobutadienylene)ethynylene units are interspersed into the phenyleneethynylene chains. The copolymers were investigated by UV-vis and fluorescence spectroscopy. Both techniques showed a dramatic influence of the presence of even small amounts of organometallic modules on the photophysical properties of the polymers.