ABSTRACT:We have investigated the optical properties of poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] containing oxadiazole in backbone (MEH-OPPV) in dilute tetrahydrofuran solution and solid solution films. There is a large dihedral angle between the two adjacent monomer units in MEH-OPPV, which restrains interchain interactions and destroys the conjugation of the polymer to result in blue shifted absorption and emission spectra. The red shifted photoluminescence (PL) peak is continuously changed in the solid solution films with increasing the concentration of MEH-OPPV. Comparison with the dilute solution, an obvious shoulder peak at 465 nm is found in the UV-vis absorption and PL excitation (PLE) spectra of the MEH-OPPV film. The intensity of the PLE shoulder at 465 nm is increased with the concentration of MEH-OPPV in the solid solution films, which is connected with the aggregation of the MEH-OPPV chains. The interchain interactions are restrained and the p-stack aggregates of the polymer chains can not form in the MEH-OPPV due to the large dihedral angle, and then the interchain species are effectively suppressed in the MEH-OPPV films.