The vinylene unit of a p-phenylene polymer was photo-oxidized under atmospheric oxygen to provide emittive patterns. Thin films of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-p-phenylene vinylene] (MDMO-PPV) were directly photo-patterned by UV light through a photo-mask having I pm-wide lines. The absorption and fluorescence studies on the MDMO-PPV film by UV irradiation indicated that the photo-patterning was mainly originated from the oxidation of the vinylic bonds to give carbonyl (C=O) containing polymers. The patterned MDMO-PPV film was applied to an electroluminescent cell, which showed 20 mu m-wide luminescent line patterns at applied potential of 5 V. (C) 2009 Elsevier B.V. All rights reserved.