Photo-oxidation of electroluminescent polymers studied by core-level photoabsorption spectroscopy

The C1s and O1s core-level photoabsorption spectra of poly[2-methoxy,5-(2'-ethyl- hexoxy)-1,4-phenylene vinylene] (MEH-PPV) before and after exposure O2 and broadband visible light were recorded to determine the degradation pathway for this polymer. The change in the O1s spectra as a function of exposure demonstrates that the O adds to the polymer chain to form a carbonyl group. Exposure to only O2 or only light causes no change in the C1s or O1s spectra. In the C1s spectra, the change in the dependence on the photon angle of incidence after exposure demonstrates that O attacks the polymer at the double bond in the vinyl group thereby altering the extended conjugation of the polymer. copyright 1996 American Institute of Physics