Intermediate states during photodegradation in MEH-PPV solutions and thin films

The dynamics of photoluminescent response during optical degradation of MEH-PPV in films and chloroform solutions were investigated using various spectroscopic techniques (PL, UV-Vis, FTIR, and XRF). A significant blue shift in photoluminescence (PL) from MEH-PPV films during degradation indicated strong interchain exciton migration and a different photochemical reaction from that of solution. Two distinct wavelength-dependent dynamic PL responses were observed in MEH-PPV, and were attributed to photoactivation in the long side chain and polymer backbone. It was verified by a control experiment with BDMO-PPV which has symmetric side chains. The dynamic PL results indicate that the degradation process involves at least two-step photochemical reactions in the side chain and backbone. We also found that chlorine showed no effect on the optical degradation process.