Luminescence properties of PPV derivatives carrying anthracene pendent groups

Photo-(PL) and electroluminescence (EL) properties of three different PPV derivatives carrying the 9,10-diphenylanthracene units are compared. One (polymer 1) of the polymers contains the 9,10-diphenylanthracene structure as an integral part of the main chain. but the other two have it as the pendent group attached to the main chain through either oxyethyleneoxy (polymer 2) or oxyhexamethyleneoxy (polymer 3) spacer. Polymers 1 and 2 exhibit very similar PL and EL spectra that are more or less of superimposed feature of the spectra from the backbones and the anthracene pendents. In contrast, polymer 3 shows an EL spectrum that is completely different from its PL spectrum. Whereas the PL spectrum of polymer 3 appears to be a combination of the spectra from the main chain and the pendents, as for polymer 1 and 2, the EL spectrum of polymer 3, however, looks as if the lights were emitted only from the backbone. This difference is explained in terms of excited state electronic interactions between the main chain and the pendents.