Syntheses and optical properties of conjugated polymers containing cross-conjugated oxadiazole units

摘要

In this paper, we report the detailed synthesis and optical properties of three new conjugated polymers with cross-conjugated oxadiazole segments containing ester substituents. It was found that, due to the electron-withdrawing nature of the four ester substituents, the pi* state of the oxadiazole segments was lowered to such an extent that it has a lower energy than the pi* state of the PPV backbone. Consequently, a charge-transfer (CT) excited state becomes the lowest-lying excited state in these polymers. As a result, these polymers exhibit dramatically different fluorescence behavior and much lower photoluminescence (PL) quantum efficiencies than the previously reported polymer containing t-butyl substituents. Although these polymers with their low PL quantum efficiencies are not suitable for LED applications, they may be highly photoconductive materials. (C) 2000 Elsevier Science S.A. All rights reserved. [References: 27]